Rapid activation of Ras by fluid flow is mediated by Galpha(q) and Gbetagamma subunits of heterotrimeric G proteins in human endothelial cells.
OBJECTIVE
Temporal gradients in fluid shear stress have been shown to induce a proatherogenic phenotype in endothelial cells. The biomechanical mechanism(s) that enables the endothelium to respond to fluid shear stress requires rapid activation and signal transduction. The small G protein Ras has been identified as an early link between rapid mechanotransduction events and the effects of shear stress on downstream signal-transduction cascades. The aim of this study was to elucidate the upstream mechanotransduction signaling events mediating the rapid activation of Ras by fluid shear stress in human endothelial cells.


RESULTS
Direct measurement of Ras-bound GTP and GDP showed that fluid-flow activation of Ras was rapid (10-fold within 5 seconds) and dose dependent on shear stress magnitude. Treatment with protein tyrosine kinase inhibitors or pertussis toxin did not significantly affect flow-induced Ras activation. However, activation was inhibited by transient transfection with antisense to Galpha(q) or the Gbetagamma scavenger beta-adrenergic receptor kinase carboxy terminus. Transfection with several Gbetagamma subunit isoforms revealed flow-induced Ras activation was most effectively enhanced by Gbeta1gamma2.


CONCLUSIONS
These results suggest that the rapid, shear-induced activation of Ras is mediated by Galpha(q) through the activity of Gbetagamma subunits in human vascular endothelial cells.
Gudi
Sivaramaprasad
S
Department of Bioengineering, University of California at San Diego, La Jolla, USA.
Huvar
Ivana
I
White
Charles R
CR
McKnight
Nathan L
NL
Dusserre
Nathalie
N
Boss
Gerry R
GR
Frangos
John A
JA
D000222:Adaptation, Physiological; D001161:Arteriosclerosis / Q000503:physiopathology; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D021122:Protein Subunits; D016283:Proto-Oncogene Proteins p21(ras) / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012212:Rheology; D013314:Stress, Mechanical; D014162:Transfection; D051552:beta-Adrenergic Receptor Kinases
D004791:Enzyme Inhibitors; D020319:Oligodeoxyribonucleotides, Antisense; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)