The orphan solute carrier SLC10A7 is a novel negative regulator of intracellular calcium signaling.

SLC10A7 represents an orphan member of the Solute Carrier Family SLC10. Recently, mutations in the human SLC10A7 gene were associated with skeletal dysplasia, amelogenesis imperfecta, and decreased bone mineral density. However, the exact molecular function of SLC10A7 and the mechanisms underlying these pathologies are still unknown. For this reason, the role of SLC10A7 on intracellular calcium signaling was investigated. SLC10A7 protein expression was negatively correlated with store-operated calcium entry (SOCE) via the plasma membrane. Whereas SLC10A7 knockout HAP1 cells showed significantly increased calcium influx after thapsigargin, ionomycin and ATP/carbachol treatment, SLC10A7 overexpression reduced this calcium influx. Intracellular Ca2+ levels were higher in the SLC10A7 knockout cells and lower in the SLC10A7-overexpressing cells. The SLC10A7 protein co-localized with STIM1, Orai1, and SERCA2. Most of the previously described human SLC10A7 mutations had no effect on the calcium influx and thus were confirmed to be functionally inactive. In the present study, SLC10A7 was established as a novel negative regulator of intracellular calcium signaling that most likely acts via STIM1, Orai1 and/or SERCA2 inhibition. Based on this, SLC10A7 is suggested to be named as negative regulator of intracellular calcium signaling (in short: RCAS).