RAB9B is a small GTPase belonging to the RAS oncogene family that regulates intracellular membrane trafficking, particularly the retrograde transport pathway from endosomes to the trans-Golgi network (TGN). RAB9B functions in alternative autophagy mechanisms, with knockdown studies demonstrating that RAB9A and RAB9B are essential for mitophagy (mitochondrial autophagy) in mammalian cells, unlike conventional macroautophagy 1. The protein can bind to RUTBC2 effector in a similar manner to RAB9A, suggesting overlapping functional roles 2. RAB9B expression is regulated by miR-199a-5p, which attenuates retrograde transport and provides cellular protection against bacterial toxins like Shiga toxin by controlling transport from endosomes to the TGN 3. Clinical relevance includes associations with various diseases: RAB9B variants have been identified in hemophagocytic lymphohistiocytosis patients and show protein-protein interactions with known HLH genes 4, while the gene is incorporated into tumor microenvironment-based prognostic models for acute myeloid leukemia 5. Additionally, RAB9B loci have been associated with Parkinson's disease risk in Latin American populations through X-chromosome X studies 6.