Nitric oxide-mediated posttranslational modifications control neurotransmitter release by modulating complexin farnesylation and enhancing its clamping ability

Abstract

Nitric oxide (NO) regulates neuronal function and thus is critical for tuning neuronal communication. Mechanisms by which NO modulates protein function and interaction include posttranslational modifications (PTMs) such as S-nitrosylation. Importantly, cross signaling between S-nitrosylation and prenylation can have major regulatory potential. However, the exact protein targets and resulting changes in function remain elusive. Here, we interrogated the role of NO-dependent PTMs and farnesylation in synaptic transmission. We found that NO compromises synaptic function at the Drosophila neuromuscular junction (NMJ) in a cGMP-independent manner. NO suppressed release and reduced the size of available vesicle pools, which was reversed by glutathione (GSH) and occluded by genetic up-regulation of GSH-generating and de-nitrosylating glutamate-cysteine-ligase and S-nitroso-glutathione reductase activities. Enhanced nitrergic activity led to S-nitrosylation of the fusion-clamp protein complexin (cpx) and altered its membrane association and interactions with active zone (AZ) and soluble N-ethyl-maleimide-sensitive fusion protein Attachment Protein Receptor (SNARE) proteins. Furthermore, genetic and pharmacological suppression of farnesylation and a nitrosylation mimetic mutant of cpx induced identical physiological and localization phenotypes as caused by NO. Together, our data provide evidence for a novel physiological nitrergic molecular switch involving S-nitrosylation, which reversibly suppresses farnesylation and thereby enhances the net-clamping function of cpx. These data illustrate a new mechanistic signaling pathway by which regulation of farnesylation can fine-tune synaptic release.

Nitric Oxide in Dental Pulp Tissue: From Molecular Understanding to Clinical Application in Regenerative Endodontic Procedures

“…25,27 The protein S-nitrosylation reaction (in which NO reacts with cysteine thiols to form S-nitrosylated proteins) is an important posttranslational modification and thus regulates protein structures and functions. 33,[39][40][41] which may cause significant oxidative damage on various target biomolecules, such as lipids, sugars, DNA, and proteins. 25,42 Functions of the NO System Inside Dental Pulp Tissue and the Involved Mechanisms…”

Alterations in neuronal metabolism contribute to the pathogenesis of prion disease

“…In the brain, physiological NO signalling contributes to regulation of neuronal excitability [45,46], neurotransmitter release involved in learning and memory, synaptic plasticity and neuroprotection [47]. Impact of NO signalling on synaptic function is mediated via posttranslational modifications of proteins involved in vesicular release across different cellular systems and species [48][49][50][51] indicating the importance of this conserved signalling route. However, cytotoxic nitrergic signalling is associated with the immune response and plays a key role in regulating inflammatory processes and redox stress, ultimately contributing to neuronal degeneration.…”

Sub-acute restraint stress progressively increases oxidative/nitrosative stress and inflammatory markers while transiently upregulating antioxidant gene expression in the rat hippocampus

“…A recent wealth of evidence has demonstrated that free radicals, and most notably NO, play a crucial role in the regulation of stress effects and may be directly involved in the pathophysiology of stress-related disorders [13][14][15][16][17]. Under normal conditions, NO produced by the neuronal isoform of nitric oxide synthase (nNOS) is an important neurotransmitter associated with synaptic plasticity, memory formation, and neurotransmitter release [18,19]. Several studies have demonstrated that the binding partner of nNOS, nitric oxide synthase 1 adaptor protein (Nos1ap; also known as Cterminal PDZ ligand of neuronal nitric oxide synthase or CAPON), plays a novel role in mediating nNOS signaling and its interaction with the NMDA receptor [20,21].…”