The Thrombin Receptor Is Present in Myoblasts and Its Expression Is Repressed upon Fusion*
- §To whom correspondence should be addressed: Friedrich Miescher-Institut, P. O. Box 2543, CH-4002 Basel, Switzerland. Tel.: 41-61-697 45 55, Fax: 41-61-697 39 76; E-mail: suidan{at}fmi.ch .
Abstract
Cultured myoblasts derived from limb muscle of newborn rats express thrombin receptor immunoreactivity on their surface. Receptor expression is repressed upon myoblast fusion. This is due at least in part to a decrease in the amount of the thrombin receptor mRNA. Addition of thrombin triggers calcium transients only in mono- but not multinucleated muscle cells. Furthermore, thrombin increases the rate of myoblast proliferation that coincides with an activation of mitogen-activated protein kinase. Northern analysis of thrombin receptor mRNA expression in skeletal muscle showed that the transcript is present at a relatively high level at birth, but is almost undetectable in the adult. By in situ hybridization, the mRNA at birth appeared to be present mostly in mononucleated cells grouped in clusters, but not in muscle fibers. Very few nuclei surrounded by a mRNA signal were present on muscle sections of rats 24 days postnatally. These results suggest that the thrombin receptor plays a role in muscle development.
Footnotes
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↵‡ The first two authors equally contributed to this manuscript.
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↵* 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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↵1 The abbreviations used are:
- ThR
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thrombin receptor
- MAP
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mitogen-activated protein
- DMEM
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Dulbecco's modified Eagle's medium
- PBS
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phosphate-buffered saline
- BSA
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bovine serum albumin.
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- Received July 26, 1996.
- Revision received August 29, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
