The p24 Complex Contributes to Specify Arf1 for COPI Coat Selection

Abstract

Golgi trafficking depends on the small GTPase Arf1 which, upon activation, drives the assembly of different coats onto budding vesicles. Two related types of guanine nucleotide exchange factors (GEFs) activate Arf1 at different Golgi sites. In yeast, Gea1 in the cis-Golgi and Gea2 in the medial-Golgi activate Arf1 to form COPI-­coated vesicles for retrograde cargo sorting, whereas Sec7 generates clathrin/adaptor­-coated vesicles at the trans-Golgi network (TGN) for forward cargo transport. A central question is how the same activated Arf1 protein manages to assemble different coats depending on the donor Golgi compartment. A previous study has postulated that the interaction between Gea1 and COPI would channel Arf1 activation for COPI vesicle budding. Here, we found that the p24 complex, a major COPI vesicle cargo, promotes the binding of Gea1 with COPI by increasing the COPI association to the membrane independently of Arf1 activation. Furthermore, the p24 complex also facilitates the interaction of Arf1 with its COPI effector. Therefore, our study supports a mechanism by which the p24 complex contributes to program Arf1 activation by Gea1 for selective COPI coat assembly at the cis-Golgi compartment.

Arf1 GTPase Regulates Golgi‐Dependent G2/M Transition and Spindle Organization in Oocyte Meiosis

“…Arf1 drives the assembly of different coats onto budding vesicles, which are closely connected with the Golgi apparatus. [42] Similarly, our data indicated that Arf1 was associated with several vesicle transport-related proteins, and Arf1 affected the localization and expression of cis-Golgi marker GM130 and GTPase Rab35. Indeed, the dominantnegative Arf1 mutant in myotubes alters the subcellular distribution of GM130, which impairs endoplasmic reticulum-Golgi traffic.…”