Role of protein kinase C in the regulation of phospholipase A2 activity in human platelets

1990 ◽  
Vol 18 (3) ◽  
pp. 467-468 ◽  
Author(s):  
CAROLINE P. D. WHEELER-JONES ◽  
YATIN PATEL ◽  
VIJAY V. KAKKAR ◽  
SUSHILA KRISHNAMURTHI
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Human Platelets ◽  
Kinase C ◽  
Phospholipase A2 Activity

scholarly journals Diradylglycerols stimulate phospholipase A2 and subsequent exocytosis in ram spermatozoa. Evidence that the effect is not mediated via protein kinase C

1994 ◽  
Vol 297 (1) ◽  
pp. 225-232 ◽  
Author(s):  
E R S Roldan ◽  
C Fragio
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Kinase Inhibitor ◽  
Ionophore A23187 ◽  
Kinase C ◽  
Acrosomal Exocytosis ◽  
Phospholipase A2 Activity

We tested the hypothesis that the role of diacylglycerol (DAG) in sperm acrosomal exocytosis is related to the activation of phospholipase A2, and that this effect is not mediated via protein kinase C. Treatment of [14C]arachidonic acid-labelled ram spermatozoa with Ca2+ and the ionophore A23187 stimulated both liberation of arachidonic acid and acrosomal exocytosis. No changes in [14C]DAG or [14C]monoacylglycerol were found after stimulation of spermatozoa, thus suggesting that arachidonic acid may be released exclusively via phospholipase A2. An increase in the endogenous levels of diradylglycerols (DRGs), resulting from exposure either to the DAG kinase inhibitor R 59022 or to exogenous 1-oleoyl-2-acetyl-sn-glycerol or 1,2-dioctanoyl-sn-glycerol, led to an increase in both phospholipase A2 activity and exocytosis when cells were stimulated with A23187 and Ca2+. Addition of DRGs that do not stimulate protein kinase C(1,3-dioctanoylglycerol, 1-O-hexadecyl-2-acetyl-rac-glycerol) also resulted in an increase in phospholipase A2 activity and exocytosis. On the other hand, phorbol esters (phorbol 12,13-dibutyrate; phorbol 12-myristate 13-acetate) did not enhance enzyme activity or exocytosis. Finally, exposure to 1-O-hexadecyl-2-O-methyl-rac-glycerol, a compound known to inhibit protein kinase C, did not affect phospholipase A2 activity or acrosomal exocytosis. We therefore conclude that in spermatozoa the messenger role of DAG is related to the activation of phospholipase A2, which in turn would generate an array of metabolites directly or indirectly involved in bringing about exocytosis of the acrosome.

scholarly journals Mechanism of inhibition of protein kinase C by 14-3-3 isoforms. 14-3-3 isoforms do not have phospholipase A2 activity.

1994 ◽  
Vol 299 (3) ◽  
pp. 853-861 ◽  
Author(s):  
K Robinson ◽  
D Jones ◽  
Y Patel ◽  
H Martin ◽  
J Madrazo ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase A2 ◽  
Kinase C ◽  
Mechanism Of Inhibition ◽  
C1 Domain ◽  
Novel Method ◽  
Original Observation ◽  
Cytosolic Pla2 ◽  
Phospholipase A2 Activity

The ability of individual members of the 14-3-3 protein family to inhibit protein kinase C (PKC) has been studied by using a synthetic peptide based on the specific 80 kDa substrate for PKC (MARCKS protein) in two different assay systems. Recombinant 14-3-3 and isoforms renatured by a novel method after separation by reverse-phase h.p.l.c. were studied. The detailed effects of diacylglycerol and the phorbol ester phorbol 12-myristate 13-acetate on the inhibition were also investigated. This suggests that one of the sites of interaction of 14-3-3 may be the cysteine-rich (C1) domain in PKC. Since a region in secreted phospholipase A2 (PLA2) shares similarity with this domain, the ability of 14-3-3 to interact with mammalian PLA2 was studied. Cytosolic PLA2 has some similarity to the C2 region of PKC, and the effect of 14-3-3 on this class of PLA2 was also analysed. In contrast with a previous report, no PLA2 activity was found in brain 14-3-3, nor in any of the recombinant proteins tested. These include zeta 14-3-3 isoform, on which the original observation was made.

Modification of Na+/H+ Exchanger in Human Platelets by 1,2-Dioctanoylglycerol, a Protein Kinase C Activator

1990 ◽  
Vol 64 (01) ◽  
pp. 165-171 ◽  
Author(s):  
Yukio Ozaki ◽  
Yuki Mastsumoto ◽  
Yutaka Yatomi ◽  
Masaaki Higashihara
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Rate Constant ◽  
Human Platelets ◽  
Kinase C ◽  
Km Value ◽  
The Difference ◽  
The One ◽  
Protein Kinase C Activation

SummaryProtein kinase C activation in human platelets has a modulatory role in maintaining intracellular pH (pHi), by adjusting pHi at a particular value (7.22). Changes in pHi induced by protein kinase C appeared to be dependent upon the difference between H+ efflux catalyzed by the Na+/H+ exchanger and H+ production. The pHi recovery after acid loading was significantly facilitated by protein kinase C activation. Analysis of the rate constant for pHi recovery suggested that the turnover rate or the apparent affinity of the Na+/H+ exchanger for H+ was increased. Protein kinase C also decreased the Km value of the Na+/H+ exchanger for extracellular Na+. Thus, it is suggested that the role of protein kinase C in platelet pHi regulation is dual, adjusting the pHi value at a certain setpoint on the one hand, and increasing the rate constant of the Na+/H+ exchanger on the other.

PROTEIN KINASE C CONTROLS CA2+ MOBILIZATION IN HUMAN PLATELETS

1987 ◽  
Author(s):  
W Siffert ◽  
P Scheid ◽  
JW N Akkerman
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Human Platelets ◽  
Cytosolic Ph ◽  
Fluorescent Indicators ◽  
Kinase C ◽  
Deutsche Forschungsgemeinschaft ◽  
Ionophore Monensin ◽  
Stimulation Of

Platelet stimulation has been shown to result in a rise of cytosolic pH (pHi) as a result of an activation of a Na+/H+ antiport. We have investigated the role of pH in Ca2+ mobilization in human platelets. pHi and free Ca2+, {Ca2+)i, were measured in platelets loaded with the fluorescent indicators BCECF and quin2, respectively. Stimulation of platelets by either thrombin or OAG, an activator of protein kinase C (Pk-C), increased pHi. Pretreatment of platelets with inhibitors of Pk-C, trifluoperazine (TFP) or sphingosine (SPH), blocked the stimulus-induced rise in pHi, suggesting a role of Pk-C in the activation of Na+/H+ exchange. Blocking Na+/H+ exchange by an amiloride analogue or by TFP similarly suppressed the thrombin-induced increase in {Ca2*}i. This effect could be prevented by increasing pHi with the Na+/H+ ionophore monensin or with NH4Cl. The thrombin-induced (0.05 U/ml) rise in {Ca2+}i was more than 3-fold enhanced when the pH was raised from 6.8 to 7.4.Our results demonstrate that pHi controls Ca2+ mobilization in human platelets and suggest that Pk-C contributes to this control by activating the Na+/H+ exchanger.Supported by the Deutsche Forschungsgemeinschaft. No Sche 46/5-2.

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