Coupling Of A Voltage-Gated Ca2+ Channel Homologue With A Plasma Membrane H+-Atpase In Yeast

Yeast has a homologue of mammalian voltage-gated Ca2+ channels (VGCCs), enabling the efficient uptake of Ca2+. It comprises two indispensable subunits, Cch1 and Mid1, equivalent to the mammalian pore-forming (1) and auxiliary (2)/ 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 Ca2+ uptake was lower in pma1-10 than in wild-type cells. Increased extracellular H+ increased the rate of Ca2+ uptake. Therefore, H+ extrusion by Pma1 may be important for Ca2+ influx through Cch1/Mid1. These results suggest that Pma1 interacts physically with Cch1/Mid1 Ca2+ channels to enhance their activity via its H+-pumping activity.