Thrombin Causes a Marked Delay in Skeletal Myogenesis That Correlates with the Delayed Expression of Myogenin and p21CIP1/WAF1*
- From the Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, California 92697-4025
Abstract
Thrombin is a multifunctional serine protease whose activity is regulated in the extravasculature by an extracellular inhibitor, protease nexin-1. Because protease nexin-1 expression has been shown to be regulated during skeletal muscle cell differentiation, we reasoned that thrombin inactivation may be an important requirement for this developmental process. To test this hypothesis, we examined the effects of thrombin on differentiating C2C12 myoblasts. We report here that myogenesis, as scored by myotube formation, is considerably delayed by thrombin. This regulation correlated with delayed expression of myogenin and p21CIP1/WAF1, both considered critical components of the skeletal muscle cell differentiation program. Regulation occurred at the RNA level, indicating that the effect of thrombin is either transcriptional or post-transcriptional. Furthermore, we present evidence suggesting that this regulation is mediated by the thrombin receptor. Although thrombin is mitogenic for certain cell types, we found that delay of myogenesis in C2C12 cells did not involve a mitogenic signal. Taken together, these results imply that inhibition of the serine protease thrombin may be required for proper progression through the myogenic differentiation program. The data point to potentially important roles that thrombin and protease nexin-1 may play during skeletal muscle development.
Footnotes
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↵* This work was supported by National Institutes of Health Grants AG 10598 and AG 00538.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Present address: Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, CB# 7295, Chapel Hill, NC 27599-7295.
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↵§ To whom correspondence should be addressed. Tel.: 714-824-7074; Fax: 714-824-8598.
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↵1 The abbreviations used are: PN-1, protease nexin-1; DM, differentiation medium; MHC, myosin heavy chain; Cdk, cyclin-dependent kinase; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.
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↵2 D. C. Guttridge, A. Lau, L. Tran, and D. D. Cunningham, unpublished observations.
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- Received May 21, 1997.
- Revision received June 27, 1997.
