Store-operated Ca²⁺ channel in renal microcirculation and glomeruli

Store-operated Ca²⁺ channel (SOC) is defined as a channel that opens in response to depletion of the internal Ca²⁺ stores. During the last decade, many investigators have made a great effort to identify and characterize SOC, and to evaluate its physiologic function and pathophysiologic relevance in a variety of cell lines, primary cultures, and native tissues. To date, accumulating evidence has demonstrated that SOC is an essential Ca ²⁺ entry mechanism in vascular smooth-muscle cells of renal microvasculature and glomerular mesangial cells, both of which tightly control glomerular hemodynamics and filtration. Store-operated Ca²⁺, combined with other types of Ca²⁺ entry channels, constitutes a profile of Ca²⁺ changes in response to physiologic vasoconstrictors and, thereby, regulates renal microcirculation and mesangial function. In addition, SOC is associated with altered Ca²⁺ signaling occurring in diseased kidneys, such as diabetic nephropathy. Although the gating mechanism and molecular identity of SOC are still enigmatic and may be cell-type and tissue specific, data from several independent groups suggest that protein kinase C plays an important role in SOC activation and that certain isoforms of canonical transient receptor potential (TRPC) proteins are candidates of SOC in renal microvessels and mesangial cells.