Les mécanismes d'entrée du calcium dans les cellules musculaires lisses vasculaires : étude du rôle des TRPC
(2009)
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- Authors
- Supervisors
- Morel, Nicole
- Abstract
- In vascular smooth muscle cells, agonists can induce an increase in the cytoplasmic Ca2+ concentration via the release of intracellular stored Ca2+ or/and via the influx of extracellular Ca2+. The Ca2+ entry pathway operates through a variety of plasmalemmal Ca2+ channels which involve voltage-dependent and voltage-independent Ca2+ channels. Voltage-independent Ca2+ channels include (1) receptor-operated channels (ROCs) activated by agonist-receptor interaction and, (2) store-operated channels (SOCs) activated by the emptying of intracellular Ca2+ store (mainly the sarcoplasmic reticulum), (3) mechanosensitive or stretch-activated channels (SACs) activated by membrane stretch. Although the molecular identity of voltage-independent Ca2+ channels is not yet fully elucidated, there are growing evidences that these channels belong to the TRPC channels family. TRPC proteins such as TRPC1 and TRPC6 are ubiquitously expressed in smooth muscle cells but their expression is varying among tissues and species. The objective of the présent thesis was to investigate the mechanisms of regulation of Ca2+ signal in vascular smooth muscle and the involvement of TRPC in Ca2+ homeostasis. Our data indicated that in aortic smooth muscle cells in primary culture as in isoled aorta TRPC1-7 were expressed with the exception of TRPC2. In cultured vascular msooth muscle cells agonist binding to its receptor activated TRPC1 channel in an IP3-dependent manner. TRPC1 was also activated by the emptying of intracellular Ca2+ stores in a receptor-independent manner. Store-dependent activation of TRPC1 did not require IP3. These two types of Ca2+ entries exhibited different pharmacological properties. In resistance mesenteric artery cultured for two days in the absence of serum, the contractile response and the Ca2+ signal were more sensitive to agonists than in freshly isolated mesenteric arteries. Our results also indicated that contractile responses of cultured arteries were more sensitive to blockers of non-voltage-dependent cation channels. Moreover, the expression of TRPC6 but not of the other TRPC isoforms, was increased after artery culture. The increased sensitivity to contractile agonists observed in cultured arteries was dependent on src kinase. Together with data reported in the literature, our results suggest that TRPC channels might be involved in the development of vascular diseases associated with increased vascular smooth muscle proliferation. In addition, the involvement of src kinase in the increaeed contractility of cultured arteries might provide a new therapeutic direction toward the treatment of vascular proliferative disorders. In conclusion, this study showed that TRPC channels play an important role in the regulation of Ca2+ signalling in vascular smooth muscle cells. However, TRPC channel function and regulation still need to be clarified. In particular, future studies will have to investigate the role of Stim1 and Orai1 in the generation of voltage-independent Ca2+ entry in vascular smooth muscles.
- Affiliations
Citations
Tai, K. (2009). Les mécanismes d’entrée du calcium dans les cellules musculaires lisses vasculaires : étude du rôle des TRPC. https://hdl.handle.net/2078.5/112020