Showing papers by "David S. Bredt published in 1999"
TL;DR: NO appears to play a major role in the pathophysiology of stroke, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis, and in the brain, NO functions as a neuromodulator and appears to mediate aspects of learning and memory.
Abstract: Modern molecular biology has revealed vast numbers of large and complex proteins and genes that regulate body function. By contrast, discoveries over the past ten years indicate that crucial features of neuronal communication, blood vessel modulation and immune response are mediated by a remarkably simple chemical, nitric oxide (NO). Endogenous NO is generated from arginine by a family of three distinct calmodulin- dependent NO synthase (NOS) enzymes. NOS from endothelial cells (eNOS) and neurons (nNOS) are both constitutively expressed enzymes, whose activities are stimulated by increases in intracellular calcium. Immune functions for NO are mediated by a calcium-independent inducible NOS (iNOS). Expression of iNOS protein requires transcriptional activation, which is mediated by specific combinations of cytokines. All three NOS use NADPH as an electron donor and employ five enzyme cofactors to catalyze a five-electron oxidation of arginine to NO with stoichiometric formation of citrulline. The highest levels of NO throughout the body are found in neurons, where NO functions as a unique messenger molecule. In the autonomic nervous system NO functions NO functions as a major non-adrenergic non-cholinergic (NANC) neurotransmitter. This NANC pathway plays a particularly important role in producing relaxation of smooth muscle in the cerebral circulation and the gastrointestinal, urogenital and respiratory tracts. Dysregulation of NOS activity in autonomic nerves plays a major role in diverse pathophysiological conditions including migraine headache, hypertrophic pyloric stenosis and male impotence. In the brain, NO functions as a neuromodulator and appears to mediate aspects of learning and memory. Although endogenous NO was originally appreciated as a mediator of smooth muscle relaxation, NO also plays a major role in skeletal muscle. Physiologically muscle-derived NO regulates skeletal muscle contractility and exercise-induced glucose uptake. nNOS occurs at the plasma membrane of skeletal muscle which facilitates diffusion of NO to the vasculature to regulate muscle perfusion. nNOS protein occurs in the dystrophin complex in skeletal muscle and NO may therefore participate in the pathophysiology of muscular dystrophy. NO signalling in excitable tissues requires rapid and controlled delivery of NO to specific cellular targets. This tight control of NO signalling is largely regulated at the level of NO biosynthesis. Acute control of nNOS activity is mediated by allosteric enzyme regulation, by posttranslational modification and by subcellular targeting of the enzyme. nNOS protein levels are also dynamically regulated by changes in gene transcription, and this affords long-lasting changes in tissue NO levels. While NO normally functions as a physiological neuronal mediator, excess production of NO mediates brain injury. Overactivation of glutamate receptors associated with cerebral ischemia and other excitotoxic processes results in massive release of NO. As a free radical, NO is inherently reactive and mediates cellular toxicity by damaging critical metabolic enzymes and by reacting with superoxide to form an even more potent oxidant, peroxynitrite. Through these mechanisms, NO appears to play a major role in the pathophysiology of stroke, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis.
771 citations
TL;DR: It is found that the nNOS PDZ domain can bind PSD-95 PDZ2 and a COOH-terminal peptide simultaneously, which further expands the scope for assembly of protein networks by PDZ domains.
541 citations
TL;DR: The PDZ protein interaction domain of neuronal nitric oxide synthase (nNOS) can heterodimerize with the PDZ domains of postsynaptic density protein 95 and syntrophin through interactions that are not mediated by recognition of a typical carboxyl-terminal motif.
Abstract: The PDZ protein interaction domain of neuronal nitric oxide synthase (nNOS) can heterodimerize with the PDZ domains of postsynaptic density protein 95 and syntrophin through interactions that are not mediated by recognition of a typical carboxyl-terminal motif. The nNOS-syntrophin PDZ complex structure revealed that the domains interact in an unusual linear head-to-tail arrangement. The nNOS PDZ domain has two opposite interaction surfaces—one face has the canonical peptide binding groove, whereas the other has a β-hairpin “finger.” This nNOS β finger docks in the syntrophin peptide binding groove, mimicking a peptide ligand, except that a sharp β turn replaces the normally required carboxyl terminus. This structure explains how PDZ domains can participate in diverse interaction modes to assemble protein networks.
539 citations
TL;DR: It is reported that a neuronal-type NO synthase (NOS) is located on cardiac sarcoplasmic reticulum (SR) membrane vesicles and that endogenous NO.
Abstract: NO⋅ is a free radical that modulates heart function and metabolism. We report that a neuronal-type NO synthase (NOS) is located on cardiac sarcoplasmic reticulum (SR) membrane vesicles and that endogenous NO⋅ produced by SR-associated NOS inhibits SR Ca2+ uptake. Ca2+-dependent biochemical conversion of l-arginine to l-citrulline was observed from isolated rabbit cardiac SR vesicles in the presence of NOS substrates and cofactors. Endogenous NO⋅ was generated from the vesicles and detected by electron paramagnetic resonance spin-trapping measurements. Immunoelectron microscopy demonstrated labeling of cardiac SR vesicles by using anti-neuronal NOS (nNOS), but not anti-endothelial NOS (eNOS) or anti-inducible NOS (iNOS) antibodies, whereas skeletal muscle SR vesicles had no nNOS immunoreactivity. The nNOS immunoreactivity also displayed a pattern consistent with SR localization in confocal micrographs of sections of human myocardium. Western blotting demonstrated that cardiac SR NOS is larger than brain NOS (160 vs. 155 kDa). No immunodetection was observed in cardiac SR vesicles from nNOS knockout mice or with an anti-nNOSμ antibody, suggesting the possibility of a new nNOS-type isoform. 45Ca uptake by cardiac SR vesicles, catalyzed by Ca2+-ATPase, was inhibited by NO⋅ produced endogenously from cardiac SR NOS, and 7-nitroindazole, a selective nNOS inhibitor, completely prevented this inhibition. These results suggest that a cardiac muscle nNOS isoform is located on SR of cardiac myocytes, where it may respond to intracellular Ca2+ concentration and modulate SR Ca2+ ion active transport in the heart.
493 citations
TL;DR: The requirements for PDZ domains and a C-terminal domain of PSD-95 indicate that protein-protein interactions cooperate with lipid interactions in synaptic targeting, suggesting that a specialized synaptic lipid environment mediates postsynaptic clustering.
335 citations
TL;DR: This work suggests a role for MALS proteins in regulating recruitment of neurotransmitter receptors to the PSD, and identifies a family of small synaptic proteins containing little more than a single PDZ domain.
Abstract: Protein assembly at the postsynaptic density (PSD) of neuronal synapses is mediated in part by protein interactions with PSD-95/discs large/zona occludens-1 (PDZ) motifs. Here, we identify MALS-1, -2, -3, a family of small synaptic proteins containing little more than a single PDZ domain. MALS-1, -2, and -3 are mammalian homologs LIN-7, a Caenorhabditis elegans protein essential for vulval development. In contrast to functions for LIN-7 in epithelial cells, MALS-1 and -2 are selectively expressed in specific neuronal populations in brain and are enriched in PSD fractions. In cultured hippocampal neurons, MALS proteins are clustered together with PSD-95 and NMDA type glutamate receptors, consistent with a postsynaptic localization for MALS proteins. Immunoprecipitation and affinity chromatography studies readily identify association of MALS with PSD-95 and an NMDA receptor subunit. The PDZ domain of MALS selectively binds to peptides terminating in E-T/S-R/X-V/I/L, which corresponds to the C terminus of NMDA type 2 receptors and numerous other ion channels at the PSD. This work suggests a role for MALS proteins in regulating recruitment of neurotransmitter receptors to the PSD.
185 citations
TL;DR: It is reported that the SH3 domain of PSD-95 mediates a specific interaction with the GK domain, which is conserved in the related Drosophila MAGUK protein DLG but not detectable for Caenorhabditis elegans LIN-2.
157 citations
TL;DR: Overexpression of cypin in hippocampal neurons specifically perturbs postsynaptic trafficking of PSD-95 and SAP-102, an effect not produced by overeexpression of other PDZ ligands.
102 citations
TL;DR: The glutamate receptor subunit δ2 has a unique distribution at the parallel fiber–Purkinje cell synapse of the cerebellum, which is developmentally regulated such thatδ2 occurs at both parallel Fiber synapses and climbing fiber synapses early in development but is restricted to parallel fiber synapse in adult animals.
Abstract: The glutamate receptor subunit δ2 has a unique distribution at the parallel fiber–Purkinje cell synapse of the cerebellum, which is developmentally regulated such that δ2 occurs at both parallel fiber synapses and climbing fiber synapses early in development but is restricted to parallel fiber synapses in adult animals. To identify proteins that might be involved in the trafficking or docking of δ2 receptors, we screened a yeast two-hybrid library with the cytosolic C terminus of δ2 and isolated a member of the postsynaptic density (PSD)-95 family of proteins, which are known to interact with the extreme C termini of NMDA receptors. We find that δ2 binds specifically to PSD-93, which is enriched in Purkinje cells. In addition, PSD-93 clusters δ2 when they are coexpressed in heterologous cells, and clustering is disrupted by point mutations of δ2 that disrupt the δ2–PSD-93 interaction. Ultrastructural localization of PSD-93 and δ2 shows they are colocalized at parallel fiber synapses; however, PSD-93 also is present at climbing fiber synapses of the adult rat, where δ2 is not found, indicating that the presence of PSD-93 alone is not sufficient for determining the synaptic expression of δ2.
98 citations
TL;DR: The muscle isoform of phosphofructokinase (PFK-M) is identified as a protein that binds to nNOS both in brain and skeletal muscle and may contribute to neuroprotection of nN OS positive cells.
73 citations
TL;DR: Mice lacking dystrophin-associated protein exhibit a new form of muscular dystrophy in which the integrity of muscle fibres is maintained, but a component of muscle-cell signalling is disrupted.
Abstract: Mice lacking dystrobrevin, a dystrophin-associated protein, exhibit a new form of muscular dystrophy in which the integrity of muscle fibres is maintained, but a component of muscle-cell signalling is disrupted.
TL;DR: PSD-93 is the predominant PSD expressed in the rat kidney and is located primarily in the basolateral membranes of distal nephron and colocalizes with a pool of nNOS in cytoplasmic vesicles and basol lateral membranes of macula densa cells.
01 Jan 1999
TL;DR: Cypin is homologous to a Shaker, and inward rectifier K 1 chan- family of hydrolytic bacterial enzymes and shares nels (Cohen et al., 1996), and to certain peripheral mem-some similarity with collapsin response mediator pro- brane proteins containing a C-terminal PDZ-binding tein (CRMP), a cytoplasmic mediator of semaphorin consensus sequence (tSXV) signalling.
Abstract: Summary hDLG),andSAP-102,allcontainmultipleprotein–protein interaction motifs, including three N-terminal PDZ do- Postsynaptic density 95 (PSD-95/SAP-90) is a mem- mains, an SH3 domain, and a C-terminal region homolo-brane associated guanylate kinase (GK) PDZ protein gous to yeast guanylate kinase (GK) (Muller et al., 1995, thatscaffoldsglutamatereceptorsandassociatedsig- 1996; Brenman et al., 1996a; Kim et al., 1996). PDZnaling networks at excitatory synapses. Affinity chro- domains from PSD-95 bind to N-methyl-D-aspartate- matography identifies cypin as a major PSD-95-binding (NMDA-) type glutamate receptors (Kornau et al., 1995),protein in brain extracts. Cypin is homologous to a Shaker (Kim et al., 1995), and inward rectifier K 1 chan- family of hydrolytic bacterial enzymes and shares nels (Cohen et al., 1996), and to certain peripheral mem-some similarity with collapsin response mediator pro- brane proteins containing a C-terminal PDZ-binding tein (CRMP), a cytoplasmic mediator of semaphorin consensus sequence (tSXV), Thr/Ser-X-Val/Ile-COOHIII signalling. Cypin is discretely expressed in neurons