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Cytosolic phospholipase A 2 ‐α and cyclooxygenase‐2 localize to intracellular membranes of EA.hy.926 endothelial cells that are distinct from the endoplasmic reticulum and the Golgi apparatus
Author(s) -
Grewal Seema,
Herbert Shane P.,
Ponnambalam Sreenivasan,
Walker John H.
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2005.04565.x
Subject(s) - endoplasmic reticulum , microbiology and biotechnology , golgi apparatus , colocalization , biology , cytosol , biochemistry , enzyme
Cytosolic phospholipase A 2 ‐α (cPLA 2 ‐α) 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 cPLA 2 ‐α in human EA.hy.926 endothelial cells following stimulation with the calcium‐mobilizing agonist, A23187. Relocation of cPLA 2 ‐α was seen to be highly cell specific, and in EA.hy.926 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 cPLA 2 ‐α with nuclear membrane markers but not with ER or Golgi markers, suggesting that the relocation of cPLA 2 ‐α 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 cPLA 2 ‐α interacting proteins, annexin I, vimentin, p11 or actin, was seen in this cell type. In contrast, cPLA 2 ‐α was seen to partially colocalize specifically with the COX‐2 isoform at the ER‐resembling structures, but not with COX‐1. These studies suggest that cPLA 2 ‐α and COX‐2 may function together at a distinct and novel compartment for eicosanoid signalling.