Mechanism of down-regulation of L-type Ca2+ channel in the proliferating smooth muscle cells of rat aorta

✍ Scribed by Eikichi Ihara; Katsuya Hirano; Mayumi Hirano; Junji Nishimura; Hajime Nawata; Hideo Kanaide

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 223 KB
• Volume: 87
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.10295

✦ Synopsis

The mechanism of down-regulation of L-type Ca(2+) channel (L-VOC) was investigated in rat aortic smooth muscle cells in primary culture. On culture days 3-5, the cells actively incorporated the 5-bromo-2'-deoxy-uridine (BrdU), and did not respond to K(+) depolarization nor express alpha(1C) subunit of L-VOC. At confluence on day 8, BrdU incorporation decreased, and the cells up-regulated alpha(1C) subunit mRNA, expressed alpha(1C) subunit protein at cell periphery, and responded to K(+) depolarization. Treating the proliferating cells on day 3 with serum-free media or 10 microM PD98059, a MAP kinase kinase inhibitor, for 2 days induced the expression of alpha(1C) subunit protein and the responsiveness to K(+) depolarization. However, the serum starvation, but not PD98059, decreased the BrdU incorporation and increased the alpha(1C) subunit mRNA. It is concluded that the expression of L-VOC is substantially suppressed in the proliferating cells due to two mechanisms; a MAP kinase-mediated post-transcriptional down-regulation and the transcriptional down-regulation by additional mitogenic signals.