Seipin localizes at endoplasmic-reticulum-mitochondria contact sites to control mitochondrial calcium import and metabolism in adipocytes.

Deficiency of the endoplasmic reticulum (ER) protein seipin results in generalized lipodystrophy by incompletely understood mechanisms. Here, we report mitochondrial abnormalities in seipin-deficient patient cells. A subset of seipin is enriched at ER-mitochondria contact sites (MAMs) in human and mouse cells and localizes in the vicinity of calcium regulators SERCA2, IP3R, and VDAC. Seipin association with MAM calcium regulators is stimulated by fasting-like stimuli, while seipin association with lipid droplets is promoted by lipid loading. Acute seipin removal does not alter ER calcium stores but leads to defective mitochondrial calcium import accompanied by a widespread reduction in Krebs cycle metabolites and ATP levels. In mice, inducible seipin deletion leads to mitochondrial dysfunctions preceding the development of metabolic complications. Together, these data suggest that seipin controls mitochondrial energy metabolism by regulating mitochondrial calcium influx at MAMs. In seipin-deficient adipose tissue, reduced ATP production compromises adipocyte properties, contributing to lipodystrophy pathogenesis. [Display omitted] • Seipin is enriched at ER-MAMs • Seipin interacts with MAM calcium regulators in a nutritionally regulated manner • Adipocyte seipin deficiency impairs mitochondrial calcium import and ATP production • Inducible seipin removal from adipose tissue leads to rapid mitochondrial dysfunction Combot et al. demonstrate that seipin is enriched at ER-mitochondria contact sites and that seipin deficiency leads to defective mitochondrial calcium import accompanied by a reduction in ATP production. In mice, inducible seipin deletion from adipocytes leads to early mitochondrial dysfunction, which probably contributes to the pathogenesis of seipin-related lipodystrophy. [ABSTRACT FROM AUTHOR]