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.

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.

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
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