Rab1b Interacts with GBF1, Modulates both ARF1 Dynamics and COPI Association

1. PABLO MONETTA, ILEANA SLAVIN, NAHUEL ROMERO, CECILIA ALVAREZ

MOLECULAR BIOLOGY OF THE CELL

American Society for Cell Biology

Lugar: Bethesda, MD; Año: 2007 vol. 18 p. 2400 - 2400

1059-1524

b> Assembly of the cytosolic coat protein I (COPI) complex at the ER–Golgi interface is directed by the ADP ribosylation factor1 (Arf1) and its guanine nucleotide exchange factor (GBF1). Rab1b GTPase modulates COPI recruitment, but the molecular mechanism underlying this action remains unclear. Our data reveal that in vivo expression of the GTPrestricted Rab1b mutant (Rab1Q67L) increased the association of GBF1 and COPI to peripheral structures localized at the ER exit sites (ERES) interface. Active Rab1b also stabilized Arf1 on Golgi membranes. Furthermore, we characterized GBF1 as a new Rab1b effector, and showed that its N-terminal domain was involved in this interaction. Rab1b small interfering RNA oligonucleotide assays suggested that Rab1b was required for GBF1 membrane association. To further