title: ATP release due to Thy-1-integrin binding induces P2X7-mediated calcium entry required for focal adhesion formation.
abstract: Thy-1, an abundant mammalian glycoprotein, interacts with αvβ3 integrin and syndecan-4 in astrocytes and thus triggers signaling events that involve RhoA and its effector p160ROCK, thereby increasing astrocyte adhesion to the extracellular matrix. The signaling cascade includes calcium-dependent activation of protein kinase Cα upstream of Rho; however, what causes the intracellular calcium transients required to promote adhesion remains unclear. Purinergic P2X7 receptors are important for astrocyte function and form large non-selective cation pores upon binding to their ligand, ATP. Thus, we evaluated whether the intracellular calcium required for Thy-1-induced cell adhesion stems from influx mediated by ATP-activated P2X7 receptors. Results show that adhesion induced by the fusion protein Thy-1-Fc was preceded by both ATP release and sustained intracellular calcium elevation. Elimination of extracellular ATP with Apyrase, chelation of extracellular calcium with EGTA, or inhibition of P2X7 with oxidized ATP, all individually blocked intracellular calcium increase and Thy-1-stimulated adhesion. Moreover, Thy-1 mutated in the integrin-binding site did not trigger ATP release, and silencing of P2X7 with specific siRNA blocked Thy-1-induced adhesion. This study is the first to demonstrate a functional link between αvβ3 integrin and P2X7 receptors, and to reveal an important, hitherto unanticipated, role for P2X7 in calcium-dependent signaling required for Thy-1-stimulated astrocyte adhesion.
authors.affiliation: Instituto de Ciencias Biomédicas, Universidad de Chil Santiago, Chile.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Henríquez
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Herrera-Molina
authors.forename: Alejandra
authors.initials: A
authors.lastname: Valdivia
authors.forename: Alvaro
authors.initials: A
authors.lastname: Alvarez
authors.forename: Milene
authors.initials: M
authors.lastname: Kong
authors.forename: Nicolás
authors.initials: N
authors.lastname: Muñoz
authors.forename: Verónica
authors.initials: V
authors.lastname: Eisner
authors.forename: Enrique
authors.initials: E
authors.lastname: Jaimovich
authors.forename: Pascal
authors.initials: P
authors.lastname: Schneider
authors.forename: Andrew F G
authors.initials: AF
authors.lastname: Quest
authors.forename: Lisette
authors.initials: L
authors.lastname: Leyton
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D019084:Fluorescent Antibody Technique, Indirect; D022001:Focal Adhesions / Q000378:metabolism*; D016023:Integrins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D058486:Receptors, Purinergic P2X7 / Q000235:genetics / Q000378:metabolism*; D018800:Thy-1 Antigens / Q000235:genetics / Q000378:metabolism*
chemical_list: D016023:Integrins; D058486:Receptors, Purinergic P2X7; D018800:Thy-1 Antigens; D000255:Adenosine Triphosphate; D002118:Calcium