Group IVA cytosolic phospholipase A2 (cPLA2alpha) and integrin alphaIIbbeta3 reinforce each other's functions during alphaIIbbeta3 signaling in platelets.
Group IVA cytosolic phospholipase A(2) (cPLA(2)alpha) catalyzes release of arachidonic acid from glycerophospholipids, leading to thromboxane A(2) (TxA(2)) production. Some platelet agonists stimulate cPLA(2)alpha, but others require fibrinogen binding to alphaIIbbeta3 to elicit TxA(2). Therefore, relationships between cPLA(2)alpha and alphaIIbbeta3 were examined. cPLA(2)alpha and a cPLA(2)alpha binding partner, vimentin, coimmunoprecipitated with alphaIIbbeta3 from platelets, independent of fibrinogen binding. Studies with purified proteins and with recombinant proteins expressed in CHO cells determined that the interaction between cPLA(2)alpha and alphaIIbbeta3 was indirect and was dependent on the alphaIIb and beta3 cytoplasmic tails. Fibrinogen binding to alphaIIbbeta3 caused an increase in integrin-associated cPLA(2)alpha activity in normal platelets, but not in cPLA(2)alpha-deficient mouse platelets or in human platelets treated with pyrrophenone, a cPLA(2)alpha inhibitor. cPLA(2)alpha activation downstream of alphaIIbbeta3 had functional consequences for platelets in that it was required for fibrinogen-dependent recruitment of activated protein kinase Cbeta to the alphaIIbbeta3 complex and for platelet spreading. Thus, cPLA(2)alpha and alphaIIbbeta3 interact to reinforce each other's functions during alphaIIbbeta3 signaling. This provides a plausible explanation for the role of alphaIIbbeta3 in TxA(2) formation and in the defective hemostatic function of mouse or human platelets deficient in cPLA(2)alpha.
Departments of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0726, USA.
Nicolas
N
Prévost
John V
JV
Mitsios
Hisashi
H
Kato
John E
JE
Burke
Edward A
EA
Dennis
Takao
T
Shimizu
Sanford J
SJ
Shattil
D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000201:enzymology*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005340:Fibrinogen / Q000235:genetics / Q000378:metabolism; D020404:Glycerophospholipids / Q000235:genetics / Q000378:metabolism; D054513:Group IV Phospholipases A2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D064546:Protein Kinase C beta; D011759:Pyrrolidines / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013928:Thromboxane A2 / Q000096:biosynthesis* / Q000235:genetics; D014746:Vimentin / Q000235:genetics / Q000378:metabolism
D004791:Enzyme Inhibitors; D020404:Glycerophospholipids; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011759:Pyrrolidines; D011994:Recombinant Proteins; D014746:Vimentin; C455981:pyrrophenone; D013928:Thromboxane A2; D005340:Fibrinogen; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D054513:Group IV Phospholipases A2; C516389:PLA2G4A protein, human