Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.21 (CPT)
 4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of activation of mitochondrial overt carnitine palmitoyltransferase (CPT I) by treatment of hepatocytes with okadaic acid (OA) was investigated. Activation was observed when cells were permeabilized with digitonin, but not when a total membrane fraction was obtained by sonication. Both cell disruption methods preserved the activation of phosphorylase observed in OA-treated hepatocytes. Activation of CPT I was also observed in crude homogenates of OA-treated hepatocytes, but it was lost upon subsequent isolation of mitochondria from such homogenates. In all experiments, any activation observed did not depend on the presence or absence of fluoride ions in the permeabilization/homogenization media. When hepatocytes were permeabilized in the absence of fluoride and further incubated with exogenous phosphatases 1 and 2A, the OA-induced activation of CPT was not reversed, whereas the activation of glycogen phosphorylase in the same cells was rapidly reversed. Treatment of hepatocytes with OA, followed by permeabilization and incubation before assay of CPT I, demonstrated that OA had no short-term effect on the sensitivity of CPT I to malonyl-CoA, although the difference in sensitivity between cells isolated from fed and starved rats was fully preserved. Incubation of isolated mitochondria or purified mitochondrial outer membranes with cyclic AMP-dependent or AMP-activated protein kinases, under phosphorylating conditions, did not affect the activity of CPT I or its sensitivity to malonyl-CoA inhibition. Under the same conditions, the use of [32P]ATP resulted in the labelling of several outer-membrane proteins but, unlike [3H]etomoxir-labelled CPT I, none of them was specifically removed from membrane extracts by a specific polyclonal antibody to the enzyme. We conclude that the increase in overt CPT activity observed in permeabilized hepatocytes is not due to direct phosphorylation of CPT I, but may involve interactions between the mitochondrial outer membrane and other membranous or soluble cytosolic components of the cell.
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PMID:Evidence against direct involvement of phosphorylation in the activation of carnitine palmitoyltransferase by okadaic acid in rat hepatocytes. 801 Sep 50

A-kinase can inhibit RhoA activation through phosphorylating ser188 of RhoA. AKAP is a novel protein that can target PKA to different subcellular compartment. Evidence has been presented that PKA anchorage by AKAP is important for the kinase to exert its function. This study analyzed the role of PKA anchorage in PKA-induced antagonism against RhoA activity and function. The cells transfected with pcDNA HT31wt/mut were treated with LPA and/or CPT-cAMP. The amount of GTP-RhoA and phosphorylation of RhoA was detected by Western blotting with specific antibodies. The formation of stress fiber was visualized under fluorescent microscope. The gene expression activity was analyzed by luciferase reporter gene assay. The motility and the anchorage-independent growth assays were carried out with stably transfected cells expressing the AKAP inhibitory peptide HT31. The results showed that HT31 not only blocked the PKA-induced phosphorylation of RhoA but also prevented the PKA-induced inhibition on RhoA activation. The disruption of PKA anchorage abolished its inhibition on the LPA-induced expression of reporter gene SRE-luciferase. The ability of PKA to antagonize the LPA-induced stress fiber formation was partly impaired upon the disruption of the PKA anchorage. The control of PKA on migration and the proliferation excited by LPA disappeared in stably transfected cells highly expressing HT31. The results revealed that PKA anchorage was necessary for the kinase to exert its inhibitory effect on RhoA activation and RhoA-dependent biological activities.
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PMID:AKAPs competing peptide HT31 disrupts the inhibitory effect of PKA on RhoA activity. 1696 90

We have previously shown that metoprolol can inhibit carnitine palmitoyltransferase-1 catalytic activity and decrease its malonyl CoA sensitivity within 30 min, suggesting the importance of a covalent modification. The aim of this study was to characterize the effects of PTMs on CPT-1 in the heart. Mitochondria were isolated from the hearts of male Wistar rats and incubated with kinases of interest (protein kinase A, CAMK-II, p38 MAPK, Akt) or with peroxynitrite and sodium nitroprusside. PKA decreased CPT-1 malonyl CoA sensitivity, associated with phosphorylation of CPT-1A, whereas CAMK-II increased malonyl CoA sensitivity by phosphorylating CPT-1B. p38 bound to CPT-1B and stimulated CPT-1 activity. The association of CPT-1 with these kinases and their scaffolding proteins was confirmed in co-localization studies. Peroxynitrite and sodium nitroprusside reversibly stimulated CPT-1 activity, and the change in CPT-1B activity was most consistently associated with glutathiolation of CPT-1B. These studies have identified a new regulatory system of kinases, scaffolding proteins and thiol redox chemistry which can control cardiac CPT-1 in vitro.
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PMID:Functional effects of protein kinases and peroxynitrite on cardiac carnitine palmitoyltransferase-1 in isolated mitochondria. 1986 3