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Thrombin downregulates muscle acetylcholine receptors via an IP3 signaling pathway by activating its G‐protein‐coupled protease‐activated receptor‐1
Author(s) -
Faraut Brice,
Barbier Julien,
RavelChapuis Aymeric,
Doyennette MarieAgnès,
JandrotPerrus Martine,
VerdièreSahuqué Martine,
Schaeffer Laurent,
Koenig Jeanine,
Hantaï Daniel
Publication year - 2003
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.10280
Subject(s) - thrombin , thrombin receptor , microbiology and biotechnology , receptor , acetylcholine receptor , inositol trisphosphate receptor , gq alpha subunit , chemistry , protease activated receptor 2 , biology , inositol , signal transduction , g protein , biochemistry , 5 ht5a receptor , platelet , immunology
Regulation of thrombin activity may be required during skeletal muscle differentiation since the thrombin tissue inhibitor protease nexin‐1 appears at the myotube stage before being localized at the neuromuscular synapse. Here, we have used a model of rat fetal myotube primary cultures to study the effect of thrombin on acetylcholine receptor (AChR) expression, which is enhanced at the myotube stage. Our results show that thrombin decreases both the number of surface AChRs (AChRn) and AChR α‐subunit gene expression. Using the agonist peptide SFLLRN, we establish that the AChRn decrease is mediated by the G protein‐coupled thrombin receptor “protease‐activated receptor‐1” (PAR‐1). Moreover, the specific thrombin inhibitor hirudin increases AChRn by inhibiting the thrombin intrinsically present in the cultures. We further demonstrate that the activation of PAR‐1 by thrombin induces intracellular calcium movements that are blocked by 2‐APB, an inhibitor of inositol 1,4,5‐triphosphate (IP3)‐induced calcium release. These calcium signals are more intense in nuclei than in the cytoplasm and are consistent with the intracellular distribution of IP3 receptor that we find in the cytoplasm in a cross‐striated pattern and at a high level in the nuclear envelope zone. Finally, we show that the blockade of these IP3‐induced calcium signals by 2‐APB prevents the AChRn decrease induced by thrombin. Our results thus demonstrate that thrombin downregulates AChR expression by activating PAR‐1 and that this effect is mediated via an IP3 signaling pathway. © 2003 Wiley‐Liss, Inc.