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Similar molecular determinants on Rem mediate two distinct modes of inhibition of Ca_V1.2 channels.

ABSTRACT: Rad/Rem/Rem2/Gem (RGK) proteins are Ras-like GTPases that potently inhibit all high-voltage-gated calcium (Ca_V1/Ca_V2) channels and are, thus, well-positioned to tune diverse physiological processes. Understanding how RGK proteins inhibit Ca_V channels is important for perspectives on their (patho)physiological roles and could advance their development and use as genetically-encoded Ca_V channel blockers. We previously reported that Rem can block surface Ca_V1.2 channels in 2 independent ways that engage distinct components of the channel complex: (1) by binding auxiliary ? subunits (?-binding-dependent inhibition, or BBD); and (2) by binding the pore-forming ?_1C subunit N-terminus (?_1C-binding-dependent inhibition, or ABD). By contrast, Gem uses only the BBD mechanism to block Ca_V1.2. Rem molecular determinants required for BBD Ca_V1.2 inhibition are the distal C-terminus and the guanine nucleotide binding G-domain which interact with the plasma membrane and Ca_V?, respectively. However, Rem determinants for ABD Ca_V1.2 inhibition are unknown. Here, combining fluorescence resonance energy transfer, electrophysiology, systematic truncations, and Rem/Gem chimeras we found that the same Rem distal C-terminus and G-domain also mediate ABD Ca_V1.2 inhibition, but with different interaction partners. Rem distal C-terminus interacts with ?_1C N-terminus to anchor the G-domain which likely interacts with an as-yet-unidentified site. In contrast to some previous studies, neither the C-terminus of Rem nor Gem was sufficient to inhibit Ca_V1/Ca_V2 channels. The results reveal that similar molecular determinants on Rem are repurposed to initiate 2 independent mechanisms of Ca_V1.2 inhibition.

SUBMITTER: Puckerin AA

PROVIDER: S-EPMC4988437 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Similar molecular determinants on Rem mediate two distinct modes of inhibition of CaV1.2 channels.

Puckerin Akil A AA Chang Donald D DD Subramanyam Prakash P Colecraft Henry M HM

Channels (Austin, Tex.) 20160426 5

Rad/Rem/Rem2/Gem (RGK) proteins are Ras-like GTPases that potently inhibit all high-voltage-gated calcium (CaV1/CaV2) channels and are, thus, well-positioned to tune diverse physiological processes. Understanding how RGK proteins inhibit CaV channels is important for perspectives on their (patho)physiological roles and could advance their development and use as genetically-encoded CaV channel blockers. We previously reported that Rem can block surface ...[more]

PMID: 27115600

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Similar molecular determinants on Rem mediate two distinct modes of inhibition of Ca_V1.2 channels.

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Similar molecular determinants on Rem mediate two distinct modes of inhibition of Ca<sub>V</sub>1.2 channels.

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