Co-regulation of the arf-activation cycle and phospholipid-signaling during golgi maturation.

The Golgi apparatus is the central protein sorting station inside eukaryotic cells. Although many regulators of Golgi trafficking have been identified, little is known about their crosstalk. Both the Arf activation cycle and phosphatidylinositol 4-phosphate metabolism have been recognized as key processes in the regulation of vesicular transport from this organelle. However, the mechanism ensuring the proper co-regulation of these processes has eluded our understanding thus far. We recently identified a physical interaction between the late yeast Golgi Arf activator Sec7p and the PI4-kinase Pik1p, and showed that the two proteins cooperate in the formation of clathrin-coated vesicles. This finding gives the first insight on the coordinated generation of a dual key signal by a small GTPase and a signaling phospholipid at the Golgi. In addition, it opens new perspectives for a better understanding of Golgi maturation through coordinated regulation of highly dynamic lipid and protein composition of this organelle.