Endogenous RhoG is rapidly activated after epidermal growth factor stimulation through multiple guanine-nucleotide exchange factors.
RhoG is a member of the Rac-like subgroup of Rho GTPases and has been linked to a variety of different cellular functions. Nevertheless, many aspects of RhoG upstream and downstream signaling remain unclear; in particular, few extracellular stimuli that modulate RhoG activity have been identified. Here, we describe that stimulation of epithelial cells with epidermal growth factor leads to strong and rapid activation of RhoG. Importantly, this rapid activation was not observed with other growth factors tested. The kinetics of RhoG activation after epidermal growth factor (EGF) stimulation parallel the previously described Rac1 activation. However, we show that both GTPases are activated independently of one another. Kinase inhibition studies indicate that the rapid activation of RhoG and Rac1 after EGF treatment requires the activity of the EGF receptor kinase, but neither phosphatidylinositol 3-kinase nor Src kinases. By using nucleotide-free RhoG pull-down assays and small interfering RNA-mediated knockdown studies, we further show that guanine-nucleotide exchange factors (GEFs) of the Vav family mediate EGF-induced rapid activation of RhoG. In addition, we found that in certain cell types the recently described RhoG GEF PLEKHG6 can also contribute to the rapid activation of RhoG after EGF stimulation. Finally, we present results that show that RhoG has functions in EGF-stimulated cell migration and in regulating EGF receptor internalization.
Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA.
Thomas
T
Samson
Christopher
C
Welch
Elizabeth
E
Monaghan-Benson
Klaus M
KM
Hahn
Keith
K
Burridge
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D020662:Guanine Nucleotide Exchange Factors; C527325:PLEKHG6 protein, human; D010982:Platelet-Derived Growth Factor; D042461:Vascular Endothelial Growth Factor A; C075397:RHOG protein, human; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins