Neurobiological Basis of Neuronal Survival

National Institute On Drug Abuse

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Abstract

The interface between the endoplasmic reticulum (ER) and mitochondria, termed the MAM (Mitochondria-Associated-ER-Membrane), plays an important role in supplying Ca2+ from the ER into mitochondria for the production of energy compound ATP for cellular survival. We report here that the sigma-1 receptor at the MAM plays a critical role in the clinical unmet disease called Wolfram Syndrome. The finding is summarized as follows. The Wolfram syndrome is a rare autosomal recessive disease affecting many organs with life-threatening consequences and currently no treatment is available. Therefore, the aim of this study was to identify and propose a novel relevant therapy. The pathology is related to the deficient activity of wolframin, an endoplasmic reticulum (ER) transmembrane protein involved in contacts between ER and mitochondria termed mitochondria associated-ER membranes (MAMs). Inherited mutations usually reduce the proteins stability, altering its homeostasis and ultimately reducing ER to mitochondria Ca2+ transfer resulting in mitochondrial dysfunction and cell death. We here demonstrate that activation of the sigma-1 receptor (S1R), an endoplasmic reticulum resident protein involved in Ca2+ transfer, could counteract the functional alterations of MAMs due to wolframin deficiency. The S1R agonist PRE-084 restored Ca2+ transfer and mitochondrial respiration in vitro and was able to alleviate the behavioral symptoms observed in the genetic animal models of the disease, i.e. hyperlocomotion in Wfs1abKO zebrafish and memory deficits and anxiety in Wfs1Exon8 mice. Our findings provide a new therapeutic strategy for Wolfram syndrome patients, by efficiently boosting MAM function using the ligand operated S1R chaperone. Moreover, such strategy could be expanded to other degenerative and mitochondrial diseases involving MAMs dysfunction.