We examined the expression of protein kinase C isoforms in infarcted tissue, penumbra and contralateral brain tissue from 10 patients who died between 1-52 days after ischaemic stroke. Ten patients aged 61-89 years were used in the study. Tissue samples were assayed for protein kinase C activity using a non-radioactive method, and specific isoforms expression determined by Western blotting and staining with anti-PKC polyclonal antibodies. There was a 2-24 fold increase in PKC gamma in the ischaemic penumbra of nine out of 10 patients compared to contralateral tissue. In infarcted tissue expression of PKC gamma was not significantly changed in any of 10 samples but the beta I isoform increased in eight and the beta II in nine patients. There was no significant change in expression in PKC alpha or in infarct or penumbra. Differences in total PKC activity were not specific in seven out of eight patients and it is difficult to estimate their significance. In conclusion after ischaemia there was an altered expression of PKC isoforms with an increase of PKC gammain the surviving penumbra and beta I and beta II in the infarcted core.
We demonstrate that sphingosylphosphorylcholine-mediated cell death involves the activation of different protein kinase C isozymes in different manners. Treating cells with sphingosylphosphorylcholine resulted in activation of protein kinase C delta, which is necessary, together with elevation of Ca2+, for sphingosylphosphorylcholine-induced apoptosis. A rapid translocation from cytosol to membrane, and a proteolytic protein kinase C delta cleavage was found, probably due to activation of caspase-3, to give a catalytically active fragment involved in cellular apoptosis. Moreover, sphingosylphosphorylcholine also induced translocation of protein kinase C zeta, resulting in an anti-apoptotic effect. To explore whether a mitochondrial pathway is involved in sphingosylphosphorylcholine-induced apoptosis, we analyzed the effect of sphingosylphosphorylcholine on cytochrome c release and caspase-3 activity. We must point out that the sphingolipid caused an increase of cytochrome c release from mitochondria to cytosol concomitantly with an increase of caspase-3 activity. Furthermore, a translocation of Bax was found, after sphingosylphosphorylcholine treatment.
Treatment of 10T1/2 cells with promoting phorbol ester drasticly enhanced migration studied fibroblasts in a serum-supplemented medium.The same cells when exposed to ionomycin or TPA in a serum-free medium did not show any migration.The addition of 1% of serum induced spontaneous and TPA stimulated migration.Also EGF and PDGE separatly or together induced the migration of 10T1/2 cells.Parallel studies of protein kinase C documented low enzymatic activity after treatment with TPA, whereas transcripts of PKC were shown independently of TPA treatment.
Protein kinase C comprises a family of at least 13 distinct serine/threonine kinase isoenzymes that have important action in transmembrane signal transduction pathways and have been reported to regulate cell proliferation, differentiation, cell-to-cell interaction, cytoskeletal functions, gene transcription, apoptosis and drug resistance. The results of investigations show differential redistribution isozymes in each organs and their specyfic activity in determined diseases.
(1) We favour a hypothesis that the delayed in is iniated by the increase of intracellular concentration, activating transiently Ca-dependent .(2) The secondary effects of the , short-lasting PKC translocation/activation could involve:an activation of cAMP signaling pathway; an activation of early response like .
Palmitoylcarnitine is synthesized through the action of palmitoylcarnitine transferase I - an enzyme specifically inhibited by etomoxir. An increase of the intracellular content of palmitoylcarnitine in neuroblastoma NB-2a cells after administration of carnitine was correlated with an inhibition of cell proliferation and a concomitant promotion of differentiation processes. The activity of protein kinase C was measured in vivo, with cells permeabilized through the use of streptolysin O and a peptide substrate. Palmitoylcarnitine inhibited the phorbol ester stimulated reaction of the peptide phosphorylation in a concentration dependent way. The degree of protein kinase C inhibition was correlated with intracellular increase of the palmitoylcarnitine content, pointing to this compound as a natural modulator of protein kinase C activity.
Carnitine (4-N-trimethylammonium-3-hydroxybutyric acid) seems to fullfil in the brain a different role than in peripheral tissues.Carnitine is accumulated by neural cells in a sodium-dependent way.The existence of a novel rtansporter in plasma membrane, specific to compounds with a polar group in the beta-position with respect to carboxyl group, has been postulated.The presence of carnitine carrier in the inner mitochondrial membrane has been proven and the protein has been purified.It is postulated that its major role in adult brain would be rtanslocation of acetyl moieties from mitochondria into the cytoplas for acetylocholine synthesis.The latter process is stimulated by carnitine and choline in a synergistic way in cells utilizing glucose as a main energetic substrate.Carnitine metabolism in neural cells leads to accumulation of different acyl derivatives of carnitine.Palmitoylcarnitine can influence directly the activity of protein kinase C.An involvment of carnitine in a decrease of palmitate pool used for palmitoylation of regulatory proteins has been postulated.
We have proposed that protein kinase C, an enzyme critical to cell regulation of growth, secretion and differentiation, is a part of a sequence of molecular events that unsderlie learning and memory. Electrophysiological, biochemical and neuro-imaging methods have been employed to show that the enzyme changes its distribution as a result of memory storage within the neural networks that are necessary for the acquisition and performance of various learning tasks in several species. We propose here, a model of protein kinase C as a molecular signal for the association of synaptic input that is parsimonious with the recent data, mainly our laboratory, concerning its function in emory formation.
In the present study the functional role of SH groups in the Ca2+ -independent K+ selective channel activity in the membrane of bovine adrenal gland chromaffin granules has been studied. Ionic channel activity has been estimated using 86Rb+, a K+ analogue, flux measurements. The inhibition of chromaffin granules K+ channel by SH modifying agents, such as N ethylmaleimide, mersalyl and phenylarsenoxide, is described.
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