RAB33B is a small GTPase that functions as a key regulator of intracellular membrane trafficking and autophagy. As a member of the Rab family, RAB33B cycles between inactive GDP-bound and active GTP-bound conformations to recruit downstream effectors 1. In Golgi homeostasis, RAB33B acts in coordination with RAB6A to regulate intra-Golgi retrograde trafficking, functioning downstream in a Rab cascade that directs cargo from trans to cis Golgi compartments 1. Notably, RAB33B plays a critical role in autophagosome formation by recruiting the ATG12-ATG5-ATG16L1 complex to phagophores through direct interaction with ATG16L1's coiled-coil domain, operating in a nucleotide-independent manner 23. This recruitment is essential for LC3 lipidation and autophagosome biogenesis 3. Beyond canonical autophagy, RAB33B participates in non-canonical autophagy-like processes, including hepatitis B virus capsid egress and influenza M2 protein trafficking 45. Clinically, RAB33B mutations cause Smith-McCort dysplasia, a spondylo-epi-metaphyseal skeletal dysplasia characterized by distinctive lacy ilia and normal cognition 678. The molecular basis linking RAB33B dysfunction to skeletal pathology remains incompletely understood but likely involves impaired autophagy and membrane trafficking during skeletal development 8.