Arfaptin 1, an ARF-binding protein, inhibits phospholipase D and endoplasmic reticulum/Golgi protein transport

Class I ADP-ribosylation factors (ARFs) are essential for coatomer and clathrin coat assembly and vesicular transport in the Golgi apparatus. However, little is known about the in vivo regulation of ARF actions. Recently we cloned arfaptin 1, a 39 kDa protein that binds active, GTPgammaS-liganded ARF and translocates with it to Golgi membranes. Here we show that phorbol ester-stimulated phospholipase D (PLD) activity is inhibited in arfaptin 1-overexpressing NIH 3T3 cells and that arfaptin 1 inhibits ARF activation of Golgi-associated PLD. Since PLD activity is thought to play a role in regulating vesicular transport in the secretory pathway, we determined the rate of glycosylation of vesicular stomatitis virus glycoprotein as a measure of protein transport from the endoplasmic reticulum through the Golgi apparatus. Arfaptin 1 overexpression was found to decrease the rate of this reaction approximately two-fold. These data suggest that arfaptin 1 is a regulator of ARF action in the Golgi apparatus.