BIN1 (bridging integrator 1) is a membrane-remodeling protein that plays critical roles in multiple cellular processes relevant to neurodegeneration and muscle function. (a) Primary function: BIN1 regulates plasma membrane curvature and is essential for T-tubule formation in muscle cells, while also controlling endocytosis and intracellular vesicle sorting 1. In microglia, BIN1 serves as a key regulator of proinflammatory responses and neurodegeneration-related activation 2. (b) Mechanism: BIN1 functions through membrane dynamics regulation and exhibits actin bundling activity. Loss of BIN1 impairs microglial type 1 interferon responses and affects the expression of disease-associated genes, particularly Ifitm3 2. BIN1 also modulates BACE1 trafficking and amyloid-beta production 3. (c) Disease relevance: BIN1 represents the second-most significant genetic risk factor for late-onset Alzheimer's disease 2. Multiple genome-wide association studies have consistently identified BIN1 variants as AD risk factors 45. BIN1 polymorphisms show ethnic-specific associations with AD risk and correlate with tau pathology through sTREM2-mediated mechanisms 6. (d) Clinical significance: BIN1 mutations also cause centronuclear myopathy type 2, highlighting its importance in muscle function 7. The protein's dual roles in neuroinflammation and membrane dynamics make it a potential therapeutic target for neurodegenerative diseases.