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Regulation of Epidermal Growth Factor Receptor Degradation by Heterotrimeric Gs Protein
Bin Zheng *,
Christine Lavoie *,
Anthony Beas, and
Marilyn G. Farquhar
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0651
Received for publication June 3, 2004.
Revision received September 15, 2004.
Accepted for publication September 17, 2004.
Monitoring Editor: Juan S. Bonifacino
Heterotrimeric G proteins have been implicated in the regulationof membrane trafficking, but the mechanisms involved are notwell understood. Here, we report that overexpression of thestimulatory G protein subunit (Gs) promotes ligand-dependentdegradation of epidermal growth factor (EGF) receptors and TexasRed EGF, and knock-down of Gs expression by RNA interference(RNAi) delays receptor degradation. We also show that Gs andits GTPase activating protein (GAP), RGS-PX1, interact withhepatocyte growth factor-regulated tyrosine kinase substrate(Hrs), a critical component of the endosomal sorting machinery.Gs coimmunoprecipitates with Hrs and binds Hrs in pull-downassays. By immunofluorescence, exogenously expressed Gs colocalizeswith myc-Hrs and GFP-RGS-PX1 on early endosomes, and expressionof either Hrs or RGS-PX1 increases the localization of Gs onendosomes. Furthermore, knock-down of both Hrs and Gs by doubleRNAi causes greater inhibition of EGF receptor degradation thanknock-down of either protein alone, suggesting that Gs and Hrshave cooperative effects on regulating EGF receptor degradation.These observations define a novel regulatory role for Gs inEGF receptor degradation and provide mechanistic insights intothe function of Gs in endocytic sorting.