# AIPL1 notes ## 2026-06-03 Proteostasis PN review - Deep research status: `just deep-research-falcon human AIPL1 --fallback perplexity-lite` was attempted. Falcon timed out after 600 seconds, then the Perplexity-lite fallback failed with a quota/401 error. No provider-generated deep-research file was created, so this review proceeds from cached GOA, UniProt, PN projection files, and cached primary literature. - PN projection context: `projects/PROTEOSTASIS/reports/pn_projection/pn_projected_annotations.tsv` projects AIPL1 to `GO:0031072 heat shock protein binding` via the HSP70-HSP90 joint cochaperone class, and also shows `GO:0003755 peptidyl-prolyl cis-trans isomerase activity` as already in GOA through the FKBP-type PPIase branch. The review accepts the direction of the HSP90/co-chaperone projection but recommends the narrower, gene-supported `GO:0051879 Hsp90 protein binding` rather than the broad `GO:0031072`. The PPIase annotation is removed because AIPL1-specific evidence contradicts catalytic PPIase activity. - AIPL1 is a photoreceptor/pineal protein with TPR motifs. The original gene paper describes "a new photoreceptor/pineal-expressed gene, AIPL1" and says its protein has "three tetratricopeptide (TPR) motifs" [PMID:10615133 "photoreceptor/pineal-expressed gene, AIPL1" / "three tetratricopeptide (TPR) motifs"]. - AIPL1 is present in human photoreceptors and interacts with NUB1, but this NUB1 binding is not the core PN proteostasis function. Akey et al. verified the interaction by co-immunoprecipitation and found AIPL1 in developing and adult photoreceptors [PMID:12374762 "The AIPL1-NUB1 interaction was verified by co-immunoprecipitation studies in Y79 retinoblastoma cells" / "AIPL1 is present in the developing photoreceptor layer of the human retina and within the photoreceptors of the adult retina"]. - Farnesyl/prenyl binding is a real AIPL1 function. Ramamurthy et al. showed that "AIPL1 interacts specifically with farnesylated proteins" and "AIPL1 enhances the processing of farnesylated proteins" [PMID:14555765]. Majumder et al. later mapped this to the FKBP-like domain, stating that "farnesylated-Cys binds exclusively to the FKBP domain of AIPL1" [PMID:23737531]. - Keep farnesyl/prenyl binding separate from the HSP90-dependent PDE6 maturation core function. Yadav et al. show that prenyl-binding-deficient AIPL1 retains co-chaperone activity and conclude that prenyl modification sequestration is not required for PDE6 maturation [PMID:35065964 "neither sequestration of the prenyl modifications is required for PDE6 maturation to proceed"]. - The FKBP-like domain should not be curated as PPIase activity. Majumder et al. state that "the FKBP domain of AIPL1 does not bind FK506 or exhibit peptidylprolylisomerase activity" [PMID:23737531]. This directly argues against retaining the InterPro/PN PPIase transfer. - The strongest PN-relevant function is AIPL1-HSP90 co-chaperone activity for PDE6 maturation. Yadav et al. report that AIPL1 "preferentially binds to HSP90 in the closed state with a stoichiometry of 1:2" and that "Disruption of the AIPL1 interaction with HSP90 impedes maturation of PDE6" [PMID:35065964]. Sacristan-Reviriego et al. also describe AIPL1 as a "photoreceptor-specific co-chaperone that interacts with the molecular chaperone HSP90" [PMID:28973376]. - High-throughput generic protein-binding rows should not drive core function. The TINF2 row comes from a telomere interactome screen over about 12,000 proteins [PMID:21044950 "we identified over 300 proteins that associated with the six core telomeric proteins"]. The HuRI rows come from a genome-scale binary interactome resource whose paper notes that "the cellular function of most individual PPIs remains to be elucidated" [PMID:32296183]. These are useful interaction-screen records but not evidence for a core AIPL1 PN role. ## Falcon deep research findings (2026-06-07) The Falcon (Edison Scientific) report largely confirms the existing PDE6 co-chaperone-centric review. Key NEW items vs the existing review: - FAT10/NUB1 proteostasis axis (genuinely new mechanistic primary study, not previously cited). Boehm et al. show that FAT10 (a cytokine-inducible ubiquitin-like modifier) is conjugated to rod PDE6 and targets it for proteasomal degradation, while also non-covalently inhibiting PDE6 cGMP hydrolysis; AIPL1 stabilizes the FAT10 monomer and the PDE6-FAT10 conjugate, and FAT10 binds AIPL1 TPR motifs [PMID:32817338 "AIPL1 interacts with the cytokine-inducible ubiquitin-like modifier FAT10" / "We found that AIPL1 stabilizes the FAT10 monomer and the PDE6-FAT10 conjugate" (doi:10.1074/jbc.RA120.013873)]. This gives mechanistic meaning to the existing (otherwise generic) AIPL1-NUB1 protein-binding annotation, connecting AIPL1 to inflammation-linked PDE6 proteostasis. I did NOT change any annotation action on this basis since it does not contradict existing calls; added as a reference and a suggested question. - Prenylation as a molecular-recognition element (prenyl-dependent assembly model). The 2024 prenylation review frames PDE6 prenylation not merely as a membrane anchor but as a recognition feature that enables AIPL1 FKBP-domain binding and stable AIPL1-HSP90-PDE6 ternary complex formation; rod PDE6A is farnesylated, PDE6B/cone PDE6 geranylgeranylated [Ashok & Rao 2024, doi:10.3389/fopht.2024.1410874, review]. Consistent with the existing review; note the existing review (citing PMID:35065964) holds that prenyl sequestration is NOT strictly required for PDE6 maturation, so this remains an open mechanistic point. Review-level, not used to change annotations. - 2024 human iPSC retinal-organoid gene-replacement study (new primary translational evidence). AAV-mediated AIPL1 replacement rescued loss of rod PDE6 and normalized elevated cGMP in AIPL1-KO and patient LCA4 organoids, with PDE6 transcripts unchanged - i.e. a post-transcriptional/proteostasis rescue, independently supporting AIPL1's chaperone (not transcriptional) mechanism [PMID:38439910 "the loss of retinal phosphodiesterase 6 was rescued and elevated cyclic guanosine monophosphate (cGMP) levels were reduced following treatment" (doi:10.1016/j.omtn.2024.102148)]. Reinforces visual perception / protein maturation annotations; added as reference. - Localization refinement (review-level, low weight). AIPL1 is placed mainly along the synapse-to-inner-segment/connecting-cilium axis, favoring a PDE6 maturation/assembly role rather than direct outer-segment trafficking; adult human retina shows strongest detection in rods with developmental expression also in cones, yet AIPL1 remains important for cone viability [galieva2025 / ashok2024, reviews]. Coherent with existing GO:0001917 photoreceptor inner segment ACCEPT; no change. - Clinical/translational context (not annotation-relevant). 2024 LCA cohort: AIPL1 variants in 4/52 (7.7%) children, recurrent c.421C>T p.Q141X [Zhou et al. 2024, doi:10.1007/s00417-024-06450-9]; active early-phase trial NCT07063030 (LX107 subretinal gene therapy for AIPL1-IRD). Background only; not used for GO annotations. - Recent review: Galieva, Karabelsky & Egorov 2025, "Restoring Sight: The Journey of AIPL1 from Discovery to Therapy" [PMID:41465493, doi:10.3390/ijms262412066] - synthesizes AIPL1 as a unique FKBP-family member essential for PDE6, useful secondary reference. PMIDs confirmed via PubMed ID conversion (DOI->PMID): Boehm 2020 = PMID:32817338; Sai 2024 = PMID:38439910; Galieva 2025 = PMID:41465493; Ashok 2024 = PMID:39026984; Zhou 2024 = PMID:38662103.