Properties of protein kinase c subspecies in human platelets

Tsukuda, Masanori; Asaoka, Yoshinori; Sekiguchi, Koichi; Kikkawa, Ushio; Nishizuka, Yasutomi

doi:10.1016/s0006-291x(88)81295-6

Cited by 54 publications

(21 citation statements)

References 19 publications

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“…The function of pleckstrin is still unknown (Tyers et aL., 1988), but phosphorylation of this protein does indicate that activation of PKC has occurred (Sano et aL., 1983). Platelets have, in fact, been shown to contain an unidentified isozyme of PKC that can phosphorylate pleckstrin in the absence of Ca2l (Tsukuda et aL., 1988), and current results show that PKC is essential for the Ca2"-independent secretion of dense and a-granule constituents, caused by GTPyS (Coorssen, Davidson, and Haslam, unpublished). These findings imply that, even in the absence of Ca2", GTPyS acts on a G-protein-coupled effector enzyme that generates a lipid second messenger capable of stimulating PKC.…”

Section: Discussionmentioning

confidence: 66%

Factors affecting dense and alpha-granule secretion from electropermeabilized human platelets: Ca(2+)-independent actions of phorbol ester and GTP gamma S.

1990

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Electropermeabilized human platelets containing 5-hydroxy[14C]tryptamine ([14C]5-HT) were suspended in a glutamate medium containing ATP and incubated for 10 min with (in various combinations) Ca2+ buffers, phorbol 12-myristate 13-acetate (PMA), guanine nucleotides, and thrombin. Release of [14C]5-HT and beta-thromboglobulin (beta TG) were used to measure secretion from dense and alpha-granules, respectively. Ca2+ alone induced secretion from both granule types; half-maximal effects were seen at a -log [Ca2+ free] (pCa) of 5.5 and maximal secretion at a pCa of 4.5, when approximately 80% of 5-HT and approximately 50% of beta TG were released. Addition of PMA, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), GTP, or thrombin shifted the Ca2+ dose-response curves for secretion of both 5-HT and beta TG to the left and caused small increases in the maximum secretion observed. These results suggested that secretion from alpha-granules, like that from dense granules, is a Ca(2+)-dependent process stimulated by the sequential activation of a G-protein, phospholipase C, and protein kinase C (PKC). However, high concentrations of PMA and GTP gamma S had distinct effects in the absence of Ca2+ (pCa greater than 9); 100 nM PMA released approximately 20% of platelet 5-HT but little beta TG, whereas 100 microM GTP gamma S stimulated secretion of approximately 25% of each. Simultaneous addition of PMA greatly enhanced these effects of GTP gamma S. Phosphorylation of pleckstrin in permeabilized platelets incubated with [gamma-32P]ATP was used as an index of the activation of PKC during secretion. In the absence of Ca2+, 100 nM PMA caused maximal phosphorylation of pleckstrin and 100 microM GTP gamma S was approximately 50% as effective as PMA; neither GTP gamma S nor Ca2+ enhanced the phosphorylation of pleckstrin caused by 100 nM PMA. These results indicate that, although activation of PKC promoted secretion, GTP gamma S exerted additional stimulatory effects on secretion from both dense and alpha-granules that were not mediated by PKC. Measurement of [3H]inositol phosphate formation in permeabilized platelets containing [3H]phosphoinositides showed that GTP gamma S did not stimulate phosphoinositide-specific phospholipase C in the absence of Ca2+. It follows that in permeabilized platelets, GTP gamma S can both stimulate PKC and enhance secretion via G-protein-linked effectors other than this phospholipase.

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Section: Discussionmentioning

confidence: 66%

Factors affecting dense and alpha-granule secretion from electropermeabilized human platelets: Ca(2+)-independent actions of phorbol ester and GTP gamma S.

1990

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“…Routtenberg and co.workers [13] have proposed that oleic acid may be involved in the maintenance of LTP by activating PKC Bliss and collaborators [28] [29]. Seifert et al [30] and Szamel et al [31] have described some evidence suggesting that unsaturated FFAs may have potentials to enhance the activation of human platelets and lymphocytes, respectively, presumably through the PKC signal pathway.…”

Section: Discussionmentioning

confidence: 99%

Protein kinase C subspecies in adult rat hippocampal synaptosomes Activation by diacylglycerol and arachidonic acid

et al. 1991

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Synaptosomes isolated from the rat hippocampus contain the α‐ and β‐subspecies of protein kinase C (PKC), but not the γ‐subspecies which is abundantly expressed in the pyramidal cells in this brain region. Although the γ‐subspecies is known to respond significantly to free arachidonic acid, it is found that both the α‐ and β‐subspecies are also activated dramatically by arachidonic acid in synergistic action with diacylglycerol. Olcic, linoleic, and linolenic acids are all active. It is possible that unsaturated fatty acids may take part in the activation of α‐ and β‐subspecies of PKC which are present in the presynaptic nerve endings terminating at the hippocampal pyramidal cells.

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“…Rabbit platelets were also a simpler model system for the study of PKC, as they appear to contain mostly the /J-isoenzyme (Pelech et al, 1990). Human platelets, by contrast, also have high levels of the z-isoenzyme of PKC (Tsukuda et al, 1988;Watanabe et al, 1988). Although PKC has long been implicated in the actions of thrombin and PAF, most of the evidence for their activation of PKC has been indirect, relying largely on the suppressive effects of PKC inhibitors.…”

Section: Discussionmentioning

confidence: 99%

Translocation-independent activation of protein kinase C by platelet-activating factor, thrombin and prostacyclin. Lack of correlation with polyphosphoinositide hydrolysis in rabbit platelets

Salari

Duronio

Howard

et al. 1990

Biochemical Journal

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The relationship between polyphosphoinositide hydrolysis and protein kinase C (PKC) activation was explored in rabbit platelets treated with the agonists platelet-activating factor (PAF), thrombin and 12-O-tetradecanoylphorbol 13-acetate (TPA), and with the anti-aggregant prostacyclin (PGI2). Measurement of the hydrolysis of radiolabelled inositolcontaining phospholipids relied upon the separation of the products [3H]inositol mono-, bis-and tris-phosphates by Dowex-l chromatography. PKC activity, measured in platelet cytosolic and Nonidet-P40-solubilized particulate extracts that were fractionated by MonoQ chromatography, was based upon the ability of the enzyme to phosphorylate either histone HI in the presence of the activators Ca2+, diacylglycerol and phosphatidylserine, or protamine in the absence of Ca2+ and lipid. Treatment of platelets for 1 min with PAF (2 nM) or thrombin (2 units/ml) led to the rapid hydrolysis of inositol-containing phospholipids, a 2-3-fold stimulation of both cytosolic and particulate-derived PKC activity, and platelet aggregation. Exposure to TPA (200 nM) for 5 min did not stimulate formation of phosphoinositides, but translocated more than 95 % of cytosolic PKC into the particulate fraction, and induced a slower rate of aggregation. PGI2 (1 ,ug/ml) did not enhance phosphoinositide production, and at higher concentrations (50 ,ug/ml) it antagonized the ability of PAF, but not that of thrombin, to induce inositol phospholipid turnover, even though platelet aggregation in response to both agonists was blocked by PGI2. On the other hand, PGI2 alone also appeared to activate (by 3-5-fold) cytosolic and particulate PKC by a translocation-independent mechanism. The activation of PKC by PGI2 was probably mediated via cyclic AMP (cAMP), as this effect was mimicked by the cAMP analogue 8-chlorophenylthio-cAMP. It is concluded that this novel mechanism of PKC regulation by platelet agonists may operate independently of polyphosphoinositide turnover, and that activation of cAMP-dependent protein kinase represents another route leading to PKC activation.

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Properties of protein kinase c subspecies in human platelets

Cited by 54 publications

References 19 publications

Factors affecting dense and alpha-granule secretion from electropermeabilized human platelets: Ca(2+)-independent actions of phorbol ester and GTP gamma S.

Factors affecting dense and alpha-granule secretion from electropermeabilized human platelets: Ca(2+)-independent actions of phorbol ester and GTP gamma S.

Protein kinase C subspecies in adult rat hippocampal synaptosomes Activation by diacylglycerol and arachidonic acid

Translocation-independent activation of protein kinase C by platelet-activating factor, thrombin and prostacyclin. Lack of correlation with polyphosphoinositide hydrolysis in rabbit platelets

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