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L-type calcium channel α-subunit and protein kinase inhibitors modulate Rem-mediated regulation of current

Authors: Shawn M, Crump; Robert N, Correll; Elizabeth A, Schroder; William C, Lester; Brian S, Finlin; Douglas A, Andres; Jonathan, Satin;

L-type calcium channel α-subunit and protein kinase inhibitors modulate Rem-mediated regulation of current

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 (CaV1.2) to CaVβ2-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). CaV1.2-S1928A current was not inhibited by Rem and when coexpression with CaVβ2a 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.

Related Organizations
Keywords

Mice, Inbred ICR, Sulfonamides, Patch-Clamp Techniques, Calcium Channels, L-Type, Mesocricetus, Thionucleotides, Isoquinolines, Cyclic AMP-Dependent Protein Kinases, Cell Line, Mice, Gene Expression Regulation, Cricetinae, Cyclic AMP, Animals, Humans, Calcium, Myocytes, Cardiac, Phosphorylation, Protein Kinase Inhibitors, Monomeric GTP-Binding Proteins

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Powered by OpenAIRE graph
citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
40
Average
Top 10%
Top 10%