RAB8A is a small GTPase functioning as a master regulator of intracellular membrane trafficking and polarized vesicular transport 1. The protein cycles between inactive GDP-bound and active GTP-bound states, recruiting downstream effectors that mediate vesicle formation, movement, and fusion 1. RAB8A promotes apical membrane formation and lumenogenesis in epithelial cells through the exocyst complex and associated proteins 1, regulates Golgi morphology 2, and participates in epithelial cell polarization with MYO5B and RAB11A 3. The protein also coordinates cilium membrane trafficking and ciliogenesis 45. Mechanistically, RAB8A functions as a mitochondrial receptor binding PLIN5 on lipid droplets, facilitating energy-dependent fatty acid mobilization during exercise via AMPK-mediated activation 6. LRRK2 phosphorylation stabilizes RAB8A on stressed lysosomes where it suppresses stress-induced enlargement through effector proteins 7. The C9orf72-SMCR8 complex negatively regulates RAB8A-dependent primary ciliogenesis by functioning as a RAB8A GTPase-activating protein 89. Disease relevance is substantial: LRRK2-mediated RAB8A phosphorylation contributes to Parkinson's disease pathology through altered lysosomal pH and α-synuclein accumulation 10, defective endolysosomal repair 11, and iron mishandling in microglia 12. C9orf72 mutations causing ALS/FTD lead to ciliary abnormalities via RAB8A dysregulation 8. Additionally, GPR137-RAB8A activation promotes ovarian cancer progression through Hedgehog pathway activation 13.