Study On The Role Of Sigma-1 Receptor In Regulating Mitochondria And Physiological Pathways

Endoplasmic reticulum(ER)calcium homeostasis is a crucial process in metabolic diseases such as obesity and diabetes,and the mitochondria-associated ER membrane(MAM)is important for ER-mitochondrial calcium flux according to the hotspot hypothesis.The sigma-1 receptor(SIG-1R)is a well-characterized MAM chaperone that regulates ER-mitochondrial calcium flux.However,the influence of SIG-1R on ER-mitochondria contact,mitochondria,metabolic pathways and neuronal pathways remain unclear.In this study,we constructed SIG-1R-knockout He La cells and rat lines through TALEN technology.We observed ER and mitochondrial in He La cells through confocal microscopy and isolated MAM from He La cells.We also observed ER and mitochondrial in rat tissues through transmission electronic microscopy(TEM)and isolated MAM from rat tissues.We found that the knockout of SIG-1R increased MAM in vitro and in vivo.To figure out the mechanism underlying this increase,we studied the regulation of mitochondrial morphology in He La cells.We demonstrated that the loss of SIG-1R induces elongated mitochondria,and the overexpression of SIG-1R rescued this alteration.Dramatic increase in the cytosolic calcium level caused severe mitochondrial division while the MAM calcium release induced rapid and reversible mitochondrial fission.ER stress responses could not alter mitochondrial morphology but caused alterations in the proteins associated with the inner mitochondrial membrane cristae.The loss or overexpression of SIG-1R could not influence the average cytosolic calcium level,and could not affect the levels and localization of proteins associated with mitochondrial dynamics.Thus we inferred that SIG-1R regulate mitochondrial morphology through regulating the MAM calcium signaling,and the increased MAM might be a compensation for the insufficient mitochondrial division.In the study of the physiological role of SIG-1R in animals,we discovered that the loss of SIG-1R affects the insulin signaling pathway and metabolic pathways in liver,cell adhesion molecules(CAMs)and extracellular matrix(ECM)pathways in spinal cord through RNA-seq analysis.We validated the alterations in gene expression through reverse-transcription quantitative PCR(RT-q PCR).Furthermore,the activated insulin signaling pathway caused by the knockout of SIG-1R protected rats from dietinduced obesity(DIO).Taken together,our results identified SIG-1R as an in vivo regulator of metabolism affecting body weight balance.In the study on spinal cord motor neurons,we found that the loss of SIG-1R altered the morphology of dentritic spines,decreased the dentritic spine density and caused demyelination,suggesting that the SIG-1R had protective effect on these neurons.These findings may contribute to the development of new therapeutics for metabolic and neuronal disorders.