RGS-PX1, a GAP for Gα s and Sorting Nexin in Vesicular Trafficking

Abstract

Heterotrimeric GTP–binding proteins (G proteins) control cellular functions by transducing signals from the outside to the inside of cells. Regulator of G protein signaling (RGS) proteins are key modulators of the amplitude and duration of G protein–mediated signaling through their ability to serve as guanosine triphosphatase–activating proteins (GAPs). We have identified RGS-PX1, a Gα_s-specific GAP. The RGS domain of RGS-PX1 specifically interacted with Gα_s, accelerated its GTP hydrolysis, and attenuated Gα_s-mediated signaling. RGS-PX1 also contains a Phox (PX) domain that resembles those in sorting nexin (SNX) proteins. Expression of RGS-PX1 delayed lysosomal degradation of the EGF receptor. Because of its bifunctional role as both a GAP and a SNX, RGS-PX1 may link heterotrimeric G protein signaling and vesicular trafficking.