Characterization of Rab22B, an astroglia-enriched Rab GTPase, and its role in Golgi and post-Golgi membrane traffic

Abstract

The small GTPase Rab22B is a brain-enriched protein, had been suspected to be involved in trafficking at trans-Golgi network (TGN). Specific antibodies raised against Rab22Bb s protein confirmed that Rab22B is brain-enriched. Detail immunohistochemical analysis reveals that Rab22B is predominantly expressed in embryonic radial glia and adult astrocytes.Immunocytochemistry analysis revealed that endogenous Rab22B is largely associated with the TGN in HeLa cells. Over-expression of a GDP-binding mutant, Rab22BS20N, specifically disrupts the localization of TGN46, a dynamic marker which cycles between the TGN and the plasma membrane. Rab22B shares itsb guanine nucleotide exchange factor, GAPex-5, with Rab5. The silencing of GAPex-5 appears to affect trafficking of EGFR. Likewise, the depletion of Rab22B affects trafficking the trafficking of EGFR in a similar manner. Affinity pull-down and co-immunoprecpitpitation assays show that the effect that Rab22B had on EGFR could be due to itsb interaction with EGFR itself.