Volume 271, Number 46,
Issue of November 15, 1996
pp. 29162-29169
©1996 by The American Society for Biochemistry and Molecular Biology, Inc.
The Thrombin Receptor Is Present in Myoblasts and Its Expression
Is Repressed upon Fusion
(Received for publication, July 26, 1996, and in revised form, August 29, 1996)
Hana S.
Suidan
,
Simone P.
Niclou
,
Jörg
Dreessen
¶
,
Nicola
Beltraminelli
and
Denis
Monard
From the Friedrich Miescher-Institut and ¶ Ciba Ltd.,
CH-4002 Basel, Switzerland
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.