Orai, RyR, and IP(3)R channels cooperatively regulate calcium signaling in brain mid-capillary pericytes

Pericytes are multifunctional cells of the vasculature that are vital to brain homeostasis, yet many of their fundamental physiological properties, such as Ca(2+) signaling pathways, remain unexplored. We performed pharmacological and ion substitution experiments to investigate the mechanisms underlying pericyte Ca(2+) signaling in acute cortical brain slices of PDGFRβ-Cre::GCaMP6f mice. We report that mid-capillary pericyte Ca(2+) signalling differs from ensheathing type pericytes in that it is largely independent of L- and T-type voltage-gated calcium channels. Instead, Ca(2+) signals in mid-capillary pericytes were inhibited by multiple Orai channel blockers, which also inhibited Ca(2+) entry triggered by endoplasmic reticulum (ER) store depletion. An investigation into store release pathways indicated that Ca(2+) transients in mid-capillary pericytes occur through a combination of IP(3)R and RyR activation, and that Orai store-operated calcium entry (SOCE) is required to sustain and amplify intracellular Ca(2+) increases evoked by the GqGPCR agonist endothelin-1. These results suggest that Ca(2+) influx via Orai channels reciprocally regulates IP(3)R and RyR release pathways in the ER, which together generate spontaneous Ca(2+) transients and amplify Gq-coupled Ca(2+) elevations in mid-capillary pericytes. Thus, SOCE is a major regulator of pericyte Ca(2+) and a target for manipulating their function in health and disease.