Phosphoinositide 3-OH Kinase Activates the β2Integrin Adhesion Pathway and Induces Membrane Recruitment of Cytohesin-1*
- Wolfgang Nagel,
- Lutz Zeitlmann,
- Pierre Schilcher,
- Christiane Geiger,
- Johanna Kolanus and
- Waldemar Kolanus‡
- From the Laboratorium für Molekulare Biologie, Genzentrum der Universität München, Feodor-Lynen-Strasse 25, 81377 München, Germany
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 β2 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 β2 integrin activation pathway by biochemical and functional analyses, we conclude that PI 3-kinase activates inside-out signaling of β2 integrins at least partially through cytohesin-1.
Footnotes
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↵* This work was supported by the Deutsche Forschungsgemeinschaft and by the Bundesministerium für Forschung, Bildung, und Technologie.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ To whom correspondence should be addressed. Tel.: 49-89-74017-222 or 215; Fax: 49-89-74017-448; E-mail:kolanus{at}lmb.uni-muenchen.de.
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↵1 The abbreviations used are: PI 3-kinase, phosphoinositide 3-OH kinase; SH, Src homology; PH, pleckstrin homology; βark, β-adrenergic receptor kinase; GST, glutathione S-transferase; PBS, phosphate-buffered saline; HBSS, Hanks’ buffered salt solution; ICAM-1, intercellular adhesion molecule 1; HS, hypotonic solution; MBSD, Mops/NaCl/Igepal CA-630; IP4, inositol (1,3,4,5)-tetrakisphosphate; PIP3, phosphatidylinositol (3,4,5)-trisphosphate; Mops, 4-morpholinepropanesulfonic acid; PMA, phorbol 12-myristate 13-acetate.
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- Received October 14, 1997.
- Revision received February 23, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
