Nitric oxide S -nitrosylates serine racemase, mediating feedback inhibition of d -serine formation

Abstract

Serine racemase (SR) generates D-serine, a coagonist with glutamate at NMDA receptors. We show that SR is physiologically S-nitrosylated leading to marked inhibition of enzyme activity. Inhibition involves interactions with the cofactor ATP reflecting juxtaposition of the ATP-binding site and cysteine-113 (C113), the site for physiological S-nitrosylation. NMDA receptor physiologically enhances SR S-nitrosylation by activating neuronal nitricoxide synthase (nNOS) . These findings support a model whereby postsynaptic stimulation of nitric-oxide (NO) formation feeds back to presynaptic cells to S-nitrosylate SR and decrease D-serine availability to postsynaptic NMDA receptors.neuronal nitric-oxide synthase ͉ NMDA receptor ͉ S-nitrosylation G lutamate neurotransmission through NMDA receptors requires a coagonist originally thought to be glycine. Recent studies indicate that in most portions of the brain, D-serine is the physiological coagonist because selective degradation of D-serine but not glycine markedly reduces NMDA transmission (1, 2), whereas retraction of D-serine-producing glia in the hypothalamus of lactating rats also diminishes NMDA transmission (2). D-serine is formed from L-serine by serine racemase (SR), which, like D-serine, is selectively enriched in glia (2, 3), although recent studies indicate some neuronal localization (4). SR, a pyridoxal phosphate-requiring enzyme, also displays an absolute requirement for ATP, which is not hydrolyzed during SR activation (5). SR binds the glutamate receptor interacting protein, which also binds to AMPA subtypes of glutamate receptors with glutamate receptor interacting protein markedly activating SR and providing a means whereby glutamate stimulation of SR-containing cells augments D-serine formation (6).In postsynaptic cells, NMDA signaling is mediated in part by neuronal nitric-oxide synthase (nNOS) because calcium entering through NMDA receptor channels binds to calmodulin associated with nNOS (7,8). Extensive studies have documented a feedback from postsynaptic to presynaptic glutamatergic nerve terminals, which modulates NMDA neurotransmission, especially in long-term potentiation (9). Nitric oxide (NO) may be a retrograde messenger of long-term potentiation (10-12), although the area is controversial (12). Because SR is a component of the NMDA synaptic complex, we wondered whether it is influenced by NO. In the present study, we demonstrate that SR is physiologically S-nitrosylated leading to inhibition of enzyme activity mediated by interactions with ATP. NMDA transmission stimulates SR S-nitrosylation suggesting a feedback mechanism to diminish presynaptic formation of D-serine. ResultsWe demonstrated S-nitrosylation of SR in multiple ways. Incubation of the NO donor S-nitroso-glutathione (GSNO) with SR in vitro leads to robust nitrosylation (Fig. 1A). In HEK293 cells, treatment with the NO donor sodium nitroprusside also provides S-nitrosylation (Fig. 1B). NO produced by nNOS S-nitrosylates SR, as is evident in HEK293 cells transfected with nNOS (Fi...

Does schizophrenia arise from oxidative dysregulation of parvalbumin-interneurons in the developing cortex?

“…Regulatory redox sites have been found in many proteins that are key to glutamatergic neurotransmission including, serine-racemase that is responsible for the synthesis of the endogenous modulator of the glycine site in NMDA receptors (Mustafa et al, 2007); glutamine synthase that is responsible for glutamate synthesis (Pinteaux et al, 1996); as well as the excitatory amino acid transporters that together with glutamine synthase are involved in the regulation of extraneuronal levels of glutamate (Volterra et al, 1994). Last, but not least, the NMDA receptor itself is highly sensitive to redox modulation through a redoxsensitive site (Herin and Aizenman, 2004), and decreases in the main antioxidant in brain, GSH, or reduced activity of GSH-peroxidase lead to oxidized hypofunctional NMDA-Rs (Jiang et al, 2000;Steullet et al, 2006).…”

Glycolytic flux controls d -serine synthesis through glyceraldehyde-3-phosphate dehydrogenase in astrocytes

“…S1I). Neither a nitric oxide (NO) synthase inhibitor, N G -nitro-L-arginine methyl ester (L-NAME), nor an NO scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), recovered D-serine reduction caused by Anti A, excluding the involvement of SRR inhibition by s-nitrosylation (20) (Fig. S1J).…”

“…SRR is regulated by interacting proteins, including glutamate receptor interacting protein (GRIP) (16), protein interacting with PRKCA 1 (17), disrupted in schizophrenia 1 (18), and golgin A3 (19). It is also known that the enzymatic activity of SRR is inhibited by nitric oxide in presynaptic neurons (20) and by phosphatidylinositol (4, 5)-bisphosphate (PIP2) in astrocytes (21), both of which are involved in feedback regulation via glutamate receptors. Thus, regulation of D-serine by SRR impacts excitatory neurotransmission through NMDA glutamate receptors.…”

NMDA- and β-Amyloid1–42-Induced Neurotoxicity Is Attenuated in Serine Racemase Knock-Out Mice

“…Enzymatic characterizations of purified SR suggest that the catalytic constant (k cat ) for D-serine in the racemization by mouse SR is ϳ1/400 of prokaryotic racemase, and the k cat /K m of SR in the dehydration of L-serine is higher than those in the racemization for serine (Yoshimura and Goto, 2008). The activity of SR is decreased by glycine at a physiological concentration (Dunlop and Neidle, 2005) and by modification with S-nitrosylation (Mustafa et al, 2007). Thus, the contribution of SR to D-serine production in the brain should be evaluated in vivo.…”