title: Phosphoinositide 3-OH kinase activates the beta2 integrin adhesion pathway and induces membrane recruitment of cytohesin-1.
abstract: Signal transduction through phosphoinositide 3-OH kinase (PI 3-kinase) has been implicated in the regulation of lymphocyte adhesion mediated by integrin receptors. Cellular phosphorylation products of PI 3-kinases interact with a subset of pleckstrin homology (PH) domains, a module that has been shown to recruit proteins to cellular membranes. We have recently identified cytohesin-1, a cytoplasmic regulator of beta2 integrin adhesion to intercellular adhesion molecule 1. We describe here that expression of a constitutively active PI 3-kinase is sufficient for the activation of Jurkat cell adhesion to intercellular adhesion molecule 1, and for enhanced membrane association of cytohesin-1. Up-regulation of cell adhesion by PI 3-kinase and membrane association of endogenous cytohesin-1 is abrogated by overexpression of the isolated cytohesin-1 PH domain, but not by a mutant of the PH domain which fails to associate with the plasma membrane. The PH domain of Bruton's tyrosine kinase (Btk), although strongly associated with the plasma membrane, had no effect on either membrane recruitment of cytohesin-1 or on induction of adhesion by PI 3-kinase. Having delineated the critical steps of the beta2 integrin activation pathway by biochemical and functional analyses, we conclude that PI 3-kinase activates inside-out signaling of beta2 integrins at least partially through cytohesin-1.
authors.affiliation: Laboratorium für Molekulare Biologie, Genzentrum der Universität München, Feodor-Lynen-Strasse 25, 81377 München, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Nagel
authors.forename: L
authors.initials: L
authors.lastname: Zeitlmann
authors.forename: P
authors.initials: P
authors.lastname: Schilcher
authors.forename: C
authors.initials: C
authors.lastname: Geiger
authors.forename: J
authors.initials: J
authors.lastname: Kolanus
authors.forename: W
authors.initials: W
authors.lastname: Kolanus
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D018821:CD18 Antigens / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D019169:Jurkat Cells; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
chemical_list: D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; D020662:Guanine Nucleotide Exchange Factors; D007074:Immunoglobulin G; D011993:Recombinant Fusion Proteins; C100723:cytohesin-1; D018799:Intercellular Adhesion Molecule-1; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human