Actin cytoskeletal association of cytohesin-1 is regulated by specific phosphorylation of its carboxyl-terminal polybasic domain

J Biol Chem. 2001 Oct 5;276(40):37472-81. doi: 10.1074/jbc.M101502200. Epub 2001 Jul 3.


Cell adhesion mediated by integrin receptors is controlled by intracellular signal transduction cascades. Cytohesin-1 is an integrin-binding protein and guanine nucleotide exchange factor that activates binding of the leukocyte integrin leukocyte function antigen-1 to its ligand, intercellular adhesion molecule 1. Cytohesin-1 bears a carboxyl-terminal pleckstrin homology domain that aids in reversible membrane recruitment and functional regulation of the protein. Although phosphoinositide-dependent membrane attachment of cytohesin-1 is mediated primarily by the pleckstrin homology domain, this function is further strengthened by a short carboxyl-terminal polybasic amino acid sequence. We show here that a serine/threonine motif within the short polybasic stretch of cytohesin-1 is phosphorylated by purified protein kinase C delta in vitro. Furthermore, the respective residues are also found to be phosphorylated after phorbol ester stimulation in vivo. Biochemical and functional analyses show that phosphorylated cytohesin-1 is able to tightly associate with the actin cytoskeleton, and we further demonstrate that phosphorylation of the protein is required for maximal leukocyte function antigen-1-mediated adhesion of Jurkat cells to intercellular adhesion molecule 1. These data suggest that both phosphatidylinositol 3-kinase and protein kinase C-dependent intracellular pathways that stimulate beta(2)-integrin-mediated adhesion of T lymphocytes converge on cytohesin-1 as functional integrator.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Animals
  • COS Cells
  • Carcinogens / pharmacology
  • Cell Adhesion / drug effects
  • Cell Adhesion Molecules / chemistry
  • Cell Adhesion Molecules / metabolism*
  • Cell Adhesion Molecules / physiology
  • Cytoskeleton / drug effects
  • Cytoskeleton / metabolism*
  • Guanine Nucleotide Exchange Factors
  • Humans
  • Intercellular Adhesion Molecule-1 / metabolism
  • Jurkat Cells
  • Phosphorylation / drug effects
  • Protein Structure, Tertiary
  • Tetradecanoylphorbol Acetate / pharmacology


  • Actins
  • Carcinogens
  • Cell Adhesion Molecules
  • Guanine Nucleotide Exchange Factors
  • cytohesin-1
  • Intercellular Adhesion Molecule-1
  • Tetradecanoylphorbol Acetate