Reversible ATP-dependent inactivation of glycerophosphate acyltransferase from rat adipose tissue

1989 ◽  
Vol 67 (1) ◽  
pp. 48-52 ◽  
Author(s):  
M. Walsh ◽  
V. Durocher ◽  
A. Rodriguez
Keyword(s):  
Adipose Tissue ◽  
Protein Kinase ◽  
Kinase Inhibitor ◽  
Lipid Synthesis ◽  
Enzyme Inactivation ◽  
Glycerol Phosphate ◽  
Dependent Inactivation ◽  
Dependent Protein ◽  
Rat Adipose Tissue ◽  
Synthesis Regulation

Microsomal glycerophosphate acyltransferase from rat adipose tissue is shown to be inactivated with time upon incubation with ATP. The inactivation can be observed in postmitochondrial supernatant as well as in washed microsomes. However, the effect is more pronounced upon addition of the cytosolic fraction. This activity is specific for ATP, is dependent on the nucleotide concentration, and is prevented when ATP is substituted by β,γ-methylene-ATP. Some protection is provided by amiloride but not by EGTA or cAMP-protein kinase inhibitor. Also, the level of enzyme inactivation is not modified by addition of cAMP-dependent protein kinase and its substrates. Inactivated glycerol-phosphate acyltransferase from ATP-treated microsomes can be reactivated by incubation with partially purified protein phosphatase from rat liver. These results suggest the existence in adipose tissue of a protein kinase (cAMP independent) that may be involved in the regulation of glycerophosphate acyltransferase.Key words: glycerophosphate acyltransferase, lipid synthesis regulation, adipose tissue, protein kinase.

scholarly journals Rat adipose-tissue glycerol phosphate acyltransferase can be inactivated by cyclic AMP-dependent protein kinase

1978 ◽  
Vol 176 (2) ◽  
pp. 607-610 ◽  
Author(s):  
H G Nimmo ◽  
B Houston
Keyword(s):  
Alkaline Phosphatase ◽  
Adipose Tissue ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Hormonal Control ◽  
Glycerol Phosphate ◽  
Dependent Protein Kinase ◽  
Phosphorylation Reaction ◽  
Dependent Protein ◽  
Rat Adipose Tissue

Rat adipose-tissue glycerol phosphate acyltransferase can be inactivated in a phosphorylation reaction catalysed by cyclic AMP-dependent protein kinase and reactivated by treatment with alkaline phosphatase. These results suggest that phosphorylation of glycerol phosphate acyltransferase may be involved in the hormonal control of esterification.

scholarly journals Studies of rat adipose-tissue microsomal glycerol phosphate acyltransferase

1984 ◽  
Vol 224 (1) ◽  
pp. 101-108 ◽  
Author(s):  
G A Nimmo ◽  
H G Nimmo
Keyword(s):  
Adipose Tissue ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Microsomal Protein ◽  
Catalytic Subunit ◽  
Glycerol Phosphate ◽  
Dependent Protein Kinase ◽  
Phosphorylated Proteins ◽  
Dependent Protein ◽  
Rat Adipose Tissue

Incubation of rat adipose-tissue microsomal fractions with iodoacetate caused an inactivation of glycerol phosphate acyltransferase that could be prevented by the presence of palmitoyl-CoA. A microsomal protein of subunit Mr 54 000 was found to react with radioactively labelled iodoacetate in the absence, but not in the presence, of palmitoyl-CoA. It is suggested that this protein is a component of glycerol phosphate acyltransferase. Incubation of rat adipose-tissue microsomal fractions with the catalytic subunit of cyclic AMP-dependent protein kinase, ATP and Mg2+ caused an inactivation of glycerol phosphate acyltransferase whose magnitude depended on the conditions used for assay of the acyltransferase. Rat adipose tissue microsomal proteins were phosphorylated by using protein kinase and [gamma-32P]ATP. One of the phosphorylated proteins was very similar, but not identical, in mobility to the Mr-54 000 protein labelled by iodoacetate. In contrast with a previous report [Sooranna & Saggerson (1976) FEBS Lett. 64, 36-39], no changes could be detected in the activity of glycerol phosphate acyltransferase in adipocytes treated with adrenaline. Adipocytes were labelled with [32P]Pi and treated with adrenaline, but no 32P was incorporated into the Mr-54000 protein labelled by iodoacetate. The results suggest that the activity of adipose-tissue microsomal glycerol phosphate acyltransferase is not directly controlled by phosphorylation.

Intracellular Cs+ activates the PKA pathway, revealing a fast, reversible, Ca2+-dependent inactivation of L-type Ca2+ current

2003 ◽  
Vol 285 (2) ◽  
pp. C310-C318 ◽  
Author(s):  
Fabien Brette ◽  
Alain Lacampagne ◽  
Laurent Sallé ◽  
Ian Findlay ◽  
Jean-Yves Le Guennec
Keyword(s):  
Protein Kinase ◽  
Kinase Inhibitor ◽  
Ventricular Myocytes ◽  
Cyclopiazonic Acid ◽  
Dependent Protein Kinase ◽  
Pipette Solution ◽  
Camp Dependent Protein Kinase ◽  
Dependent Inactivation ◽  
Dependent Protein ◽  
Pka Pathway

Inactivation of the L-type Ca2+ current ( ICaL) was studied in isolated guinea pig ventricular myocytes with different ionic solutions. Under basal conditions, ICaL of 82% of cells infused with Cs+-based intracellular solutions showed enhanced amplitude with multiphasic decay and diastolic depolarization-induced facilitation. The characteristics of ICaL in this population of cells were not due to contamination by other currents or an artifact. These phenomena were reduced by ryanodine, caffeine, cyclopiazonic acid, the protein kinase A inhibitor H-89, and the cAMP-dependent protein kinase inhibitor. Forskolin and isoproterenol increased ICaL by only ∼60% in these cells. Cells infused with either N-methyl-d-glucamine or K+-based intracellular solutions did not show multiphasic decay or facilitation under basal conditions. Isoproterenol increased ICaL by ∼200% in these cells. In conclusion, we show that multiphasic inactivation of ICaL is due to Ca2+-dependent inactivation that is reversible on a time scale of tens of milliseconds. Cs+ seems to activate the cAMP-dependent protein kinase pathway when used as a substitute for K+ in the pipette solution.

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.

Cloning and mapping of human PKIB and PKIG, and comparison of tissue expression patterns of three members of the protein kinase inhibitor family, including PKIA

2000 ◽  
Vol 349 (2) ◽  
pp. 403-407 ◽  
Author(s):  
Lihua ZHENG ◽  
Long YU ◽  
Qiang TU ◽  
Min ZHANG ◽  
Hua HE ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Nuclear Export ◽  
Kinase Inhibitor ◽  
Expression Patterns ◽  
Nuclear Export Signal ◽  
Tissue Expression ◽  
Protein Kinase Inhibitor ◽  
The Other ◽  
Dependent Protein

Two novel members of the human cAMP-dependent protein kinase inhibitor (PKI) gene family, PKIB and PKIG, were cloned. The deduced proteins showed 70% and 90% identity with mouse PKIβ and PKIγ respectively. Both the already identified pseudosubstrate site and leucine-rich nuclear export signal motifs were defined from the 11 PKIs of different species. The PKIB and PKIG genes were mapped respectively to chromosome 6q21-22.1, using a radiation hybrid GB4 panel, and to chromosome 20q13.12-13.13, using a Stanford G3 panel. Northern-blot analysis of three PKI isoforms, including the PKIA identified previously, revealed significant differences in their expression patterns. PKIB had two transcripts of 1.9 kb and 1.4 kb. The former transcript was abundant in both placenta and brain and the latter was expressed most abundantly in placenta, highly in brain, heart, liver, pancreas, moderately in kidney, skeletal muscle and colon, and very little in the other eight tissues tested. PKIG was widely expressed as a 1.5-kb transcript with the highest level in heart, hardly detectable in thymus and peripheral blood leucocytes and was moderately expressed in the other tissues, with slightly different levels. However, PKIA was specifically expressed as two transcripts of 3.3 kb and 1.5 kb in heart and skeletal muscle. The distinct expression patterns of the three PKIs suggest that their roles in various tissues are probably different.

Sign in / Sign up

Export Citation Format

Share Document