The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research plan
Objective 1: Verify BAIAP2L1 (IRTKS) identity, organism, and domains. Status: completed. Evidence confirms human BAIAP2L1/IRTKS is an I-BAR (IMD) domain scaffold with SH3 and PPPDY motifs, consistent with UniProt Q9UHR4. (williams2013oncogenicfgfr3gene pages 1-2, zhang2025insulinreceptortyrosine pages 1-2)
Objective 2: Gather recent (2023–2024) literature on function/localization. Status: completed. Key advances include IRTKS condensates in heterochromatin (EMBO J 2024) and nanoscale mechanosensing via I-BAR proteins (eLife 2023). (xie2024heterochromatinformationand pages 1-2, quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16)
Objective 3: Define pathway roles and interactions. Status: completed. Roles in membrane/actin coupling, nuclear chromatin maintenance, and interactions with FMNL2 identified. (zhang2025insulinreceptortyrosine pages 1-2, fox2024identificationofan pages 10-11)
Objective 4: Clinical applications/disease links. Status: completed. FGFR3–BAIAP2L1 fusion prevalence/sensitivity and BAIAP2L1–BRAF fusions summarized; biomarker data in ovarian cancer included. (williams2013oncogenicfgfr3gene pages 1-2, nakanishi2015mechanismofoncogenic pages 9-12, renaud2022multiomicanalysisof pages 7-10, wu2016thelandscapeof pages 5-9, chao2015bai1associatedprotein2like pages 6-9)
Objective 5: Expert opinions/statistics. Status: completed. Quantitative prevalence and cohort sizes provided; authoritative reviews integrated. (zhang2025insulinreceptortyrosine pages 1-2, williams2013oncogenicfgfr3gene pages 1-2, nakanishi2015mechanismofoncogenic pages 9-12)
Objective 6: Synthesize and submit report. Status: completed.

Comprehensive research report: BAIAP2L1 (IRTKS) — functional annotation and recent advances

Executive verification (critical identity checks)
• Gene/protein match: BAIAP2L1 encodes insulin receptor tyrosine kinase substrate (IRTKS), also known as BAI1-associated protein 2-like 1, in Homo sapiens. Literature describes IRTKS as a BAR-superfamily scaffold with an inverse-BAR (I-BAR/IMD) domain, SH3 domain, and a PPPDY WW-binding motif, matching UniProt’s description. (Williams 2013; DOI: 10.1093/hmg/dds486; Zhang & Zhang 2025; DOI: 10.3892/mmr.2025.13437) (williams2013oncogenicfgfr3gene pages 1-2, zhang2025insulinreceptortyrosine pages 1-2)
• Organism: All sources cited here study the human protein or human tumors/cell lines; no conflicting gene symbol usage detected. (williams2013oncogenicfgfr3gene pages 1-2, nakanishi2015mechanismofoncogenic pages 9-12, renaud2022multiomicanalysisof pages 7-10, xie2024heterochromatinformationand pages 1-2)
• Domain/family alignment: IRTKS belongs to the IRSp53/MIM I-BAR family; domain composition (I-BAR/IMD, SH3) and motifs (PPPDY) are consistently reported, including their retention/utilization in oncogenic fusions. (williams2013oncogenicfgfr3gene pages 1-2, zhang2025insulinreceptortyrosine pages 1-2)

1) Key concepts and definitions
• Molecular identity and domains: IRTKS/BAIAP2L1 is a multi-domain adaptor that couples plasma-membrane curvature with the actin cytoskeleton via an I-BAR/IMD domain (negative curvature sensing/induction), an SH3 domain mediating interactions with actin regulators, and a PPPDY motif that can engage WW domains. These features underpin roles in filopodia and membrane remodeling. (Zhang & Zhang 2025, accepted 19 Dec 2024; DOI: 10.3892/mmr.2025.13437; Williams 2013, online 21 Nov 2012; DOI: 10.1093/hmg/dds486) (zhang2025insulinreceptortyrosine pages 1-2, williams2013oncogenicfgfr3gene pages 1-2)
• Cellular localization: IRTKS localizes to plasma-membrane protrusions/filopodial structures and, unexpectedly, to nuclear puncta/condensates where it contributes to heterochromatin organization. (EMBO J 27 Aug 2024; DOI: 10.1038/s44318-024-00212-3) (xie2024heterochromatinformationand pages 1-2)
• Primary functional theme: IRTKS acts as a curvature-sensing and actin-assembling scaffold integrating signaling inputs (including insulin receptor pathways) with membrane/actin dynamics and, as newly shown, nuclear chromatin maintenance. (zhang2025insulinreceptortyrosine pages 1-2, xie2024heterochromatinformationand pages 1-2)

2) Recent developments and latest research (priority to 2023–2024)
• Nanoscale mechanosensing by I-BAR proteins: Quiroga et al. (eLife, 25 Sep 2023; DOI: 10.7554/eLife.72316) demonstrated that mechanical stretch/compression generates ~100 nm plasma-membrane evaginations that are recognized by I-BAR proteins (including IRSp53 family). Recognition triggers Rac1→WAVE/Arp2/3-dependent actin polymerization that re-flattens the membrane. The resorption requires Arp2/3/WRC but not formins or myosin, defining a local curvature→actin feedback circuit. This general mechanism directly supports a role for IRTKS in nanoscale membrane-shape homeostasis. (quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16)
• IRTKS condensates enforce heterochromatin (EMBO J 2024): Xie et al. showed IRTKS undergoes LLPS, infiltrates HP1α condensates, and recruits the E2 ligase Ubc9 to SUMOylate/stabilize HP1α. IRTKS loss leads to heterochromatin erosion, genome-wide chromatin accessibility changes, cGAS–STING activation, type I interferon signaling, and cellular senescence/SASP. This establishes IRTKS as an epigenetic mediator of chromatin integrity and inflammation restraint. (Published online 27 Aug 2024; DOI: 10.1038/s44318-024-00212-3) (xie2024heterochromatinformationand pages 1-2)
• FMNL2 interactome (IJMS 2024): Quantitative BioID/SILAC proteomics identified BAIAP2L1 (IRTKS) as a proximal interactor of the formin FMNL2, implicating coordinated regulation of actin assembly and subcellular trafficking; the study also shows FMNL2 presence in exosomes. (Int J Mol Sci, 31 May 2024; DOI: 10.3390/ijms25115686) (fox2024identificationofan pages 10-11)

3) Functions, pathways, and subcellular site of action
• Membrane/actin coupling at the cortex: Through its I-BAR domain, IRTKS senses and/or generates negative curvature at the plasma membrane, recruiting actin machinery via SH3-mediated interactions. The eLife 2023 work places I-BAR proteins at the core of a mechanochemical feedback that restores local membrane flatness, mechanistically aligning with IRTKS’s established role in membrane protrusions and filopodia. (quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16, zhang2025insulinreceptortyrosine pages 1-2)
• Nuclear/epigenetic role: IRTKS LLPS within heterochromatin and stabilization of HP1α consolidates constitutive heterochromatin; its loss activates immune signaling and senescence, localizing a major IRTKS function to the nucleus under specific contexts. (xie2024heterochromatinformationand pages 1-2)
• Signaling crosstalk: Historically linked to insulin receptor signaling and membrane dynamics, IRTKS’s domain architecture supports scaffolding of small GTPases and actin regulators (Ena/VASP, WAVE, formins), and its SH3/WW-binding motifs enable broader signaling assemblies at membranes and, via LLPS, in the nucleus. (zhang2025insulinreceptortyrosine pages 1-2, xie2024heterochromatinformationand pages 1-2)
• Interaction with formins: The FMNL2 proximity labeling result suggests IRTKS coordinates with formins in location-specific actin assembly, potentially bridging curvature sensing with linear actin polymerization pathways in trafficking and protrusion contexts. (fox2024identificationofan pages 10-11)

4) Disease relevance, applications, and real-world implementations
• FGFR3–BAIAP2L1 fusion oncogene (urothelial/lung):
– Discovery and domain architecture: A t(4;7) translocation fuses FGFR3 to BAIAP2L1, retaining FGFR3 residues 1–760 and BAIAP2L1 IRSp53/IMD and SH3 domains plus PPPDY motif. Fusion proteins are constitutively active and transform NIH/3T3 cells; in immortalized urothelial cells, they activate MAPK but not PLCγ1 due to loss of the PLCγ1-binding exon in FGFR3. (Human Mol Genet, 21 Nov 2012 online; DOI: 10.1093/hmg/dds486) (williams2013oncogenicfgfr3gene pages 1-2, williams2013oncogenicfgfr3gene pages 2-3)
– Prevalence statistics: Williams et al. detected FGFR3–BAIAP2L1 in 4/43 bladder tumor cell lines and 2/32 selected bladder tumor tissues. Nakanishi et al. reported fusion transcripts in 1/28 lung adenocarcinoma, 1/28 lung squamous carcinoma, and 2/46 bladder cancers; an additional bladder cohort showed 2/89 cases. (Mol Cancer Ther, Mar 2015; DOI: 10.1158/1535-7163.MCT-14-0927-T; HMG 2013) (nakanishi2015mechanismofoncogenic pages 9-12, williams2013oncogenicfgfr3gene pages 1-2)
– Mechanism of activation and domain requirements: The BAIAP2L1 BAR/I-BAR dimerization motif is essential for fusion-driven activation; kinase-dead mutants abrogate oncogenicity. (nakanishi2015mechanismofoncogenic pages 9-12)
– Therapeutic sensitivity: Fusion-positive lines (e.g., SW780) show marked sensitivity to selective FGFR inhibitors. CH5183284/Debio 1347 inhibited proliferation, induced apoptosis, suppressed FRS/ERK phosphorylation, and showed in vivo activity in xenografts, while sparing wild-type FGFR tumors. Other FGFR TKIs also suppressed growth. These findings support fusion-guided FGFR-targeted therapy. (nakanishi2015mechanismofoncogenic pages 9-12)
• BAIAP2L1–BRAF fusion (thyroid, spitzoid melanocytic tumors):
– Thyroid cancer (PTC): A BAIAP2L1–BRAF rearrangement (patient with thyroiditis) transformed immortalized human thyroid cells; oncogenicity requires BRAF kinase activity and the BAIAP2L1 coiled-coil domain. MAPK pathway activation was robust; pharmacologic testing indicated paradoxical MAPK activation by low-dose vemurafenib, with additional testing of trametinib and PLX-8394. (Molecular Cancer, 13 Oct 2022; DOI: 10.1186/s12943-022-01665-y) (renaud2022multiomicanalysisof pages 7-10)
– Spitzoid tumors: RNA-seq identified BAIAP2L1–BRAF among kinase fusions with intact kinase domains; FISH confirmed rearrangement in ≥30% of cells in the BAIAP2L1 case. (Modern Pathology, Apr 2016; DOI: 10.1038/modpathol.2016.37) (wu2016thelandscapeof pages 5-9)
• Biomarker evidence in ovarian cancer: BAIAP2L1 is upregulated by IHC in 193 ovarian cancers vs 20 normals, with higher expression in 12/14 metastatic lesions compared to matched primaries; public datasets corroborate upregulation (e.g., GSE14407 p=0.004). Knockdown reduces proliferation and increases apoptosis, suggesting oncogenic support functions. (PLoS ONE, 15 Jul 2015; DOI: 10.1371/journal.pone.0133081) (chao2015bai1associatedprotein2like pages 6-9)

5) Expert opinions and analysis from authoritative sources
• Authoritative mechanistic frameworks: The eLife 2023 study provides an experimentally supported model in which I-BAR proteins decode nanoscale curvature into localized Arp2/3-mediated actin polymerization to restore membrane topology; this places IRTKS/BAIAP2L1 within a generalizable curvature→actin homeostasis circuit at the cortex. (quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16)
• Epigenetic paradigm shift: EMBO J 2024 establishes IRTKS as a heterochromatin organizer via LLPS and HP1α SUMOylation, expanding its functional repertoire beyond the cortex to nuclear chromatin integrity and inflammation control. This suggests disease links not only through membrane signaling but also chromatin-state maintenance and senescence. (xie2024heterochromatinformationand pages 1-2)
• Fusion oncogene logic: Mechanistic analyses underscore that scaffold domains contributed by BAIAP2L1 (I-BAR dimerization, CC) can drive receptor tyrosine kinase (FGFR3) or RAF kinase oligomerization/activation, rationalizing sensitivity to pathway-targeted inhibitors (FGFR TKIs; RAF/MEK modulators) with attention to paradoxical activation phenomena. (nakanishi2015mechanismofoncogenic pages 9-12, renaud2022multiomicanalysisof pages 7-10)

6) Quantitative statistics and key data points
• FGFR3–BAIAP2L1 prevalence:
– Bladder cell lines: 4/43; bladder tissues: 2/32 selected. (HMG 2013; DOI: 10.1093/hmg/dds486) (williams2013oncogenicfgfr3gene pages 1-2)
– Additional screening: 2/46 bladder; 2/89 bladder in broader cohort; 1/28 lung adenocarcinoma; 1/28 lung squamous carcinoma. (MCT 2015; DOI: 10.1158/1535-7163.MCT-14-0927-T) (nakanishi2015mechanismofoncogenic pages 9-12)
• Therapeutic experiments: Debio 1347 (CH5183284) suppressed growth and ERK signaling and induced apoptosis in FGFR3–BAIAP2L1-positive models; in vivo anti-tumor activity was demonstrated in SW780 and Rat-2_F3-B xenografts. (nakanishi2015mechanismofoncogenic pages 9-12)
• BAIAP2L1–BRAF: Oncogenic transformation depends on kinase activity and BAIAP2L1 CC domain; MEK/ERK activation is robust; responses to RAF/MEK agents require careful dosing to avoid paradoxical activation. (renaud2022multiomicanalysisof pages 7-10)
• Ovarian cancer cohorts: IHC n=193 tumors vs 20 normals; 12/14 metastasis pairs with higher BAIAP2L1; multiple external datasets show significant overexpression (e.g., GSE14407 p=0.004). (chao2015bai1associatedprotein2like pages 6-9)

Mechanistic synthesis: primary function and site of action
• Primary function: IRTKS is a curvature-sensing adaptor that coordinates membrane topology with actin assembly to shape protrusions and restore membrane homeostasis; it also forms nuclear condensates essential for heterochromatin stability. (quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16, xie2024heterochromatinformationand pages 1-2)
• Site(s) of action: Plasma membrane/cortex (I-BAR-mediated curvature recognition and actin recruitment) and nucleus (LLPS with HP1α to maintain heterochromatin and restrain innate immune activation). (quiroga2023amechanosensingmechanism pages 1-2, xie2024heterochromatinformationand pages 1-2)
• Pathways: Cortical actin via Rac1-WAVE-Arp2/3; MAPK activation via oncogenic fusions (FGFR3–BAIAP2L1, BAIAP2L1–BRAF); historical insulin receptor signaling scaffolding consistent with its “substrate” nomenclature. (quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16, williams2013oncogenicfgfr3gene pages 1-2, renaud2022multiomicanalysisof pages 7-10, zhang2025insulinreceptortyrosine pages 1-2)

Therapeutic and implementation implications
• Diagnostics: Detect FGFR3–BAIAP2L1 by RNA-based fusion panels/FISH in bladder and lung tumors; consider BAIAP2L1–BRAF in thyroid or spitzoid melanocytic lesions. (williams2013oncogenicfgfr3gene pages 1-2, nakanishi2015mechanismofoncogenic pages 9-12, wu2016thelandscapeof pages 5-9, renaud2022multiomicanalysisof pages 7-10)
• Targeted therapy: FGFR3–BAIAP2L1 predicts sensitivity to selective FGFR inhibitors (e.g., Debio 1347) in preclinical models; MAPK-pathway inhibitors may be applicable to BAIAP2L1–BRAF with attention to paradoxical RAF inhibitor effects and MEK/ERK blockade strategies. (nakanishi2015mechanismofoncogenic pages 9-12, renaud2022multiomicanalysisof pages 7-10)
• Prognostic/biomarker roles: Elevated BAIAP2L1 associates with proliferative and anti-apoptotic phenotypes in ovarian cancer and is higher in metastases, supporting its consideration as a biomarker and potential target in select contexts. (chao2015bai1associatedprotein2like pages 6-9)

Quick-reference artifact
| Category | Key finding / definition | Primary source (year) with DOI | URL |
|---|---|---:|---|
| UniProt identity & synonyms | BAIAP2L1 (also IRTKS; insulin receptor tyrosine kinase substrate; brain‑specific angiogenesis inhibitor 1‑associated protein 2‑like 1); human gene encoding ~511 aa scaffold linking membrane curvature and actin dynamics (chromosome 7q21.3–q22.1). (zhang2025insulinreceptortyrosine pages 1-2) | Zhang & Zhang 2025; DOI: 10.3892/mmr.2025.13437 | https://doi.org/10.3892/mmr.2025.13437 |
| Domains retained in FGFR3–BAIAP2L1 fusion | FGFR3–BAIAP2L1 fusions preserve FGFR3 kinase region fused to BAIAP2L1 N‑terminal I‑BAR/IMD, SH3 domain and PPPDY motif, producing constitutively active kinases. (williams2013oncogenicfgfr3gene pages 1-2) | Williams et al. 2013; DOI: 10.1093/hmg/dds486 | https://doi.org/10.1093/hmg/dds486 |
| Core domains (function) | I‑BAR/IMD (membrane curvature sensing/generation, promotes protrusions), SH3 (protein–protein interactions), PPPDY motif (WW interactions); supports actin assembly via Ena/VASP, WAVE, formins. (zhang2025insulinreceptortyrosine pages 1-2, williams2013oncogenicfgfr3gene pages 1-2) | Zhang & Zhang 2025; DOI: 10.3892/mmr.2025.13437 | https://doi.org/10.3892/mmr.2025.13437 |
| Cellular localization | Localizes to plasma‑membrane protrusions/filopodia and cortical sites; also nuclear puncta/condensates with functional nuclear roles (heterochromatin LLPS). (xie2024heterochromatinformationand pages 1-2) | Xie et al. 2024; DOI: 10.1038/s44318-024-00212-3 | https://doi.org/10.1038/s44318-024-00212-3 |
| Mechanosensing (I‑BAR → actin feedback) | I‑BAR proteins (including IRTKS) recognize ~100 nm membrane evaginations after stretch/compression, recruiting Rac1→WAVE/Arp2/3 to polymerize actin and re‑flatten membrane; resorption depends on Arp2/3 but not formins/myosin. (quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16) | Quiroga et al. 2023; DOI: 10.7554/eLife.72316 | https://doi.org/10.7554/eLife.72316 |
| Heterochromatin / LLPS role | IRTKS undergoes liquid–liquid phase separation, infiltrates HP1α condensates, recruits Ubc9 to SUMOylate/stabilize HP1α; IRTKS loss → heterochromatin loss, cGAS–STING activation, IFN‑I signaling and senescence. (xie2024heterochromatinformationand pages 1-2) | Xie et al. 2024; DOI: 10.1038/s44318-024-00212-3 | https://doi.org/10.1038/s44318-024-00212-3 |
| FMNL2 interaction (proteomics) | BioID/SILAC identified BAIAP2L1 (IRTKS) as an FMNL2 proximal interactor, suggesting roles in actin/formin‑linked trafficking and presence in exosomes. (fox2024identificationofan pages 10-11) | Fox et al. 2024; DOI: 10.3390/ijms25115686 | https://doi.org/10.3390/ijms25115686 |
| FGFR3–BAIAP2L1 prevalence & inhibitor sensitivity | FGFR3–BAIAP2L1 reported in bladder and lung: detected in 4/43 bladder cell lines and 2/32 selected bladder tissues (Williams 2013); Nakanishi et al. found ~1/28 lung adenocarcinoma, 1/28 lung SCC and 2/46 bladder in initial screens and 2/89 in broader bladder screen. Fusion‑positive lines (e.g., SW780) show ligand‑independent activation and selective sensitivity to FGFR inhibitors (CH5183284/Debio 1347 and other FGFR TKIs). (williams2013oncogenicfgfr3gene pages 1-2, nakanishi2015mechanismofoncogenic pages 9-12) | Williams 2013; DOI: 10.1093/hmg/dds486; Nakanishi 2015; DOI: 10.1158/1535-7163.MCT-14-0927-T | https://doi.org/10.1093/hmg/dds486, https://doi.org/10.1158/1535-7163.mct-14-0927-t |
| BAIAP2L1–BRAF fusions (thyroid, spitzoid) | BAIAP2L1–BRAF fusion identified in papillary thyroid carcinoma (oncogenic, kinase‑ and CC‑domain dependent) and reported as a BRAF partner in spitzoid melanocytic tumors; fusion drives MAPK activation and transformation. (renaud2022multiomicanalysisof pages 7-10, wu2016thelandscapeof pages 5-9) | Renaud et al. 2022; DOI: 10.1186/s12943-022-01665-y; Wu et al. 2016; DOI: 10.1038/modpathol.2016.37 | https://doi.org/10.1186/s12943-022-01665-y, https://doi.org/10.1038/modpathol.2016.37 |
| Ovarian cancer biomarker data | BAIAP2L1 upregulated in ovarian tumors vs normals (IHC cohort: 193 tumors vs 20 normals); in 14 matched primary/metastatic pairs 12 showed higher expression in metastases; public datasets (GSE14407 p=0.004 etc.) support upregulation and functional assays show decreased proliferation and increased apoptosis after knockdown. (chao2015bai1associatedprotein2like pages 6-9) | Chao et al. 2015; DOI: 10.1371/journal.pone.0133081 | https://doi.org/10.1371/journal.pone.0133081 |
| Domain requirements for fusion oncogenicity | For FGFR3–BAIAP2L1 the BAIAP2L1 BAR/I‑BAR dimerization motif is essential for activation; for BAIAP2L1–BRAF kinase activity and the BAIAP2L1 coiled‑coil (CC) are required for transformation, indicating fusion partner domains (BAR/CC) enable constitutive activation. (nakanishi2015mechanismofoncogenic pages 9-12, renaud2022multiomicanalysisof pages 7-10) | Nakanishi et al. 2015; DOI: 10.1158/1535-7163.MCT-14-0927-T; Renaud et al. 2022; DOI: 10.1186/s12943-022-01665-y | https://doi.org/10.1158/1535-7163.mct-14-0927-t, https://doi.org/10.1186/s12943-022-01665-y |

Table: Compact, sourced summary of BAIAP2L1/IRTKS identity, domains, localization, mechanisms (2023–2024), fusion oncogenes and therapeutic sensitivity, with primary-source DOIs and URLs for quick reference.

Key source list with URLs and dates
• Xie et al., Heterochromatin formation and remodeling by IRTKS condensates counteract cellular senescence. The EMBO Journal, published online 27 Aug 2024. DOI: 10.1038/s44318-024-00212-3. URL: https://doi.org/10.1038/s44318-024-00212-3 (xie2024heterochromatinformationand pages 1-2)
• Quiroga et al., A mechanosensing mechanism controls plasma membrane shape homeostasis at the nanoscale. eLife, published 25 Sep 2023. DOI: 10.7554/eLife.72316. URL: https://doi.org/10.7554/eLife.72316 (quiroga2023amechanosensingmechanism pages 1-2, quiroga2023amechanosensingmechanism pages 15-16)
• Fox et al., Identification of an FMNL2 Interactome by Quantitative Mass Spectrometry. Int J Mol Sci, 31 May 2024. DOI: 10.3390/ijms25115686. URL: https://doi.org/10.3390/ijms25115686 (fox2024identificationofan pages 10-11)
• Williams et al., Oncogenic FGFR3 gene fusions in bladder cancer. Human Molecular Genetics, advance access 21 Nov 2012; Vol. 22(4), 2013. DOI: 10.1093/hmg/dds486. URL: https://doi.org/10.1093/hmg/dds486 (williams2013oncogenicfgfr3gene pages 1-2, williams2013oncogenicfgfr3gene pages 2-3)
• Nakanishi et al., Mechanism of Oncogenic Signal Activation by the Novel Fusion Kinase FGFR3–BAIAP2L1. Mol Cancer Ther, Mar 2015; OnlineFirst 14 Jan 2015. DOI: 10.1158/1535-7163.MCT-14-0927-T. URL: https://doi.org/10.1158/1535-7163.mct-14-0927-t (nakanishi2015mechanismofoncogenic pages 9-12)
• Renaud et al., Multiomic analysis of papillary thyroid cancers identifies BAIAP2L1–BRAF fusion… Molecular Cancer, 13 Oct 2022. DOI: 10.1186/s12943-022-01665-y. URL: https://doi.org/10.1186/s12943-022-01665-y (renaud2022multiomicanalysisof pages 7-10)
• Wu et al., The landscape of fusion transcripts in spitzoid melanoma… Modern Pathology, Apr 2016. DOI: 10.1038/modpathol.2016.37. URL: https://doi.org/10.1038/modpathol.2016.37 (wu2016thelandscapeof pages 5-9)
• Chao et al., BAIAP2L1 Is a Potential Biomarker in Ovarian Cancer. PLoS ONE, 15 Jul 2015. DOI: 10.1371/journal.pone.0133081. URL: https://doi.org/10.1371/journal.pone.0133081 (chao2015bai1associatedprotein2like pages 6-9)
• Zhang & Zhang, Insulin receptor tyrosine kinase substrate in health and disease (Review). Molecular Medicine Reports, Jan 2025 (accepted 19 Dec 2024). DOI: 10.3892/mmr.2025.13437. URL: https://doi.org/10.3892/mmr.2025.13437 (zhang2025insulinreceptortyrosine pages 1-2)

References

1. (williams2013oncogenicfgfr3gene pages 1-2): Sarah V. Williams, Carolyn D. Hurst, and Margaret A. Knowles. Oncogenic fgfr3 gene fusions in bladder cancer. Human Molecular Genetics, 22:795-803, Nov 2013. URL: https://doi.org/10.1093/hmg/dds486, doi:10.1093/hmg/dds486. This article has 474 citations and is from a domain leading peer-reviewed journal.

2. (zhang2025insulinreceptortyrosine pages 1-2): Xueyan Zhang and Zhewen Zhang. Insulin receptor tyrosine kinase substrate in health and disease (review). Molecular Medicine Reports, Jan 2025. URL: https://doi.org/10.3892/mmr.2025.13437, doi:10.3892/mmr.2025.13437. This article has 0 citations and is from a peer-reviewed journal.

3. (xie2024heterochromatinformationand pages 1-2): Jia Xie, Zhao-Ning Lu, Shi-Hao Bai, Xiao-Fang Cui, He-Yuan Lian, Chen-Yi Xie, Na Wang, Lan Wang, and Ze-Guang Han. Heterochromatin formation and remodeling by irtks condensates counteract cellular senescence. The EMBO Journal, 43:4542-4577, Aug 2024. URL: https://doi.org/10.1038/s44318-024-00212-3, doi:10.1038/s44318-024-00212-3. This article has 9 citations.

4. (quiroga2023amechanosensingmechanism pages 1-2): Xarxa Quiroga, Nikhil Walani, Andrea Disanza, Albert Chavero, Alexandra Mittens, Francesc Tebar, Xavier Trepat, Robert G Parton, María Isabel Geli, Giorgio Scita, Marino Arroyo, Anabel-Lise Le Roux, and Pere Roca-Cusachs. A mechanosensing mechanism controls plasma membrane shape homeostasis at the nanoscale. eLife, Sep 2023. URL: https://doi.org/10.7554/elife.72316, doi:10.7554/elife.72316. This article has 17 citations and is from a domain leading peer-reviewed journal.

5. (quiroga2023amechanosensingmechanism pages 15-16): Xarxa Quiroga, Nikhil Walani, Andrea Disanza, Albert Chavero, Alexandra Mittens, Francesc Tebar, Xavier Trepat, Robert G Parton, María Isabel Geli, Giorgio Scita, Marino Arroyo, Anabel-Lise Le Roux, and Pere Roca-Cusachs. A mechanosensing mechanism controls plasma membrane shape homeostasis at the nanoscale. eLife, Sep 2023. URL: https://doi.org/10.7554/elife.72316, doi:10.7554/elife.72316. This article has 17 citations and is from a domain leading peer-reviewed journal.

6. (fox2024identificationofan pages 10-11): Sarah Fox, Antoine Gaudreau-LaPierre, Ryan Reshke, Irina Podinic, Derrick J. Gibbings, Laura Trinkle-Mulcahy, and John W. Copeland. Identification of an fmnl2 interactome by quantitative mass spectrometry. International Journal of Molecular Sciences, 25:5686, May 2024. URL: https://doi.org/10.3390/ijms25115686, doi:10.3390/ijms25115686. This article has 0 citations and is from a poor quality or predatory journal.

7. (nakanishi2015mechanismofoncogenic pages 9-12): Yoshito Nakanishi, Nukinori Akiyama, Toshiyuki Tsukaguchi, Toshihiko Fujii, Yasuko Satoh, Nobuya Ishii, and Masahiro Aoki. Mechanism of oncogenic signal activation by the novel fusion kinase fgfr3–baiap2l1. Molecular Cancer Therapeutics, 14:704-712, Mar 2015. URL: https://doi.org/10.1158/1535-7163.mct-14-0927-t, doi:10.1158/1535-7163.mct-14-0927-t. This article has 78 citations and is from a peer-reviewed journal.

8. (renaud2022multiomicanalysisof pages 7-10): Emilie Renaud, Kristina Riegel, Rossana Romero, Kushal Suryamohan, Ute Distler, Stefan Tenzer, Arno Schad, Thomas J. Musholt, and Krishnaraj Rajalingam. Multiomic analysis of papillary thyroid cancers identifies baiap2l1-braf fusion and requirement of trim25, pde5a and pkcδ for tumorigenesis. Molecular Cancer, Oct 2022. URL: https://doi.org/10.1186/s12943-022-01665-y, doi:10.1186/s12943-022-01665-y. This article has 6 citations and is from a highest quality peer-reviewed journal.

9. (wu2016thelandscapeof pages 5-9): Gang Wu, Raymond L Barnhill, Seungjae Lee, Yongjin Li, Ying Shao, John Easton, James Dalton, Jinghui Zhang, Alberto Pappo, and Armita Bahrami. The landscape of fusion transcripts in spitzoid melanoma and biologically indeterminate spitzoid tumors by rna sequencing. Modern Pathology, 29:359-369, Apr 2016. URL: https://doi.org/10.1038/modpathol.2016.37, doi:10.1038/modpathol.2016.37. This article has 77 citations and is from a domain leading peer-reviewed journal.

10. (chao2015bai1associatedprotein2like pages 6-9): Angel Chao, Chia-Lung Tsai, Shih-Ming Jung, Wei-Chi Chuang, Chieh Kao, An Hsu, Shun-Hua Chen, Chiao-Yun Lin, Yi-Chao Lee, Yun-Shien Lee, Tzu-Hao Wang, Hsin-Shih Wang, and Chyong-Huey Lai. Bai1-associated protein 2-like 1 (baiap2l1) is a potential biomarker in ovarian cancer. PLoS ONE, 10:e0133081, Jul 2015. URL: https://doi.org/10.1371/journal.pone.0133081, doi:10.1371/journal.pone.0133081. This article has 40 citations and is from a peer-reviewed journal.

11. (williams2013oncogenicfgfr3gene pages 2-3): Sarah V. Williams, Carolyn D. Hurst, and Margaret A. Knowles. Oncogenic fgfr3 gene fusions in bladder cancer. Human Molecular Genetics, 22:795-803, Nov 2013. URL: https://doi.org/10.1093/hmg/dds486, doi:10.1093/hmg/dds486. This article has 474 citations and is from a domain leading peer-reviewed journal.

Citations

1. xie2024heterochromatinformationand pages 1-2
2. fox2024identificationofan pages 10-11
3. nakanishi2015mechanismofoncogenic pages 9-12
4. renaud2022multiomicanalysisof pages 7-10
5. wu2016thelandscapeof pages 5-9
6. zhang2025insulinreceptortyrosine pages 1-2
7. quiroga2023amechanosensingmechanism pages 1-2
8. quiroga2023amechanosensingmechanism pages 15-16
9. https://doi.org/10.3892/mmr.2025.13437
10. https://doi.org/10.1093/hmg/dds486
11. https://doi.org/10.1038/s44318-024-00212-3
12. https://doi.org/10.7554/eLife.72316
13. https://doi.org/10.3390/ijms25115686
14. https://doi.org/10.1093/hmg/dds486,
15. https://doi.org/10.1158/1535-7163.mct-14-0927-t
16. https://doi.org/10.1186/s12943-022-01665-y,
17. https://doi.org/10.1038/modpathol.2016.37
18. https://doi.org/10.1371/journal.pone.0133081
19. https://doi.org/10.1158/1535-7163.mct-14-0927-t,
20. https://doi.org/10.1186/s12943-022-01665-y
21. https://doi.org/10.3892/mmr.2025.13437,
22. https://doi.org/10.1038/s44318-024-00212-3,
23. https://doi.org/10.7554/elife.72316,
24. https://doi.org/10.3390/ijms25115686,
25. https://doi.org/10.1038/modpathol.2016.37,
26. https://doi.org/10.1371/journal.pone.0133081,

BAIAP2L1 (IRTKS): A Comprehensive Analysis of Structure, Function, and Biological Roles

BAIAP2L1, also designated as Insulin Receptor Tyrosine Kinase Substrate (IRTKS), represents a critical adapter protein that serves as a molecular bridge linking membrane deformation to cytoskeletal reorganization. This multidomain protein has emerged as a fundamental regulator of actin dynamics with far-reaching implications in cellular morphogenesis, pathogenic responses, metabolic signaling, and oncogenic progression. The protein is encoded by the BAIAP2L1 gene located on human chromosome 7 at position q21.3-q22.1[1][23], with the NCBI gene identifier 55971 and UniProt accession Q9UHR4. Over the past two decades, accumulating evidence has demonstrated that BAIAP2L1 functions as a versatile signaling node whose dysregulation contributes to multiple pathological conditions, making it a subject of considerable biomedical interest for understanding both fundamental cell biological processes and therapeutic intervention strategies.

Molecular Architecture and Structural Organization

Domain Composition and Functional Modules

The BAIAP2L1 protein exhibits a highly organized modular architecture that reflects its diverse functional capabilities. The protein belongs to the IMD family, which encompasses proteins characterized by the presence of an IRSp53/MIM homology domain[1][31]. More specifically, BAIAP2L1 is classified within the IRSp53-like subgroup based on the presence of multiple functional domains arrayed along its primary sequence. The N-terminal region of BAIAP2L1 contains the I-BAR domain, also known as the inverse Bin-Amphiphysin-Rvs domain[16]. This domain adopts a distinctive zeppelin-like structure composed of two alpha-helical anti-parallel dimers that confer a crescent-shaped geometry[16]. The I-BAR domain represents a critical feature that distinguishes BAIAP2L1 from other cytoskeletal regulators, as it specifically recognizes and binds to regions of outward membrane curvature, thereby promoting negative curvature in the plasma membrane[13][49][59].

In close proximity to the I-BAR domain, BAIAP2L1 contains a canonical SH3 (Src homology 3) domain located near the C-terminus of the protein[1][31][38]. The SH3 domain represents a conserved protein interaction module that recognizes proline-rich sequences in target proteins, typically those containing the consensus motif PxxP[16][17]. This domain serves as a critical mediator of protein-protein interactions, allowing BAIAP2L1 to recruit binding partners and coordinate complex signaling cascades. The SH3 domain of BAIAP2L1 has been shown to possess an autoregulatory function that controls the activity of the I-BAR domain, representing an important mechanism for fine-tuning the protein's biological effects[45].

The C-terminal region of BAIAP2L1 encompasses a WH2 domain, also referred to as a WASP homology 2 domain[16][40]. This domain represents a relatively short actin-binding motif present in numerous actin regulatory proteins. However, the WH2 domain of BAIAP2L1 differs somewhat from classical WH2 domains found in other proteins. The IRTKS WH2 domain contains the sequence 'LRPT' rather than the more highly conserved 'LKKV' motif that typically contributes to G-actin monomer binding, and the IRTKS WH2 domain is missing certain canonical hydrophobic residues upstream of this motif[40]. Consequently, the IRTKS WH2 domain does not function as a classical monomer-sequestering domain, but rather exhibits preferential binding to actin filaments rather than monomers[40][37]. This distinction has important functional implications for how BAIAP2L1 modulates actin polymerization dynamics.

Protein Classification and Family Relationships

BAIAP2L1 belongs to the I-BAR protein family, a subfamily within the broader BAR domain protein superfamily that plays critical roles in cellular membrane dynamics and actin regulation[13][49]. Five genes encode I-BAR family members in humans: BAIAP2 (also known as IRSp53), BAIAP2L1 (IRTKS), BAIAP2L2 (FLJ22582), MIM (missing-in-metastasis), and ABBA (actin-binding protein with BAIAP2 homology)[23][25]. Among these family members, BAIAP2L1 shares substantial sequence homology with BAIAP2/IRSp53, with which it shares approximately 40.9% sequence identity[45]. Despite this similarity, BAIAP2L1 and related family members exhibit distinct tissue expression patterns and functional specializations. An important paralog of BAIAP2L1 is BAIAP2, with which it shares considerable conservation in the IMD domain, SH3 domain, and WW domain interaction motif[17]. The presence of related family members suggests that while BAIAP2L1 has evolved specialized roles, functional redundancy may exist in some biological contexts, as evidenced by the fact that loss of individual I-BAR proteins does not always result in severe developmental or functional deficits.

Primary Functions and Molecular Mechanisms

Actin Cytoskeleton Remodeling and Membrane Protrusion Formation

The fundamental biological role of BAIAP2L1 centers on its capacity to coordinately regulate membrane topology and actin polymerization, thereby controlling the formation and elongation of membrane protrusions. At the molecular level, BAIAP2L1 functions as an adapter protein that mediates communication between membrane deformation sensors and actin polymerization machinery[1][4][6]. The protein may function through two distinct but complementary mechanisms. First, through its I-BAR domain, BAIAP2L1 directly binds to membranes displaying outward curvature and promotes the clustering of phosphoinositides, particularly phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂)[13][49]. This phosphoinositide clustering and recruitment activity creates a molecular platform that attracts downstream actin nucleation factors such as N-WASP (neuronal Wiskott-Aldrich syndrome protein) and the Arp2/3 complex[13][45].

The second mechanism involves the SH3 domain-mediated recruitment of binding partners that directly influence actin filament behavior. In the context of microvillar elongation, for example, the BAIAP2L1 SH3 domain binds with high affinity to the actin bundling and capping protein EPS8, with a dissociation constant of approximately 500 nanoMolar[9][40][45]. This interaction positions EPS8 at sites of active actin assembly where it can exert anti-capping and bundling activities. The WH2 domain, in turn, contributes to the microvillar elongation process through its capacity to directly interact with actin filaments, potentially increasing local actin filament density at sites of protrusion growth[40].

Membrane Curvature Sensing and Mechanotransduction

Recent mechanistic studies have revealed that BAIAP2L1, like other I-BAR proteins, functions as a sensitive detector of membrane topology, with the capacity to preferentially localize to regions of outward membrane curvature. This curvature-sensing function extends beyond passive recognition; cells employ this property as part of an active mechanosensing system that responds to mechanical stress and membrane deformation. When cells experience compression or stretch, the plasma membrane develops transient nanoscale deformations on the order of 100 nanometers in which BAIAP2L1 (and related I-BAR proteins like IRSp53) becomes rapidly enriched[56][59]. This enrichment occurs through the membrane-binding properties of the I-BAR domain, which exhibits a structural geometry that is well-matched to outward membrane curvature[16]. Once localized to these curved membrane domains, BAIAP2L1 nucleates a mechanochemical feedback loop wherein the protein recruits downstream signaling components, including the small GTPase Rac1 and the Arp2/3 complex, leading to a burst of actin polymerization that flattens the membrane deformation and restores membrane homeostasis[56][59].

This mechanosensing mechanism appears to operate through a concentration-dependent mechanism in which BAIAP2L1 levels directly influence both the frequency of membrane deformations and the speed of their resolution[21]. At lower protein concentrations, BAIAP2L1 acts primarily as a curvature sensor that recruits other proteins to already-curved membranes. At higher concentrations, BAIAP2L1 can form oligomeric arrays on the membrane that actively propagate curvature and engage the actin polymerization machinery[49]. This concentration-dependent switching between sensing and generating membrane curvature represents an elegant regulatory mechanism that allows cells to tune their response to mechanical stimuli.

Insulin Signaling and Metabolic Regulation

Originally identified as a substrate for insulin receptor (IR) tyrosine kinase, BAIAP2L1 has been established as a functional participant in insulin signaling pathways that regulate glucose homeostasis and metabolic function[8][11][23][45]. Upon insulin stimulation, the insulin receptor phosphorylates multiple tyrosine residues on BAIAP2L1 (including Y37, Y156, Y163, Y274, Y293, and Y439), creating docking sites for downstream signaling molecules[47][51]. Studies employing genetic knockout approaches have demonstrated that IRTKS-deficient mice display characteristics of insulin resistance, including hyperglycemia, hyperinsulinemia, and glucose intolerance[8]. These metabolic abnormalities can be reversed through ectopic expression of BAIAP2L1, indicating that the protein functions as a positive regulator of insulin signaling[8].

The molecular mechanism underlying BAIAP2L1's role in insulin signaling involves its participation in the IR-IRS-PI3K-AKT pathway. Phosphorylated BAIAP2L1 positively regulates insulin signaling by modulating the activity of the phosphatase SHIP2, which normally acts as a negative regulator of the insulin pathway by converting the second messenger PI(3,4,5)P₃ to PI(3,4)P₂[8][54]. In hepatocellular carcinoma cells, BAIAP2L1 overexpression directly inhibits SHIP2 activity, leading to the accumulation of PI(3,4,5)P₃ and the downstream phosphorylation of AKT, mTOR, and GSK-3β[8][54]. This inhibition of SHIP2 partially relieves the inhibitory effect of the phosphatase on insulin pathway components and promotes signaling through the pathway. Additionally, expression of the BAIAP2L1 gene is downregulated in the livers of both diabetic patients and diabetic mouse models, and this downregulation is associated with DNA hypermethylation of the BAIAP2L1 promoter region[8]. This epigenetic silencing may contribute to the insulin resistance observed in type 2 diabetes mellitus.

Cellular Localization and Subcellular Distribution

Membrane and Cytoskeletal Targeting

BAIAP2L1 exhibits a distinctive subcellular localization pattern that reflects its biological function as a membrane-associated adapter protein. The protein is predominantly localized to the plasma membrane, with additional cytoplasmic and cytoskeletal compartmentalization[34][36]. This membrane localization is achieved through the I-BAR domain, which contains a lipid-binding surface capable of interacting with the inner leaflet of phosphoinositide-rich membranes[16][40]. The I-BAR domain alone is sufficient to direct targeting to the membrane and promote tip targeting of protrusions, whereas deletion of the I-BAR domain completely eliminates all membrane localization and tip targeting capacity[40]. However, the SH3 domain refines tip targeting, as loss-of-function mutations in this domain result in partial loss of tip targeting with accumulation of BAIAP2L1 near the base of microvilli[40].

More specifically, BAIAP2L1 exhibits striking and highly localized accumulation at the distal tips of epithelial microvilli, a localization pattern that is particularly pronounced in polarized intestinal epithelial cells undergoing differentiation[9][16]. Super-resolution microscopy studies have revealed that BAIAP2L1 marks the barbed ends of actin filaments at microvillar distal tips, positioning the protein at sites of active actin filament elongation[15]. This apical membrane targeting is achieved through mechanisms that depend on the protein's I-BAR domain, which recognizes the distinctive outward membrane curvature present at the tips of growing microvilli. The protein's presence at these specialized membrane domains places it in proximity to the sites where actin polymerization occurs, allowing it to directly modulate filament dynamics through its WH2 domain and to recruit regulatory proteins such as EPS8 through its SH3 domain.

Tissue-Specific Expression Patterns

Analysis of BAIAP2L1 expression using the Human Protein Atlas and other expression databases reveals that the protein is expressed across multiple tissue types, with notably high expression in tissues characterized by polarized epithelial organization and extensive membrane protrusions[36]. The protein is particularly abundant in the small intestine, where it plays a critical role in microvillar development and maintenance. Within the intestinal epithelium, BAIAP2L1 expression is localized to enterocytes, the columnar absorptive cells that comprise the lining of the intestinal mucosa. Expression is also detected in other tissues with specialized membrane structures dependent on actin polymerization, including the hair cells of the inner ear, where the protein participates in stereocilia formation and maintenance[28].

The tissue distribution of BAIAP2L1 expression is particularly enriched in transporting epithelial cells that require large plasma membrane surface areas for nutrient absorption and ion transport. This distribution pattern is consistent with the protein's recognized roles in promoting the formation and elongation of actin-based membrane protrusions. Expression analysis also indicates prominent BAIAP2L1 expression in cancer tissues, particularly those derived from epithelial lineages, suggesting that upregulation of this protein may contribute to the cellular invasiveness characteristic of malignant tumors[19][22][33].

Role in Epithelial Microvillar Assembly and Maintenance

Mechanisms of Microvillar Elongation

BAIAP2L1 has emerged as a critical regulator of brush border microvillus formation and elongation, a role that was elucidated through detailed cellular and molecular studies in intestinal epithelial cell culture systems and using super-resolution microscopy approaches. Intestinal enterocytes build hundreds of densely packed microvilli that collectively form the brush border, a specialized apical membrane domain that dramatically amplifies the functional surface area available for nutrient absorption[9][15][16]. The formation of these protrusions requires the coordinated assembly of approximately 20-30 actin filaments into a paracrystalline bundle, with precise control of filament number, length, and organization being essential for proper microvillar function[15][16].

BAIAP2L1 promotes microvillar elongation through multiple parallel mechanisms that depend on distinct functional domains. First, the I-BAR domain directs the protein to the distal tips of growing microvilli through its capacity to recognize outward membrane curvature[40][15]. Once positioned at the tips of microvilli, BAIAP2L1 promotes elongation through a direct mechanism involving its C-terminal WH2 domain, which binds to actin filaments[40]. Studies employing overexpression and loss-of-function approaches indicate that the BAIAP2L1 WH2 domain is essential for microvillar elongation, as a mutant lacking this domain fails to rescue microvillus length defects[15]. The precise mechanism by which the WH2 domain promotes elongation remains incompletely understood, but the domain may function to increase local actin monomer concentration at the distal tips, thereby promoting filament elongation, or it may modify the mechanical properties of the actin bundle in ways that facilitate elongation.

Second, BAIAP2L1 drives microvillar elongation indirectly through its SH3 domain, which recruits the actin-bundling and capping protein EPS8[9][15][40]. EPS8 represents a multifunctional actin regulatory protein that exhibits actin bundling and capping activities through its C-terminal region, and it has been established as a critical regulator of protrusion length in multiple cellular contexts[15]. By recruiting EPS8 to microvillar tips through high-affinity SH3-mediated interactions, BAIAP2L1 positions EPS8 at sites where it can exert its anti-capping and bundling functions. The coordinated action of BAIAP2L1 and EPS8 at microvillar tips represents a mechanism through which the cell ensures that nascent actin filaments can undergo sustained elongation, an outcome that is essential for achieving the proper length of mature microvilli.

Regulation of Microvillar Actin Dynamics

Recent studies employing fluorescence recovery after photobleaching (FRAP) and live-cell imaging approaches have demonstrated that BAIAP2L1 plays an important role not only in promoting the initial formation of microvilli but also in regulating the ongoing dynamics of actin filaments within mature microvillar bundles[15][40]. The actin filaments that comprise the microvillar core bundle exhibit substantial treadmilling activity, wherein filaments polymerize at the barbed ends at the microvillar tip while simultaneously depolymerizing at the pointed ends at the base[15]. Interestingly, BAIAP2L1 and EPS8 exhibit retrograde movement along the length of the microvillar bundle that has been hypothesized to reflect a subset of filaments that have lagged behind other filaments during elongation and subsequently restart elongation near the base of the microvillus where monomer concentrations are presumed to be higher[15].

This dynamic behavior suggests that BAIAP2L1 participates not only in the initiation and elongation of microvillar growth but also in the ongoing regulation of filament treadmilling rates and the organization of microvillar actin bundles. Loss-of-function studies have demonstrated that BAIAP2L1 knockdown results in shorter microvilli with reduced core bundle lengths, indicating that the protein is required for proper microvillar growth during epithelial cell differentiation[9]. Furthermore, the knockdown or loss of BAIAP2L1 has minimal impact on the overall treadmilling rates of actin within the brush border, suggesting that the protein's effects on microvillar length are achieved through mechanisms that are largely independent of alterations in filament polymerization kinetics.

Evolutionary and Pathogenic Implications

The essential role of BAIAP2L1 in controlling microvillar structure has been further illuminated by studies of pathogenic bacterial manipulation of this protein. The enterohemorrhagic bacterium Escherichia coli (EHEC) produces a secreted virulence factor designated EspFU that directly targets BAIAP2L1 during infection of intestinal epithelial cells[8][9][16][40]. This pathogenic mechanism evolved because EHEC requires the destruction or significant modification of the brush border to establish a successful infection. EspFU contains tandem polyproline motifs that bind with high affinity to the SH3 domain of BAIAP2L1, creating a ternary complex of EHEC effector proteins[9]. This interaction is notable for its high affinity, with a dissociation constant of approximately 500 nanoMolar[9][40]. The apically localized IRTKS-EspFU complex recruits N-WASP and the Arp2/3 actin nucleator complex, leading to a massive induction of actin assembly and pedestal formation beneath adherent EHEC bacteria[9][41].

The evolutionary conservation of this EHEC-targeting mechanism across diverse pathogenic isolates suggests that BAIAP2L1 represents a critical and conserved component of the apical epithelial actin cytoskeleton that pathogens have evolved to exploit for their own benefit. The fact that EHEC specifically targets BAIAP2L1 rather than other cytoskeletal regulatory proteins underscores the protein's central importance in controlling apical actin assembly in response to microbial contact[9]. This pathogenic utilization of BAIAP2L1 provides strong evolutionary evidence that the protein's normal physiological role is to sense and respond to challenges to epithelial barrier function, with both its capacity to regulate microvillar morphology and its potential to respond to bacterial attachment being essential biological functions.

Role in Hair Cell Stereocilia Formation and Maintenance

Stereociliary Tip Complex Function

Recent studies have revealed an important role for BAIAP2L1 in the regulation of hair cell stereocilia, the actin-based sensory organelles of mechanosensory cells in the inner ear[25][28]. Inner ear sensory hair cells are characterized by their apical F-actin-based cell protrusions named stereocilia, which are organized into rows of different heights to form a distinctive staircase-like pattern[25]. The height of stereocilia is tightly regulated by protein complexes localized at stereociliary tips, designated the row-1 and row-2 tip complexes, which are positioned at the tips of the tallest-row and shorter-row stereocilia, respectively[25]. BAIAP2L1 localizes specifically at the tips of tallest-row stereocilia in a manner dependent on known row-1 complex proteins EPS8 and MYO15A[25].

Interestingly, unlike BAIAP2L2 (a paralogue that localizes to shorter-row stereocilia), the localization of BAIAP2L1 to the tips of tallest-row stereocilia is calcium-independent[25]. This calcium-independence may reflect distinct mechanisms of localization or distinct roles in tip complex function. Loss-of-function studies indicate that loss of BAIAP2L1 does not significantly affect the row-1 protein complex or the auditory and balance function of Baiap2l1 knockout mice, suggesting that other orthologous proteins such as BAIAP2 may compensate for the loss of BAIAP2L1 in hair cells[25]. Nevertheless, the localization of BAIAP2L1 at stereociliary tips and its association with the row-1 tip complex indicates that the protein participates in the regulation of stereocilia morphology, a role consistent with its established functions in controlling the growth and organization of other actin-based membrane protrusions.

Role in Dendritic Spine Formation and Synaptic Plasticity

Filopodia Formation and Spine Initiation

The I-BAR family of proteins, including BAIAP2L1, has been implicated in the formation of dendritic filopodia and the initiation of dendritic spines, which are critical for synaptic plasticity and learning-related changes in neural circuits[13][21][60]. Dendritic spines are small actin-rich protrusions that extend from the dendritic shaft and serve as postsynaptic sites for excitatory synaptic transmission. The formation of spines begins with the initiation of filopodia-like structures, which subsequently mature into spines through a process involving actin cytoskeleton reorganization[13]. BAIAP2 and related I-BAR proteins promote the initiation of exploratory filopodia by stabilizing stochastic membrane deformations that are subsequently used as templates for actin polymerization[21].

Recent work has established that membrane curvature-sensing proteins, including BAIAP2, form self-organizing signaling circuits that control the initiation frequency of exploratory filopodia in developing neurons[21]. In this model, transient nanoscale membrane deformations are recognized by the curvature-sensing I-BAR domain of BAIAP2, leading to the recruitment of actin polymerization machinery. This nucleates the formation of filopodia that then stabilize and potentially mature into dendritic spines. BAIAP2 and the related protein ARHGAP44 (which promotes negative membrane curvature) form interlinked positive and negative feedback loops that determine the frequency of filopodial initiation in a dosage-dependent manner[21]. The role of BAIAP2L1 in this process may be similar, though direct evidence for BAIAP2L1-mediated spine formation is more limited compared to that for BAIAP2.

Activity-Dependent Plasticity

The spatial and temporal profile of I-BAR proteins in synaptic plasticity and brain function is intriguing, particularly given potential interactions among I-BAR family members and the ability of some BAR domain proteins to modulate the function of other family members through heteroligomerization[60]. While direct evidence for BAIAP2L1's specific roles in synaptic plasticity is somewhat limited, the broader I-BAR protein family has been implicated in activity-dependent changes in dendritic spine morphology and postsynaptic plasticity. These proteins are well-positioned to modulate the synaptic actin cytoskeleton and membrane substructures during dendritic spine formation and synaptic plasticity, particularly given their capacity to sense and generate membrane curvature while simultaneously recruiting actin polymerization machinery[60]. Activity-dependent recruitment of I-BAR proteins, including potentially BAIAP2L1, could stimulate actin cytoskeleton growth and facilitate the elongation of filopodia and the further maturation of dendritic spines[13].

Signaling Pathways and Protein Interactions

Rac GTPase Signaling

BAIAP2L1 interacts with the small GTPase Rac through its I-BAR domain, representing a critical signaling interaction that links the protein to the broader Rho family GTPase signaling network[1][5][45]. The I-BAR domain of BAIAP2L1 binds to activated, GTP-loaded forms of Rac, while the SH3 domain maintains an autoregulatory function that controls I-BAR activity[45]. This interaction positions BAIAP2L1 at the nexus of Rac-dependent signaling pathways that regulate cell morphology, migration, and actin polymerization. Unlike BAIAP2/IRSp53, BAIAP2L1 does not efficiently interact with Cdc42 or RhoA according to some studies, though this may reflect context-dependent differences in how these proteins associate with different members of the Rho family[27][45].

The Rho-IRTKS-Eps8-WAVE2 pathway represents a specific signaling axis in which the Rho GTPase Rif interacts with BAIAP2L1 via its I-BAR domain, with EPS8 and WAVE2 acting as downstream modulators[29][45]. In this pathway, EPS8 reduces the size and increases the number of dorsal filopodia and membrane ruffles, while WAVE2 modulates the activity of dorsal membrane ruffling. This signaling pathway illustrates the integration of BAIAP2L1 into broader cellular circuits that coordinate membrane dynamics and actin polymerization in response to signaling inputs.

Src Kinase-Mediated Phosphorylation and Cell Migration

BAIAP2L1 is subject to phosphorylation by the non-receptor tyrosine kinase Src in response to diverse cellular stimuli and signals[47][55]. Src-stimulated phosphorylation of BAIAP2L1 has been shown to enhance cell migration, a function that has been particularly well-characterized in the context of cancer cell invasion and metastasis[44][47][55]. Mapping and mutagenesis studies have identified six tyrosine residues (Y37, Y156, Y163, Y274, Y293, and Y439) that serve as sites of Src-dependent phosphorylation[47]. Phosphorylation at these sites creates docking sites for downstream signaling molecules and modulates the functional properties of BAIAP2L1.

In the context of cancer cell migration, BAIAP2L1 overexpression significantly increases the cellular levels of phosphorylated cofilin (pCofilin) and potentiates the localization of pCofilin in the cytosol[55]. Cofilin represents a critical actin depolymerizing factor that initiates early steps in the motility cycle by severing actin filaments, and the asymmetric distribution of active and inactive cofilin is essential for directional cell migration. The enhanced phosphorylation and altered localization of cofilin in BAIAP2L1-overexpressing cells promotes the formation of filopodia and facilitates directional migration, contributing to cancer cell invasiveness and metastatic potential.

Sumoylation and Immune Modulation

BAIAP2L1 participates in post-translational modification pathways involving conjugation of the small ubiquitin-like modifier (SUMO), representing a regulatory mechanism distinct from traditional phosphorylation[23][35]. The protein recruits the E2 ubiquitin-conjugating enzyme Ubc9 to catalyze the sumoylation of target proteins, including PCBP2 (poly(rC) binding protein 2) and HP1α (heterochromatin protein 1-alpha)[23]. The sumoylation of PCBP2 at lysine 37 by BAIAP2L1-recruited Ubc9 results in the nuclear export of PCBP2 to the cytoplasm[23][35]. In the cytoplasm, sumoylated PCBP2 interacts with and promotes the degradation of MAVS (mitochondrial antiviral signaling protein), a critical adaptor protein in the innate immune response to RNA viruses[23][35].

This BAIAP2L1-dependent sumoylation pathway represents an important mechanism through which cells regulate antiviral innate immunity. By promoting PCBP2 sumoylation and MAVS degradation, BAIAP2L1 acts as a negative regulator of antiviral immunity, dampening the inflammatory response to viral infection[23]. IRTKS deficiency augments the innate immune response of mice against RNA viruses but not against DNA viruses or bacteria, indicating that BAIAP2L1 functions as a selective negative modulator of the RIG-I-MAVS signaling pathway[23]. This function appears to be crucial for balancing the potentially damaging inflammation induced by viral infection while preventing excessive cell damage due to uncontrolled innate immune activation.

Role in Cancer Progression and Metastasis

Breast Cancer Progression and Chemoresistance

Multiple lines of evidence establish BAIAP2L1 as an important driver of cancer progression, with particularly well-characterized roles in breast cancer[19][22][55]. BAIAP2L1 expression is significantly elevated in breast cancer specimens compared to paired normal tissues, with the highest expression observed in basal-like and triple-negative breast cancer subtypes[19][22]. High BAIAP2L1 expression is correlated with advanced TNM staging, increased lymph node metastasis, and poor prognosis, though BAIAP2L1 expression does not qualify as an independent prognostic factor when subjected to comprehensive multivariate analysis[19].

The mechanisms through which BAIAP2L1 promotes breast cancer progression have been elucidated through functional studies demonstrating that the protein drives cancer cell proliferation and invasion by activating the AKT signaling pathway[19][22]. BAIAP2L1 achieves this activation through interaction with the ribosomal protein RPL3 via its SH3 domain, leading to the stabilization of PIK3CA (the gene encoding the catalytic subunit of PI3K)[19]. By promoting PI3K expression and activity, BAIAP2L1 increases the accumulation of PI(3,4,5)P₃ and the subsequent phosphorylation of AKT, leading to enhanced cancer cell proliferation and invasion. BAIAP2L1 overexpression also promotes epithelial-mesenchymal transition (EMT), upregulates the cancer stem cell marker ALDH1, and contributes to chemotherapy resistance by mechanisms involving AKT pathway activation[19].

Furthermore, high BAIAP2L1 expression in HER2-positive breast cancer is particularly strongly associated with metastatic disease and poor clinical outcomes, with both distant metastasis-free survival and overall survival being significantly reduced in BAIAP2L1-high HER2-positive patients[55]. The protein's role in cancer cell migration is mediated in part through its effects on the actin cytoskeleton and its capacity to promote the formation of filopodia, which facilitate the early steps of the cancer cell metastatic cascade.

Hepatocellular Carcinoma and EGFR-ERK Signaling

BAIAP2L1 has been reported to promote hepatocellular carcinoma (HCC) cell proliferation through multiple signaling pathways. In HCC cells, BAIAP2L1 can interact with the epidermal growth factor receptor (EGFR) and positively regulate the EGFR-ERK signaling pathway, resulting in increased cell proliferation that is associated with increased G1-to-S cell cycle transition[8][51]. In addition to these direct effects on growth factor signaling, BAIAP2L1 interacts with SHIP2 and attenuates SHIP2 phosphatase activity, leading to the accumulation of PI(3,4,5)P₃ and the downstream phosphorylation of AKT, mTOR, and GSK-3β[8][54]. These effects on insulin signaling machinery contribute to cancer cell proliferation in HCC through multiple overlapping mechanisms.

Ovarian Cancer and Metastatic Progression

BAIAP2L1 is significantly upregulated in human ovarian cancers compared to normal ovarian tissues and is expressed at higher levels in metastatic lesions relative to primary tumors[33]. Functional assays in ovarian cancer cells have demonstrated that BAIAP2L1 promotes cell proliferation and cell survival by avoiding apoptosis. The protein's role in promoting cell migration, through actin-dependent mechanisms, has been implicated in facilitating tumor invasion and metastasis. BAIAP2L1 histoscores of metastatic sites are consistently higher than those of corresponding primary tumors, suggesting that BAIAP2L1 expression correlates with the capacity of cancer cells to disseminate to distant organ sites.

Cervical and Colorectal Cancer

BAIAP2L1 has additionally been reported to contribute to the malignant progression of cervical cancer cells and to promote colorectal cancer (CRC) progression and cell proliferation[2][54]. In colorectal cancer, BAIAP2L1 overexpression promotes cell proliferation in response to basic fibroblast growth factor (bFGF) through mechanisms involving the phosphorylation of AKT[54]. The expression of IRTKS in CRC tissues is higher than that in adjacent and normal tissues, and functional assays demonstrate that IRTKS knockdown significantly decreases the proliferation rate of tumor cells and reduces the phosphorylation level of AKT induced by bFGF. These results indicate that BAIAP2L1 mediates bFGF-induced cell proliferation in CRC through activation of the AKT signaling pathway and may represent a potential therapeutic target.

Diseases Associated with BAIAP2L1 Dysregulation

Genetic and Metabolic Diseases

While BAIAP2L1 is most extensively characterized in the context of cancer biology, the protein has been associated with several other disease conditions. The GeneCards database indicates associations between BAIAP2L1 and Dentatorubral-Pallidoluysian Atrophy (DRPLA) and Donohue Syndrome, though the precise molecular mechanisms underlying these associations require further investigation[1][31]. DRPLA is a rare neurodegenerative disorder characterized by progressive cerebellar ataxia and cognitive decline, whereas Donohue Syndrome (also known as leprechaunism) is a severe form of congenital insulin resistance. The potential role of BAIAP2L1 dysregulation in these genetic conditions remains an area for future research.

The well-established role of BAIAP2L1 in insulin signaling suggests that dysregulation of this protein could contribute to metabolic dysfunction. Indeed, BAIAP2L1 expression is downregulated in the livers of diabetic patients and diabetic mice, and this downregulation is associated with DNA hypermethylation of the BAIAP2L1 promoter region[8]. The loss of BAIAP2L1 expression in diabetic individuals may represent a consequence rather than a cause of the disease, but the correlation between reduced BAIAP2L1 expression and insulin resistance suggests that restoration of BAIAP2L1 function could potentially provide therapeutic benefits for metabolic disease.

Inflammatory and Autoimmune Conditions

BAIAP2L1 has been implicated in disease progression of rheumatoid arthritis, where BAIAP2L1 expression in fibroblast-like synovial cells is positively correlated with C-reactive protein (CRP), a common clinical marker of inflammation[33]. The capacity of BAIAP2L1 to promote fibroblast migration and actin cytoskeleton remodeling may contribute to synovial inflammation and the pathologic tissue remodeling characteristic of rheumatoid arthritis. Additionally, BAIAP2L1's established role as a negative modulator of antiviral immunity suggests that dysregulation of this protein could potentially contribute to excessive or inadequately controlled antiviral immune responses, though this remains a hypothesis requiring further investigation.

Forensic Application: Hypothermia Biomarker

In an intriguing forensic medicine application, BAIAP2L1 has been identified as a candidate biomarker for postmortem detection of death by hypothermia[23]. Hypothermia, characterized by a core body temperature below 35°C, can result from excessive cold exposure, drug poisoning, or metabolic or nervous system dysfunction. Although postmortem biochemical exploration has revealed several biomarkers of hypothermia, including catecholamines, cortisol, ketone bodies, and free fatty acids, death by hypothermia remains a diagnosis of exclusion due to the lack of definitive and specific biomarkers[23]. The potential utility of BAIAP2L1 as a forensic biomarker suggests that the protein's expression or modification is sensitive to the physiological stress of severe hypothermia, an observation that could have practical applications in forensic pathology.

Post-Translational Modifications and Regulation

Phosphorylation and Functional Activation

Beyond the well-characterized Src-dependent phosphorylation discussed previously, BAIAP2L1 is subject to phosphorylation by multiple other kinases that modulate its biological activities. The N-terminal I-BAR domain and central regions of the protein serve as substrates for various serine-threonine kinases, as indicated by analysis of phosphoproteomics databases[7][11]. The insulin receptor itself phosphorylates BAIAP2L1 on tyrosine residues, creating docking sites for downstream signaling molecules that extend the insulin signaling cascade. These multiple phosphorylation events represent mechanisms through which upstream signals are integrated to modulate BAIAP2L1 function in response to diverse cellular stimuli.

DNA Methylation and Epigenetic Silencing

The expression of BAIAP2L1 is subject to epigenetic regulation through DNA methylation of the gene promoter region. In diabetic individuals and animal models of diabetes, DNA hypermethylation of the human BAIAP2L1 promoter is detected via bisulfite-treatment DNA sequencing and is associated with the downregulation of BAIAP2L1 expression[8]. This epigenetic silencing likely contributes to the impaired insulin signaling observed in type 2 diabetes mellitus. The association between DNA methylation status and BAIAP2L1 expression suggests that pharmacological approaches aimed at modulating DNA methyltransferase activity could potentially restore BAIAP2L1 expression and improve metabolic function in diabetic individuals.

MicroRNA Regulation

Computational analysis using miRNA target prediction databases indicates that multiple microRNAs are predicted to regulate BAIAP2L1 gene expression, though experimental validation of these predictions has been limited[7]. The TargetScan database identifies both conserved and nonconserved microRNA targets for BAIAP2L1, suggesting that post-transcriptional regulation of BAIAP2L1 expression by small RNA regulatory mechanisms may represent an additional layer of control over the protein's expression levels.

Comparative and Evolutionary Perspectives

Structural Conservation Within the I-BAR Family

The molecular structure of BAIAP2L1 demonstrates high conservation with other members of the I-BAR protein family, particularly in the N-terminal I-BAR domain and the C-terminal SH3 domain[1][23][31][45]. This structural conservation extends across species, with homologous I-BAR proteins identified in model organisms from fruit flies to zebrafish to mammals. The conservation of the I-BAR domain across hundreds of millions of years of evolution indicates that the fundamental capacity to sense and respond to membrane curvature represents a deeply conserved cellular function essential for organismal survival and function.

The C-terminal WH2 domain of BAIAP2L1, while present in related family members, exhibits somewhat greater sequence variation compared to the highly conserved I-BAR and SH3 domains. This relative divergence in the WH2 domain may reflect functional specialization among family members, with different I-BAR proteins potentially exhibiting distinct preferences for actin filaments versus actin monomers or possessing distinct effects on filament dynamics.

Redundancy and Functional Specialization

The existence of five I-BAR family members in humans raises important questions regarding functional redundancy and specialization. While BAIAP2L1 and BAIAP2 share substantial sequence homology and can perform overlapping functions in some biological contexts, they exhibit distinct tissue distribution patterns and display functional specialization in other contexts. For example, in stereocilia, BAIAP2L1 and BAIAP2L2 localize at different positions along the stereociliary bundle and appear to function in the development and maintenance of stereocilia of different heights[25][28]. This spatial segregation of function suggests that while these proteins share a common structural scaffold, they have evolved specialized roles that depend on their distinct protein-protein interaction partners and regulatory mechanisms.

The existence of functional redundancy is demonstrated by the observation that loss of BAIAP2L1 alone does not result in severe developmental or functional deficits in many tissues, a finding consistent with the possibility that related I-BAR proteins can partially compensate for the loss of BAIAP2L1. However, in specialized contexts such as stereocilia formation, BAIAP2L1 appears to have acquired specific roles that cannot be fully compensated by other family members, highlighting the importance of examining these proteins in tissue-specific contexts.

Therapeutic Implications and Future Directions

Cancer Therapy Targets

Given the prominent role of BAIAP2L1 in promoting cancer progression and chemotherapy resistance across multiple tumor types, the protein represents an attractive target for cancer therapeutic development. Several approaches could be envisioned: direct inhibition of BAIAP2L1 using small molecules or biologics, disruption of critical protein-protein interactions such as those involving the SH3 domain and RPL3 or EPS8, or downstream pharmacological targeting of the signaling pathways activated by BAIAP2L1 (such as the PI3K-AKT axis). The development of BAIAP2L1 inhibitors could potentially improve outcomes in patients with BAIAP2L1-high tumors by reducing cancer cell proliferation and restoring chemotherapy sensitivity.

Metabolic and Inflammatory Diseases

The established role of BAIAP2L1 in positive regulation of insulin signaling suggests that restoration of BAIAP2L1 expression or enhancement of its activity could provide therapeutic benefits for type 2 diabetes mellitus. Approaches might include pharmacological demethylation of the BAIAP2L1 promoter to restore gene expression in diabetic tissues, delivery of recombinant BAIAP2L1 protein, or gene therapy approaches to restore BAIAP2L1 expression. Additionally, understanding the role of BAIAP2L1 in antiviral immunity may reveal opportunities to modulate the protein's function for therapeutic benefit in chronic viral infections or for optimizing immune responses to viral vaccines.

Neurological Applications

The established roles of I-BAR proteins in synaptic plasticity and the potential involvement of BAIAP2L1 in dendritic spine formation suggest that modulation of BAIAP2L1 expression or activity could have applications in neurological disorders characterized by impaired synaptic plasticity or spine pathology. These disorders include autism spectrum disorder, intellectual disabilities, and potentially certain forms of dementia. Further research is needed to establish whether BAIAP2L1 dysregulation contributes to these conditions and whether therapeutically targeting BAIAP2L1 could provide beneficial effects.

Conclusion

BAIAP2L1, also known as insulin receptor tyrosine kinase substrate (IRTKS), represents a multifunctional adapter protein whose diverse biological roles reflect the sophisticated integration of membrane topology sensing with cytoskeletal dynamics and signaling pathway activation. Through its distinctive I-BAR domain, BAIAP2L1 detects and responds to membrane curvature, serving as a nexus between physical membrane properties and molecular signaling cascades. The protein's SH3 and WH2 domains enable recruitment of downstream effector proteins and direct actin filament regulation, respectively, positioning BAIAP2L1 as a central coordinator of actin polymerization in response to diverse cellular stimuli. From its original identification as a substrate for the insulin receptor, BAIAP2L1 has been shown to participate in insulin signaling, epithelial microvillus formation, bacterial pathogenesis, synaptic plasticity, antiviral immunity, and cancer progression. The protein's prominent role in promoting multiple aspects of cancer biology, combined with its roles in metabolic and immune regulation, makes BAIAP2L1 an important target for future biomedical research and potential therapeutic intervention. As our understanding of BAIAP2L1's functions continues to expand, particularly through the application of emerging structural biology and cell biological approaches, new opportunities will undoubtedly emerge for translating this fundamental knowledge into therapeutic advances for cancer, metabolic disease, and potentially neurological disorders.

Citations

1. https://www.genecards.org/cgi-bin/carddisp.pl?gene=BAIAP2L1
2. https://www.ncbi.nlm.nih.gov/gene/55971
3. https://www.abbexa.com/baiap2l1-antibody-1
4. https://www.uniprot.org/uniprotkb/Q9UHR4/entry
5. https://www.sigmaaldrich.com/TC/en/genes/baiap2l1
6. https://www.uniprot.org/uniprotkb/Q9DBJ3/entry
7. https://maayanlab.cloud/Harmonizome/gene/BAIAP2L1
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC11795247/
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC6156988/
10. https://www.spandidos-publications.com/10.3892/mmr.2025.13437/abstract
11. https://www.msesupplies.com/products/baiap2l1-polyclonal-antibody-reactivity-human
12. https://www.frontiersin.org/journals/neural-circuits/articles/10.3389/fncir.2021.787436/full
13. https://faseb.onlinelibrary.wiley.com/doi/full/10.1096/fj.202400121R
14. https://pmc.ncbi.nlm.nih.gov/articles/PMC10033394/
15. https://marrvel.org/human/gene/55971
16. https://www.molbiolcell.org/doi/10.1091/mbc.e15-06-0443
17. https://pmc.ncbi.nlm.nih.gov/articles/PMC9986062/
18. https://pmc.ncbi.nlm.nih.gov/articles/PMC8652540/
19. https://pmc.ncbi.nlm.nih.gov/articles/PMC8639351/
20. https://pubmed.ncbi.nlm.nih.gov/36308067/
21. https://www.spandidos-publications.com/10.3892/mmr.2025.13437
22. https://pmc.ncbi.nlm.nih.gov/articles/PMC6097459/
23. https://pubmed.ncbi.nlm.nih.gov/39093051/
24. https://pubmed.ncbi.nlm.nih.gov/28067313/
25. https://journals.biologists.com/jcs/article/129/14/2829/55774/The-Rho-GTPase-Rif-signals-through-IRTKS-Eps8-and
26. https://string-db.org/network/9606.ENSP00000005260
27. https://royalsocietypublishing.org/doi/10.1098/rsob.170167
28. https://pmc.ncbi.nlm.nih.gov/articles/PMC4519316/
29. https://www.proteinatlas.org/ENSG00000006453-BAIAP2L1/subcellular
30. https://pmc.ncbi.nlm.nih.gov/articles/PMC4569712/
31. https://www.proteinatlas.org/ENSG00000006453-BAIAP2L1/tissue
32. https://journals.biologists.com/jcs/article/120/9/1663/30265/Characterisation-of-IRTKS-a-novel-IRSp53-MIM
33. https://pubmed.ncbi.nlm.nih.gov/15625304/
34. https://elifesciences.org/articles/00884
35. https://febs.onlinelibrary.wiley.com/doi/abs/10.1016/j.febslet.2011.08.005
36. https://www.deciphergenomics.org/gene/baiap2l1/overview
37. https://pubmed.ncbi.nlm.nih.gov/21840312/
38. https://pmc.ncbi.nlm.nih.gov/articles/PMC5067245/
39. https://pmc.ncbi.nlm.nih.gov/articles/PMC5199207/
40. https://pmc.ncbi.nlm.nih.gov/articles/PMC6743356/
41. https://pubmed.ncbi.nlm.nih.gov/23693078/
42. https://journals.biologists.com/jcs/article/127/6/1279/54851/The-inverse-BAR-domain-protein-IBARa-drives
43. https://platform.opentargets.org/target/ENSG00000006453
44. https://academic.oup.com/gastro/article/9/2/166/5876209
45. https://pmc.ncbi.nlm.nih.gov/articles/PMC8753306/
46. https://pmc.ncbi.nlm.nih.gov/articles/PMC10569792/
47. https://pmc.ncbi.nlm.nih.gov/articles/PMC4396478/
48. https://elifesciences.org/articles/72316
49. https://pmc.ncbi.nlm.nih.gov/articles/PMC8716821/
50. some studies