title: Requirement of JNK-mediated phosphorylation for translocation of group IVA phospholipase A2 to phagosomes in human macrophages.
abstract: Eicosanoids are a broad family of lipids that play a critical role in host defense against bacterial and fungal infections. The first enzyme in the metabolic pathway for the generation of eicosanoids is group IVA phospholipase A(2), also known as cytosolic phospholipase A(2)alpha (cPLA(2)alpha). During phagocytosis, cPLA(2)alpha has been found to translocate to the phagosome, although the molecular mechanism involved in such a translocation has not been elucidated. By using enhanced GFP-tagged proteins we show in this work that a nonphosphorylatable cPLA(2)alpha mutant (S505A) does not translocate to the phagosomes, but a mutant that mimics phosphorylation on Ser(505) (S505E) does it so readily. During phagocytosis, endogenous cPLA(2)alpha is phosphorylated at Ser(505), and inhibitors of JNK, but not of other related kinases such as p38 or the extracellular-regulated kinases 1 and 2, completely block such a phosphorylation. Inhibition of JNK activity also inhibits the translocation of cPLA(2)alpha to phagosomal membranes, as well as arachidonic acid release to the extracellular medium. Moreover, the S505E mutant makes the enzyme refractory to JNK inhibition, translocating normally to phagosomal membranes. Collectively, these data support a key role for JNK-mediated cPLA(2)alpha phosphorylation at Ser(505) in the sequence of events leading to translocation and activation of the enzyme to phagosomal membranes in human macrophages.
authors.affiliation: Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Valladolid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Casas
authors.forename: Clara
authors.initials: C
authors.lastname: Meana
authors.forename: Esperanza
authors.initials: E
authors.lastname: Esquinas
authors.forename: Martín
authors.initials: M
authors.lastname: Valdearcos
authors.forename: José
authors.initials: J
authors.lastname: Pindado
authors.forename: Jesús
authors.initials: J
authors.lastname: Balsinde
authors.forename: María A
authors.initials: MA
authors.lastname: Balboa
mesh_terms: D002478:Cells, Cultured; D015777:Eicosanoids / Q000096:biosynthesis; D004789:Enzyme Activation / Q000276:immunology; D054513:Group IV Phospholipases A2 / Q000378:metabolism*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000502:physiology*; D008264:Macrophages / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D010587:Phagocytosis / Q000276:immunology; D010588:Phagosomes / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding / Q000276:immunology; D021381:Protein Transport / Q000276:immunology
chemical_list: D015777:Eicosanoids; D048031:JNK Mitogen-Activated Protein Kinases; D054513:Group IV Phospholipases A2; C516389:PLA2G4A protein, human