Figure 1. Rem inhibition of reconstituted Ca_V1.2 channels.

A, exemplar family of whole‐cell Ba²⁺ currents from recombinant Ca_V1.2 channels (α_1C + β_2a) reconstituted in HEK293 cells either without (left) or with (right) co‐expression of Rem. B, population I‐V curves from Ca_V1.2 channels in the absence (■) or presence () of co‐expressed Rem. C, schematic diagram showing three distinct mechanisms (I‐III) utilized by Rem to inhibit recombinant Ca_V1.2 channels. In mechanism I, co‐expressed Rem results in a decrease in the number of channels at the cell surface (N) due to enhanced Ca_V1.2 endocytosis. Mechanism II involves a reduction in the open probability (P _o) of channels residing on the plasma membrane without impacting on voltage sensor movement as measured by total gating charge (Q _max). This mechanism requires Rem simultaneously binding to the Ca_Vβ subunit (using the guanine nucleotide binding domain) and the plasma membrane (via the polybasic distal C‐terminus). Mechanism III involves an impaired movement of the voltage sensor movement of surface channels as measured by a decreased Q _max (observed even when N is completely rescued by co‐expressing dominant negative dynamin). Mechanism III is blocked by a mutation (T94N) that favours GDP over GTP binding to Rem, suggesting it requires GTP‐bound Rem.