Cisd2 modulates the differentiation and functioning of adipocytes by regulating intracellular Ca²⁺ homeostasis

CISD2 is a causative gene associated with Wolfram syndrome (WFS). However, it remains a mystery as to how the loss of CISD2 causes metabolic defects in patients with WFS. Investigation on the role played by Cisd2 in specific cell types may help us to resolve these underlying mechanisms. White adipose tissue (WAT) is central to the maintenance of energy metabolism and glucose homeostasis in humans. In this study, adipocyte-specific Cisd2 knockout (KO) mice showed impairment in the development of epididymal WAT (eWAT) in the cell autonomous manner. A lack of Cisd2 caused defects in the biogenesis and function of mitochondria during differentiation of adipocytes in vitro. Insulin-stimulated glucose uptake and secretion of adiponectin by the Cisd2 KO adipocytes were decreased. Moreover, Cisd2 deficiency increased the cytosolic level of Ca²⁺ and induced Ca²⁺-calcineurin-dependent signaling that inhibited adipogenesis. Importantly, Cisd2 was found to interact with Gimap5 on the mitochondrial and ER membranes and thereby modulate mitochondrial Ca²⁺ uptake associated with the maintenance of intracellular Ca²⁺ homeostasis in adipocytes. Thus, it would seem that Cisd2 plays an important role in intracellular Ca²⁺ homeostasis, which is required for the differentiation and functioning of adipocytes as well as the regulation of glucose homeostasis in mice.