id: Q8N4X5 gene_symbol: AFAP1L2 product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: AFAP1L2 (XB130, PI3KAP) is an 818-residue intracellular adaptor and actin-associated scaffold of the AFAP family. Its N-terminal region carries proline-rich SH3-binding and tyrosine-containing SH2-binding motifs, followed by two pleckstrin homology domains and a C-terminal coiled-coil and actin-binding region. It is a substrate of Src-family and RET/PTC tyrosine kinases. Once tyrosine phosphorylated, Tyr54 docks the SH2 domains of the PI3K regulatory subunit p85alpha, coupling these kinases to PI3K-Akt signaling that sustains G1/S progression and cell survival. It also binds Src and enhances Src activation. Its N-terminus binds the fifth SH3 domain of the scaffold Tks5. XB130 is cytoplasmic at rest and translocates to the branched F-actin of lamellipodia on Rac activation or EGF stimulation. The rodent ortholog binds and crosslinks actin filaments by multimerizing. In thyroid follicular cells, where expression is highest, the mouse protein sits at the apical membrane and is needed for apical membrane organization, follicle lumen formation and thyroid hormone production. alternative_products: - name: '1' id: Q8N4X5-1 - name: '2' id: Q8N4X5-2 sequence_note: VSP_014255 - name: '3' id: Q8N4X5-3 sequence_note: VSP_014254, VSP_014256 - name: '4' id: Q8N4X5-4 sequence_note: VSP_036211, VSP_014255 existing_annotations: - term: id: GO:0005737 label: cytoplasm evidence_type: IDA original_reference_id: PMID:17412687 qualifier: located_in review: action: ACCEPT summary: XB130 is a cytoplasmic adaptor at rest; this is the basal location from which it is recruited to lamellipodial F-actin and, in thyrocytes, to the apical cortex. reason: The original characterization and the curated UniProt location place XB130 in the cytoplasm. Lodyga et al. 2010 describe it as a cytosolic adaptor that translocates to the cell periphery on stimulation. The Tks5 study shows endogenous XB130 in cytoplasmic and perinuclear puncta. Cytoplasm is correct and appropriately broad for the resting protein. The more specific dynamic locations (lamellipodium, apical plasma membrane) are proposed as NEW rows. supported_by: &id001 - reference_id: file:human/AFAP1L2/AFAP1L2-uniprot.txt record_section: ["CC:SUBCELLULAR LOCATION"] supporting_text: 'CC -!- SUBCELLULAR LOCATION: Cytoplasm {ECO:0000269|PubMed:17412687}.' - reference_id: PMID:21084565 supporting_text: XB130 is a newly described cytosolic adaptor protein and tyrosine kinase substrate - reference_id: PMID:26446840 supporting_text: Coimmunofluorescence microscopy showed that endogenous XB130 and Tks5 are colocalized in fine punctate structures in the cytoplasm and in perinuclear regions - term: id: GO:0005737 label: cytoplasm evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in supporting_entities: - UniProtKB-SubCell:SL-0086 review: action: ACCEPT summary: Electronic mapping of the curated UniProt location Cytoplasm, which rests on PMID:17412687. reason: The SubCell mapping reproduces a curated, publication-backed location. It agrees with the IDA row for the same term. supported_by: *id001 - term: id: GO:0005829 label: cytosol evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: is_active_in supporting_entities: - PANTHER:PTN001023816 - UniProtKB:Q8N4X5 review: action: ACCEPT summary: PAINT places cytosol at the deuterostome-level AFAP family node PTN001023816. Human XB130 is the seed. reason: Every characterized AFAP family member (AFAP1, AFAP1L1, AFAP1L2) is a soluble, non-membrane-spanning adaptor that is recruited to actin structures from a cytosolic pool. XB130 has no transmembrane segment or signal peptide in UniProt. Human XB130 sits inside the clade that inherits the node, and there is no evidence of a lineage-specific loss. Its own cytoplasmic/cytosolic IDA data are the expected descendant evidence and are not circular. supported_by: *id001 - term: id: GO:0005829 label: cytosol evidence_type: IDA original_reference_id: GO_REF:0000052 qualifier: located_in review: action: ACCEPT summary: Human Protein Atlas immunofluorescence curation places AFAP1L2 in the cytosol. This is consistent with the published cytoplasmic distribution. reason: The HPA immunofluorescence curation agrees with the published cytoplasmic distribution of XB130 and with the IBA row for the same term. supported_by: *id001 - term: id: GO:0006954 label: inflammatory response evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in supporting_entities: - PANTHER:PTN002682769 - UniProtKB:Q8N4X5 review: action: MARK_AS_OVER_ANNOTATED summary: The only basis is reduced IL-8 (and IL-6) release from a human bronchial epithelial cell line after XB130 siRNA. PAINT propagated it from the human IDA to the AFAP1L2 subfamily node PTN002682769. reason: Reduced cytokine output from cultured BEAS-2B cells shows that XB130 signaling affects IL-8 and IL-6 production in that cell type. It does not show that XB130 does any of the work of an organismal inflammatory response. No in vivo inflammation model with XB130 loss is cited for this row. The cytokine effect is already captured, at the right specificity, by the existing IL-8 and IL-6 production rows. I do not dispute the node placement, since human is the only seed and the subfamily is a clean 1:1 AFAP1L2 ortholog group. What I mark is the scope of the term, which says more than the descendant evidence. The row is kept but not core. propagation_review: root_cause: TERM_SCOPING_PROBLEM failure_modes: - GRANULARITY_MISMATCH source_entities: - source_id: PANTHER:PTN002682769 source_status: SOURCE_WEAK_OR_INFERRED comment: AFAP1L2-subfamily node (Euteleostomi), seeded only by the human IDA from PMID:17412687. That IDA rests on IL-8 and IL-6 release from a cultured epithelial line, so it supports the cytokine-production terms rather than an organismal inflammatory response. supported_by: &id002 - &id003 reference_id: PMID:17412687 supporting_text: 'Down-regulation of endogenous XB130 with siRNA reduced c-Src activity, IL-8 production, EGF-induced phosphorylation of Akt and GSK3beta, and altered cell cycles in human lung epithelial cells.' - &id007 reference_id: file:human/AFAP1L2/AFAP1L2-Xu2007-excerpt.md supporting_text: In addition to IL-8, the protein level of IL-6 was also reduced by siRNA treatment. - term: id: GO:0006954 label: inflammatory response evidence_type: IDA original_reference_id: PMID:17412687 qualifier: involved_in review: action: MARK_AS_OVER_ANNOTATED summary: Cell-line cytokine readout (IL-8, IL-6 after XB130 siRNA) annotated to the organismal inflammatory response. reason: The experiment measures cytokine release from cultured airway epithelial cells. It supports regulation of IL-8 and IL-6 production, which other rows capture, but not participation in an inflammatory response. The action matches the IBA row for this term. supported_by: *id002 - term: id: GO:0007346 label: regulation of mitotic cell cycle evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in supporting_entities: - PANTHER:PTN002682769 - UniProtKB:Q8N4X5 review: action: KEEP_AS_NON_CORE summary: XB130 knockdown impairs G1/S progression in airway epithelial and thyroid carcinoma cells. This follows from its role as a PI3K-Akt adaptor. reason: Three independent studies report altered cell-cycle distribution after XB130 depletion. In Xu 2007 it is altered cell cycles; in Lodyga 2009 it is inhibited cell-cycle progression in TPC1 cells; in Moodley 2015 it is G1 accumulation with p21 up-regulation in BEAS-2B cells. Lodyga 2009 links this to loss of PI3K-Akt coupling. XB130 regulates the cell cycle as an upstream signaling adaptor, not as a component of the cell-cycle machinery, so the term is kept but marked non-core. supported_by: &id004 - *id003 - &id011 reference_id: PMID:19060924 supporting_text: downregulation of XB130 in TPC1 papillary thyroid cancer cells, harboring the RET/PTC1 kinase, strongly reduced Akt activity without altering ERK1/2 phosphorylation, and concomitantly inhibited cell-cycle progression and survival in suspension - reference_id: PMID:26446840 supporting_text: Down-regulation of XB130 and/or Tks5 results in the accumulation of cells in the G1 (resting) phase and a decrease of cells in the DNA synthesis and G2 cell growth phase - term: id: GO:0007346 label: regulation of mitotic cell cycle evidence_type: IDA original_reference_id: PMID:17412687 qualifier: involved_in review: action: KEEP_AS_NON_CORE summary: siRNA depletion of XB130 altered cell-cycle distribution in human lung epithelial cells. reason: This is the same downstream signaling consequence as the IBA row. It is supported and replicated in later studies, but it is not core. supported_by: *id004 - term: id: GO:0017124 label: SH3 domain binding evidence_type: IPI original_reference_id: PMID:17412687 qualifier: enables supporting_entities: - UniProtKB:P12931 review: action: ACCEPT summary: XB130's N-terminal proline-rich SH3-binding motif engages SH3 domains. These include c-Src (this IPI) and the fifth SH3 domain of Tks5. reason: Xu 2007 shows the XB130-Src interaction. Deleting the N-terminal region that holds the SH3-binding motif impairs Src signaling. Moodley 2015 maps the binding directly. XB130 binds only the fifth SH3 domain of Tks5, and both the Tks5 W1108A mutation in that SH3 ligand pocket and XB130 P101A in the PPPxxxP motif reduce binding. SH3 domain binding is the specific adaptor activity of the motif-rich N-terminus. AFAP1L2 has no SH3 domain itself. supported_by: &id008 - reference_id: PMID:17412687 supporting_text: 'XB130DeltaN, an N-terminal deletion mutant lacking a putative SH3-binding motif and several putative SH2-binding sites, reduced its ability to mediate Src signal transduction.' - reference_id: PMID:26446840 supporting_text: XB130 was found to bind specifically to the fifth SH3 domain of Tks5 - term: id: GO:0030296 label: protein tyrosine kinase activator activity evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: enables supporting_entities: - PANTHER:PTN002682769 - UniProtKB:Q8N4X5 review: action: ACCEPT summary: PAINT places Src-activator activity at the AFAP1L2 subfamily node PTN002682769 (Euteleostomi), seeded by human XB130. reason: Co-expression of XB130 with c-Src raises Src activity and tyrosine phosphorylation of cellular proteins. Endogenous XB130 depletion lowers c-Src activity (Xu 2007) and blocks FBS- or EGF-induced Src Y416 phosphorylation (Moodley 2015). In rat thyroid cells, Src associates with PI3KAP/XB130 and is activated in a Src-dependent cAMP response (Yamanaka 2012). The node sits in the AFAP1L2-specific subfamily (PTHR14338:SF4) and is not propagated to AFAP1 or AFAP1L1, which keeps the inference within the 1:1 ortholog clade. The term says XB130 activates a kinase without being one, which is accurate. supported_by: &id006 - &id005 reference_id: PMID:17412687 supporting_text: 'Their co-expression in COS-7 cells resulted in activation of c-Src and elevated tyrosine phosphorylation of multiple proteins, including XB130 itself.' - *id003 - reference_id: PMID:26446840 supporting_text: Down-regulation of XB130, Tks5, or both XB130 and Tks5 inhibited the FBS- or EGF-induced tyrosine phosphorylation of cellular proteins and inhibited the phosphorylation of Src Y416 - term: id: GO:0030296 label: protein tyrosine kinase activator activity evidence_type: IDA original_reference_id: PMID:17412687 qualifier: enables review: action: ACCEPT summary: Co-expression of XB130 activates c-Src, and depletion reduces endogenous c-Src activity. reason: This is the primary evidence for the Src-activating adaptor function. It is consistent with the IBA row and with the later Tks5 study. supported_by: *id006 - term: id: GO:0032675 label: regulation of interleukin-6 production evidence_type: IDA original_reference_id: PMID:17412687 qualifier: involved_in review: action: KEEP_AS_NON_CORE summary: XB130 siRNA reduced IL-6 protein release from BEAS-2B airway epithelial cells. The result is reported in the full-text Results. reason: The result is a single cell-line readout of a downstream signaling output. It supports the regulation term in that context, but it is not a core function. The PMID cache is abstract-only, so the IL-6 sentence is preserved in a separate excerpt file inspected from the full paper. The curator saw the full text. supported_by: - *id007 - term: id: GO:0032757 label: positive regulation of interleukin-8 production evidence_type: IDA original_reference_id: PMID:17412687 qualifier: involved_in review: action: KEEP_AS_NON_CORE summary: XB130 depletion reduced IL-8 production in human lung epithelial cells. reason: Loss of XB130 lowered IL-8 output, so the sign of the regulation term is correct. It is a downstream consequence of Src signaling in one epithelial context and is not core. supported_by: - *id003 - term: id: GO:0042169 label: SH2 domain binding evidence_type: IPI original_reference_id: PMID:17412687 qualifier: enables supporting_entities: - UniProtKB:P12931 review: action: ACCEPT summary: Tyrosine-phosphorylated XB130 motifs are docking sites for SH2 domains, including Src (this IPI) and the p85alpha subunit of PI3K (pTyr54). reason: Xu 2007 shows that the N-terminal region with putative SH2-binding sites is needed for Src signaling. Lodyga 2009 identifies Tyr54 as the main RET/PTC phosphorylation site and as a critical binding site for the p85alpha SH2 domains. This SH2-docking function is the mechanistic core of the adaptor. The more specific p85-binding activity is proposed as a NEW row. supported_by: - reference_id: PMID:17412687 supporting_text: 'XB130DeltaN, an N-terminal deletion mutant lacking a putative SH3-binding motif and several putative SH2-binding sites, reduced its ability to mediate Src signal transduction.' - &id012 reference_id: PMID:19060924 supporting_text: We identified tyrosine 54 of XB130 as the major target of RET/PTC-mediated phosphorylation and a critical binding site for the SH2 domains of p85alpha. - term: id: GO:0045742 label: positive regulation of epidermal growth factor receptor signaling pathway evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in supporting_entities: - PANTHER:PTN002682769 - UniProtKB:Q8N4X5 review: action: KEEP_AS_NON_CORE summary: XB130 is needed for full EGF-induced Akt and GSK3beta phosphorylation and EGF-induced Src activation in airway epithelial cells. reason: The EGF evidence (Xu 2007; Moodley 2015) supports positive regulation of downstream EGF receptor signaling, probably through the same Src and p85-PI3K docking mechanism. XB130 also couples RET/PTC, TSH/cAMP-Src and serum signaling to PI3K. EGFR is therefore one input among several rather than the defining pathway. The PI3K-Akt coupling is the core process and is proposed as NEW. This row is kept, but as non-core. supported_by: &id009 - *id003 - reference_id: PMID:26446840 supporting_text: XB130 and/or Tks5 siRNA also blocked FBS- or EGF-induced phosphorylation of PI3K p85α subunit and Akt - term: id: GO:0045742 label: positive regulation of epidermal growth factor receptor signaling pathway evidence_type: IDA original_reference_id: PMID:17412687 qualifier: involved_in review: action: KEEP_AS_NON_CORE summary: XB130 depletion reduces EGF-induced Akt and GSK3beta phosphorylation. reason: The action matches the IBA row. This is a supported, context-specific signaling role. supported_by: *id009 - term: id: GO:0045893 label: positive regulation of DNA-templated transcription evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in supporting_entities: - PANTHER:PTN002682769 - UniProtKB:Q8N4X5 review: action: MARK_AS_OVER_ANNOTATED summary: The only basis is SRE- and AP-1-luciferase reporter enhancement when XB130 is overexpressed with c-Src in HEK293 cells. reason: XB130 is a cytoplasmic adaptor with no DNA-binding domain or nuclear role. The reporter gain is a distal readout of its Src-activating activity, many signaling steps upstream of the transcription factors. GO convention does not use transcription-regulation process terms for upstream cytoplasmic signaling components without a more direct link. The Src-activator MF and the PI3K-Akt signaling process describe the real contribution. The PAINT curator propagated what the human IDA asserted. The node placement is not at fault; the scope of the term is. propagation_review: root_cause: TERM_SCOPING_PROBLEM failure_modes: - ROLE_CONFLATION source_entities: - source_id: PANTHER:PTN002682769 source_status: SOURCE_WEAK_OR_INFERRED comment: Node seeded only by the human IDA from PMID:17412687, which is an SRE/AP-1 luciferase reporter gain with overexpressed XB130 and c-Src. That treats an upstream cytoplasmic adaptor as a transcription regulator. supported_by: &id010 - reference_id: PMID:17412687 supporting_text: 'XB130 expression in HEK293 cells enhanced serum response element- and AP-1-dependent transcriptional activation mediated by c-Src.' - term: id: GO:0045893 label: positive regulation of DNA-templated transcription evidence_type: IDA original_reference_id: PMID:17412687 qualifier: involved_in review: action: MARK_AS_OVER_ANNOTATED summary: Reporter-gene enhancement downstream of Src by an overexpressed cytoplasmic adaptor. reason: The action matches the IBA row. The experiment supports Src signaling output, not regulation of transcription by AFAP1L2 itself. supported_by: *id010 - term: id: GO:0036312 label: phosphatidylinositol 3-kinase regulatory subunit binding evidence_type: IPI original_reference_id: PMID:19060924 qualifier: enables review: action: NEW summary: Tyrosine-phosphorylated XB130 (pTyr54, YxxM) binds the SH2 domains of the PI3K regulatory subunit p85alpha. reason: This is the defining adaptor contact by which XB130 links RET/PTC and Src to PI3K. Lodyga 2009 mapped it to Tyr54 in human XB130. The rat ortholog PI3KAP/XB130 (PTHR14338:SF4) was independently identified as the p125 protein that associates with p85 PI3K and carries PI3K activity (Yamanaka 2012). It is informative where SH2 domain binding alone is not, because it names the partner class and the pathway it couples to. supported_by: - *id012 - reference_id: PMID:22496359 supporting_text: cAMP treatment elevated PI3KAP/XB130 mRNA and protein levels as well as tyrosine phosphorylation and interaction with p85 PI3K leading to increased PI3K activities associated with PI3KAP/XB130 - term: id: GO:0051897 label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction evidence_type: IMP original_reference_id: PMID:19060924 qualifier: involved_in review: action: NEW summary: XB130 couples RET/PTC (and Src) tyrosine kinase activity to PI3K-Akt signaling. Its depletion strongly reduces Akt activity without affecting ERK. reason: 'Participation test: XB130 is not just required for the pathway. It contributes the phosphotyrosine docking site (Tyr54) that recruits p85alpha, a scaffold contribution to the signaling step itself. Depletion lowers Akt activity selectively in TPC1 cells (Lodyga 2009) and lowers EGF/FBS-induced p85alpha and Akt phosphorylation in BEAS-2B cells (Moodley 2015). Comparator check: other docking adaptors that recruit p85 through YxxM motifs, carry the term: QuickGO, checked 2026-10-20, lists GO:0051897 for human IRS1 (P35568, ISS) and GAB1 (Q13480, TAS). So the term is used for this adaptor role and is not reserved for the kinases.' supported_by: - *id011 - *id012 - reference_id: PMID:26446840 supporting_text: XB130 and/or Tks5 siRNA also blocked FBS- or EGF-induced phosphorylation of PI3K p85α subunit and Akt - term: id: GO:0051015 label: actin filament binding evidence_type: ISS original_reference_id: PMID:27462298 qualifier: enables review: action: NEW summary: The C-terminal actin-binding region of PI3KAP/XB130 binds F-actin directly in vitro and is conserved across vertebrate orthologs, including human. reason: Yamanaka 2016 used mouse PI3KAP/XB130 (variant 1). Its ortholog Q5DTU0 sits in the same PANTHER subfamily PTHR14338:SF4 as human Q8N4X5. A GST fusion of the C-terminal region co-sedimented with F-actin, and the full-length recombinant protein crosslinked filaments. The authors' alignment shows the binding region is highly conserved in vertebrate XB130 orthologs, human included. Lodyga 2010 shows independently that human XB130 associates with lamellipodial branched F-actin through its N- and C-terminal regions. The transfer rests on subfamily membership and conservation of the mapped region, not on name or best hit. This region differs from the classical actin-binding domain of AFAP1 and AFAP1L1, so the function is not inferred from those paralogs. supported_by: - reference_id: PMID:27462298 supporting_text: that the carboxyl terminal region of PI3KAP/XB130 containing amino acid residues 830-840 was required and sufficient for localization to F-actin in NIH3T3 cells, and this region is directly bound to F-actin in vitro - reference_id: PMID:27462298 supporting_text: Furthermore, homology search analysis revealed that this region was highly conserved in many vertebrate species (Figure 2C). - reference_id: PMID:27462298 supporting_text: However, this motif is not conserved in mouse PI3KAP/XB130 that we used in this study (variant 1; GenBank Accession # NM_001177796) - term: id: GO:0030027 label: lamellipodium evidence_type: IDA original_reference_id: PMID:21084565 qualifier: located_in review: action: NEW summary: On EGF, wounding or active Rac, XB130 translocates to the cell periphery and localizes to the lamellipodial F-actin meshwork. reason: Lodyga 2010 is a dedicated localization and structure-function study of XB130 in lamellipodia. Recruitment depends on branched F-actin and on the XB130 N- and C-termini. Endogenous XB130 silencing in human TPC1 cells reduced lamellipodial persistence. This stimulus-dependent location adds information beyond cytoplasm. Only the abstract is cached; the localization claim is stated in it. supported_by: - reference_id: PMID:21084565 supporting_text: In stimulated cells, XB130 localized to the lamellipodial F-actin meshwork. - term: id: GO:0016324 label: apical plasma membrane evidence_type: ISS original_reference_id: PMID:34470464 qualifier: located_in review: action: NEW summary: In thyroid follicular cells, endogenous XB130 is mainly at the apical membrane, at both embryonic and postnatal stages (mouse). reason: Wang et al. 2021 localized endogenous mouse XB130 (Q5DTU0, same PANTHER subfamily PTHR14338:SF4 as human) to the apical membrane of thyrocytes. In its absence, apical microvilli, ezrin and TPO staining and follicle lumen formation are disrupted. Thyroid is also where human AFAP1L2 expression is highest. The location is a structural fact about the 1:1 ortholog in its main tissue. The knockout phenotypes (congenital hypothyroidism, delayed folliculogenesis) are not proposed as process annotations, because they are necessity evidence and the mechanism linking the scaffold to each step is not resolved. supported_by: - reference_id: PMID:34470464 supporting_text: XB130 was found mainly on the apical membrane of thyroid follicles. references: - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt findings: [] - id: GO_REF:0000052 title: Gene Ontology annotation based on curation of immunofluorescence data findings: [] - id: PMID:17412687 title: XB130, a novel adaptor protein for signal transduction. findings: [] full_text_unavailable: true reference_review: relevance: HIGH correctness: VERIFIED review_notes: Original cloning and characterization of human XB130 (818 aa, 10q25.3). It is the source of all experimental GOA rows. The abstract is cached; the IL-6 result comes from the full text and is kept in the excerpt file. - id: PMID:19060924 title: XB130, a tissue-specific adaptor protein that couples the RET/PTC oncogenic kinase to PI 3-kinase pathway. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Establishes the RET/PTC phosphorylation site Tyr54 as the p85alpha SH2 docking site, with selective Akt dependence in TPC1 cells. Abstract-only cache; the quotes are from the abstract. - id: PMID:21084565 title: Adaptor protein XB130 is a Rac-controlled component of lamellipodia that regulates cell motility and invasion. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Localization of XB130 to lamellipodial branched F-actin and its effect on motility. Abstract-only cache. - id: PMID:22496359 title: Phosphatidylinositol 3-kinase-binding protein, PI3KAP/XB130, is required for cAMP-induced amplification of IGF mitogenic activity in FRTL-5 thyroid cells. findings: [] reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: Independent identification of rat PI3KAP/XB130 as a p85 PI3K-associated, Src-associated phosphoprotein in thyroid cells. It corroborates the human data in a SF4 ortholog. - id: PMID:26446840 title: XB130/Tks5 scaffold protein interaction regulates Src-mediated cell proliferation and survival. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Full text cached. Maps the binding of the XB130 N-terminus to the Tks5 SH3 domain 5 and shows the knockdown effects on Src Y416, p85alpha, Akt and G1 arrest in BEAS-2B cells. - id: PMID:27462298 title: Phosphatidylinositol 3-Kinase-Associated Protein (PI3KAP)/XB130 Crosslinks Actin Filaments through Its Actin Binding and Multimerization Properties In Vitro and Enhances Endocytosis in HEK293 Cells. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Full text cached. Direct F-actin binding and crosslinking by mouse PI3KAP/XB130 (variant 1), with N-terminal multimerization. Residue numbers (830-840) refer to the mouse construct, not the 818-aa human protein. - id: PMID:34470464 title: XB130 Deficiency Causes Congenital Hypothyroidism in Mice due to Disorganized Apical Membrane Structure and Function of Thyrocytes. findings: [] reference_review: relevance: HIGH correctness: VERIFIED review_notes: Full text cached. Mouse Xb130 knockout gives congenital hypothyroidism. Endogenous XB130 is at the thyrocyte apical membrane. Used here for location only; the phenotypes are necessity evidence and are not process annotations. - id: file:human/AFAP1L2/AFAP1L2-uniprot.txt title: human/AFAP1L2/AFAP1L2-uniprot.txt findings: [] - id: file:human/AFAP1L2/AFAP1L2-Xu2007-excerpt.md title: human/AFAP1L2/AFAP1L2-Xu2007-excerpt.md findings: [] core_functions: - description: Phosphotyrosine-dependent adaptor that couples Src-family and RET/PTC tyrosine kinases to PI3K. Phosphorylated Tyr54 (YxxM) docks the p85alpha SH2 domains and promotes PI3K-Akt signaling that supports G1/S progression and cell survival. molecular_function: id: GO:0036312 label: phosphatidylinositol 3-kinase regulatory subunit binding directly_involved_in: - id: GO:0051897 label: positive regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction locations: - id: GO:0005829 label: cytosol supported_by: - *id012 - *id011 - description: Binds c-Src through its SH2/SH3-binding motif-rich N-terminus and enhances Src activation (Tyr416 phosphorylation) as a non-catalytic activator. The same N-terminal motifs engage the fifth SH3 domain of the scaffold Tks5. molecular_function: id: GO:0030296 label: protein tyrosine kinase activator activity locations: - id: GO:0005737 label: cytoplasm supported_by: - *id005 - *id003 - description: Actin-associated scaffold. It is recruited to the branched F-actin of lamellipodia on stimulation. Its C-terminal region binds F-actin directly, and N-terminal multimerization lets it crosslink filaments (shown for the mouse SF4 ortholog). In thyrocytes, the mouse ortholog sits at the apical membrane cortex. molecular_function: id: GO:0051015 label: actin filament binding locations: - id: GO:0030027 label: lamellipodium - id: GO:0016324 label: apical plasma membrane supported_by: - reference_id: PMID:21084565 supporting_text: In stimulated cells, XB130 localized to the lamellipodial F-actin meshwork. - reference_id: PMID:27462298 supporting_text: Furthermore, homology search analysis revealed that this region was highly conserved in many vertebrate species (Figure 2C). suggested_questions: - question: Does the C-terminal actin-binding region mapped in mouse PI3KAP/XB130 (residues 830-840 of the mouse construct) correspond to a conserved segment near the C-terminus of the 818-residue human protein, and does human XB130 crosslink F-actin in vitro? - question: Which PH domain lipid specificities, if any, target XB130 to the thyrocyte apical membrane, and is the thyroid apical-cortex role conserved in human (are AFAP1L2 variants found in congenital hypothyroidism cohorts)? suggested_experiments: - description: Purify recombinant human XB130 (full length, and with C-terminal and N-terminal-40 deletions). Test F-actin co-sedimentation and low-speed crosslinking assays, and test multimerization by blue-native PAGE, so the actin-binding function is established directly on the human protein.