Coupling of a voltage-gated Ca(2+) channel homologue with a plasma membrane H(+) -ATPase in yeast.

Yeast has a homologue of mammalian voltage-gated Ca(2+) channels (VGCCs), enabling the efficient uptake of Ca(2+) . It comprises two indispensable subunits, Cch1 and Mid1, equivalent to the mammalian pore-forming α1 and auxiliary α2 /δ subunits, respectively. Unlike the physiological roles of Cch1/Mid1 channels, the regulatory mechanisms of the yeast VGCC homologue remain unclear. Therefore, we screened candidate proteins that interact with Mid1 by an unbiased proteomic approach and identified a plasma membrane H(+) -ATPase, Pma1, as a candidate. Mid1 coimmunoprecipitated with Pma1, and Mid1-EGFP colocalized with Pma1-mCherry at the plasma membrane. The physiological relevance of their interaction was determined using the temperature-sensitive mutant, pma1-10. At the nonpermissive temperature, the membrane potential was less negative and Ca(2+) uptake was lower in pma1-10 than in wild-type cells. Increased extracellular H(+) increased the rate of Ca(2+) uptake. Therefore, H(+) extrusion by Pma1 may be important for Ca(2+) influx through Cch1/Mid1. These results suggest that Pma1 interacts physically with Cch1/Mid1 Ca(2+) channels to enhance their activity via its H(+) -pumping activity.

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