Succinate receptor 1 signaling mutually depends on subcellular localization and cellular metabolism.

Abstract

Succinate is a pivotal tricarboxylic acid cycle metabolite but also specifically activates the G_i- and G_q-coupled succinate receptor 1 (SUCNR1). Contradictory roles of succinate and succinate-SUCNR1 signaling include reports about its anti- or pro-inflammatory effects. The link between cellular metabolism and localization-dependent SUCNR1 signaling qualifies as a potential cause for the reported conflicts. To systematically address this connection, we used a diverse set of methods, including several bioluminescence resonance energy transfer-based biosensors, dynamic mass redistribution measurements, second messenger and kinase phosphorylation assays, calcium imaging, and metabolic analyses. Different cellular metabolic states were mimicked using glucose (Glc) or glutamine (Gln) as available energy substrates to provoke differential endogenous succinate (SUC) production. We show that SUCNR1 signaling, localization, and metabolism are mutually dependent, with SUCNR1 showing distinct spatial and energy substrate-dependent G_i and G_q protein activation. We found that Gln-consumption associated with a higher rate of oxidative phosphorylation causes increased extracellular SUC concentrations, accompanied by a higher rate of SUCNR1 internalization, reduced miniG_q protein recruitment to the plasma membrane, and lower Ca²⁺ signals. In Glc, under basal conditions, SUCNR1 causes stronger G_q than G_i protein activation, while the opposite is true upon stimulation with an agonist. In addition, SUCNR1 specifically interacts with miniG proteins in endosomal compartments. In THP-1 cells, polarized to M2-like macrophages, endogenous SUCNR1-mediated G_i signaling stimulates glycolysis, while G_q signaling inhibits the glycolytic rate. Our results suggest that the metabolic context determines spatially dependent SUCNR1 signaling, which in turn modulates cellular energy homeostasis and mediates adaptations to changes in SUC concentrations.