SH3BP5 (SH3 domain binding protein 5) functions primarily as a guanine nucleotide exchange factor (GEF) with specificity for RAB11A and RAB25, facilitating GDP release and promoting GTP binding to regulate membrane trafficking 1. The protein exhibits a V-shaped structure comprising two coiled coils, with the coiled coil containing α1 and α4 helices being solely responsible for Rab11a binding and GEF activity 1. SH3BP5 localizes to Rab11-positive recycling endosomes and shows GEF activity for all Rab11 family members but not for Rab14 1. Additionally, SH3BP5 serves as a negative regulator of BTK kinase, inhibiting its auto- and transphosphorylation activity and playing a regulatory role in BTK-related cytoplasmic signaling in B-cells 2. The protein mediates acetaminophen hepatotoxicity through mitochondrial dysfunction and JNK phosphorylation 3. In cancer contexts, SH3BP5 expression is associated with poor prognosis in diffuse large B-cell lymphoma, particularly the ABC subtype, where it correlates with advanced-stage disease, elderly onset, and immunosuppressive microenvironment 45. The protein appears to promote metabolic reprogramming toward oxidative phosphorylation and may contribute to therapy resistance 4.