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BIN1 (Bridging Integrator 1), also known as Myc box-dependent-interacting protein 1 and Amphiphysin 2, is a ubiquitously expressed membrane-remodeling protein encoded by a single gene located on human chromosome 2q14 (spooner2025benditlike pages 1-2, spooner2025benditlike pages 2-4, saha2025acomprehensivereview pages 1-2). The protein was originally discovered in 1996 through a yeast two-hybrid screen designed to identify proteins interacting with the Myc oncoprotein, with the hypothesis that such interactors might function as tumor suppressors (spooner2025benditlike pages 1-2, spooner2025benditlike pages 2-4). Subsequently, the protein was independently identified through screens targeting SH3 domain-containing proteins and through sequence homology with amphiphysin 1, establishing its classification within the amphiphysin subfamily with which it shares 55% amino acid identity and 71% similarity (spooner2025benditlike pages 1-2, spooner2025benditlike pages 2-4).
The human BIN1 gene comprises 20 exons that undergo extensive alternative splicing to generate tissue-specific isoforms with distinct functional properties (spooner2025benditlike pages 1-2, spooner2025benditlike pages 2-4). The protein contains several functionally specialized domains arranged from N- to C-terminus, each contributing to BIN1's diverse cellular roles.
| Domain name | Exons encoding | Structural features | Primary molecular function | Key binding partners/substrates | Regulatory mechanisms |
|---|---|---|---|---|---|
| BAR domain | Exons 1–10 | N-terminal N-BAR; coiled-coil of three α-helices; positively charged concave membrane-binding surface; N-terminal amphipathic helix-0 inserts into bilayer; forms banana-shaped symmetric homodimers that can generate vesicles/tubules of ~220 Å radius (spooner2025benditlike pages 2-4, spooner2025benditlike pages 4-6) | Senses and generates membrane curvature; drives membrane tubulation/remodeling; anchors cytoskeletal delivery tracks at curved membranes; foundational structural scaffold for t-tubules, endocytic membranes, and other membrane microdomains (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 4-6, spooner2025benditlike pages 9-11) | Acidic phospholipids including PI(4,5)P2 and other phosphoinositides; CLIP-170; indirectly coordinates DNM2 recruitment through overall BIN1 architecture; membrane tubules associated with CaV1.2 delivery platforms (spooner2025benditlike pages 4-6, spooner2025benditlike pages 9-11, spooner2025benditlike pages 11-12) | Membrane binding is highly sensitive to lipid composition, especially PI(4,5)P2 and cholesterol; Lys164/Lys165/Lys166 in the BAR region are important for phospholipid anchoring; exon 7 within the BAR region modulates targeting specificity and may affect dynamin interaction (spooner2025benditlike pages 4-6, spooner2025benditlike pages 9-11) |
| PI-binding domain | Exon 11 | Phosphoinositide-binding segment adjacent to BAR domain; present in selected muscle-enriched and some cardiac/neuronal isoforms; can contact the SH3 domain to form a closed conformation (spooner2025benditlike pages 2-4, spooner2025benditlike pages 4-6) | Enhances membrane targeting specificity for PI(4,5)P2-rich membranes; augments curvature sensing/generation; helps localize active BIN1 to tubulating membrane domains such as T-tubules (spooner2025benditlike pages 4-6) | PI(4,5)P2; intramolecular interaction with SH3 domain; MTM1/myotubularin binding depends strongly on PI-domain-containing configurations in skeletal-muscle contexts (spooner2025benditlike pages 4-6, spooner2025benditlike pages 11-12) | Mediates autoinhibition by binding SH3; PI(4,5)P2 binding releases the closed state and activates membrane-sculpting function; SH3 engagement by proline-rich partners can also relieve autoinhibition (spooner2025benditlike pages 4-6, spooner2025benditlike pages 11-12) |
| PS linker domain | Exon 12 | Proline/serine-rich linker region positioned between membrane- and interaction-focused regions; no definitive folded structure or discrete biochemical activity established in the cited review (spooner2025benditlike pages 2-4) | Likely contributes to conformational flexibility, spacing, and/or structural integrity between domains rather than acting as a standalone catalytic or binding module (spooner2025benditlike pages 2-4) | No major dedicated binding partner definitively assigned in the cited sources (spooner2025benditlike pages 2-4) | Consistently retained across isoforms, suggesting selective pressure for structural or organizational importance even though its mechanistic role remains unresolved (spooner2025benditlike pages 2-4) |
| CLAP domain | Exons 13–16 | Clathrin and adaptor protein 2-binding region; exon 13 also contains an SH3-binding motif for endophilin; exons 14–15 harbor two clathrin-binding sites; variably included by alternative splicing, especially in neuronal isoforms and some cardiac isoforms containing exon 13 (spooner2025benditlike pages 2-4, spooner2025benditlike pages 6-7) | Organizes endocytic machinery; promotes clathrin-coated pit/vesicle formation, membrane trafficking, and vesicle biogenesis at plasma membrane and trans-Golgi/endosomal compartments (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14) | Clathrin, AP2, endophilin; contributes to pathways involving dynamin, synaptojanin, amphiphysin-related endocytic machinery (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14) | Exon 13 can interact intramolecularly with SH3 to impose an autoinhibited closed conformation; partner binding to CLAP or SH3 can shift BIN1 toward an open active state; extensive alternative splicing tunes tissue specificity (spooner2025benditlike pages 6-7) |
| Myc-binding domain (MBD) | Exons 17–18 | C-terminal region preceding SH3; exon 18 is constitutive while exon 17 is alternatively spliced and required for full Myc-binding activity; associated with nuclear-localized isoforms (spooner2025benditlike pages 6-7) | Mediates interaction with c-Myc/N-Myc; suppresses Myc-driven transformation; promotes Myc-dependent apoptosis and contributes to tumor-suppressor functions; implicated in nuclear regulatory roles (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14) | c-Myc, N-Myc; reported links to PARP1, Ku, XRCC4, and ABL1 in BIN1-associated nuclear/DNA damage regulatory functions (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14) | Functional output depends on alternative splicing of exon 17; Myc can reciprocally repress BIN1 transcription via MIZ1, creating a feedback circuit; some evidence suggests possible intramolecular MBD-SH3 interaction (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9) |
| SH3 domain | Exons 19–20 | Conserved C-terminal Src homology 3 domain; β-barrel of 5–6 antiparallel β-strands; surface enriched in aromatic and acidic residues for proline-rich motif recognition; retained in all functional isoforms (spooner2025benditlike pages 2-4, spooner2025benditlike pages 7-9) | Principal protein-protein interaction hub; recruits fission/scaffold/signaling proteins to curved membranes; central to endocytosis, T-tubule biology, actin remodeling, directed trafficking, and disease-linked interaction networks (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 7-9) | DNM2/dynamin-2; synaptojanin; tau via Tau 216PTPP219 region; N-WASP; ABL1; MTM1; many additional partners from interactome studies (zambo2024uncoveringthebin1sh3 pages 1-2, lasorsa2023conformationandaffinity pages 1-5, spooner2025benditlike pages 7-9) | Binds proline-rich motifs; can be sequestered intramolecularly by PI or CLAP domains in autoinhibited states; release occurs upon PI(4,5)P2 engagement or partner binding; pathogenic SH3 truncation/variant states disrupt affinity networks and DNM2 recruitment (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 4-6, lasorsa2023conformationandaffinity pages 1-5) |
Table: This table summarizes the major BIN1 protein domains, the exons that encode them, their structural properties, molecular functions, binding partners, and known regulatory mechanisms. It is useful for linking BIN1 isoform architecture to its membrane-remodeling, endocytic, nuclear, and disease-relevant functions.
The N-terminal BAR (Bin/Amphiphysin/Rvs) domain (exons 1-10) constitutes the fundamental membrane-binding module of BIN1 (spooner2025benditlike pages 2-4, spooner2025benditlike pages 4-6). Structurally, the BAR domain adopts a coiled-coil architecture composed of three α-helices that pack tightly together following a characteristic knob-socket pattern of nonpolar residue interactions (spooner2025benditlike pages 4-6). This domain forms symmetrical banana-shaped homodimers with a positively charged concave surface that engages negatively charged phospholipid headgroups through electrostatic interactions (spooner2025benditlike pages 2-4, spooner2025benditlike pages 4-6). The N-terminal region contains a disordered segment that forms an amphipathic helix (helix-0) upon insertion into the lipid bilayer, enhancing membrane curvature generation (spooner2025benditlike pages 4-6). These BAR domain dimers can generate vesicular and tubular structures with an approximate radius of 220 Å, though varying dimer arrangements along membrane surfaces produce structures of diverse dimensions (spooner2025benditlike pages 4-6).
Adjacent to the BAR domain, exon 11 encodes a phosphoinositide (PI)-binding domain present in muscle-enriched and select cardiac/neuronal isoforms (spooner2025benditlike pages 2-4, spooner2025benditlike pages 4-6). This domain specifically recognizes phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2], significantly augmenting membrane interaction specificity and curvature generation (spooner2025benditlike pages 4-6). The PI domain participates in an autoinhibitory regulatory mechanism whereby it can bind intramolecularly to the C-terminal SH3 domain, shifting BIN1 into a closed, conformationally restrained state in which membrane curvature induction is substantially inhibited (spooner2025benditlike pages 4-6, spooner2025benditlike pages 11-12). Membrane-embedded PI(4,5)P2 triggers a conformational switch by engaging the PI domain with higher affinity than the SH3 domain, promoting adoption of an open, active conformation that spatially restricts BIN1's scaffolding activities to PI(4,5)P2-enriched membrane microdomains (spooner2025benditlike pages 4-6, spooner2025benditlike pages 11-12).
Exon 12 contains a proline- and serine-rich linker region (PS domain) consistently retained across all isoforms, suggesting importance for proper protein folding and structural integrity, though its precise functional role remains to be fully elucidated (spooner2025benditlike pages 2-4).
The CLAP (Clathrin and Adaptor Protein 2 binding) domain (exons 13-16) exhibits pronounced variability across isoforms through alternative splicing (spooner2025benditlike pages 2-4, spooner2025benditlike pages 6-7). Exon 13 contains an SH3-binding motif for endophilin interaction, while exons 14-15 harbor two distinct clathrin-binding sites (spooner2025benditlike pages 6-7). This domain orchestrates endocytic processes through recruitment and assembly of protein complexes within clathrin-coated pits, facilitating both plasma membrane endocytosis and vesicle biogenesis at the trans-Golgi network (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14). Similar to the PI domain, exon 13 can interact intramolecularly with the SH3 domain to impose an autoinhibited closed conformation, with partner binding to either CLAP or SH3 shifting BIN1 toward an open active state (spooner2025benditlike pages 6-7).
The Myc-binding domain (MBD, exons 17-18) mediates BIN1's tumor suppressor functions through direct interaction with c-Myc and N-Myc transcription factors (spooner2025benditlike pages 2-4, spooner2025benditlike pages 6-7). While exon 18 is consistently retained, exon 17 displays selective inclusion and is critically required for Myc-binding functionality (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9). Nuclear-localized BIN1 isoforms containing this domain bind the N-terminal regulatory domain of Myc, inhibiting Myc-mediated transcriptional activity and neoplastic transformation while promoting Myc-dependent apoptosis (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9).
The C-terminal SH3 (Src Homology 3) domain (exons 19-20) serves as BIN1's primary molecular interface for protein-protein interactions (spooner2025benditlike pages 2-4, spooner2025benditlike pages 7-9). This domain adopts a characteristic β-barrel configuration composed of five to six anti-parallel β-strands, with a surface enriched in aromatic and carboxylic acid residues that recognize and bind proline-rich motifs in partner proteins (spooner2025benditlike pages 7-9). The SH3 domain is invariably retained across all functional BIN1 isoforms, and mutations within this region are causally linked to centronuclear myopathy, underscoring its physiological significance (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 7-9).
BIN1's fundamental molecular function centers on sensing and generating membrane curvature, a property that underpins its diverse cellular roles (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 4-6). The BAR domain constitutes the primary determinant of this membrane-sculpting capacity, engaging membranes through electrostatic interactions and mechanically deforming lipid bilayers into highly curved tubular and vesicular structures (spooner2025benditlike pages 2-4, spooner2025benditlike pages 4-6). This membrane remodeling activity is exquisitely sensitive to lipid composition, particularly requiring PI(4,5)P2 for optimal tubulation, with activity increasing to a plateau at approximately 3% PI(4,5)P2 concentration (spooner2025benditlike pages 4-6). Additionally, membrane cholesterol content is critical for supporting the high degree of curvature found within tubules (spooner2025benditlike pages 4-6).
Specific lysine residues (Lys164, Lys165, Lys166) located within the BAR domain have been identified as critical for anchoring BIN1 to negatively charged membrane phospholipids (spooner2025benditlike pages 9-11). When these lysines are mutated to negatively charged amino acids in experimental systems, BIN1 redistributes from membrane-associated structures to a diffuse cytosolic pattern with complete loss of membrane tubulation capability (spooner2025benditlike pages 9-11).
The membrane curvature-generating function is further modulated by the PI domain in isoforms where it is present. PI(4,5)P2 binding by this domain not only enhances membrane targeting specificity but also regulates BIN1's conformational state through the autoinhibitory mechanism described above, ensuring that active membrane sculpting is spatially restricted to appropriate cellular locations (spooner2025benditlike pages 4-6, spooner2025benditlike pages 11-12).
Beyond its direct membrane-remodeling activities, BIN1 functions as a versatile molecular scaffold that organizes multi-protein complexes at curved membranes (spooner2025benditlike pages 2-4, spooner2025benditlike pages 7-9). The SH3 domain mediates the majority of BIN1's documented protein-protein interactions, engaging numerous partners spanning diverse cellular functions (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 7-9). This scaffolding capacity enables BIN1 to couple membrane remodeling with recruitment of enzymatic activities, structural proteins, and signaling molecules required for specialized cellular processes.
| Protein partner | Domain of BIN1 involved in interaction | Cellular pathway/process | Functional consequence of interaction | Tissue/cell type specificity |
|---|---|---|---|---|
| Dynamin-2 (DNM2) | Primarily SH3 domain; BAR domain functionally cooperates by generating curved membranes | Clathrin-mediated endocytosis, vesicle scission, T-tubule biogenesis | BIN1 recruits DNM2 to curved membranes; this supports vesicle scission in endocytosis and contributes to T-tubule formation/remodeling. Loss of SH3-mediated recruitment is central to BIN1-related centronuclear myopathy (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 7-9) | Broadly relevant; especially skeletal muscle and cardiac muscle, also endocytic membranes in other cells (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 12-14) |
| Tau (MAPT) | SH3 domain binds Tau proline-rich motif | Alzheimer-related tau biology, tau aggregation/propagation | Direct BIN1-Tau binding is modulated by Tau phosphorylation; BIN1 cleavage fragment BIN1(1-277) can bind Tau and accelerate aggregation while enhancing clathrin-mediated endocytosis-dependent propagation (lasorsa2023conformationandaffinity pages 1-5, zhang2024bridgingintegrator1 pages 1-2) | Neurons/brain; especially relevant to Alzheimer’s disease (zhang2024bridgingintegrator1 pages 1-2, saha2025acomprehensivereview pages 1-2) |
| c-Myc / N-Myc | Myc-binding domain (MBD; exons 17-18) | Nuclear signaling, cell-cycle control, tumor suppression, apoptosis | BIN1 binds Myc and suppresses Myc-driven transcriptional and transforming activity; supports Myc-dependent apoptosis and broader tumor suppressor functions (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14) | Nuclear isoforms in proliferative contexts; cancer-relevant tissues, and some cardiac/brain cell contexts with nuclear BIN1 isoforms (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9) |
| Clathrin | CLAP domain (especially exons 14-15); neuronal isoforms may be particularly relevant | Clathrin-mediated endocytosis, vesicle biogenesis | BIN1 helps assemble clathrin-coated pits/vesicles and participates in membrane budding and trafficking from plasma membrane, Golgi, and endosomes (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14) | Strongly established in neuronal/brain isoforms; likely also relevant in other tissues with CLAP-containing isoforms (spooner2025benditlike pages 2-4, spooner2025benditlike pages 12-14) |
| AP2 (Adaptor protein 2) | CLAP domain, especially exon 13 | Clathrin-mediated endocytosis and membrane trafficking | BIN1 association with AP2 helps coordinate endocytic complex assembly and cargo internalization at the plasma membrane (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14) | Best established in neuronal/endocytic contexts; potentially relevant in cardiac isoforms containing exon 13 (spooner2025benditlike pages 6-7) |
| N-WASP | SH3 domain | Actin remodeling, membrane-cytoskeleton coupling, directed trafficking | BIN1-N-WASP interaction promotes ARP2/3-mediated actin polymerization and helps anchor actin to BIN1-associated membranes, supporting tubulation and membrane organization (spooner2025benditlike pages 7-9, spooner2025benditlike pages 9-11) | Neuronal and muscle contexts; implicated in t-tubule anchoring and membrane remodeling (spooner2025benditlike pages 9-11) |
| CaV1.2 (L-type calcium channel) | Not mapped to a single motif with the same precision as SH3 ligands; interaction/functionally linked to BAR-dependent membrane platforms and BIN1 scaffolding | Excitation-contraction coupling, targeted ion-channel trafficking | BIN1 colocalizes and co-immunoprecipitates with CaV1.2, promotes microtubule-dependent delivery to T-tubules, and supports channel clustering at dyads (spooner2025benditlike pages 9-11, spooner2025benditlike pages 12-14) | Cardiac myocytes; t-tubule sarcolemma (spooner2025benditlike pages 9-11, spooner2025benditlike pages 14-15) |
| RyR2 (ryanodine receptor 2) | Precise binding interface not yet clearly defined; likely scaffolded indirectly within BIN1-organized dyads | Excitation-contraction coupling, dyad organization | BIN1 supports RyR2 localization to dyads and proper junctional organization; BIN1 loss disrupts RyR2 positioning and calcium release synchrony (spooner2025benditlike pages 9-11, spooner2025benditlike pages 12-14) | Cardiac myocytes (spooner2025benditlike pages 9-11, spooner2025benditlike pages 14-15) |
| CLIP-170 | BAR domain | Microtubule anchoring, directed trafficking, membrane remodeling | BIN1-BAR interaction with CLIP-170 anchors microtubules to membrane tubules, enabling targeted delivery of cargo such as CaV1.2 to T-tubules (spooner2025benditlike pages 4-6, spooner2025benditlike pages 9-11) | Cardiac myocytes and cultured cells; likely broader relevance in membrane-directed trafficking (spooner2025benditlike pages 9-11, spooner2025benditlike pages 12-14) |
| MTM1 (myotubularin 1) | BAR and SH3 domains; interaction strongly influenced by PI domain-dependent conformation | Phosphoinositide-regulated membrane remodeling, T-tubule growth | MTM1 cooperates with BIN1 to promote elongated tubules in muscle; interaction is favored when BIN1 adopts an open conformation and links phosphoinositide homeostasis to membrane tubulation (spooner2025benditlike pages 11-12) | Strongly established in skeletal muscle; direct interaction less clear for exon 11-lacking cardiac isoforms, though MTM1 still influences cardiac t-tubule growth (spooner2025benditlike pages 11-12) |
| RIN2 | Specific BIN1 interaction interface not yet fully resolved in cited source | Early endosome targeting, Rab5-associated endosomal trafficking | RIN2 recruits BIN1 to RAB5-positive early endosomes, identifying a neuron-specific endosomal localization mechanism linked to Alzheimer-relevant trafficking pathways (wei2026interactomemappingin pages 1-3) | Human excitatory neurons / neuron-specific interactome context (wei2026interactomemappingin pages 1-3) |
Table: This table summarizes major BIN1 protein interaction partners, the BIN1 domains involved, and the pathways they influence. It is useful for connecting BIN1’s membrane-remodeling scaffold function to tissue-specific roles in endocytosis, muscle excitation-contraction coupling, and Alzheimer’s disease biology.
A prototypical example is BIN1's role in coordinating membrane fission during endocytosis. The BAR domain generates initial membrane curvature while the SH3 domain recruits dynamin-2 (DNM2), a GTPase whose oligomerization and enzymatic activity drive vesicle scission (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 7-9, spooner2025benditlike pages 12-14). This spatial and temporal coupling of curvature generation and membrane fission is essential for efficient endocytic vesicle formation (zambo2024uncoveringthebin1sh3 pages 1-2).
Similarly, in striated muscle, BIN1 organizes elaborate protein complexes at specialized membrane microdomains. The BAR domain binds the microtubule-associated protein CLIP-170, anchoring microtubule plus-ends to membrane tubules and enabling targeted delivery of cargo proteins such as CaV1.2 calcium channels to transverse tubules (t-tubules) (spooner2025benditlike pages 4-6, spooner2025benditlike pages 9-11, spooner2025benditlike pages 12-14). Simultaneously, the SH3 domain engages N-WASP to promote actin polymerization, linking t-tubules to the sarcomeric cytoskeleton (spooner2025benditlike pages 7-9, spooner2025benditlike pages 9-11).
BIN1's cellular distribution is highly context-dependent, reflecting both isoform-specific properties and the dynamic membrane-remodeling processes in which it participates (spooner2025benditlike pages 1-2, spooner2025benditlike pages 2-4).
In striated muscle cells (both cardiac and skeletal), BIN1 exhibits specific localization to t-tubules, which are sarcolemmal invaginations that penetrate deep into the myocyte interior (spooner2025benditlike pages 1-2, spooner2025benditlike pages 7-9, spooner2025benditlike pages 9-11). These structures are essential for rapid propagation of action potentials throughout the cell volume and proper excitation-contraction coupling (spooner2025benditlike pages 7-9, spooner2025benditlike pages 9-11). BIN1 colocalizes at t-tubules with voltage-gated CaV1.2 calcium channels and is positioned adjacent to type 2 ryanodine receptors (RyR2) on the junctional sarcoplasmic reticulum, forming dyadic junctions where calcium influx through CaV1.2 triggers calcium release from RyR2 (spooner2025benditlike pages 7-9, spooner2025benditlike pages 9-11).
In neurons, BIN1 localizes to nerve terminals and synaptic regions where it participates in synaptic vesicle endocytosis and neurotransmitter receptor trafficking (spooner2025benditlike pages 7-9, spooner2025benditlike pages 12-14).
BIN1 is found associated with various endosomal compartments throughout the endocytic pathway (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14). At clathrin-coated pits, CLAP domain-containing isoforms organize endocytic machinery and coordinate vesicle formation (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14). Recent neuron-specific interactome studies identified RIN2 as a BIN1 binding partner that recruits BIN1 to RAB5-positive early endosomes, revealing neuron-specific endosomal targeting mechanisms linked to Alzheimer-relevant trafficking pathways (wei2026interactomemappingin pages 1-3).
Changes in BIN1 expression levels have been shown to alter endosomal morphology and trafficking dynamics, with BIN1 modulation associated with enlarged endosomes and altered protein trafficking patterns—early hallmarks of Alzheimer's disease that also occur in aging hearts (spooner2025benditlike pages 12-14).
In certain cellular contexts, particularly in proliferative cells and specific isoforms containing the full Myc-binding domain, BIN1 exhibits nuclear localization (spooner2025benditlike pages 1-2, spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9). Nuclear BIN1 directly interacts with and regulates transcription factors, most notably c-Myc, executing tumor suppressor functions through transcriptional repression and promotion of apoptosis in cells with DNA damage (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9, spooner2025benditlike pages 12-14).
BIN1 plays a central coordinating role in clathrin-mediated endocytosis (CME), the predominant pathway for internalization of plasma membrane receptors and extracellular material (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14). Through its CLAP domain, BIN1 recruits and organizes core endocytic machinery including clathrin, adaptor protein 2 (AP2), and accessory proteins such as endophilin (spooner2025benditlike pages 6-7, spooner2025benditlike pages 12-14). The BAR domain generates membrane curvature at nascent endocytic pits, while the SH3 domain recruits dynamin-2 to execute membrane fission and vesicle release (zambo2024uncoveringthebin1sh3 pages 1-2, spooner2025benditlike pages 12-14).
This endocytic function extends beyond constitutive cargo internalization to include specialized roles in synaptic vesicle recycling at neuronal terminals, receptor downregulation, and pathological processes such as tau aggregate uptake in Alzheimer's disease (zhang2024bridgingintegrator1 pages 1-2, spooner2025benditlike pages 12-14). Notably, isoforms containing the CLAP domain have been found to exert direct negative regulatory effects on endocytic flux, with BIN1 expression changes associated with "endosomal traffic jams" featuring enlarged endosomes and altered protein trafficking (spooner2025benditlike pages 12-14).
In cardiac and skeletal muscle, BIN1 functions as an essential architect of the t-tubule system and dyadic junctions that mediate excitation-contraction coupling (spooner2025benditlike pages 7-9, spooner2025benditlike pages 9-11). BIN1's membrane-sculpting capacity drives t-tubule biogenesis, generating the tubular sarcolemmal invaginations that allow electrical signals to rapidly reach the cell interior (spooner2025benditlike pages 7-9, spooner2025benditlike pages 9-11).
Beyond structural roles, BIN1 coordinates the spatial organization and targeted delivery of key calcium-handling proteins (spooner2025benditlike pages 9-11, spooner2025benditlike pages 12-14). Through interaction with CLIP-170, BIN1 anchors microtubules to t-tubule membranes, establishing tracks for directed trafficking of CaV1.2 channels to specific t-tubule locations (spooner2025benditlike pages 9-11, spooner2025benditlike pages 12-14). This directed delivery results in clusters of CaV1.2 channels around delivery points that can cooperate through local gating interactions, amplifying calcium influx signals (spooner2025benditlike pages 12-14). BIN1 also supports RyR2 localization to dyads and proper junctional organization between t-tubules and sarcoplasmic reticulum, with BIN1 loss disrupting RyR2 positioning and calcium release synchrony (spooner2025benditlike pages 9-11, spooner2025benditlike pages 12-14).
The phosphoinositide phosphatase myotubularin 1 (MTM1) cooperates with BIN1 in regulating t-tubule development (spooner2025benditlike pages 11-12). MTM1 promotes PI(4,5)P2 formation by metabolizing PI(3)P and PI(3,5)P2, and its interaction with BIN1 is critical for producing elongated, reticulated tubular networks in muscle cells (spooner2025benditlike pages 11-12). This partnership links phosphoinositide homeostasis to membrane tubulation, with MTM1's catalytic activity required for BIN1-dependent t-tubule growth (spooner2025benditlike pages 11-12).
BIN1 was originally identified as a tumor suppressor that binds to and inhibits the Myc oncoprotein (spooner2025benditlike pages 1-2, spooner2025benditlike pages 6-7). Nuclear-localized BIN1 isoforms containing exons 17-18 interact with the N-terminal regulatory domain of c-Myc and N-Myc, suppressing their transcriptional activity and inhibiting neoplastic transformation (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9). Concurrently, BIN1 promotes Myc-dependent apoptosis, contributing to elimination of cells with DNA damage that pose cancer risk (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9).
This relationship involves a reciprocal regulatory circuit wherein Myc can repress BIN1 expression by blocking its transcriptional activation by MIZ1 (MYC interacting zinc finger transcription factor 1), establishing a homeostatic balance where perturbation of either component disrupts expression profiles and downstream signaling cascades (spooner2025benditlike pages 7-9). BIN1 also interacts with DNA repair proteins including PARP1, Ku, and XRCC4, inhibiting DNA repair after sufficient damage to ensure that damaged cells undergo apoptosis rather than persist with genomic instability (spooner2025benditlike pages 12-14).
BIN1 has emerged as the second most significant genetic risk factor for late-onset Alzheimer's disease after APOE (saha2025acomprehensivereview pages 1-2, hu2025newinsightson pages 1-6, zhang2024bridgingintegrator1 pages 1-2). The protein directly interacts with tau via SH3 domain binding to tau's proline-rich region (specifically the 216PTPP219 motif), and this interaction is modulated by tau phosphorylation (lasorsa2023conformationandaffinity pages 1-5).
Recent mechanistic studies have revealed that neuronal BIN1 is cleaved by the cysteine protease legumain at residues N277 and N288, generating a BIN1(1-277) fragment detectable in brain tissues from Alzheimer's disease patients (zhang2024bridgingintegrator1 pages 1-2). This fragment retains the ability to interact with tau and accelerates tau aggregation (zhang2024bridgingintegrator1 pages 1-2). Furthermore, the BIN1(1-277) fragment promotes propagation of tau aggregates by enhancing clathrin-mediated endocytosis, facilitating uptake and transcellular spread of pathological tau (zhang2024bridgingintegrator1 pages 1-2). Experimental overexpression of this fragment in tau transgenic mice facilitates tau pathology propagation and induces cognitive deficits, while blocking endogenous BIN1 cleavage ameliorates tau pathology and behavioral deficits (zhang2024bridgingintegrator1 pages 1-2).
Beyond this pathological cleavage, BIN1 participates in normal endosomal trafficking processes relevant to Alzheimer's pathogenesis (saha2025acomprehensivereview pages 1-2, wei2026interactomemappingin pages 1-3). BIN1 controls membrane curvature and participates in clathrin-dependent endocytosis, with changes in BIN1 expression levels impairing endocytic flux likely due to problems with vesicle scission and trafficking (saha2025acomprehensivereview pages 1-2). The recent identification of RIN2 as a neuron-specific BIN1 interactor that recruits BIN1 to RAB5-positive early endosomes suggests additional mechanisms whereby BIN1 modulates endosomal processes linked to Alzheimer's disease etiology (wei2026interactomemappingin pages 1-3).
The extensive alternative splicing of BIN1's 20 exons generates tissue-specific isoforms with distinct functional properties and cellular distributions (spooner2025benditlike pages 1-2, spooner2025benditlike pages 2-4, hu2025newinsightson pages 1-6). In the brain, neuronal isoforms (containing exons 13-16 encoding the full CLAP domain) and glial isoforms (lacking these exons) are differentially expressed and implicated in distinct aspects of Alzheimer's pathology (saha2025acomprehensivereview pages 1-2, hu2025newinsightson pages 1-6). In Alzheimer's disease, there is a significant shift in isoform expression characterized by upregulation of shorter glial-specific isoforms and downregulation of longer neuronal isoforms, with this isoform imbalance interfering with neuronal function and contributing to disease pathogenesis (saha2025acomprehensivereview pages 1-2, hu2025newinsightson pages 1-6).
In cardiac tissue, isoform patterns differ across mammalian species but generally include ubiquitous isoforms (9, 10) and muscle-enriched isoforms, with some species expressing PI domain-containing isoforms (4, 8, 13) that confer enhanced curvature generation and conformational regulation (spooner2025benditlike pages 1-2, spooner2025benditlike pages 2-4). Cardiac-specific isoform 6 (BIN1+13+17) has been shown to uniquely restore t-tubule microfolding in BIN1-deficient cardiomyocytes, highlighting isoform-specific functional specialization even among closely related variants (spooner2025benditlike pages 9-11).
Mutations and altered expression of BIN1 are causally linked to multiple human diseases (zambo2024uncoveringthebin1sh3 pages 1-2, saha2025acomprehensivereview pages 1-2, zhang2024bridgingintegrator1 pages 1-2). Autosomal recessive centronuclear myopathy results from BIN1 mutations in the BAR domain that prevent membrane-remodeling function, or from truncations of the SH3 domain that eliminate DNM2 recruitment while preserving membrane tubulation capacity (zambo2024uncoveringthebin1sh3 pages 1-2). Reduced BIN1 expression characterizes human heart failure, where decreased levels correlate with CaV1.2 mislocalization, RyR2 dysfunction, t-tubule disruption, and impaired calcium handling (spooner2025benditlike pages 12-14, spooner2025benditlike pages 14-15). In Alzheimer's disease, BIN1 genetic variants confer disease risk through effects on isoform expression and splicing patterns, while legumain-mediated BIN1 cleavage actively promotes tau pathology progression (saha2025acomprehensivereview pages 1-2, hu2025newinsightson pages 1-6, zhang2024bridgingintegrator1 pages 1-2). Loss of BIN1 expression is frequent in human malignancies, consistent with its tumor suppressor functions through Myc inhibition (spooner2025benditlike pages 6-7, spooner2025benditlike pages 7-9).
BIN1 functions as a versatile membrane-remodeling and scaffolding protein whose modular domain architecture enables integration of membrane curvature generation with recruitment of diverse protein partners to execute tissue-specific cellular programs. Through its BAR domain-mediated membrane sculpting, PI domain-regulated targeting, CLAP domain-organized endocytosis, Myc-binding domain nuclear functions, and SH3 domain protein interaction networks, BIN1 orchestrates critical processes ranging from t-tubule biogenesis in muscle to endocytic trafficking in neurons to tumor suppression in proliferative cells. The extensive alternative splicing that generates tissue-specific isoform repertoires provides an additional regulatory layer that tunes BIN1 function to particular cellular contexts. Dysregulation of BIN1 expression, splicing, or post-translational processing contributes to diverse human pathologies including centronuclear myopathy, heart failure, Alzheimer's disease, and cancer, highlighting the protein's essential physiological roles and therapeutic potential.
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