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Biomedical subjects

A Kishimoto

Publications and source records attributed to A Kishimoto.

At least 55 records · Page 3Linked to original sources
PubMed1990

Dual action of hydroxylated diphenylethylene estrogens on protein kinase C1.

Protein kinase C (PKC) I (gamma), II (beta) and III (alpha) subspecies are all activated by 1,1-di-(p-hydroxyphenyl)ethylene derivatives (DPE) at micromolar concentrations. This PKC activation depends on the presence of both Ca2+ and phosphatidylserine (PS) but does not require diacylglycerol (DG). DPEs enhance PKC activity at low PS concentrations, but not at saturating PS concentrations. Like DG, DPEs increase the apparent affinity of PKC for PS as well as for Ca2+, but lead to a decrease in the catalytic activity (Vmax). In the presence of saturating DG concentrations, DPEs exhibit an inhibitory action. The derivatives also inhibit the activity of the proteolytic fragment of PKC, protein kinase M. It is concluded that DPEs are mixed-type inhibitors, probably interacting with the catalytic domain of the enzyme.

Animals↗
PubMed1990

Protein kinase C in Saccharomyces cerevisiae: comparison with the mammalian enzyme.

Protein kinase C (PKC) was detected in the yeast Saccharomyces cerevisiae with bovine myelin basic protein as the phosphate acceptor. The enzyme was purified at least 500-fold by a four-step column chromatographic procedure (phenyl-Sepharose CL-4B, Mono Q, Heparin-5PW, and hydroxyapatite). The molecular mass was approximately 90 kDa, as estimated by gel-filtration analysis. Yeast PKC was activated by the simultaneous addition of Ca2+, diacylglycerol, and phosphatidylserine. Free arachidonic acid alone could activate the enzyme to some extent. However, yeast PKC did not respond significantly to tumor-promoting phorbol esters. GTP did not serve as phosphate donor. The yeast enzyme showed substrate specificity distinctly different from that of mammalian PKCs. H1 histone and protamine were poor substrates. With myelin basic protein as a model substrate, yeast PKC phosphorylated threonyl residues preferentially, whereas rat brain PKCs phosphorylated seryl residues preferentially. Further studies should elucidate the role of yeast PKC in cellular regulation and cell cycle control.

Amino Acid Sequence↗
PubMed1990

Activation of resting human T cells requires prolonged stimulation of protein kinase C.

Purified resting human T cells can be induced to express the alpha subunit of the interleukin 2 receptor and to proliferate by treatment with 12-O-tetradecanoylphorbol-13-acetate plus ionomycin but not with 1,2-dioctanoylglycerol plus ionomycin. Determination of the translocation of protein kinase C showed that 12-O-tetradecanoylphorbol-13-acetate plus ionomycin caused a prolonged membrane association of the enzyme for more than 4 hr, whereas 1,2-dioctanoylglycerol plus ionomycin induced a transient membrane association, which was maximal at 20 min. Delivery of multiple additions of 1,2-dioctanoylglycerol plus ionomycin to the T cells resulted in progressively increased expression of the alpha subunit of the interleukin 2 receptor and proliferation commensurate with the number of multiple additions delivered, suggesting that prolonged protein kinase C activity is required for T-cell activation.

Cell Membrane↗
PubMed1990

Immunocytochemical localization of the alpha subspecies of protein kinase C in rat brain.

The distribution of the alpha subspecies of protein kinase C (PKC) in rat brain was demonstrated immunocytochemically by using polyclonal antibodies raised against a synthetic oligopeptide corresponding to the carboxyl-terminal sequence of alpha-PKC. The alpha-PKC-specific immunoreactivity was widely but discretely distributed in both gray and white matter. The immunoreactivity was associated predominantly with neurons, particularly with perikaryon, dendrite, or axon, but little was seen in the nucleus. Glial cells expressed this PKC subspecies poorly, if at all. The highest density of immunoreactivity was seen in the olfactory bulb, septohippocampal nucleus, indusium griseum, islands of Calleja, intermediate part of the lateral septal nucleus, and Ammon's horn. A moderately high density of the immunoreactivity was seen in the anterior olfactory nucleus, anterior commissure, cingulate cortex, dentate gyrus, compact part of the substantia nigra, interpeduncular nucleus, inferior olive, and olivocerebellar tract. This distribution pattern was consistent with that obtained by in situ hybridization histochemistry. The distribution of alpha-PKC immunoreactivity was different from that of beta I-, beta II-, and gamma-PKC immunoreactivity. These findings suggest that alpha-PKC is involved heavily in the control of specific functions of some restricted neurons.

Amino Acid Sequence↗
PubMed1990

Avoiding neurotoxicity with lithium-carbamazepine combinations.

A therapeutic synergism has been well documented with carbamazepine (CBZ) and lithium in some patients who do not respond adequately to either drug alone. Because both of these drugs can induce neurotoxicity, concern has been expressed about their safety when combined. The serum levels for effective and safe dosage have been determined when these drugs are used alone. Unfortunately, this information does not give us automatic insight into the range of safe serum levels for each drug when these drugs are combined. We do not know whether the contribution of each drug to the neurotoxicity is the same. We have plotted the paired serum levels on a two-dimensional graph and quantitatively determined the region where we begin to encounter neurotoxicity. When we examine the available data on this graph, we see no evidence for synergistic neurotoxicity.

Carbamazepine↗
PubMed1989

Modes of inhibition of protein kinase C by triphenylacrylonitrile antiestrogens.

Protein kinase C (PKC) I (gamma), II (beta) and III (alpha) subspecies' activities are inhibited by three triphenylacrylonitrile (TPE) antiestrogens at micromolar concentrations. TPE 1 (having a p-hydroxy and a p-diethylaminoethoxy group on the 3-, and 3'- phenyl rings respectively) and TPE 2 (having a p-diethylaminoethoxy group on both the 3-, and 3'- phenyl rings) are competitive with the mechanism of activation by phosphatidylserine (PS). TPE 3 (having p-hydroxy groups on each of the three phenyl rings) is non-competitive with PS and inhibits the Ca2+- and PS-independent phosphorylation of protamine sulfate by PKC subspecies. This evidence suggests that PKC activity can be inhibited by different routes depending on the TPE structure: diethylaminoethoxy side chain-substituted TPEs (TPE 1 and 2) interact with PS as well as with the regulatory domain, whereas the trihydroxylated derivative (TPE 3) inhibits the enzyme by interacting with the catalytically active site.

Acrylonitrile↗
PubMed1989

Human T cell activation by phorbol esters and diacylglycerol analogues.

Activation of protein kinase C (PKC), by the phorbol ester PMA, or the membrane-permeable diacylglycerol 1-oleoyl 2-acetylglycerol (OAG), had different effects on the proliferation-associated responses of a more than 99% pure population of human T cells. Treatment with PMA or OAG caused down-regulation of the TCR-CD3 complex, but only PMA, in combination with ionomycin, was capable of stimulating IL-2R expression and proliferation. Immunocytochemical staining with antisera specific for the PKC subspecies alpha, beta I, beta II, and gamma showed that untreated resting T cells normally coexpress alpha, beta I, and beta II PKC subspecies, which are distributed diffusely throughout the cell, with some localization around the periphery of the nucleus. There was no difference between the responses of these PKC subspecies to OAG and PMA, redistributing, after 10 min of treatment, to a discrete focal area within the cell. Treatment with OAG resulted in transient redistribution of PKC, maximal at 10 min, while in PMA-stimulated cells, the PKC redistribution was prolonged, persisting for at least 24 h. The results suggest that the difference in cellular response to treatment with PMA and OAG is not a consequence of differential activation of various PKC subspecies.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Limited proteolysis of protein kinase C subspecies by calcium-dependent neutral protease (calpain).

Limited proteolysis of three distinct subspecies of protein kinase C (Ca2+/phospholipid-dependent enzyme, PKC), types I (gamma), II (beta I and beta II), and III (alpha), with Ca2+-dependent neutral proteases I and II (calpains I and II) was studied. All forms of PKC (82 kDa) were converted to two major fragments: a 45-49-kDa catalytic fragment and a 36-kDa regulatory fragment. The cleavage of these PKC subspecies by calpain I (active in the micromolar range Ca2+/ion concentration), and, to a lesser extent, by calpain II (active in the millimolar range), was enhanced by the simultaneous presence of phospholipid and diacylglycerol or phorbol ester, suggesting that the activated form of PKC is the preferred target for proteolysis. Analysis of the NH2-terminal sequence of the resulting catalytic fragments indicated that both calpains I and II cleave at one or two specific sites in the third variable region (V3) of each PKC molecule. Under comparable conditions with calpains I and II, the relative rates of cleavage of types I, II, and III PKC were approximately 100:16:2 and 100:48:23, respectively. The results imply that within the cell various PKC subspecies may be cleaved at different rates under different physiological conditions.

Amino Acid Sequence↗
PubMed1989

Selective activation of the gamma-subspecies of protein kinase C from bovine cerebellum by arachidonic acid and its lipoxygenase metabolites.

The gamma-subspecies of protein kinase C (PKC) apparently is expressed only in central nervous tissues, and at a high level in the cerebellum and hippocampus. gamma-PKC from bovine cerebellum, but not the alpha- or beta I/beta II-subspecies, is activated by micromolar concentrations of arachidonic acid (AA), in the absence of both phospholipid and diacylglycerol. A significant component of this activation is also calcium independent. Other unsaturated fatty acids are much less active in this respect. Among the AA metabolites tested, lipoxin A (5(S),6(R),15(S)-11-cis-isomer) was a potent, selective activator of the gamma-subspecies, and also, to a lesser extent, 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid could support activation. These results raise the possibility that AA and some of its lipoxygenase metabolites may function as messenger molecules in neurones to activate the gamma-subspecies of PKC.

Animals↗
PubMed1988

Differential down-regulation of protein kinase C subspecies in KM3 cells.

The down-regulation of protein kinase C (PKC) subspecies in KM3 cells (a pre-B, pre-T cell line) has been examined. The PKC from KM3 cells was resolved into two subspecies, type II (mainly beta II) and type III (alpha), upon hydroxyapatite column chromatography. Biochemical and immunocytochemical analysis revealed that, when these cells were treated with 12-O-tetradecanoylphorbol 13-acetate (TPA), the time course of down-regulation of the PKC subspecies was different; type II PKC was translocated and depleted from the cell more quickly than type III enzyme. The results suggest that each PKC subspecies plays a different role in the cellular response to TPA and probably to other external stimuli.

Cell Compartmentation↗