Monocyte adherence induced by lipopolysaccharide involves CD14, LFA-1, and cytohesin-1. Regulation by Rho and phosphatidylinositol 3-kinase

• Published in: The Journal of biological chemistry 1999-01, Vol.274 (2), p.1050-1057
• Main Authors: Hmama, Z, Knutson, K L, Herrera-Velit, P, Nandan, D, Reiner, N E
• Format: Article
• Language: English
• Subjects: Cell Adhesion - drug effects; Cell Adhesion Molecules - metabolism; Cell Line; Enzyme Activation; GTP-Binding Proteins - metabolism; Guanine Nucleotide Exchange Factors; Intercellular Adhesion Molecule-1 - metabolism; Lipopolysaccharide Receptors - metabolism; Lipopolysaccharides - pharmacology; Lymphocyte Function-Associated Antigen-1 - metabolism; Monocytes - cytology; Phenotype; Phosphatidylinositol 3-Kinases - metabolism
• ISSN: 0021-9258
• DOI: 10.1074/jbc.274.2.1050

Mechanisms regulating lipopolysaccharide (LPS)-induced adherence to intercellular adhesion molecule (ICAM)-1 were examined using THP-1 cells transfected with CD14-cDNA (THP-1wt). THP-1wt adherence to ICAM-1 was LPS dose-related, time-dependent, and inhibited by antibodies to either CD14 or leukocyte function associated antigen (LFA)-1, but was independent of any change in the number of surface expressed LFA-1 molecules. A potential role for phosphatidylinositol (PI) 3-kinase (PI 3-kinase) in LPS-induced adherence was examined using the PI 3-kinase inhibitors LY294002 and Wortmannin. Both inhibitors selectively attenuated LPS-induced, but not phorbol 12-myristate 13-acetate-induced adherence. Inhibition by these agents was unrelated to any changes in either LPS binding to or LFA-1 expression by THP-1wt cells. LPS-induced adherence was also abrogated in U937 cells transfected with a dominant negative mutant of of PI 3-kinase. Toxin B from Clostridium difficile, an inhibitor of the Rho family of GTP-binding proteins, abrogated both PI-3 kinase activation and adherence induced by LPS. Cytohesin-1, a phosphatidylinositol 3,4,5-triphosphate-regulated adaptor molecule for LFA-1 activation, was found to be expressed in THP-1wt cells. In addition, treatment of THP-1wt with cytohesin-1 antisense attenuated LPS-induced adherence. These findings suggest a model in which LPS induces adherence through a process of "inside-out" signaling involving CD14, Rho, and PI 3-kinase. This converts low avidity LFA-1 into an active form capable of increased binding to ICAM-1. This change in LFA-1 appears to be cytohesin-1-dependent.