Regulation of epidermal growth factor receptor degradation by heterotrimeric Galphas protein.
Heterotrimeric G proteins have been implicated in the regulation of membrane trafficking, but the mechanisms involved are not well understood. Here, we report that overexpression of the stimulatory G protein subunit (Galphas) promotes ligand-dependent degradation of epidermal growth factor (EGF) receptors and Texas Red EGF, and knock-down of Galphas expression by RNA interference (RNAi) delays receptor degradation. We also show that Galphas and its GTPase activating protein (GAP), RGS-PX1, interact with hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), a critical component of the endosomal sorting machinery. Galphas coimmunoprecipitates with Hrs and binds Hrs in pull-down assays. By immunofluorescence, exogenously expressed Galphas colocalizes with myc-Hrs and GFP-RGS-PX1 on early endosomes, and expression of either Hrs or RGS-PX1 increases the localization of Galphas on endosomes. Furthermore, knock-down of both Hrs and Galphas by double RNAi causes greater inhibition of EGF receptor degradation than knock-down of either protein alone, suggesting that Galphas and Hrs have cooperative effects on regulating EGF receptor degradation. These observations define a novel regulatory role for Galphas in EGF receptor degradation and provide mechanistic insights into the function of Galphas in endocytic sorting.
Zheng
Bin
B
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0651, USA.
Lavoie
Christine
C
Tang
Ting-Dong
TD
Ma
Phuong
P
Meerloo
Timo
T
Beas
Anthony
A
Farquhar
Marilyn G
MG
D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism; D006801:Humans; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D020710:RGS Proteins / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors; D014966:Xanthenes / Q000494:pharmacology
D056827:Endosomal Sorting Complexes Required for Transport; D020690:GTPase-Activating Proteins; D010750:Phosphoproteins; D020710:RGS Proteins; D014966:Xanthenes; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; D004815:Epidermal Growth Factor; C034657:Texas red; D066246:ErbB Receptors; D019205:GTP-Binding Protein alpha Subunits, Gs