RGK GTPase-dependent Ca V 2.1 Ca 2 channel inhibition is independent of Ca V (cid:2) -subunit-induced current potentiation

RGK (Rad-Gem-Rem) GTPases have been described as potent negative regulators of the Ca 2 (cid:1) influx via high-threshold voltage-activated Ca 2 (cid:1) channels. Recent work, mostly performed on Ca V 1.2 Ca 2 (cid:1) channels, has highlighted the crucial role played by the channel auxiliary Ca V (cid:2) subunits and identified several GTPase and (cid:2) -subunit protein domains involved in this regulation. We now extend these conclusions by producing the first complete characterization of the effects of Gem, Rem, and Rem2 on the neuronal Ca V 2.1 Ca 2 (cid:1) channels expressed with Ca V (cid:2) 1 or Ca V (cid:2) 2 subunits. Current inhibition is limited to a decrease in amplitude with no modification in the voltage dependence or kinetics of the current. We demonstrate that this inhibition can occur for Ca V (cid:2) constructs with impaired capacity to induce current potentiation, but that it is lost for Ca V (cid:2) constructs deleted for their (cid:2) -interaction domain. The RGK C-terminal last (cid:1) 80 amino acids are sufficient to allow potent current inhibition and in vivo (cid:2) -subunit/Gem interaction. Inter-estingly, although Gem and Gem carboxy-terminus induce a completely different pattern of (cid:2) -subunit cellular localization, they both potently inhibit Ca V 2.1 channels. These data therefore set the status of neuronal

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