Physical and functional interaction of rabphilin-11 with mammalian Sec13 protein - Implication in vesicle trafficking

Rab11a small G protein (Rab11p) is implicated in vesicle trafficking, espec ially vesicle recycling. We have previously isolated a downstream effector of Rab11p, named rabphilin-11. We found here that rabphilin-11 directly bou nd the mammalian counterpart of yeast Sec13 protein (mSec13p) in cell-free and intact cell systems. Yeast Sec13p is involved as a component of coat pr oteins II in the Sar1p-induced vesicle formation from the endoplasmic retic ulum, but the precise role of mSec13p is unknown. The interaction of rabphi lin-11 with mSec13p was enhanced by GTP-Rab11p. Rabphilin-11 localized on t he vesicles in perinuclear regions and along microtubules oriented toward t he plasma membrane, whereas mSec13p partly colocalized with rabphilin-11 in the perinuclear regions, most presumably the Golgi complex. Disruption of the rabphilin-11-mSec13p interaction by overexpression of the mSec13p-bindi ng region of rabphilin-11 impaired vesicle trafficking. These results indic ate that the rabphilin-11-mSec13p interaction is implicated in vesicle traf ficking.