RABEP1 (rabaptin, RAB GTPase binding effector protein 1) is a Rab effector protein that functions as a linker between gamma-adaptin and RAB4A/RAB5A, mediating endocytic membrane fusion and recycling endosome trafficking. RABEP1 forms complexes with RABGEF1 to stimulate nucleotide exchange on RAB5A and regulates the trafficking of ion channels like KCNH1 to the cell membrane. The protein operates through a conserved Rab4/Rab5 binding domain essential for its function 1. Mechanistically, RABEP1 drives endosomal recycling and actin polymerization at the leading edge of cells through Rac activation, with ITSN2L acting as a negative regulator by promoting RABEP1 degradation 2. The protein exists as multiple splice variants 3. Clinically, RABEP1 dysregulation contributes to multiple diseases. In chr17 pancreatitis, RABEP1-mediated endocytosis of trypsinogen promotes pancreatic stellate cell activation 4. In neutrophils, RABEP1 is essential for cell motility and chemotaxis 1. RABEP1 represents a pleiotropic gene linked to schizophrenia and inflammatory bowel disease susceptibility 5. In Alzheimer's disease, RABEP1 mutations (p.R845W) dysregulate endocytosis and exacerbate amyloid-β accumulation 6, with the protein identified as a predictive biomarker across disease stages 7. RABEP1 also inhibits autophagy in atherosclerosis through miR-224-3p regulation 8.