Affinage

APBA2

Amyloid-beta A4 precursor protein-binding family A member 2 · UniProt Q99767

Length
749 aa
Mass
82.5 kDa
Annotated
2026-06-09
24 papers in source corpus 14 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

APBA2 (Mint2/X11L) is a neuronal adaptor protein that controls the trafficking and proteolytic processing of the amyloid precursor protein (APP) and other transmembrane partners (PMID:10336668, PMID:17032642). It binds the APP cytoplasmic domain through its PTB domain, an interaction gated by an autoinhibitory ARM domain that occludes the PTB peptide-binding groove in a closed state and swings away upon APP engagement, allowing conformational locking to bidirectionally tune APP metabolism (PMID:22730553); APP binding is further enhanced by phosphorylation at Ser236/Ser238 in an N-terminal regulatory region under stress (PMID:19222704). In vivo, loss of APBA2 selectively increases β-secretase-derived APP C-terminal fragments and Aβ in hippocampus, establishing it as a suppressor of amyloidogenic processing (PMID:17032642), while at the cellular level Src-mediated phosphorylation of Mint2 directs internalized APP between autophagic degradation and surface recycling, with corresponding shifts in Aβ production (PMID:22787047). APBA2 also acts as a presynaptic trafficking factor: through its PDZ2 domain it stabilizes and delivers neurexin-1α to presynaptic terminals, and the autism-linked N723S mutation disrupts this without abolishing direct binding, reducing synaptogenesis and excitatory transmission (PMID:30988517). Independently, through its PTB domain it retains TrkA in the Golgi to restrain NGF-induced neurite outgrowth (PMID:19265194). Its APP-suppressive activity is itself regulated by the binding partner XB51, whose isoforms either block or enhance Aβ generation (PMID:10833507, PMID:12780348).

Mechanistic history

Synthesis pass · year-by-year structured walk · 14 steps
  1. 1999 Medium

    Established APBA2/Mint2 as a physical and functional regulator of APP rather than an unrelated neuronal protein, by showing it colocalizes with APP and reshapes its distribution and steady-state levels.

    Evidence Immunofluorescence colocalization and co-transfection distribution analysis in primary neurons and CHO cells

    PMID:10336668

    Open questions at the time
    • Did not define the binding interface or domain
    • Effect on APP cleavage products not measured
    • No in vivo confirmation
  2. 2000 Medium

    Identified XB51 as an upstream regulator of the Mint2–APP axis, showing that the amyloid-suppressing activity of Mint2 is itself modulated by a binding partner.

    Evidence Yeast two-hybrid, reciprocal co-IP, Aβ production assay, and subcellular fractionation

    PMID:10833507

    Open questions at the time
    • Non-competitive inhibition mechanism not structurally defined
    • Physiological relevance not tested in vivo
  3. 2003 Medium

    Resolved that XB51 effects on Aβ are isoform-specific, with hXB51alpha forming a tripartite complex that blocks Mint2 suppression while hXB51beta lowers Aβ by a Mint2-independent route.

    Evidence Co-IP and Aβ assays with isoform-specific constructs

    PMID:12780348

    Open questions at the time
    • Mint2-independent mechanism of hXB51beta undefined
    • No structural basis for tripartite complex
  4. 2004 Medium

    Showed Mint2 has a kinase-coupling function specific among X11 family members, facilitating JNK-mediated phosphorylation of APP/APLP2 under stress.

    Evidence Cell-based stress phosphorylation assays with family-member comparison

    PMID:14970211

    Open questions at the time
    • Direct vs scaffolded JNK action not separated
    • Downstream consequence of Thr668 phosphorylation on Aβ not established here
  5. 2006 High

    Provided the decisive in vivo demonstration that APBA2 selectively suppresses amyloidogenic APP processing, by showing knockout mice accumulate β-secretase CTFs and Aβ in hippocampus.

    Evidence X11L knockout mouse with biochemical quantification of APP CTFs and Aβ in brain

    PMID:17032642

    Open questions at the time
    • Mechanism of pathway selectivity (β vs α) not resolved
    • Cellular trafficking basis not addressed
  6. 2007 Medium

    Revealed APBA2 undergoes CRM1-dependent nucleo-cytoplasmic shuttling, expanding its potential roles beyond cytoplasmic trafficking.

    Evidence EGFP-fusion imaging, leptomycin B, FLIP, and NES mutagenesis

    PMID:18201694

    Open questions at the time
    • Nuclear function of Mint2 unknown
    • NES mapped directly only for X11L2
  7. 2007 Low

    Connected Mint2 levels to neurodegeneration by showing calpain cleaves it, with consequent APP elevation.

    Evidence Okadaic acid degeneration model with western blot and calpain inhibitor

    PMID:18007179

    Open questions at the time
    • Single biochemical method with pharmacological inhibitor
    • Calpain cleavage sites not mapped
    • Causality between Mint loss and APP rise not isolated
  8. 2009 Medium

    Defined a stress-responsive phospho-switch (Ser236/Ser238) outside the PTB domain that tunes Mint2–APP binding strength.

    Evidence Ser→Ala mutagenesis with co-IP under osmotic stress

    PMID:19222704

    Open questions at the time
    • Responsible kinase not identified
    • In vivo relevance of these sites untested
  9. 2009 High

    Extended Mint2 function beyond APP, showing it retains TrkA in the Golgi via its PTB domain to negatively regulate NGF-induced neurite outgrowth.

    Evidence Yeast two-hybrid, endogenous reciprocal co-IP, gain/loss-of-function in PC12 and DRG neurons, Golgi retention assay

    PMID:19265194

    Open questions at the time
    • How a single PTB domain selects APP vs TrkA cargo unclear
    • In vivo neurite/NGF phenotype not shown
  10. 2012 High

    Provided the structural mechanism of Mint2 autoregulation: an ARM domain occludes the PTB groove in a closed state and releases it on APP binding, with conformation-locked mutants bidirectionally controlling APP metabolism.

    Evidence X-ray crystallography of free and APP-bound mutants with structure-guided mutagenesis in vitro and in vivo

    PMID:22730553

    Open questions at the time
    • Trigger that drives the open–closed switch in cells not defined
    • Relationship of switch to Ser236/238 phosphorylation not integrated
  11. 2012 High

    Showed Src-mediated phosphorylation of Mint2 acts as a sorting switch routing internalized APP between autophagic degradation and recycling, directly coupling Mint2 to Aβ fate.

    Evidence Mint knockout neurons, phosphomimetic and phospho-resistant mutants, trafficking analysis, Aβ measurement

    PMID:22787047

    Open questions at the time
    • Src phosphorylation site(s) on Mint2 not fully mapped
    • Reconciliation with in vivo β-secretase suppression role incomplete
  12. 2018 Medium

    Systematically validated APP and presenilin-1 as domain-specific Mint2 partners and showed the C-terminal residues mediate an intramolecular PDZ1 interaction governing Mint2 stability.

    Evidence Peptide binding and domain-mapping with truncation analysis

    PMID:29578633

    Open questions at the time
    • Functional consequence of presenilin-1 binding not tested
    • Stability mechanism not linked to turnover in cells
  13. 2019 High

    Linked APBA2 directly to autism pathophysiology by showing the PDZ2 N723S mutation impairs neurexin-1α trafficking, synaptogenesis, and excitatory transmission without disrupting binding.

    Evidence PDZ2 mutagenesis, time-lapse imaging, surface biotinylation, synaptogenesis assay, and mEPSC recording in mouse neurons

    PMID:30988517

    Open questions at the time
    • How a binding-competent mutant fails at trafficking unresolved
    • In vivo behavioral consequence not tested
  14. 2021 Medium

    Demonstrated the APP–Mint2 interaction is a druggable node, since both a binding-deficient variant and a PTB-targeting peptide inhibitor lower Aβ42 in a neuronal AD model.

    Evidence APP-binding-deficient mutant and cell-permeable PPI inhibitor with Aβ42 ELISA

    PMID:33398998

    Open questions at the time
    • Apparent facilitative role for Aβ contrasts with in vivo suppressor phenotype, unresolved
    • No in vivo efficacy of inhibitor

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how APBA2 can act as both an in vivo suppressor of amyloidogenic APP processing and a facilitator of Aβ formation in neuronal models, and what physiological cue selects among its conformational, phosphorylation, and cargo-sorting states.
  • Context-dependence of pro- vs anti-amyloidogenic activity undefined
  • Nuclear function of shuttling Mint2 unknown
  • Unified regulation of ARM switch, Ser/Src phosphorylation, and cargo choice not established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 4 GO:0098772 molecular function regulator activity 2 GO:0140096 catalytic activity, acting on a protein 1
Localization
GO:0005886 plasma membrane 2 GO:0005634 nucleus 1 GO:0005794 Golgi apparatus 1 GO:0005829 cytosol 1
Pathway
R-HSA-9609507 Protein localization 3 R-HSA-1643685 Disease 2 R-HSA-5653656 Vesicle-mediated transport 1
Partners
APBA2BPAPLP2APPNRXN1NTRK1PSEN1

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1999 Mint2/X11L colocalizes with APP in primary cortical neurons and transfected CHO cells; Mint2 reorganizes the subcellular distribution of APP and increases steady-state APP levels when co-expressed, consistent with a role in APP trafficking and metabolism. Immunofluorescence colocalization in primary neurons and transfected CHO cells; co-transfection with subcellular distribution analysis The European journal of neuroscience Medium 10336668
2000 XB51, a novel protein, interacts with the amino-terminal domain of X11L (APBA2/Mint2), inhibits the X11L–APP association through a non-competitive mechanism, and abolishes X11L-mediated suppression of beta-amyloid production. Association with X11L redistributes XB51 from a CHAPS-insoluble to a CHAPS-soluble fraction. Yeast two-hybrid screening, co-immunoprecipitation, beta-amyloid production assay, subcellular fractionation The Journal of biological chemistry Medium 10833507
2003 hXB51alpha binds X11L to form a tripartite complex (hXB51alpha–X11L–APP) that blocks X11L-mediated suppression of Aβ generation, while hXB51beta binds X11L and inhibits its interaction with APP but suppresses Aβ generation via an X11L-independent mechanism. Co-immunoprecipitation, Aβ production assays, isoform-specific expression constructs The Biochemical journal Medium 12780348
2004 X11L (APBA2/Mint2) facilitates JNK-mediated phosphorylation of APP at Thr668 and APLP2 at Thr736 in response to cellular stress, elevating phosphorylation levels. Other X11 family members (X11 and X11L2) did not share this activity. Cell-based phosphorylation assays under osmotic/stress conditions, immunoprecipitation, kinase identification The Journal of biological chemistry Medium 14970211
2006 X11L-deficient (knockout) mice show increased APP C-terminal fragments generated by β-secretase (but not α-secretase) cleavage in the hippocampus, and elevated Aβ levels in aged hippocampus, demonstrating that X11L suppresses amyloidogenic (but not non-amyloidogenic) APP processing in vivo. X11L knockout mouse model, biochemical quantification of APP CTFs and Aβ levels in brain tissue The Journal of biological chemistry High 17032642
2007 X11L (APBA2) and X11L2 shuttle between the cytoplasm and nucleus; nuclear export is CRM1-dependent (blocked by leptomycin B). FLIP analysis confirmed nucleo-cytoplasmic shuttling. A nuclear export signal (NES) was identified in the N-terminus of X11L2; mutation of this NES caused nuclear accumulation. EGFP-fusion localization, leptomycin B treatment, FLIP (fluorescence loss in photobleaching), NES mutagenesis Experimental cell research Medium 18201694
2009 Phosphorylation of X11L at Ser236 and Ser238 within the amino-terminal regulatory region (aa 221–250) enhances its interaction with APP under osmotic stress. Alanyl substitution of either serine abolished the stress-enhanced APP association, indicating that this phosphorylation event, outside the PTB domain, modulates APP binding. Site-directed mutagenesis (Ser→Ala), co-immunoprecipitation under osmotic stress, phosphorylation site identification by mass spectrometry/mutagenesis Journal of neurochemistry Medium 19222704
2009 Mint2 interacts with TrkA through its PTB domain in a phosphorylation- and ligand-independent manner. Endogenous Mint2–TrkA interaction was confirmed in rat tissue. Mint2 overexpression inhibited NGF-induced neurite outgrowth in PC12 cells and DRG neurons; Mint2 knockdown facilitated it. Mechanistically, Mint2 promotes TrkA retention in the Golgi, inhibiting surface sorting. Yeast two-hybrid screening, co-immunoprecipitation from rat tissue, immunohistochemistry colocalization, overexpression and siRNA knockdown in PC12 and DRG neurons, Golgi retention assay The Journal of biological chemistry High 19265194
2012 Crystal structures of APP peptide-free (2.7 Å) and APP peptide-bound (3.3 Å) Mint2 C-terminal mutants revealed that the ARM domain blocks the PTB domain peptide-binding groove in the closed (unbound) state and swings away in the open (APP-bound) state. Mutants locking Mint2 in open or closed conformations dynamically regulated APP metabolism in vitro and in vivo. X-ray crystallography, structure-guided mutagenesis, in vitro APP metabolism assays, in vivo mouse model Journal of molecular cell biology High 22730553
2012 Src-mediated phosphorylation of Mint2 regulates APP endocytic sorting: a phosphomimetic Mint2 mutant directed internalized APP toward the autophagic pathway and increased intracellular Aβ accumulation, while the phospho-resistant mutant increased APP recycling to the cell surface and enhanced Aβ42 secretion. APP endocytosis was attenuated in Mint knockout neurons. Mint knockout neurons (endocytosis assay), phosphomimetic/phospho-resistant Mint2 mutants, intracellular trafficking pathway analysis, Aβ measurement The Journal of neuroscience High 22787047
2018 Systematic characterization of the Mint2 protein-protein interaction network showed that APP and presenilin-1 are bona fide Mint2 interaction partners with defined domain specificities. The last two C-terminal amino acids of Mint2 are required for the intramolecular PDZ1 interaction and for Mint2 stability. Peptide binding assays, domain-specific interaction mapping, truncation/deletion analysis Chembiochem Medium 29578633
2019 The autism-linked Mint2 N723S mutation (in PDZ2 domain) impairs Nrxn1α stabilization and trafficking to the membrane without affecting direct Nrxn1α binding. The mutant caused more immobile Mint2 puncta in neuronal processes, reduced Nrxn1α at presynaptic terminals, decreased Nrxn-mediated synaptogenesis, and reduced miniature excitatory event frequency. Mutation of conserved PDZ2 residue, time-lapse imaging in primary mouse neurons, surface biotinylation/trafficking assays, synaptogenesis assay, electrophysiology (mEPSC recording) Scientific reports High 30988517
2021 Disruption of the APP–Mint2 protein-protein interaction, either by an APP-binding-deficient Mint2 variant or by a cell-permeable peptide inhibitor targeting the Mint2 PTB domain, significantly reduced Aβ42 levels in a neuronal in vitro AD model, demonstrating that Mint2 plays a facilitative role in Aβ formation. APP-binding-deficient Mint2 mutant, cell-permeable PPI inhibitor peptide, Aβ42 ELISA in neuronal AD model cells Journal of the American Chemical Society Medium 33398998
2007 Mint proteins (Mint1 and Mint2) are cleaved by calpain upon neurodegeneration induced by okadaic acid (a PP2A inhibitor) in neurons, and their reduction is followed by an increase in APP levels. Calpain inhibitors prevented Mint cleavage and APP overexpression. Okadaic acid neuronal degeneration model, western blot for Mint1/2 and APP, calpain inhibitor treatment Neuroreport Low 18007179

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 Comparative genome hybridization suggests a role for NRXN1 and APBA2 in schizophrenia. Human molecular genetics 303 17989066
1999 Mint2/X11-like colocalizes with the Alzheimer's disease amyloid precursor protein and is associated with neuritic plaques in Alzheimer's disease. The European journal of neuroscience 77 10336668
2006 Enhanced amyloidogenic metabolism of the amyloid beta-protein precursor in the X11L-deficient mouse brain. The Journal of biological chemistry 49 17032642
2004 Facilitation of stress-induced phosphorylation of beta-amyloid precursor protein family members by X11-like/Mint2 protein. The Journal of biological chemistry 43 14970211
2000 Regulation of X11L-dependent amyloid precursor protein metabolism by XB51, a novel X11L-binding protein. The Journal of biological chemistry 37 10833507
2012 Intracellular amyloid precursor protein sorting and amyloid-β secretion are regulated by Src-mediated phosphorylation of Mint2. The Journal of neuroscience : the official journal of the Society for Neuroscience 36 22787047
2009 Copy number and sequence variants implicate APBA2 as an autism candidate gene. Autism research : official journal of the International Society for Autism Research 31 20029827
2001 Neuronal expression of mint1 and mint2, novel multimodular proteins, in adult murine brain. Brain research. Molecular brain research 25 11483239
2003 Partial duplication of the APBA2 gene in chromosome 15q13 corresponds to duplicon structures. BMC genomics 21 12720574
2009 Interaction of Mint2 with TrkA is involved in regulation of nerve growth factor-induced neurite outgrowth. The Journal of biological chemistry 20 19265194
2003 XB51 isoforms mediate Alzheimer's beta-amyloid peptide production by X11L (X11-like protein)-dependent and -independent mechanisms. The Biochemical journal 20 12780348
2021 Targeting the APP-Mint2 Protein-Protein Interaction with a Peptide-Based Inhibitor Reduces Amyloid-β Formation. Journal of the American Chemical Society 17 33398998
2021 Progressive alteration of DNA methylation of Alu, MGMT, MINT2, and TFPI2 genes in colonic mucosa during colorectal cancer development. Cancer biomarkers : section A of Disease markers 14 34092617
2012 Open-closed motion of Mint2 regulates APP metabolism. Journal of molecular cell biology 14 22730553
2007 The X11L/X11beta/MINT2 and X11L2/X11gamma/MINT3 scaffold proteins shuttle between the nucleus and cytoplasm. Experimental cell research 14 18201694
2009 Phosphorylation of the amino-terminal region of X11L regulates its interaction with APP. Journal of neurochemistry 13 19222704
2023 Comprehensive Peptide Cyclization Examination Yields Optimized APP Scaffolds with Improved Affinity toward Mint2. Journal of medicinal chemistry 10 36749163
2019 A rare autism-associated MINT2/APBA2 mutation disrupts neurexin trafficking and synaptic function. Scientific reports 10 30988517
2018 Probing the Mint2 Protein-Protein Interaction Network Relevant to the Pathophysiology of Alzheimer's Disease. Chembiochem : a European journal of chemical biology 7 29578633
2012 Promoter characterization and genomic organization of the human X11β gene APBA2. Neuroreport 7 22222501
2007 Reduction of mint-1, mint-2, and APP overexpression in okadaic acid-treated neurons. Neuroreport 5 18007179
2024 Molecular dynamics simulations to explore the binding mode between the amyloid-β protein precursor (APP) and adaptor protein Mint2. Scientific reports 4 38575686
2010 Expression and ultrastructural localization of Mint2 in the spinal cord of rats. Molecular biology reports 2 20369384
2014 Increased transcriptome sequencing efficiency with modified Mint-2 digestion-ligation protocol. Analytical biochemistry 1 25513723

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