title: Shoc2 is targeted to late endosomes and required for Erk1/2 activation in EGF-stimulated cells.
abstract: Shoc2 is the putative scaffold protein that interacts with RAS and RAF, and positively regulates signaling to extracellular signal-regulated protein kinases 1 and 2 (ERK1/2). To elucidate the mechanism by which Shoc2 regulates ERK1/2 activation by the epidermal growth factor (EGF) receptor (EGFR), we studied subcellular localization of Shoc2. Upon EGFR activation, endogenous Shoc2 and red fluorescent protein tagged Shoc2 were translocated from the cytosol to a subset of late endosomes containing Rab7. The endosomal recruitment of Shoc2 was blocked by overexpression of a GDP-bound H-RAS (N17S) mutant and RNAi knockdown of clathrin, suggesting the requirement of RAS activity and clathrin-dependent endocytosis. RNAi depletion of Shoc2 strongly inhibited activation of ERK1/2 by low, physiological EGF concentrations, which was rescued by expression of wild-type recombinant Shoc2. In contrast, the Shoc2 (S2G) mutant, that is myristoylated and found in patients with the Noonan-like syndrome, did not rescue ERK1/2 activation in Shoc2-depleted cells. Shoc2 (S2G) was not located in late endosomes but was present on the plasma membrane and early endosomes. These data suggest that targeting of Shoc2 to late endosomes may facilitate EGFR-induced ERK activation under physiological conditions of cell stimulation by EGF, and therefore, may be involved in the spatiotemporal regulation of signaling through the RAS-RAF module.
authors.affiliation: Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky, United States of America. emilia.galperin@uky.edu
authors.forename: Emilia
authors.initials: E
authors.lastname: Galperin
authors.forename: Lina
authors.initials: L
authors.lastname: Abdelmoti
authors.forename: Alexander
authors.initials: A
authors.lastname: Sorkin
mesh_terms: D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D033922:Clathrin Heavy Chains / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D050505:Mutant Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C112913:SHOC2 protein, human; D033922:Clathrin Heavy Chains; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D018631:ras Proteins