CLCA2 is a positive regulator of store-operated calcium entry and TMEM16A

The Chloride Channel Accessory (CLCA) protein family was first characterized as regulators of calcium-activated chloride channel (CaCC) currents (I(CaCC)), but the mechanism has not been fully established. We hypothesized that CLCAs might regulate I(CaCC) by modulating intracellular calcium levels. In cells stably expressing human CLCA2 or vector, we found by calcium imaging that CLCA2 moderately enhanced intracellular-store release but dramatically increased store-operated entry of calcium upon cytosolic depletion. Moreover, another family member, CLCA1, produced similar effects on intracellular calcium mobilization. Co-immunoprecipitation revealed that CLCA2 interacted with the plasma membrane store-operated calcium channel ORAI-1 and the ER calcium sensor STIM-1. The effect of CLCA2 on I(CaCC) was tested in HEK293 stably expressing calcium-activated chloride channel TMEM16A. Co-expression of CLCA2 nearly doubled I(CaCC) in response to a calcium ionophore. These results unveil a new mechanism by which CLCA family members activate I(CaCC) and suggest a broader role in calcium-dependent processes.