TY - JOUR
T1 - cAMP does not inhibit convulxin-induced tyrosyl-phosphorylation of human platelet proteins, including PLCγ2, but completely blocks the integrin α(IIb)β3- dependent dephosphorylation step
T2 - Comparisons with RGDS peptide, cytochalasin D, and phenylarsine oxide
AU - Francischetti, Ivo M.B.
AU - Carlini, Célia R.
AU - Guimarães, Jorge A.
N1 - Funding Information:
The authors acknowledge Dr. Faika Abu Ghazaleh and Dr. Ricardo Reis for helpfull discussions and IP measurements. This work was supported by funds from Conselho Nacional de Desenvolvi-mento Cientifico e Tecnológico (CNPq) (Brasilia, Brazil), Financia-dora de Estudos e projetos (FINEP) (Brasilia, Brazil), and European Community (Contract CI1-CT94-0073).
PY - 1998/6/15
Y1 - 1998/6/15
N2 - Convulxin (Cvx) isolated from Crotalus durissus terrificus venom, induces platelet aggregation, phospholipase C (PLC) activation, and tyrosyl- phosphorylation (PTP) of multiple proteins, including PLCγ2 by a mechanism independent of integrin {IIb)β3. However, PTP induced by Cvx is followed by a dephosphorylation step in a platelet aggregation-dependent manner. Here we show that increasing intraplatelet content of cAMP with forskolin is associated with the inhibition of Cvx-induced platelet aggregation, ATP secretion, and inositol-phosphates production. However, the early onset of Cvx-induced PTP is not sensitive to cAMP (including PLCγ2), and it also occurs in the presence of integrin α(IIb)β3-antagonist (RGDS peptide, RGDS) or inhibitors of actin polymerization (cytochalasin D, CD) and tyrosine-phosphatases (phenylarsine oxide, PAO). However, forskolin, RGDS, and CD prevented the dephosphorylation step together with inhibition of platelet aggregation, whereas in the presence of phenylarsine oxide (PAO) the dephosphorylation step was replaced by an increase in the number and intensity of tyrosyl-phosphorylated proteins. Our data provide evidence to conclude that (i) cAMP inhibits platelet aggregation at a downstream site to PLCγ2 tyrosyl-phosphorylation; (ii) Cvx-induced PTP is independent on integrin α(IIb)β3 engagement, actin polymerization, and tyrosine- phosphatases activation; (iii) integrin α(IIb)β3 mediates the dephosphorylation step in a platelet aggregation-dependent manner; and (iv) Cvx and collagen stimulate platelets by a similar signal transduction pathway.
AB - Convulxin (Cvx) isolated from Crotalus durissus terrificus venom, induces platelet aggregation, phospholipase C (PLC) activation, and tyrosyl- phosphorylation (PTP) of multiple proteins, including PLCγ2 by a mechanism independent of integrin {IIb)β3. However, PTP induced by Cvx is followed by a dephosphorylation step in a platelet aggregation-dependent manner. Here we show that increasing intraplatelet content of cAMP with forskolin is associated with the inhibition of Cvx-induced platelet aggregation, ATP secretion, and inositol-phosphates production. However, the early onset of Cvx-induced PTP is not sensitive to cAMP (including PLCγ2), and it also occurs in the presence of integrin α(IIb)β3-antagonist (RGDS peptide, RGDS) or inhibitors of actin polymerization (cytochalasin D, CD) and tyrosine-phosphatases (phenylarsine oxide, PAO). However, forskolin, RGDS, and CD prevented the dephosphorylation step together with inhibition of platelet aggregation, whereas in the presence of phenylarsine oxide (PAO) the dephosphorylation step was replaced by an increase in the number and intensity of tyrosyl-phosphorylated proteins. Our data provide evidence to conclude that (i) cAMP inhibits platelet aggregation at a downstream site to PLCγ2 tyrosyl-phosphorylation; (ii) Cvx-induced PTP is independent on integrin α(IIb)β3 engagement, actin polymerization, and tyrosine- phosphatases activation; (iii) integrin α(IIb)β3 mediates the dephosphorylation step in a platelet aggregation-dependent manner; and (iv) Cvx and collagen stimulate platelets by a similar signal transduction pathway.
KW - Collagen
KW - Convulxin
KW - GPVI
KW - PLCγ2
KW - Snake venoms
KW - Tyrosine- kinases
KW - Tyrosine-phosphatases
KW - cAMP
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U2 - 10.1006/abbi.1998.0637
DO - 10.1006/abbi.1998.0637
M3 - Article
C2 - 9637734
AN - SCOPUS:0032526552
SN - 0003-9861
VL - 354
SP - 255
EP - 262
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -