Role of PKCα–p38MAPK–Giα axis in NADPH oxidase derived O2·--mediated activation of cPLA2 under U46619 stimulation in pulmonary artery smooth muscle cells

► U46619 treatment to pulmonary smooth muscle cells stimulates cPLA2 in the membrane. ► The cPLA2 activation occurs via phosphorylation of Giα by PKCα activated p38MAPK. ► PKCα appears to be proteolytically activated by an aprotinin sensitive protease. ► The protease activation occurs via stimulation of NADPH oxidase derived O2·-. ► U46619 activates cPLA2 upon stimulating PKCα-p38MAPK-Giα axis by an increase in O2·-. We have recently reported that treatment of bovine pulmonary artery smooth muscle cells with the thromboxane A2 mimetic, U46619 stimulated NADPH oxidase derived O2·- level, which subsequently caused marked increase in [Ca2+]i[17]. Herein, we demonstrated that O2·--mediated increase in [Ca2+]i stimulates an aprotinin sensitive proteinase activity, which proteolytically activates PKC-α under U46619 treatment to the cells. The activated PKC-α then phosphorylates p38MAPK and that subsequently caused Giα phosphorylation leading to stimulation of cPLA2 activity in the cell membrane.