Abstract
BackgroundSmall Rho-GTPases are critical mediators of neuronal plasticity and are involved in the pathogenesis of several psychiatric and neurological disorders. Rac-GTPase forms a multiprotein complex with upstream and downstream regulators that are essential for the spatiotemporal transmission of Rac signaling. The sigma-1 receptor (Sig1R) is a ligand-regulated membrane protein chaperone, and multiprotein complex assembly is essential to sigma-receptor function.ResultsUsing immunoprecipitation techniques, we have shown that in mitochondrial membranes Sig1R could directly interact with Rac1. Besides Rac1, the Sig1R forms complexes with inositol 1,4,5-trisphosphate receptor and Bcl2, suggesting that mitochondrial associated membranes (MAM) are involved in this macromolecular complex formation. Assembly of this complex is ligand-specific and depends on the presence of sigma agonist/antagonist, as well as on the presence of GTP/GDP. Treatment of mitochondrial membranes with (+)-pentazocine leads to the (+)-pentazocine-sensitive phosphorylation of Bad and the pentazocine-sensitive NADPH-dependent production of ROS.ConclusionWe suggest that Sig1R through Rac1 signaling induces mild oxidative stress that possibly is involved in the regulation of neuroplasticity, as well as in the prevention of apoptosis and autophagy.
Highlights
Small Rho-GTPases are critical mediators of neuronal plasticity and are involved in the pathogenesis of several psychiatric and neurological disorders
After incubation mitochondria were precipitated by centrifugation at 20,000 × g for 20 min, pellets were resuspended in ice-cold lysis buffer (20 mM Tris–HCl pH 8.0, 137 mM NaCl, 10% glycerol, 1% Triton X-100, 2 mM Ethylenediaminetetraacetic acid (EDTA)) and unsolubilized material was removed by centrifugation (60 min at 20 000 × g)
Rac1 interacts with sigma-1 receptor (Sig1R) through the multiprotein complex To investigate the association of Sig1R with Rac1 and other mitochondrial proteins immunoprecipitation experiments were performed
Summary
We have shown that in mitochondrial membranes Sig1R could directly interact with Rac. Besides Rac, the Sig1R forms complexes with inositol 1,4,5-trisphosphate receptor and Bcl, suggesting that mitochondrial associated membranes (MAM) are involved in this macromolecular complex formation. Of this complex is ligand-specific and depends on the presence of sigma agonist/antagonist, as well as on the presence of GTP/GDP. Treatment of mitochondrial membranes with (+)-pentazocine leads to the (+)-pentazocine-sensitive phosphorylation of Bad and the pentazocine-sensitive NADPH-dependent production of ROS
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