tailieunhanh - Báo cáo khoa học: Cytosolic phospholipase A2-a and cyclooxygenase-2 localize to intracellular membranes of EA.hy.926 endothelial cells that are distinct from the endoplasmic reticulum and the Golgi apparatus

Cytosolic phospholipase A2-a(cPLA2-a) is a calcium-activated enzyme that plays an important role in agonist-induced arachidonic acid release. In endothelial cells, free arachidonic acid can be converted subsequently into prostacyclin, a potent vasodilator and inhibitor of platelet activation, through the action of cyclooxygenase (COX) enzymes. Here we study the relocation of cPLA2 -a in human endothelial cells following stimulation with the calcium-mobilizing agonist, A23187. | iFEBS Journal Cytosolic phospholipase A2-a and cyclooxygenase-2 localize to intracellular membranes of endothelial cells that are distinct from the endoplasmic reticulum and the Golgi apparatus Seema Grewal Shane P. Herbert Sreenivasan Ponnambalam and John H. Walker Schoolof Biochemistry and Microbiology University of Leeds UK Keywords arachidonic acid calcium cPLA2-a cyclooxygenase endothelium Correspondence J. H. Walker Schoolof Biochemistry and Microbiology University of Leeds Leeds LS2 9JT UK Fax 44 113 3433167 Tel. 44 113 3433119 E-mail Present address Department of Developmentaland Cell Biology University of California USA Received 29 October 2004 revised 21 December 2004 accepted 11 January 2005 doi Cytosolic phospholipase A2-a cPLA2-a is a calcium-activated enzyme that plays an important role in agonist-induced arachidonic acid release. In endothelial cells free arachidonic acid can be converted subsequently into prostacyclin a potent vasodilator and inhibitor of platelet activation through the action of cyclooxygenase COX enzymes. Here we study the relocation of cPLA2-a in human endothelial cells following stimulation with the calcium-mobilizing agonist A23187. Relocation of cPLA2-a was seen to be highly cell specific and in cells occurred primarily to intracellular structures resembling the endoplasmic reticulum ER and Golgi. In addition relocation to both the inner and outer surfaces of the nuclear membrane was observed. Colocalization studies with markers for these subcellular organelles however showed colocalization of cPLA2-a with nuclear membrane markers but not with ER or Golgi markers suggesting that the relocation of cPLA2-a occurs to sites that are separate from these organelles. Colocalization with annexin V was also observed at the nuclear envelope however little overlap with staining patterns for the potential cPLA2-a interacting proteins annexin I .