PDI-mediated S-nitrosylation of DRP1 facilitates DRP1-S616 phosphorylation and mitochondrial fission in CA1 neurons

Dynamin-related protein 1 (DRP1) is a key molecule to regulate mitochondrial fission. DRP1 activity is modulated by phosphorylation and S-nitrosylation on serine and cysteine residues, respectively. However, it is still unexplored whether S-nitrosylation of DRP1 affects its phosphorylation. In the present study, we found that N-omega-nitro-L-arginine methyl ester hydrochloride (L-NAME, a NOS inhibitor) abolished S-nitrosylated (SNO-DRP1) and DRP1-serine (S) 616 phosphorylation levels in CA1 neurons under physiological condition. L-NAME led to mitochondrial elongation. In spite of the sustained NO synthesis, status epilepticus (a prolonged seizure activity, SE) diminished SNO-DRP1 and DRP1-S616 levels in CA1 neurons, accompanied by the reduced protein disulfide isomerase (PDI) expression and mitochondrial elongation. SE did not influence thioredoxin 1 (Trx1, a denitrosylating enzyme) activity, which was unaffected by L-NAME under physiological and post-SE condition. PDI knockdown decreased SNO-DRP1 and DRP1-S616 levels concomitant with mitochondrial elongation in CA1 neurons without altered NO synthesis under physiological condition. These findings indicate that PDI may be a NO donor of DRP1 to regulate DRP1-S616 phosphorylation, independent of Trx1 activity. Therefore, we suggest that PDI-mediated S-nitrosylation of DRP1 may be one of the major regulatory modifications for mitochondrial dynamics.