Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although the skeletal muscle sodium channel is a good substrate for cAMP-dependent protein kinase (PKA), no functional consequence was observed for this channel expressed in heterologous systems. Therefore, we investigated the effect of 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP), a membrane-permeable cAMP analog, on the native sodium channels of freshly dissociated rat skeletal muscle fibers by means of the cell-attached patch-clamp technique. Externally applied CPT-cAMP (0.5 mM) reduced peak ensemble average currents by approximately 75% with no change in kinetics. Single-channel conductance and normalized activation curves were unchanged by CPT-cAMP. In contrast, steady-state inactivation curves showed a reduction of the maximal available current and a negative shift of the half-inactivation potential. Similar effects were observed with dibutyryl adenosine 3',5'-cyclic monophosphate but not with cAMP, which does not easily permeate the cell membrane. Incubation of fibers for 1 h with 10 microM H-89, a PKA inhibitor, did not prevent the effect of CPT-cAMP. Finally, the beta-adrenoreceptor agonist isoproterenol mimicked CPT-cAMP when applied at 0.5 mM but had no effect at 0.1 mM. These results indicate that cAMP inhibits native skeletal muscle sodium channels by acting within the fiber, independently of PKA activation.
...
PMID:Blockade by cAMP of native sodium channels of adult rat skeletal muscle fibers. 984 7

The functional expression of the amiloride-sensitive epithelial sodium channel (ENaC) in select epithelia is critical for maintaining electrolyte and fluid homeostasis. Although ENaC activity is strictly dependent upon its alpha-subunit expression, little is known about the molecular mechanisms by which cells modulate alpha-ENaC gene expression. Previously, we have shown that salivary alpha-ENaC expression is transcriptionally repressed by the activation of Raf/extracellular signal-regulated protein kinase pathway. Here, this work further investigates the molecular mechanism(s) by which alpha-ENaC expression is regulated in salivary epithelial Pa-4 cells. A region located between -1.5 and -1.0 kilobase pairs of the alpha-ENaC 5'-flanking region is demonstrated to be indispensable for the maximal and Ras-repressible reporter expression. Deletional analyses using heterologous promoter constructs reveal that a DNA sequence between -1355 and -1269 base pairs functions as an enhancer conferring the high level of expression on reporter constructs, and this induction effect is inhibited by Ras pathway activation. Mutational analyses indicate that full induction and Ras-mediated repression require a glucocorticoid response element (GRE) located between -1323 and -1309 base pairs. The identified alpha-ENaC GRE encompassing sequence (-1334/-1306) is sufficient to confer glucocorticoid receptor/dexamethasone-dependent and Ras-repressible expression on both heterologous and homologous promoters. This report demon- strates for the first time that the cross-talk between glucocorticoid receptor and Ras/extracellular signal-regulated protein kinase signaling pathways results in an antagonistic effect at the transcriptional level to modulate alpha-ENaC expression through the identified GRE. In summary, this study presents a mechanism by which alpha-ENaC expression is regulated in salivary epithelial cells.
...
PMID:The gene expression of the amiloride-sensitive epithelial sodium channel alpha-subunit is regulated by antagonistic effects between glucocorticoid hormone and ras pathways in salivary epithelial cells. 1041 59

The voltage-gated sodium channels that are responsible for action potential generation in central neurons are important targets for the actions of antiepileptic drugs. These channels consist of a complex of three glycoprotein subunits: a pore-forming alpha subunit of 260 kd associated noncovalently with a beta 1 subunit of 36 kd and disulfide-linked to a beta 2 subunit of 33 kd. The alpha subunit forms a functional voltage-gated sodium channel by itself, whereas the beta 1 and beta 2 subunits modulate channel gating. The beta 1 and beta 2 subunits also have immunoglobulin-like folds in their extracellular domains that are predicted to interact with extracellular proteins. The alpha subunit is comprised of four homologous domains containing six transmembrane alpha helices (S1 through S6) and additional membrane-associated segments (SS1/SS2). The S4 segments in each domain function as voltage sensors for voltage-dependent activation of the sodium channel. The S5 and S6 segments in each domain and the short SS1/SS2 segments between them form the pore of the channel. The intracellular loop between domains III and IV forms the inactivation gate, which folds into the pore and occludes it within 1 msec of channel opening. The activity of brain sodium channels in modulated by protein phosphorylation G proteins. Activation of muscarinic acetylcholine receptors in hippocampal neurons slows the inactivation of sodium channels and reduces peak sodium currents through activation of protein kinase C (PKC) phosphorylation of sites in the inactivation gate and the intracellular loop between domains I and II of the alpha subunit. Other neurotransmitters that activate the PKC pathway are likely to have similar effects. Activation of D1-like dopamine receptors in hippocampal neurons reduces peak sodium currents through activation of cyclic adenosine monophosphate (cAMP)-dependent protein kinase phosphorylation of sites in the intracellular loop between domains I and II. Modulation by PKC and cAMP-dependent protein kinase is convergent--phosphorylation of the inactivation gate by PKC is required before phosphorylation of sites in the intracellular loop between domains I and II can reduce peak sodium currents. Brain sodium channels are also modulated by G proteins. Activation of endogenous G protein-coupled receptors causes negative shifts in the voltage dependence of sodium channel activation and inactivation. Overexpression of G protein beta gamma subunits induces persistent sodium currents. Regulation of sodium channel function by these multiple pathways can produce a flexible tuning of electrical excitability of central neurons in response to neurotransmitters, hormones, and second messengers. The antiepileptic drugs phenytoin, carbamazepine, and lamotrigine inhibit brain sodium channels substantially at clinically relevant concentrations. Their inhibition of sodium channels is increased by depolarization because they bind preferentially to the inactivated state of the channels. This effect increases the inhibition of sodium channels in depolarized tissue at the center of an epileptic focus. Local anesthetics also inhibit sodium channels by preferential binding to the inactivated state. Site-directed mutagenesis experiments show that antiepileptic drugs and local anesthetics bind to a common receptor site in the pore of the channel that is formed in part by three critical amino acid residues in transmembrane segment S6 in domain IV. Mutations in these amino acid residues prevents preferential binding to the inactivated state and thereby greatly reduces the affinity for inhibition of sodium channels by these drugs. Knowledge of the structure-function relationships for drug binding at this receptor site may open the way to development of novel classes of antiepileptic drugs.
...
PMID:Molecular properties of brain sodium channels: an important target for anticonvulsant drugs. 1051 34

The sgk, an aldosterone-induced gene in mineralocorticoid target cells, regulates the epithelial sodium channel. Aldosterone increases sodium reabsorption in tight epithelia. The early phase of this stimulatory effect is thought to involve activation of apical sodium channels. To identify immediate-early genes that initiate this effect, we used a combination of polymerase chain reaction-based subtractive hybridization and differential display techniques. This review summarizes our recent findings. Aldosterone rapidly increases mRNA levels of a putative Ser/Thr kinase, sgk (or serum- and glucocorticoid-regulated kinase), in the native mineralocorticoid target cells, that is, in cortical collecting duct (CCD) cells. The induction of sgk mRNA occurs within 30 minutes of the addition of aldosterone and does not require de novo protein synthesis, indicating that sgk is an immediate/early aldosterone-induced gene. Induction of sgk by aldosterone is mediated through mineralocorticoid receptors (MRs), since it is prevented by ZK91857, an MR antagonist, but not by RU486, a glucocorticoid antagonist. In addition to aldosterone, RU28362, a pure glucocorticoid receptor agonist, also induced sgk mRNA, both in primary cultures of rabbit CCD cells and in the M-1 mouse CCD cell line. Sgk mRNA levels are also influenced by changes in the osmolality of the medium. In M-1 cells, incubation of cells for one hour in a mildly hypotonic medium decreased sgk mRNA levels, whereas incubation in hypertonic medium brought about opposite changes. To determine whether sgk is involved in the regulation of the epithelial sodium channel (ENaC), we coexpressed the full-length sgk cRNA in Xenopus oocytes with the three ENaC subunits. Expression of sgk resulted in a significant increase in the amiloride-sensitive Na current, suggesting that this protein kinase plays an important role in the early phase of aldosterone-stimulated Na transport. These results indicate that sgk is an aldosterone-induced immediate/early gene in native MR target cells, and is involved in the regulation of ion transport and possibly cell volume.
...
PMID:The sgk, an aldosterone-induced gene in mineralocorticoid target cells, regulates the epithelial sodium channel. 1076 56

In previous studies we developed and introduced a method to examine the transport mechanisms of ions in primary cell cultures of human nasal epithelium. In the current study, substances, especially nicotine, that influence these mechanisms are investigated. Specimens of nasal and paranasal epithelium of patients treated by endonasal surgery because of chronic sinusitis (n = 217) were used as primary cell cultures. Cell cultures of smokers (n = 83) and non-smokers (n = 134) were differentiated. Transepithelial Ussing chamber measurements were performed to examine sodium channel functions and to evaluate the influence of nicotine. These examinations were accompanied by simultaneous continuous capacitance measurements. Whereas transepithelial parameters, such as short-circuit current, (Isc), potential (Vt) and resistance (Rt), in tissues derived from smokers and non-smokers showed no difference, the transepithelial conductance was reduced immediately in cell cultures with apical application of nicotine (2 mM). This decrease was accompanied by a marked reduction of epithelial surface area. In the presence of nicotine, amiloride (100 microM) completely lost its inhibitory capacity. Amiloride-insensitive sodium channels were unaffected by nicotine, as proved by Na+ substitution. Furthermore, the Na+ channel blocker was accompanied by an increase in intracellular Ca2+. We conclude that the nicotine-induced increase in intracellular calcium (Ca2+) has stimulated Ca2+-dependent protein kinase (PKC). PKC promotes endocytosis removing amiloride-sensitive Na+ channels from the cell membrane into the cell by means of vesicular transport.
...
PMID:Nicotine-induced endocytosis of amiloride-sensitive sodium channels in human nasal epithelium. 1160 91

C-type dorsal root ganglion (DRG) neurons express three types of Na+ currents: fast TTX-sensitive, slow TTX-resistant, and persistent TTX-resistant Na+ currents. The nitric oxide (NO) donors papa-NONOate and S-nitroso-N-acetyl-DL-penicillamine inhibit all three types of Na+ currents. The NO scavenger hemoglobin abolished the effects of papa-NONOate on Na+ currents, indicating that NO or NO-related species inhibit these Na+ currents. NO donor inhibition of all three types of Na+ currents was reversed by washout. Incubation of neurons with 8-bromo cGMP, a membrane-permeable analogue of cGMP, and cG-PKI, an inhibitor of cGMP-dependent protein kinase, had no effect on papa-NONOate-mediated Na+ current block, demonstrating that Na+ current inhibition is independent of cGMP. Alkylation of free thiols with N-ethylmaleimide prevented the actions of papa-NONOate, suggesting that NO, or a related reactive nitrogen species, modifies sulfhydryl groups on Na+ channels or a closely associated protein. Papa-NONOate-mediated block of Na+ currents is not due to a hyperpolarizing shift in steady state voltage-dependent inactivation. The absence of NO-mediated enhancement of slow inactivation in fast and slow Na+ channels indicates that NO does not inhibit fast and slow Na+ channels by facilitating the transition to a slow inactivated state. These results demonstrate that inhibition of Na+ currents is not due to the modulation of fast and slow sodium channel inactivation. Taken together, these results show that NO or NO-related products modify the sulfhydryl groups on Na+ channels and inhibit Na+ currents by blocking the channel conductance.
...
PMID:Nitric oxide blocks fast, slow, and persistent Na+ channels in C-type DRG neurons by S-nitrosylation. 1182 45

This study demonstrates that caveolae, omega-shaped membrane invaginations, are involved in cardiac sodium channel regulation by a mechanism involving the alpha subunit of the stimulatory heterotrimeric G-protein, Galpha(s), via stimulation of the cell surface beta-adrenergic receptor. Stimulation of beta-adrenergic receptors with 10 micromol/L isoproterenol in the presence of a protein kinase A inhibitor increased the whole-cell sodium current by a "direct" cAMP-independent G-protein mechanism. The addition of antibodies against caveolin-3 to the cell's cytoplasm via the pipette solution abrogated this direct G protein-induced increase in sodium current, whereas antibodies to caveolin-1 or caveolin-2 did not. Voltage-gated sodium channel proteins were found to associate with caveolin-rich membranes obtained by detergent-free buoyant density separation. The purity of the caveolar membrane fraction was verified by Western blot analyses, which indicated that endoplasmic/sarcoplasmic reticulum, endosomal compartments, Golgi apparatus, clathrin-coated vesicles, and sarcolemmal membranes were excluded from the caveolin-rich membrane fraction. Additionally, the sodium channel was found to colocalize with caveolar membranes by immunoprecipitation, indirect immunofluorescence, and immunogold transmission electron microscopy. These results suggest that stimulation of beta-adrenergic receptors, and thereby Galpha(s), promotes the presentation of cardiac sodium channels associated with caveolar membranes to the sarcolemma.
...
PMID:Localization of cardiac sodium channels in caveolin-rich membrane domains: regulation of sodium current amplitude. 1188 62

Arginine vasopressin (AVP) is synthesized in and secreted by the suprachiasmatic nucleus (SCN) in a circadian pattern. Transcription of the AVP gene in organotypic cultures of rat SCN was studied by using an intronic in situ hybridization. AVP gene transcription in the cultured SCN maintained a daily rhythm with a peak in the daytime. Inhibition of spontaneous activity by the sodium channel blocker, tetrodotoxin (TTX), dramatically decreased AVP heteronuclear RNA levels and suppressed rhythmicity, indicating that ongoing neural activity was required for the AVP gene transcription. In the presence of TTX, the adenylate cyclase stimulator, forskolin, increased AVP transcription in the SCN. In contrast, the protein kinase C activator, phorbol 12-myristate 13-acetate, greatly increased AVP transcription in the absence of TTX, but this effect was blocked by TTX, indicating that the phorbol 12-myristate 13-acetate acted indirectly via synaptic input. Neither protein kinase A nor protein kinase C pathways appear to be involved in the rhythmicity of AVP transcription in the SCN because selective inhibitors of these protein kinases were without effect. In contrast, the MAPK pathway inhibitor, PD98059, profoundly decreased AVP transcription and abolished its daily rhythm. Hence, a functional MAPK signaling pathway appears to be critical for AVP gene expression in the SCN.
...
PMID:Neuronal activity is required for the circadian rhythm of vasopressin gene transcription in the suprachiasmatic nucleus in vitro. 1239 8

Renal cell apoptosis contributes significantly to the pathogenesis of acute renal failure. Local anesthetics induce apoptosis in neuronal and lymphocytic cell lines. We examined the effects of chronic (48 h) local anesthetic treatment (lidocaine, bupivacaine and tetracaine) on human proximal tubular (HK-2) cells. Apoptosis induction was assessed by detecting poly(ADP)-ribose polymerase fragmentation, caspase activation, terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining, DNA laddering and by cellular morphology. Cell death was quantified by measuring neutral red dye uptake and lactate dehydrogenase released into the cell culture medium. All 3 local anesthetics caused concentration-dependent cell death, induced HK-2 cell apoptosis and potentiated TNF-alpha induced apoptosis. Local anesthetics induced HK-2 cell apoptosis by activation of caspases 3, 6, 7, 8 and 9. ZVAD-fmk, a pan-caspase inhibitor, blocked the local anesthetic induced HK-2 cell apoptosis. Local anesthetics also inhibited the activities of anti-apoptotic kinases protein kinase B (Akt) and extracellular signal regulated mitrogen-activated protein kinase. Local anesthetic's pro-apoptotic effects are independent of sodium channel inhibition as tetrodotoxin, a selective voltage-gated sodium channel blocker, failed to mimic local anesthetic-mediated induction or potentiation of HK-2 cell apoptosis. We conclude that local anesthetics induce human renal cell apoptotic signaling by caspase activation and via inhibition of pro-survival signaling pathways.
...
PMID:Local anesthetics induce human renal cell apoptosis. 1258 58

Voltage-gated sodium channels initiate and propagate action potentials in excitable cells. The tetrodotoxin-resistant Na(+) channel (Na(V)1.8/SNS) is expressed in damage-sensing neurons (nociceptors) and plays an important role in pain pathways. Expression of high levels of functional Na(V)1.8 in heterologous cells has proved problematic, even in the presence of known sodium channel accessory beta-subunits. This suggests that other regulatory proteins are required for normal levels of Na(V)1.8 expression. Here we report the use of a yeast two-hybrid system and a rat dorsal root ganglion cDNA library to identify 28 different clones encoding proteins which interact with intracellular domains of Na(V)1.8. Many clones are expressed at high levels in small diameter DRG neurons as judged by in situ hybridization. Interacting proteins include cytoplasmic elements and linker proteins (e.g. beta-actin and moesin), enzymes (e.g. inositol polyphosphate 5-phosphatase and TAO2 thousand and one protein kinase), channels and membrane-associated proteins (voltage-dependent anion channel VDAC3V and tetraspanin), as well as motor proteins (dynein intermediate and light chain) and transcripts encoding previously undescribed proteins. Immunoprecipitation (pull-down) assays confirm that some of the proteins interact with, and may hence regulate, Na(V)1.8 in vivo.
...
PMID:Sensory neuron proteins interact with the intracellular domains of sodium channel NaV1.8. 1259 Nov 66


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---