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L-type calcium channel a-subunit and protein kinase inhibitors modulate Rem-mediated regulation of current.
- Source :
-
American Journal of Physiology: Heart & Circulatory Physiology . Oct2006, Vol. 291 Issue 4, pH1959-H1971. 13p. 1 Diagram, 2 Charts, 8 Graphs. - Publication Year :
- 2006
-
Abstract
- Cardiac voltage-gated L-type Ca channels (Cav) are multiprotein complexes, including accessory subunits such as Cavβ2 that increase current expression. Recently, members of the Rad and Gem/Kir-related family of small GTPases have been shown to decrease current, although the mechanism remains poorly defined. In this study, we evaluated the contribution of the L-type Ca channel α-subunit (Cav 1.2) to Caβvβ2-Rem inhibition of Ca channel current. Specifically, we addressed whether protein kinase A (PKA) modulation of the Ca channel modifies Cavβ2-Rem inhibition of Ca channel current. We first tested the effect of Rem on Cav1.2 in human embryonic kidney 293 (HEK-293) cells using the whole cell patch-clamp configuration. Rem coexpression with Cav1.2 reduces Ba current expression under basal conditions, and Cavβ2a coexpression enhances Rem block of Cav1.2 current. Surprisingly, PKA inhibition by 133 nM H-89 or 50 µM Rp-cAMP-S partially relieved the Rem-mediated inhibition of current activity both with and without Cavβ2a. To test whether the H-89 action was a consequence of the phosphorylation status of Cav1.2, we examined Rem regulation of the PKA-insensitive Cav1.2 serine 1928 (S1928) to alanine mutation (Cav1.2-S1928A). Cav 1.2-S1928A current was not inhibited by Rem and when coexpression with Cavβa was not completely blocked by Rem coexpression, suggesting that the phosphorylation of S1928 contributes to Rem-mediated Ca channel modulation. As a model for native Ca channel complexes, we tested the ability of Rem overexpression in HIT-T15 cells and embryonic ventricular myocytes to interfere with native current. We find that native current is also sensitive to Rem block and that H-89 pretreatment relieves the ability of Rem to regulate Ca current. We conclude that Rem is capable of regulating L-type current, that release of Rem block is modulated by cellular kinase pathways, and that the Cav1.2 COOH terminus contributes to Rem-dependent channel inhibition. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 03636135
- Volume :
- 291
- Issue :
- 4
- Database :
- Academic Search Index
- Journal :
- American Journal of Physiology: Heart & Circulatory Physiology
- Publication Type :
- Academic Journal
- Accession number :
- 22739915
- Full Text :
- https://doi.org/10.1152/ajpheart.00956.2005