Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.12 (PKG)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Multiple processes lead to neuronal death after ischemia, but the generation of nitric oxide (NO) is a key component in this cascade of events. The mechanisms that regulate the extent of neuronal degeneration during anoxia and NO toxicity are multifactorial. Neuronal death may be modulated by the activity of signal transduction systems that influence the toxicity of NO or its metabolic products such as cGMP. The enzyme responsible for the production of NO, nitric oxide synthase (NOS), is phosphorylated by protein kinase C (PKC), the cAMP-dependent protein kinase (PKA), and the calcium/calmodulin-dependent protein kinase II (CaM-II). We examined in primary cultured hippocampal neurons whether the protein kinases PKC, PKA, CaM-II, and cGMP-dependent protein kinase modified the toxic effects of anoxia and NO. Down-regulation of PKC activity with PMA (1 microM) increased hippocampal neuronal survival during anoxia and NO exposure from approximately 22% to 88%. Inhibitors of PKC activity (H-7, H-8, sphingosine, and staurosporine) also were neuroprotective. Down-regulation of PKC activity increased survival during anoxia even in the presence of the NOS inhibitor, N omega-methyl-L-arginine. Thus, although down-regulation of PKC activity may increase neuronal survival by decreasing NOS activity, it also is likely that PKC contributes to ischemic neuronal death by mechanisms that are independent of NOS. Inhibition of the cGMP-dependent protein kinase activity, but not the activity of the CaM-II also was neuroprotective during NO administration. In contrast to the protective effects of inhibition of PKC and the cGMP-dependent protein kinase, activation rather than inhibition of PKA increased hippocampal neuronal survival during NO exposure. These results indicate that neuronal survival during anoxia and NO exposure is linked to the modulation of PKC, PKA, and cGMP-dependent protein kinase activity but is not dependent on the CaM-II pathway. Understanding the involvement of PKC, PKA, and the cGMP-dependent protein kinase in modulating the effect of neuronal death during ischemia and NO toxicity may help in directing future therapeutic modalities for cerebrovascular disease.
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PMID:Protein kinases modulate the sensitivity of hippocampal neurons to nitric oxide toxicity and anoxia. 823 Mar 23

Nitric oxide and cGMP influence plasticity of nociceptive processing in spinal cord. However, effectors for cGMP have not been identified in sensory pathways. We now demonstrate that cGMP-dependent protein kinase I (cGKl) occurs in the DRGs at levels comparable to that in cerebellum, the richest source of cGKl in the body. Immunohistochemical studies reveal that cGKl is concentrated in a subpopulation of small- and medium-diameter DRG neurons that partially overlap with substance P and calcitonin gene-related polypeptide containing cells. During development, cGKl expression throughout the embryo is essentially restricted to sensory neurons and to the spinal floor and roof plates. Neuronal nitric oxide synthase (nNOS) is coexpressed with cGKl in sensory neurons during embryonic development and after peripheral nerve axotomy. The primary target for cGKl in cerebellum, G-substrate, is not present in developing, mature, or regenerating sensory neurons, indicating that other proteins serve as effectors for cGKl in sensory processing. These data establish sensory neurons as a primary locus for cGMP actions during development and suggest a role for cGKl in plasticity of nociception.
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PMID:cGMP-dependent protein kinase in dorsal root ganglion: relationship with nitric oxide synthase and nociceptive neurons. 862 52

Neuronal alpha1E subunits are thought to form R-type Ca channels. When expressed in human embryonic kidney cells with M2 muscarinic acetylcholine receptors, Ca channels encoded by rabbit alpha1E exhibit striking biphasic modulation. Receptor activation first produces rapid inhibition of current amplitude and activation rate. However, in the continued presence of agonist, alpha1E currents subsequently increase. Kinetic slowing persists during this secondary stimulation phase. After receptor deactivation, kinetic slowing is quickly relieved, and current amplitude over-recovers before returning toward control levels. These features indicate that inhibition and stimulation of alpha1E are separate processes, with stimulation superimposed on inhibition. Pertussis toxin eliminates inhibition without affecting stimulation, demonstrating that inhibition and stimulation involve distinct signaling pathways. Neither inhibition nor stimulation is altered by coexpression of Ca channel beta2a or beta3 subunits. Stimulation is abolished by staurosporine and reduced by intracellular 5'-adenylylimidodiphosphate, suggesting that phosphorylation is required. However, stimulation does not seem to involve cAMP-dependent protein kinase, protein kinase C, cGMP-dependent protein kinase, tyrosine kinases, or phosphoinositide 3-kinases. Stimulation does not require a Ca signal, because it is not specifically altered by varying intracellular Ca buffering or by substituting Ba as the charge carrier. In contrast to those formed by alpha1E, Ca channels formed by alpha1A or alpha1B display only inhibition and no stimulation during prolonged activation of M2 receptors. The dual modulation of alpha1E may confer unique physiological properties on native R-type Ca channels. As one possibility, R-type channels may continue to mediate Ca influx during steady inhibition of N-type and P/Q-type channels by muscarinic or other receptors.
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PMID:Biphasic, opposing modulation of cloned neuronal alpha1E Ca channels by distinct signaling pathways coupled to M2 muscarinic acetylcholine receptors. 1043 38

Neuronal death is a prominent neuropathological component of fetal alcohol syndrome (FAS). Identification of molecular agents and pathways that can ameliorate alcohol-induced cell loss offers possible therapeutic strategies for FAS and potential insight into its pathogenesis. This study investigated the effects of growth factors on cellular survival in alcohol-exposed cerebellar granule cell (CGC) cultures and examined the role of the nitric oxide (NO)-cGMP-PKG (cGMP-dependent protein kinase) pathway in the cell survival-promoting effects of these growth factors. Primary CGC cultures were exposed to 0 or 400 mg/dl ethanol, accompanied by either no growth factor or 30 ng/ml fibroblast growth factor-2 (FGF-2), nerve growth factor (NGF), insulin-like growth factor-1 (IGF-1), brain-derived neurotrophic factor (BDNF) or epidermal growth factor (EGF). Viable neurons were quantified after 1 day of exposure. Two distinct types of cell survival-promoting effects of growth factors were detectable: (1) a neurotrophic effect, in which the growth factors diminished the background death of neurons that occurred in alcohol-free cultures; and (2) a neuroprotective effect, in which the growth factors diminished alcohol-induced cell death. The various growth factors differed markedly in their patterns of cell survival promotion. While BDNF and FGF-2 exerted both a neurotrophic and a neuroprotective effect, IGF-1 had only a neurotrophic effect and did not protect against alcohol toxicity, and NGF had only a neuroprotective effect and did not diminish background cell death. EGF had neither a neurotrophic nor a neuroprotective effect. In order to determine the role of the NO-cGMP-PKG pathway in the cell survival-promoting effects mediated by growth factors, cultures were exposed to one of several pharmacological inhibitors of the pathway, including NAME, LY83583 and PKG inhibitor. The cell survival-promoting effects of FGF-2, NGF and IGF-1 were all substantially reduced by each of the pathway inhibitors. In contrast, neither the neurotrophic nor the neuroprotective effects of BDNF were altered by any of the pathway inhibitors. Thus, growth factors differ in their patterns of neurotrophic and neuroprotective effects, and they differ in their reliance on the NO-cGMP-PKG pathway. While FGF-2, NGF and IGF-1 all signal their survival-promoting effects through the NO-cGMP-PKG pathway, BDNF does not rely upon this pathway for signal transduction in CGC cultures.
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PMID:FGF-2, NGF and IGF-1, but not BDNF, utilize a nitric oxide pathway to signal neurotrophic and neuroprotective effects against alcohol toxicity in cerebellar granule cell cultures. 1252 73

Nitric oxide (NO) is an inhibitory signalling molecule in the gastrointestinal (GI) tract that is released from neurons and from leucocytes during inflammation. NO stimulates soluble guanylate cyclase (sGC), elevates cyclic guanosine 3',5'-monophospate (cGMP), and subsequently activates cGMP-dependent protein kinase (PKG). Targets for NO in the guinea pig caecum were investigated by characterizing the cellular distribution of sGC, cGMP and PKG. Immunoreactivity for both isoforms of sGC, sGCalpha1 and sGCbeta1, was observed in the interstitial cells of Cajal (ICC) and enteric neurons in the tunica muscularis. Double labelling with anti-Kit and anti-sGC antibodies showed sGCalpha1 and sGCbeta1-like immunoreactivity (LI) in almost all intramuscular (IM) and myenteric ICC. Neuronal processes with neuronal NO synthase were closely apposed to ICC expressing sGC-LI. Cells with sGC-LI possessed ultrastructural features of ICC-IM: caveolae, close association with nerve bundles and contacts with smooth muscle cells (SMC). Sodium nitroprusside, added with the phosphodiesterase inhibitors (3-isobutyl-1-methylxanthine and zaprinast), enhanced cGMP-LI in almost all ICC and in some enteric neurons. Nerve stimulation also increased cGMP-LI in ICC and enteric neurons. In contrast, no resolvable increase in cGMP-LI was observed in any cells when the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one was present. ICC and SMC also expressed PKG type I-LI. These data show that ICC express the downstream signalling molecules necessary to transduce nitrergic signals and activate inhibitory pathways and thus are primary targets for NO released from neurons and other cells in the GI tract.
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PMID:Interstitial cells of Cajal contain signalling molecules for transduction of nitrergic stimulation in guinea pig caecum. 1917 50

Brain aromatic L-amino acid decarboxylase (AAAD) is subject to regulation, and phosphorylation might be involved in the short-term activation of the enzyme. Sites for serine/threonine phosphorylation are present in the deduced amino acid sequence of AAAD, and cAMP-dependent protein kinase phosphorylates and activates neuronal AAAD in vitro. We now report that cGMP-dependent protein kinase (PKG) is able to phosphorylate and activate neuronal AAAD. In an in vitro kinase assay, immunoprecipitated native and recombinant mouse brain AAAD was rapidly phosphorylated by exogenous PKGIalpha. When added to striatal homogenates, PKGIalpha increased AAAD activity in a temporal fashion similar to phosphorylation. Recombinant AAAD was also activated by the kinase demonstrating a direct effect. Native enzyme activation was moderate and characterized by increased V(max) and K(m) for L-DOPA. A PKG peptide inhibitor prevented AAAD phosphorylation and activation providing specificity, and causally linking the two events. Together, the findings provide evidence for PKGIalpha-dependent phosphorylation and activation of neuronal AAAD in vitro, and introduce AAAD as a putative PKGIalpha substrate. Neuronal AAAD is best known for its role in the biosynthesis of catecholamines, indoleamines and trace amines in the nervous system, and the biological importance of PKGIalpha phosphorylation in these processes remains to be determined.
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PMID:Aromatic L-amino acid decarboxylase phosphorylation and activation by PKGIalpha in vitro. 2045 15

Angiotensin II (Ang II) is critical in myocardial pathogenesis, mostly via stimulating NADPH oxidase. Neuronal nitric oxide synthase (nNOS) has recently been shown to play important roles in modulating myocardial oxidative stress and contractility. Here, we examine whether nNOS is regulated by Ang II and affects NADPH oxidase production of intracellular reactive oxygen species (ROS(i)) and contractile function in left ventricular (LV) myocytes. Our results showed that Ang II induced biphasic effects on ROS(i) and LV myocyte relaxation (TR(50)) without affecting the amplitude of sarcomere shortening and L-type Ca(2+) current density: TR(50) was prolonged at 30 min but was shortened after 3h (or after Ang II treatment in vivo). Correspondingly, ROS(i) was increased, followed by a reduction to control level. Quantitative RT-PCR and immunoblotting experiments showed that Ang II (3h) increased the mRNA and protein expression of nNOS and increased NO production (nitrite assay) in LV myocyte homogenates, suggesting that nNOS activity may be enhanced and involved in mediating the effects of Ang II. Indeed, n(omega)-nitro-l-arginine methyl ester (l-NAME) or a selective nNOS inhibitor, S-methyl-l-thiocitrulline (SMTC) increased NADPH oxidase production of superoxide/ROS(i) and abolished faster myocyte relaxation induced by Ang II. The positive lusitropic effect of Ang II was not mediated by PKA-, CaMKII-dependent signaling or peroxynitrite. Conversely, inhibition of cGMP/PKG pathway abolished the Ang II-induced faster relaxation by reducing phospholamban (PLN) Ser(16) phosphorylation. Taken together, these results clearly demonstrate that myocardial nNOS is up-regulated by Ang II and functions as an early adaptive mechanism to attenuate NADPH oxidase activity and facilitate myocardial relaxation.
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PMID:Neuronal nitric oxide synthase is up-regulated by angiotensin II and attenuates NADPH oxidase activity and facilitates relaxation in murine left ventricular myocytes. 2248 19

Neuronal nitric oxide synthase (NOS1 or nNOS) exerts negative inotropic and positive lusitropic effects through Ca(2+) handling processes in cardiac myocytes from healthy hearts. However, underlying mechanisms of NOS1 in diseased hearts remain unclear. The present study aims to investigate this question in angiotensin II (Ang II)-induced hypertensive rat hearts (HP). Our results showed that the systolic function of left ventricle (LV) was reduced and diastolic function was unaltered (echocardiographic assessment) in HP compared to those in shams. In isolated LV myocytes, contraction was unchanged but peak [Ca(2+)]i transient was increased in HP. Concomitantly, relaxation and time constant of [Ca(2+)]i decay (tau) were faster and the phosphorylated fraction of phospholamban (PLN-Ser(16)/PLN) was greater. NOS1 protein expression and activity were increased in LV myocyte homogenates from HP. Surprisingly, inhibition of NOS1 did not affect contraction but reduced peak [Ca(2+)]i transient; prevented faster relaxation without affecting the tau of [Ca(2+)]i transient or PLN-Ser(16)/PLN in HP, suggesting myofilament Ca(2+) desensitization by NOS1. Indeed, relaxation phase of the sarcomere length-[Ca(2+)]i relationship of LV myocytes shifted to the right and increased [Ca(2+)]i for 50% of sarcomere shortening (EC50) in HP. Phosphorylations of cardiac myosin binding protein-C (cMyBP-C(282) and cMyBP-C(273)) were increased and cardiac troponin I (cTnI(23/24)) was reduced in HP. Importantly, NOS1 or PKG inhibition reduced cMyBP-C(273) and cTnI(23/24) and reversed myofilament Ca(2+) sensitivity. These results reveal that NOS1 is up-regulated in LV myocytes from HP and exerts positive lusitropic effect by modulating myofilament Ca(2+) sensitivity through phosphorylation of key regulators in sarcomere.
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PMID:Myofilament Ca2+ desensitization mediates positive lusitropic effect of neuronal nitric oxide synthase in left ventricular myocytes from murine hypertensive heart. 2362 88

Neuronal activity regulates AMPA receptor trafficking, a process that mediates changes in synaptic strength, a key component of learning and memory. This form of plasticity may be induced by stimulation of the NMDA receptor which, among its activities, increases cyclic guanosine monophosphate (cGMP) through the nitric oxide synthase pathway. cGMP-dependent protein kinase type II (cGKII) is ultimately activated via this mechanism and AMPA receptor subunit GluA1 is phosphorylated at serine 845. This phosphorylation contributes to the delivery of GluA1 to the synapse, a step that increases synaptic strength. Previous studies have shown that cGKII-deficient mice display striking spatial learning deficits in the Morris Water Maze compared to wild-type littermates as well as lowered GluA1 phosphorylation in the postsynaptic density of the prefrontal cortex (Serulle et al., 2007; Wincott et al., 2013). In the current study, we show that cGKII knockout mice exhibit impaired working memory as determined using the prefrontal cortex-dependent Radial Arm Maze (RAM). Additionally, we report reduced repetitive behavior in the Marble Burying task (MB), and heightened anxiety-like traits in the Novelty Suppressed Feeding Test (NSFT). These data suggest that cGKII may play a role in the integration of information that conveys both anxiety-provoking stimuli as well as the spatial and environmental cues that facilitate functional memory processes and appropriate behavioral response.
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PMID:cGMP-dependent protein kinase type II knockout mice exhibit working memory impairments, decreased repetitive behavior, and increased anxiety-like traits. 2475 51

Neuronal nitric oxide synthase (nNOS or NOS1) is the major endogenous source of myocardial nitric oxide (NO), which facilitates cardiac relaxation and modulates contraction. In the healthy heart it regulates intracellular Ca(2+), signalling pathways and oxidative homeostasis and is upregulated from early phases upon pathogenic insult. nNOS plays pivotal roles in protecting the myocardium from increased oxidative stress, systolic/diastolic dysfunction, adverse structural remodelling and arrhythmias in the failing heart. Here, we show that the downstream target proteins of nNOS and underlying post-transcriptional modifications are shifted during disease progression from Ca(2+)-handling proteins [e.g. PKA-dependent phospholamban phosphorylation (PLN-Ser(16))] in the healthy heart to cGMP/PKG-dependent PLN-Ser(16) with acute angiotensin II (Ang II) treatment. In early hypertension, nNOS-derived NO is involved in increases of cGMP/PKG-dependent troponin I (TnI-Ser(23/24)) and cardiac myosin binding protein C (cMBP-C-Ser(273)). However, nNOS-derived NO is shown to increase S-nitrosylation of various Ca(2+)-handling proteins in failing myocardium. The spatial compartmentation of nNOS and its translocation for diverse binding partners in the diseased heart or various nNOS splicing variants and regulation in response to pathological stress may be responsible for varied underlying mechanisms and functions. In this review, we endeavour to outline recent advances in knowledge of the molecular mechanisms mediating the functions of nNOS in the myocardium in both normal and diseased hearts. Insights into nNOS gene regulation in various tissues are discussed. Overall, nNOS is an important cardiac protector in the diseased heart. The dynamic localization and various mediating mechanisms of nNOS ensure that it is able to regulate functions effectively in the heart under stress.
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PMID:Molecular mechanisms of neuronal nitric oxide synthase in cardiac function and pathophysiology. 2508 73


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