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 clat hrin coat assembly and vesicular transport in the Golgi apparatus. However, little is known about the in vivo regulation of ARF actions. Recently me c loned arfaptin 1, a 39 kDa protein that binds active, GTP gamma S-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 regu lating vesicular transport in the secretory pathway, we determined the rate of glycosylation of vesicular stomatitis virus glycoprotein as a measure o f protein transport from the endoplasmic reticulum through the Golgi appara tus. Arfaptin 1 overexpression mas found to decrease the rate of this react ion approximately two-fold. These data suggest that arfaptin 1 is a regulat or of ARF action in the Golgi apparatus.