Affinage

AP1B1

AP-1 complex subunit beta-1 · UniProt Q10567

Length
949 aa
Mass
104.6 kDa
Annotated
2026-06-09
12 papers in source corpus 6 papers cited in narrative 6 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

AP1B1 encodes the β1/β'-adaptin subunit of the heterotetrameric AP-1 clathrin adaptor complex that drives intracellular receptor transport via clathrin-coated vesicles (PMID:8812422). As a structural subunit, AP1B1 is required for AP-1 complex stability and normal vesicular trafficking in epithelial cells: loss-of-function in patient keratinocytes destabilizes the complex (sharply reducing the γ subunit), produces an excess of abnormal vesicles, and deranges intercellular junction proteins, with wild-type AP1B1 transduction rescuing the vesicular phenotype (PMID:31630788). Through AP-1-mediated sorting of transmembrane cargo, AP1B1 directs the correct trafficking of the copper-transporting ATPases ATP7A and ATP7B; loss-of-function mutations mistraffic these cargoes both at baseline and under copper stimulation, producing abnormal copper homeostasis with low serum copper and ceruloplasmin (PMID:31630791, PMID:40101690). In zebrafish hair cells, ap1b1 mediates basolateral targeting of the Na+/K+-ATPase, and its loss mislocalizes the pump to apical hair bundles with consequent loss of ion homeostasis and impaired mechanotransduction (PMID:23593334). Homozygous loss-of-function mutations in AP1B1 cause a human disorder of copper metabolism with epithelial and ATP7A/B trafficking defects resembling MEDNIK syndrome (PMID:31630791, PMID:31630788).

Mechanistic history

Synthesis pass · year-by-year structured walk · 4 steps
  1. 1996 Medium

    Established the molecular identity of AP1B1, defining the gene that encodes a β'-adaptin subunit of clathrin-associated adaptor complexes and placing it in the machinery of intracellular receptor transport.

    Evidence Genomic cloning, exon mapping, and promoter sequencing of the gene on chromosome 22q12

    PMID:8812422

    Open questions at the time
    • No functional assay of the encoded subunit
    • Cargo specificity and complex partners not addressed
    • Tissue-specific roles unexplored
  2. 2013 High

    Showed that the AP-1 β subunit is required for polarized cargo sorting in vivo, answering whether AP1B1 directs basolateral membrane protein targeting in differentiated cells.

    Evidence Forward genetic screen in zebrafish with NKA immunofluorescence, intracellular Na+ imaging, and mechanically-evoked calcium imaging in hair cells

    PMID:23593334

    Open questions at the time
    • Direct cargo-adaptor binding not demonstrated
    • Mechanism of basolateral signal recognition not defined
    • Mammalian/human relevance not tested in this study
  3. 2019 High

    Defined AP1B1 as required for AP-1 complex stability and identified its loss-of-function as a cause of human epithelial trafficking disease, with rescue confirming causality.

    Evidence Patient keratinocyte immunoblot/microscopy of complex subunits and vesicle morphology, plus lentiviral wild-type AP1B1 rescue; patient-fibroblast ATP7A trafficking assays under basal and copper-stimulated conditions

    PMID:31630788 PMID:31630791

    Open questions at the time
    • Structural basis of γ-subunit destabilization not resolved
    • Direct interaction of AP-1 with ATP7A/B not biochemically mapped
    • Range of mistrafficked cargoes incompletely catalogued
  4. 2025 Medium

    Extended the AP1B1 disease spectrum by linking a new frameshift variant to impaired AP-1 assembly and ATP7A/ATP7B mistrafficking with abnormal copper metabolism overlapping Menkes and Wilson's diseases.

    Evidence Patient-derived cell biology with biochemical copper measurements and genetic variant analysis; corroborating review synthesis of AP1B1/AP1S1 cases

    PMID:40101690 PMID:41404470

    Open questions at the time
    • Single-study cell biology with limited methodological detail
    • Genotype-phenotype correlation across variants not established
    • Mechanism distinguishing AP1B1 from AP1S1 disease not resolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How AP-1, via AP1B1, recognizes and selects specific cargoes such as ATP7A/B and Na+/K+-ATPase, and the structural basis of complex assembly and subunit stabilization, remain unresolved.
  • No direct structural model of AP-1 cargo binding in the corpus
  • Cargo-sorting signal recognition mechanism uncharacterized
  • Full cargo repertoire dependent on AP1B1 not enumerated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 2 GO:0060090 molecular adaptor activity 2
Localization
GO:0031410 cytoplasmic vesicle 2 GO:0005794 Golgi apparatus 1
Pathway
R-HSA-5653656 Vesicle-mediated transport 2 R-HSA-9609507 Protein localization 2
Complex memberships
AP-1 adaptor complex

Evidence

Reading pass · 6 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2019 Homozygous loss-of-function mutations in AP1B1 (encoding the β1 subunit of AP-1) cause abnormal trafficking of copper transporters ATP7A and ATP7B; fibroblasts from affected individuals showed abnormal ATP7A trafficking both at baseline and in response to copper treatment, closely resembling the defect seen in MEDNIK syndrome (caused by AP1S1 mutations). Functional characterization of patient-derived fibroblasts; immunofluorescence/trafficking assays for ATP7A localization under basal and copper-stimulated conditions American journal of human genetics Medium 31630791
2019 Loss of AP1B1 (β1 subunit of AP-1) in affected keratinocytes destabilizes the AP-1 complex (γ subunit greatly reduced), leads to an abundance of abnormal vesicles, hyperproliferation, abnormal epidermal differentiation, and derangement of intercellular junction proteins. Transduction of affected cells with wild-type AP1B1 rescues the vesicular phenotype, establishing AP1B1 as required for AP-1 complex stability and normal vesicular trafficking in epithelial cells. Analysis of patient-derived keratinocytes (immunoblot, microscopy for vesicle morphology, junction protein localization); rescue by lentiviral transduction of wild-type AP1B1 American journal of human genetics High 31630788
2013 In zebrafish hair cells, ap1b1 (AP-1 β subunit) is required for basolateral targeting of the Na+/K+-ATPase pump (NKA); in ap1b1 mutants, NKA is mislocalized from the basolateral membrane to apical hair bundles, accompanied by elevated intracellular Na+ and reduced mechanically-evoked calcium transients, indicating loss of ion homeostasis and impaired mechanotransduction. Forward genetic screen in zebrafish; immunofluorescence for NKA localization in hair cells; intracellular Na+ imaging; mechanically-evoked calcium imaging PloS one High 23593334
2025 A novel homozygous frameshift variant in AP1B1 impairs intracellular AP-1 complex assembly and disrupts trafficking of the copper-transporting ATPases ATP7A and ATP7B, resulting in abnormal copper metabolism (low serum copper and ceruloplasmin), consistent with AP1B1's role in AP-1-mediated sorting of transmembrane cargo to the trans-Golgi compartment and plasma membrane. Cell biological characterization of patient-derived cells; biochemical copper measurements; genetic variant analysis Molecular genetics and metabolism Medium 40101690
2025 AP1B1 loss-of-function mutations impair intracellular vesicle trafficking, disrupting the sorting and transport of the copper-transporting ATPases ATP7A and ATP7B, leading to defective copper homeostasis with a clinical phenotype overlapping Menkes and Wilson's diseases. Review synthesizing genetic and cell biological data from reported AP1B1 and AP1S1 mutation cases; no new primary experiments Frontiers in neurology Low 41404470
1996 AP1B1 (BAM22/ADTB1) encodes the β'-adaptin subunit of heterotetrameric adaptor protein complexes involved in intracellular receptor transport via clathrin-coated vesicles; the gene spans ~100 kb comprising 22 exons on chromosome 22q12 and has a CG-rich promoter. Genomic cloning, exon mapping, sequencing of promoter region Genomics Medium 8812422

Source papers

Stage 0 corpus · 12 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2019 Homozygous Loss-of-Function Mutations in AP1B1, Encoding Beta-1 Subunit of Adaptor-Related Protein Complex 1, Cause MEDNIK-like Syndrome. American journal of human genetics 45 31630791
2004 Dual effects of intrathecal BAM22 on nociceptive responses in acute and persistent pain--potential function of a novel receptor. British journal of pharmacology 33 14718254
2019 Recessive Mutations in AP1B1 Cause Ichthyosis, Deafness, and Photophobia. American journal of human genetics 29 31630788
2004 Effects of intrathecal BAM22 on noxious stimulus-evoked c-fos expression in the rat spinal dorsal horn. Brain research 25 15527742
2013 Mutations in ap1b1 cause mistargeting of the Na(+)/K(+)-ATPase pump in sensory hair cells. PloS one 24 23593334
1996 Structure of the promoter and genomic organization of the human beta'-adaptin gene (BAM22) from chromosome 22q12. Genomics 22 8812422
2025 Clinical, biochemical and cell biological characterization of KIDAR syndrome associated with a novel AP1B1 variant. Molecular genetics and metabolism 5 40101690
2023 Severe KIDAR syndrome caused by deletion in the AP1B1 gene: Report of a teenage patient and systematic review of the literature. European journal of medical genetics 5 37657632
2012 Role of bovine adrenal medulla 22 (BAM22) in the pathogenesis of neuropathic pain in rats with spinal nerve ligation. European journal of pharmacology 4 22521859
2025 IDEDNIK syndrome: a newly recognized rare genetic disorder caused by AP1S1 and AP1B1 mutations. Frontiers in neurology 1 41404470
2025 Novel homozygous pathogenic AP1B1 variant in autosomal recessive keratitis-ichthyosis-deafness syndrome treated with acitretin. BMJ case reports 1 41453769
2026 Expanding the Clinical Spectrum of KIDAR Syndrome: A Case of Multisystemic Involvement in a Palestinian Child with AP1B1 Deficiency. Sage open pediatrics 0 41948131

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