Thrombin, phorbol ester, and cAMP regulate thrombin receptor protein and mRNA expression by different pathways

Item Type:	Article
Title:	Thrombin, phorbol ester, and cAMP regulate thrombin receptor protein and mRNA expression by different pathways
Creators Name:	Zacharias, U. and Xu, Y.C. and Hagege, J. and Sraer, J.D. and Brass, L.F. and Rondeau, E.
Abstract:	Human mesangial cells have been used to study the regulation of thrombin receptor protein and mRNA expression during cross-talk between different signal transduction pathways. Persistent activation of thrombin receptor by thrombin led to homologous down-regulation of thrombin receptor protein. However, thrombin receptor mRNA expression was not affected, suggesting that increased receptor degradation is responsible for homologous down-regulation. Chronic activation of protein kinase C by phorbol 12-myristate 13-acetate (PMA) and of adenylylcyclase by prostaglandin E1 (PGE1) resulted in heterologous down-regulation of thrombin receptor protein. In contrast to thrombin, PMA and PGE1 reduced in parallel thrombin receptor mRNA levels to 51% and 24% of control, respectively, indicating that heterologous down-regulation of thrombin receptor protein is, at least in part, due to inhibition of receptor mRNA expression. The mechanisms of heterologous down-regulation of thrombin receptor protein have been studied in detail and compared to homologous down-regulation. PMA-induced down-regulation was completely blocked by GF 109 203 X, an inhibitor of protein kinase C. However, the loss of thrombin receptor induced by thrombin was not prevented by GF 109 203 X, indicating that homologous regulation is not dependent on protein kinase C activation. The heterologous effect of PGE1 was mimicked by 8-bromo-cAMP, isobutylmethylxanthine, and forskolin, suggesting that an increase in intracellular cAMP level is involved in heterologous regulation. Interestingly, heterologous down-regulation induced by PGE1 seems not to require previous internalization of thrombin receptor. These data indicate that thrombin receptor protein and mRNA expression can be regulated in homologous and heterologous ways by different mechanisms.
Keywords:	Cultured Cells, Cyclic AMP, Down-Regulation, Messenger RNA, Protein Kinase C, Tetradecanoylphorbol Acetate, Thrombin, Thrombin Receptors
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	270
Number:	2
Page Range:	545-550
Date:	13 January 1995
Official Publication:	https://doi.org/10.1074/jbc.270.2.545
PubMed:	View item in PubMed

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