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

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

The regulation of cardiac delayed rectifier potassium (Kv) currents by cAMP-dependent protein kinase (PKA) contributes to the control of blood pressure and heart rate. We investigated the modulation by PKA and protein phosphatases of cloned Kv1.5 channels expressed in Xenopus laevis oocytes. Exposure of oocytes to activators of PKA (100 nM forskolin, 1 mM 8-bromo-cAMP, or 1 mM 3-isobutyl-1-methylxanthine) had no effect on the amplitude of Kv1.5 currents. Inhibition of PKA by injection of protein kinase A inhibitor peptide or exposure to myristoylated protein kinase A inhibitor peptide (M-PKI; 100 nM) reduced currents mediated by Kv1.5. M-PKI also reduced the amplitude of currents mediated by mutated Kv1.5 channels in which the COOH terminal PKA phosphorylation sites and PSD-95, Disc-large, and ZO-1-binding domain were removed. The reduction of Kv1.5 currents by M-PKI was attenuated by inhibition of actin polymerization by 1 microM cytochalasins B and D, but was not affected by 10 microM phalloidin (stabilizes actin filaments) or 50 microM colchicine (disrupts microtubules). Treatment of oocytes with antisense oligonucleotides against alpha-actinin-2 abolished the reduction in Kv1.5 current by M-PKI. These observations suggest that Kv1.5 currents are activated by endogenous PKA in "resting" oocytes and that inhibition of PKA activity reveals the action of endogenous phosphatases. Indeed, injection of alkaline phosphatase reduced currents mediated by Kv1.5. Further preincubation of oocytes with 1 mM sodium orthovanadate (a protein tyrosine phosphatase inhibitor) abolished the reduction in Kv1.5 currents by M-PKI. We conclude that currents encoded by Kv1.5 are regulated by PKA and protein tyrosine phosphatase and that this regulation requires an intact actin cytoskeleton and alpha-actinin-2.
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PMID:Modulation of Kv1.5 currents by protein kinase A, tyrosine kinase, and protein tyrosine phosphatase requires an intact cytoskeleton. 1180 52

Previous studies in neurons have demonstrated a rapid decrease in NMDA receptor currents following tyrosine kinase inhibition or exposure to platelet-derived growth factor (PDGF). Inhibitors of protein kinase A (PKA) block the PDGF-induced rundown suggesting a multistep pathway that leads to decreased amplitudes of NMDA-activated currents. In this study, HEK293 cells expressing different NMDA receptor subunits were used to study the effects of prostacyclin receptor-mediated PKA activation on the magnitude of glutamate-activated currents. The prostacyclin agonist iloprost induced a rapid and time-dependent depression of otherwise stable glutamate-activated currents in cells expressing NR1-2a/2A or NR1-2a/2D receptors but not NR1-2a/2B or NR1-2a/2C receptors. This rundown was prevented by treatment of cells with the PKA inhibitor H89. The iloprost effect persisted in cells coexpressing NR1-2a/2A receptors and either wild-type or mutant Src kinase (SrcS17A). Co-expression of PSD-95 with NR1-2a/2A receptors reduced but did not eliminate the extent of rundown. Iloprost also produced current rundown in cells expressing NR1-2a and a C-terminal truncated NR2A subunit (NR2A1050stop) but not in those transfected with an NR2A tyrosine mutant (Y842F). The iloprost-induced rundown of wild-type NR1-2a/2A receptors was prevented by prior exposure of cells to hypertonic sucrose. These results suggest that PKA influences the functional activity of NMDA receptors in an NR2 subunit-selective fashion.
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PMID:Prostacyclin-induced rundown of N-methyl-D-aspartate receptor currents in HEK293 cells is protein kinase A-dependent and NR2 subunit-selective. 1184 67

We have cloned ClC-3B, a novel alternative splicing variant of ClC-3 (ClC-3A) that is expressed predominantly in epithelial cells. ClC-3B has a different, slightly longer C-terminal end than ClC-3A and contains a consensus motif for binding to the second PDZ (PSD95/Dlg/ZO-1) domain of the epithelium-specific scaffolding protein EBP50. Both in vitro and in vivo binding assays demonstrate interaction between ClC-3B and EBP50. C127 mouse mammary epithelial cells transfected with ClC-3B alone showed diffuse immunoreactivity for ClC-3B in the cytoplasmic region. In contrast, when EBP50 was cotransfected with ClC-3B, strong immunoreactivity for ClC-3B appeared at the leading edges of membrane ruffles. Patch-clamp experiments revealed that cotransfection of ClC-3B and EBP50 resulted in a remarkable increase in outwardly rectifying Cl- channel (ORCC) activities at the leading edges of membrane ruffles in C127 cells. The electrophysiological properties of the ClC-3B-induced ORCCs are similar to those of ORCCs described in native epithelial cells. When cystic fibrosis transmembrane conductance regulator (CFTR) was cotransfected with ClC-3B and EBP50, ClC-3B-dependent ORCCs were activated via the protein kinase A-dependent pathway. These findings indicate that ClC-3B is itself a CFTR-regulated ORCC molecule or its activator.
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PMID:ClC-3B, a novel ClC-3 splicing variant that interacts with EBP50 and facilitates expression of CFTR-regulated ORCC. 1196 29

Homomeric assembly of Kir5.1, an inward-rectifying K+ channel subunit, is believed to be nonfunctional, although the subunit exists abundantly in the brain. We show that HEK293T cells cotransfected with Kir5.1 and PSD-95 exhibit a Ba(2+)-sensitive inward-rectifying K+ current. Kir5.1 coexpressed with PSD-95 located on the plasma membrane in a clustered manner, while the Kir5.1 subunit expressed alone distributed mostly in cytoplasm, probably due to rapid internalization. The binding of Kir5.1 with PSD-95 was prevented by protein kinase A (PKA)-mediated phosphorylation of its carboxyl terminus. The currents flowing through Kir5.1/PSD-95 were suppressed promptly and reversibly by PKA activation. Because the Kir5.1/PSD-95 complex was detected in the brain, this functional brain K+ channel is potentially a novel physiological target of PKA-mediated signaling.
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PMID:PSD-95 mediates formation of a functional homomeric Kir5.1 channel in the brain. 1198 70

Beta(1) and beta(2) adrenergic receptors (AR) regulate the intrinsic contraction rate in neonatal mouse cardiac myocytes through distinct signaling pathways. It has been shown that stimulation of beta(1)ARs leads to a protein kinase A-dependent increase in contraction rate. In contrast, stimulation of beta(2)ARs has a biphasic effect on contraction rate, with an initial protein kinase A-independent increase followed by a sustained decrease that is blocked by pertussis toxin. The beta(2)AR undergoes agonist-induced endocytosis in cardiac myocytes while the beta(1)AR remains on the cell surface. It has been shown that a PDZ domain binding motif at the carboxyl terminus of beta(1)AR interacts with the postsynaptic density protein PSD-95 when both are expressed in HEK293 cells. We found that mutation of this PDZ binding motif in the beta(1)AR (beta(1)AR-PDZ) enabled agonist-induced internalization in cardiac myocytes. Moreover, stimulation of beta(1)AR-PDZ had a biphasic effect on the myocyte contraction rate similar to that observed following stimulation of the beta(2)AR. The secondary decrease in the contraction rate was mediated by G(i) and could be blocked by pertussis toxin. Furthermore, a non-selective endocytosis inhibitor, concanavalin A, inhibited the internalization of wild type beta(2)AR and the mutated beta(1)AR-PDZ, and blocked the coupling of both receptors to G(i). Finally, treating myocytes with a membrane-permeable peptide representing beta(1)AR PDZ motif caused the endogenous beta(1)AR to behave like beta(1)AR-PDZ. These studies suggest that association of the beta(1)AR with PSD-95 or a related protein dictates signaling specificity by retaining the receptor at the cell surface and preventing interaction with G(i).
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PMID:The PDZ binding motif of the beta 1 adrenergic receptor modulates receptor trafficking and signaling in cardiac myocytes. 1209 26

Na+/H+ exchanger regulatory factor (NHERF)-1 and NHERF-2, two structurally related protein adapters containing tandem PSD-95/Discs large/ZO-1 (PDZ) domains, were identified as essential factors for protein kinase A-mediated inhibition of the sodium-hydrogen exchanger, NHE3. NHERF-1 and NHERF-2 also bound other cellular targets including the sodium-phosphate cotransporter type IIa encoded by the NPT2 gene. Targeted disruption of the mouse NHERF-1 gene eliminated NHERF-1 expression in kidney and other tissues of the mutant mice without altering NHERF-2 levels in these tissues. NHERF-1 (+/-) and (-/-) male mice maintained normal blood electrolytes but showed increased urinary excretion of phosphate when compared with wild-type (+/+) animals. Although the overall levels of renal NHERF-1 targets, NHE3 and Npt2, were unchanged in the mutant mice, immunocytochemistry showed that the Npt2 protein was aberrantly localized at internal sites in the renal proximal tubule cells. The mislocalization of Npt2 paralleled a reduction in the transporter protein in renal brush-border membranes isolated from the mutant mice. In contrast, NHE3 was appropriately localized at the apical surface of proximal tubules in both wild-type and mutant mice. These data suggested that NHERF-1 played a unique role in the apical targeting and/or trafficking of Npt2 in the mammalian kidney, a function not shared by NHERF-2 or other renal PDZ proteins. Phosphate wasting seen in the NHERF-1(-/-) null mice provided a new experimental system for defining the role of PDZ adapters in the hormonal control of ion transport and renal disease.
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PMID:Targeted disruption of the mouse NHERF-1 gene promotes internalization of proximal tubule sodium-phosphate cotransporter type IIa and renal phosphate wasting. 1216 61

The Na(+)/H(+) exchanger regulatory factor 2 (NHERF2/TKA-1/E3KARP) contains two PSD-95/Dlg/ZO-1 (PDZ) domains which interact with the PDZ docking motif (X-(S/T)-X-(V/L)) of proteins to mediate the assembly of transmembrane and cytosolic proteins into functional signal transduction complexes. One of the PDZ domains of NHERF2 interacts specifically with the DSLL, DSFL, and DTRL motifs present at the carboxy-termini of the 2-adrenergic receptor, the platelet-derived growth factor receptor, and the cystic fibrosis transmembrane conductance regulator, respectively. Serum- and glucocorticoid-induced protein kinase 1 (SGK1) also carries a putative PDZ-binding motif (D-S-F-L) at its carboxy tail, implicated in the specific interaction with NHERF2. There is a 3-phosphoinositide-dependent protein kinase 1 (PDK1) interacting fragment (PIF) in the tail of NHERF2. Using pull-down assays and co-transfection experiments, we demonstrated that the DSFL tail of SGK1 interacts with the first PDZ domain of NHERF2 and the PIF of NHERF2 binds to the PIF-binding pocket of PDK1 to form an SGK1-NHERF2-PDK1 complex. Formation of the protein complex promoted the phosphorylation and activation of SGK1 by PDK1. Thus, it was suggested that NHERF2 mediates the activation and phosphorylation of SGK1 by PDK1 through its first PDZ domain and PIF motif, as a novel SGK1 activation mechanism.
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PMID:The Na(+)/H(+) exchanger regulatory factor 2 mediates phosphorylation of serum- and glucocorticoid-induced protein kinase 1 by 3-phosphoinositide-dependent protein kinase 1. 1238 17

Spatial and temporal regulation of intracellular Ca(2+) is a key event in many signaling pathways. Plasma membrane Ca(2+)-ATPases (PMCAs) are major regulators of Ca(2+) homeostasis and bind to PDZ (PSD-95/Dlg/ZO-1) domains via their C termini. Various membrane-associated guanylate kinase family members have been identified as interaction partners of PMCAs. In particular, SAP90/PSD95, PSD93/chapsyn-110, SAP97, and SAP102 all bind to the C-terminal tails of PMCA "b" splice variants. Additionally, it has been demonstrated that PMCA4b interacts with neuronal nitric-oxide synthase and that isoform 2b interacts with Na(+)/H(+) exchanger regulatory factor 2, both via a PDZ domain. CASK (calcium/calmodulin-dependent serine protein kinase) contains a calmodulin-dependent protein kinase-like domain followed by PDZ, SH3, and guanylate kinase-like domains. In adult brain CASK is located at neuronal synapses and interacts with various proteins, e.g. neurexin and Veli/LIN-7. In kidney it is localized to renal epithelia. Surprisingly, interaction with the Tbr-1 transcription factor, nuclear transport, binding to DNA T-elements (in a complex with Tbr-1), and transcriptional competence has been shown. Here we show that the C terminus of PMCA4b binds to CASK and that both proteins co-precipitate from brain and kidney tissue lysates. Immunofluorescence staining revealed co-expression of PMCA, CASK, and calbindin-d-28K in distal tubuli of rat kidney sections. To test if physical interaction of both proteins results in functional consequences we constructed a T-element-dependent reporter vector and investigated luciferase activity in HEK293 lysates, previously co-transfected with PMCA4b expression and control vectors. Expression of wild-type PMCA resulted in an 80% decrease in T-element-dependent transcriptional activity, whereas co-expression of a point-mutated PMCA, with nearly eliminated Ca(2+) pumping activity, had only a small influence on regulation of transcriptional activity. These results provide evidence of a new direct Ca(2+)-dependent link from the plasma membrane to the nucleus.
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PMID:Interaction of the plasma membrane Ca2+ pump 4b/CI with the Ca2+/calmodulin-dependent membrane-associated kinase CASK. 1251 55

PSD-95/Dlg-A/ZO-1 (PDZ) domains play an essential role in determining cell polarity. The Na(+)/H(+) exchanger regulatory factor (NHERF), also known as EBP50, contains two PDZ domains that mediate the assembly of transmembrane and cytosolic proteins into functional signal transduction complexes. Moreover, it has been shown that cystic fibrosis transmembrane conductance regulator (CFTR) and beta(2)-adrenergic receptor (beta(2)AR) bind equally well to the PDZ1 domain of EBP50. We hypothesized that beta(2)AR activation may regulate CFTR protein expression. To verify this, we evaluated the effects of a pharmacologically relevant concentration of salmeterol (2.10(-7) m), a long acting beta(2)AR agonist, on CFTR expression in primary human airway epithelial cells (HAEC). beta(2)AR stimulation induced a time-dependent increase in apical CFTR protein expression, with a maximal response reached after treatment for 24 h. This effect was post-transcriptional, dependent upon the beta(2)AR agonist binding to beta(2)AR and independent of the known beta(2)AR agonist-mediated cAMP/PKA pathway. We demonstrated by immunohistochemistry that CFTR, beta(2)AR, and EBP50 localize to the apical membrane of HAEC. Analyses of anti-EBP50 protein immunoprecipitate showed that salmeterol induced an increase in the amount of CFTR that binds to EBP50. These data suggest that beta(2)AR activation regulates the association of CFTR with EBP50 in polarized HAEC.
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PMID:Stimulation of beta 2-adrenergic receptor increases cystic fibrosis transmembrane conductance regulator expression in human airway epithelial cells through a cAMP/protein kinase A-independent pathway. 1262 Oct 35

The conserved C-terminal peptide motif (1476DTRL) of the cystic fibrosis transmembrane conductance regulator (CFTR) ensures high affinity binding to different PSD-95/Disc-large/zonula occludens-1 (PDZ) domain-containing molecules, including the Na+/H+ exchanger regulatory factor (NHERF)/ezrin-radixin-moesin-binding phosphoprotein of 50 kDa. The physiological relevance of NHERF binding to CFTR is not fully understood. Individuals with mutations resulting in premature termination of CFTR (S1455X or Delta26 CFTR) have moderately elevated sweat Cl- concentration, without an obvious lung and pancreatic phenotype, implying that the CFTR function is largely preserved. Surprisingly, when expressed heterologously, the Delta26 mutation was reported to abrogate channel activity by destabilizing the protein at the apical domain and inducing its accumulation at the basolateral membrane (Moyer, B., Denton, J., Karlson, K., Reynolds, D., Wang, S., Mickle, J., Milewski, M., Cutting, G., Guggino, W., Li, M., and Stanton, B. (1999) J. Clin. Invest. 104, 1353-1361). The goals of this study were to resolve the contrasting clinical and cellular phenotype of the Delta26 CFTR mutation and evaluate the role of NHERF in the functional expression of CFTR at the plasma membrane. Complex formation between CFTR and NHERF was disrupted by C-terminal deletions, C-terminal epitope tag attachments, or overexpression of a dominant negative NHERF mutant. These perturbations did not alter CFTR expression, metabolic stability, or function in nonpolarized cells. Likewise, inhibition of NHERF binding had no discernible effect on the apical localization of CFTR in polarized tracheal, pancreatic, intestinal, and kidney epithelia and did not influence the metabolic stability or the cAMP-dependent protein kinase-activated chloride channel conductance in polarized pancreatic epithelia. On the other hand, electrophysiological studies demonstrated that NHERF is able to stimulate the cAMP-dependent protein kinase-phosphorylated CFTR channel activity in intact cells. These results help to reconcile the discordant genotype-phenotype relationship in individuals with C-terminal truncations and indicate that apical localization of CFTR involves sorting signals other than the C-terminal 26 amino acid residues and the PDZ-binding motif in differentiated epithelia.
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PMID:The role of the C terminus and Na+/H+ exchanger regulatory factor in the functional expression of cystic fibrosis transmembrane conductance regulator in nonpolarized cells and epithelia. 1265 58


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