| Cysteine S-nitrosation is a post-translational modification that reversibly regulates the activities of proteins sensitive to the alteration of redox environment. It has been shown to modulate several mitochondrial functions, including respiration and apoptosis. However, the regulation and the target proteins of such modification in rat brain mitochondria remain elusive. In this dissertation, it is shown that GSNO, a physiological carrier of NO + and a potent effector of S-nitrosation, induces protein S-nitrosation in all compartments of intact rat brain mitochondria, and such modification is efficiently reversed by both exogenous and endogenous GSH, thus demonstrating the importance of GSH as an anti-nitrosative agent in the mitochondria. In the last decade, unique form of NOS is discovered in the mitochondria, termed mtNOS, with tremendous implication in mitochondria NO chemistry. Here the mtNOS activity is demonstrated to be regulated by mitochondrial respiratory activities, which at the same time are inhibited by RNS from mtNOS, forming a regulatory loop. It is also shown that the activation of mtNOS in isolated rat brain mitochondria induces significant protein S-nitrosation. Intriguingly, ATP synthase F1 complex alpha subunit and adenine nucleotide translocase are identified as common targets of S-nitrosation for both extra-mitochondrial GSNO and intra-mitochondrial mtNOS. S-nitrosation of critical cysteines inhibits the ATPase activity and potentiates the Ca2+-induced permeability transition. This study highlights the importance of post-translational modification on mitochondrial protein in response to NO regulation. It also provides additional mechanistic insight to help us understand the NO-mediated modulation of mitochondrial energy production and Ca2+ homeostasis/apoptosis. |
