Metabolic regulation of calcium homeostasis via SERCA succination.

Although calcium homeostasis is disrupted in metabolic diseases, its metabolic regulation remains unclear. Here, we identify a mechanism by which fumarate suppresses sarco/endoplasmic reticulum (ER) calcium ion-adenosine triphosphatase (SERCA) activity via succination of a conserved cysteine residue, impairing ER calcium uptake and promoting metabolic dysfunction in Drosophila. In mammalian cells, high glucose or fumarate inhibits SERCA activity and increases ER calcium release and cytosolic and mitochondrial calcium levels. Mechanistically, we show that fumarate covalently modifies SERCA2b at Cys875 and that a Cys875Ser mutant resists fumarate-induced inhibition. In Drosophila, knock-in flies with the corresponding Cys875Ser mutation preserve ER calcium homeostasis and are protected from hyperglycemia, glucose intolerance, and reduced survival on a high-sugar diet. These effects are phenocopied by pharmacological fumarate reduction or allosteric SERCA activation. Collectively, these findings suggest that fumarate-mediated SERCA inhibition provides a mechanistic link between glucose metabolism and calcium homeostasis, with potential relevance to metabolic dysfunction.