Stretch activation of GTP-binding proteins in C2C12 myoblasts.
Mechanical stimulation has been proposed as a fundamental determinant of muscle physiology. The mechanotransduction of strain and strain rate in C2C12 myoblasts were investigated utilizing a radiolabeled GTP analogue to detect stretch-induced GTP-binding protein activation. Cyclic uniaxial strains of 10% and 20% at a strain rate of 20% s(-1) rapidly (within 1 min) activated a 25-kDa GTPase (183 +/- 17% and 186 +/- 19%, respectively), while 2% strain failed to elicit a response (109 +/- 11%) relative to controls. One, five, and sixty cycles of 10% strain elicited 187 +/- 20%, 183 +/- 17%, and 276 +/- 38% increases in activation. A single 10% stretch at 20% s(-1), but not 0.3% s(-1), resulted in activation. Insulin activated the same 25-kDa band in a dose-dependent manner. Western blot analysis revealed a panel of GTP-binding proteins in C2C12 myoblasts, and tentatively identified the 25-kDa GTPase as rab5. In separate experiments, a 40-kDa protein tentatively identified as Galpha(i) was activated (240 +/- 16%) by 10% strain at 1 Hz for 15 min. These results demonstrate the rapid activation of GTP-binding proteins by mechanical strain in myoblasts in both a strain magnitude- and strain rate-dependent manner.
Clark
Craig B
CB
Department of Bioengineering, University of California San Diego, La Jolla, CA 92093-0142, USA.
McKnight
Nathan L
NL
Frangos
John A
JA
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010812:Physical Stimulation; D011930:Reaction Time / Q000502:physiology; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism
D007328:Insulin; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020696:rab5 GTP-Binding Proteins