RAB1 GTPase INTERACTS WITH COPII AND MODULATES

SLAVIN I, MONETTA P, ROMERO N, ALVAREZ C

Pinamar, Buenos Aires. Argentina

Congreso; SAIB; 2005

Rab1 is an essential regulator of ER to Golgi transport and participates in traffic events at the donor and acceptor membranes through its interaction with effectors. A dominant negative Rab1 mutant (Rab1N121I) inhibits sorting of cargo proteins into ER exit sites (ERES) suggesting that Rab1 modulates cargo sorting. COPII protein complex (Sar1GTPase, Sec23/24 and Sec13/31) is required for sorting and concentration of cargo into ERES. To test if COPII components act as Rab1 effectors we performed GST-pull down assays using Rab1GTP and rat liver cytosol. Analysis of the bounded proteins indicates that Rab1, in its active form (Rab1Q67L), interacts with Sec23. In agreement, double immunofluorescence assay showed that Rab1Q67L colocalized with COPII structures. Furthermore, FRAP experiments performed in HeLa cells coexpressing GFP-Sec13 and Rab1Q67L indicate that Rab1 activity affects Sec13 membrane association-dissociation kinetics at the ERES. These data show that Rab1 interacts with a COPII component, modulates COPII membrane association dynamic and strongly suggest that Rab1 activity modulates COPII sorting function at ERES interfaces