Adenosine-A2a Receptor Down-Regulates Cerebral Smooth Muscle L-Type Ca2+ Channel Activity via Protein Tyrosine Phosphatase, Not cAMP-Dependent Protein Kinase

2003 ◽  
Vol 64 (3) ◽  
pp. 640-649 ◽  
Author(s):  
Katrina Murphy ◽  
Volodymyr Gerzanich ◽  
Hui Zhou ◽  
Svetlana Ivanova ◽  
Yafeng Dong ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Adenosine A2a Receptor ◽  
Channel Activity ◽  
Dependent Protein Kinase ◽  
A2a Receptor ◽  
Dependent Protein ◽  
Adenosine A2a

PKC activates BKCa channels in rat pulmonary arterial smooth muscle via cGMP-dependent protein kinase

2004 ◽  
Vol 286 (6) ◽  
pp. L1275-L1281 ◽  
Author(s):  
Scott A. Barman ◽  
Shu Zhu ◽  
Richard E. White
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase ◽  
Channel Activity ◽  
Sprague Dawley ◽  
Dependent Protein Kinase ◽  
Pulmonary Vasoconstriction ◽  
Sprague Dawley Rat ◽  
Dependent Protein ◽  
Pulmonary Arterial ◽  
Pulmonary Arterial Smooth Muscle

Normally, signaling mechanisms that activate large-conductance, calcium- and voltage-activated potassium (BKCa) channels in pulmonary vascular smooth muscle cause pulmonary vasodilatation. BKCa-channel modulation is important in the regulation of pulmonary arterial pressure, and inhibition (decrease in the opening probability) of the BKCa channel has been implicated in the development of pulmonary vasoconstriction. Protein kinase C (PKC) causes pulmonary vasoconstriction, but little is known about the effect of PKC on BKCa-channel activity in pulmonary vascular smooth muscle. Accordingly, studies were done to determine the effect of PKC on BKCa-channel activity using patch-clamp studies in pulmonary arterial smooth muscle cells (PASMCs) of the Sprague-Dawley rat. The PKC activators phorbol myristate acetate (PMA) and thymeleatoxin opened BKCa channels in single Sprague-Dawley rat PASMC. The activator response to both PMA and thymeleatoxin on BKCa-channel activity was blocked by Gö-6983, which selectively blocks PKC-α, -δ, -γ, and -ζ, and by rottlerin, which selectively inhibits PKC-δ. In addition, the specific cyclic GMP-dependent protein kinase antagonist KT-5823 blocked the responses to PMA and thymelatoxin, whereas the specific cyclic AMP-dependent protein kinase blocker KT-5720 had no effect. In isolated pulmonary arterial vessels, both PMA and forskolin caused vasodilatation, which was inhibited by KT-5823, Gö-6983, or the BKCa-channel blocker tetraethylammonium. The results of this study indicate that activation of specific PKC isozymes increases BKCa-channel activity in Sprague-Dawley rat PASMC via cyclic GMP-dependent protein kinase, which suggests a unique signaling mechanism for vasodilatation.

scholarly journals Haematopoietic protein tyrosine phosphatase (HePTP) phosphorylation by cAMP-dependent protein kinase in T-cells: dynamics and subcellular location

2004 ◽  
Vol 378 (2) ◽  
pp. 335-342 ◽  
Author(s):  
Konstantina NIKA ◽  
Huong HYUNH ◽  
Scott WILLIAMS ◽  
Surojit PAUL ◽  
Nunzio BOTTINI ◽  
...  
Keyword(s):  
T Cells ◽  
Protein Kinase ◽  
Protein Tyrosine Phosphatase ◽  
Map Kinases ◽  
Tyrosine Phosphatase ◽  
Continuous Control ◽  
Dependent Protein Kinase ◽  
Protein Tyrosine ◽  
Camp Dependent Protein Kinase ◽  
Dependent Protein

The HePTP (haematopoietic protein tyrosine phosphatase) is a negative regulator of the ERK2 (extracellular signal-regulated protein kinase 2) and p38 MAP kinases (mitogen-activated protein kinases) in T-cells. This inhibitory function requires a physical association of HePTP through an N-terminal KIM (kinase-interaction motif) with ERK and p38. We previously reported that PKA (cAMP-dependent protein kinase) phosphorylates Ser-23 within the KIM of HePTP, resulting in dissociation of HePTP from ERK2. Here we follow the phosphorylation of this site in intact T-cells. We find that HePTP is phosphorylated at Ser-23 in resting T-cells and that this phosphorylation increases upon treatment of the cells with agents that elevate intracellular cAMP, such as prostaglandin E2. HePTP phosphorylation occurred at discrete regions at the cell surface. Phosphorylation was reduced by inhibitors of PKA and increased by inhibitors of protein phosphatases PP1 and PP2A, but not by inhibitors of calcineurin. In vitro, PP1 efficiently dephosphorylated HePTP at Ser-23, while PP2A was much less efficient. Activation of PP1 by treatment of the cells with ceramide suppressed Ser-23 phosphorylation, as did transfection of the catalytic subunit of PP1. Phosphorylation at Ser-23 is also increased in a transient manner upon T-cell antigen receptor ligation. In contrast, treatment of cells with phorbol ester had no effect on HePTP phosphorylation at Ser-23. We conclude from these results that HePTP is under continuous control by PKA and a serine-specific phosphatase, probably PP1, in T-cells and that this basal phosphorylation at Ser-23 can rapidly change in response to external stimuli. This, in turn, will affect the ability of HePTP to inhibit the ERK and p38 MAP kinases.

cAMP activates BKCa channels in pulmonary arterial smooth muscle via cGMP-dependent protein kinase

2003 ◽  
Vol 284 (6) ◽  
pp. L1004-L1011 ◽  
Author(s):  
Scott A. Barman ◽  
Shu Zhu ◽  
Guichan Han ◽  
Richard E. White
Keyword(s):  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Protein Kinase ◽  
Channel Activity ◽  
Dependent Protein Kinase ◽  
Arterial Smooth Muscle ◽  
Cgmp Dependent Protein Kinase ◽  
Dependent Protein ◽  
Pulmonary Arterial ◽  
Pulmonary Arterial Smooth Muscle

The signal transduction mechanisms defining the role of cyclic nucleotides in the regulation of pulmonary vascular tone is currently an area of great interest. Normally, signaling mechanisms that elevate cAMP and guanosine-3′,5′-cyclic monophosphate (cGMP) maintain the pulmonary vasculature in a relaxed state. Modulation of the large-conductance, calcium- and voltage-activated potassium (BKCa) channel is important in the regulation of pulmonary arterial pressure, and inhibition (closing) of the BKCa channel has been implicated in the development of pulmonary hypertension. Accordingly, studies were done to determine the effect of cAMP-elevating agents on BKCa channel activity using patch-clamp studies in pulmonary arterial smooth muscle cells (PASMC) of the fawn-hooded rat (FHR), a recognized animal model of pulmonary hypertension. Forskolin (10 μM), a stimulator of adenylate cyclase and an activator of cAMP-dependent protein kinase (PKA), and 8–4-chlorophenylthio (CPT)-cAMP (100 μM), a membrane-permeable derivative of cAMP, opened BKCa channels in single FHR PASMC. Treatment of FHR PASMC with 300 nM KT5823, a selective inhibitor of cGMP-dependent protein kinase (PKG) activity inhibited the effect of both forskolin and CPT-cAMP. In contrast, blocking PKA activation with 300 nM KT5720 had no effect on forskolin or CPT-cAMP-stimulated BKCa channel activity. These results indicate that cAMP-dependent vasodilators activate BKCa channels in PASMC of FHR via PKG-dependent and PKA-independent signaling pathways, which suggests cross-activation between cyclic nucleotide-dependent protein kinases in pulmonary arterial smooth muscle and therefore, a unique signaling pathway for cAMP-induced pulmonary vasodilation.

scholarly journals ATP mediates both activation and inhibition of K(ATP) channel activity via cAMP-dependent protein kinase in insulin-secreting cell lines.

1989 ◽  
Vol 94 (4) ◽  
pp. 693-717 ◽  
Author(s):  
B Ribalet ◽  
S Ciani ◽  
G T Eddlestone
Keyword(s):  
Protein Kinase ◽  
Kinase Inhibitor ◽  
Single Channel ◽  
K Channel ◽  
Channel Activity ◽  
Dependent Protein Kinase ◽  
Camp Dependent Protein Kinase ◽  
Insulin Secreting Cells ◽  
Dependent Protein ◽  
Inside Out

The single-channel recording technique was employed to investigate the mechanism conferring ATP sensitivity to a metabolite-sensitive K channel in insulin-secreting cells. ATP stimulated channel activity in the 0-10 microM range, but depressed it at higher concentrations. In inside-out patches, addition of the cAMP-dependent protein kinase inhibitor (PKI) reduced channel activity, suggesting that the stimulatory effect of ATP occurs via cAMP-dependent protein kinase-mediated phosphorylation. Raising ATP between 10 and 500 microM in the presence of exogenous PKI progressively reduced the channel activity; it is proposed that this inactivation results from a reduction in kinase activity owing to an ATP-dependent binding of PKI or a protein with similar inhibitory properties to the kinase. A model describing the effects of ATP was developed, incorporating these two separate roles for the nucleotide. Assuming that the efficacy of ATP in controlling the channel activity depends upon the relative concentrations of inhibitor and catalytic subunit associated with the membrane, our model predicts that the channel sensitivity to ATP will vary when the ratio of these two modulators is altered. Based upon this, it is shown that the apparent discrepancy existing between the sensitivity of the channel to low ATP concentrations in the excised patch and the elevated intracellular level of ATP may be explained by postulating a change in the inhibitor/kinase ratio from 1:1 to 3:2 owing to the loss of protein kinase after patch excision. At a low concentration of ATP (10-20 microM), a nonhydrolyzable ATP analogue, AMP-PNP, enhanced the channel activity when present below 10 microM, whereas the analogue blocked the channel activity at higher concentrations. It is postulated that AMP-PNP inhibits the formation of the kinase-inhibitor complex in the former case, and prevents phosphate transfer in the latter. A similar mechanism would explain the interaction between ATP and ADP which is characterized by enhanced activity at low ADP concentrations and blocking at higher concentrations.

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