title: Elucidation of the integrin LFA-1-mediated signaling pathway of actin polarization in natural killer cells.
abstract: The leukocyte integrin LFA-1 is critical for natural killer (NK) cell cytotoxicity as it mediates NK-cell adhesion to target cells and generates activating signals that lead to polarization of the actin cytoskeleton. However, the LFA-1-mediated signaling pathway is not fully understood. Here, we examined the subcellular localization of actin-associated proteins in wild-type, talin-deficient, and Wiskott-Aldrich Syndrome protein (WASP)-deficient NK cells bound to beads coated with the LFA-1 ligand intercellular adhesion molecule-1 (ICAM-1). In addition, we carried out coimmunoprecipitation analyses and also used a pharmacologic reagent to reduce the level of phosphatidylinositol-4,5-bisphosphate (PIP(2)). The results revealed the following signaling pathways. Upon ICAM-1 binding to LFA-1, talin redistributes to the site of LFA-1 ligation and initiates 2 signaling pathways. First, talin recruits the actin nucleating protein complex Arp2/3 via constitutive association of vinculin with talin and Arp2/3. Second, talin also associates with type I phosphatidylinositol 4-phosphate 5-kinase (PIPKI) and binding of LFA-1 to ICAM-1 results in localized increase in PIP(2). This increase in PIP(2) recruits WASP to the site of LFA-1 ligation where WASP promotes Arp2/3-mediated actin polymerization. These processes are critical for the initiation of NK cell-mediated cytotoxicity.
authors.affiliation: Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Mace
authors.forename: Jinyi
authors.initials: J
authors.lastname: Zhang
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Siminovitch
authors.forename: Fumio
authors.initials: F
authors.lastname: Takei
mesh_terms: D051377:Actin-Related Protein 2 / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D053595:Embryonic Stem Cells / Q000378:metabolism; D005260:Female; D047468:Immunoprecipitation; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007694:Killer Cells, Natural / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D017154:Stromal Cells / Q000378:metabolism; D016608:Talin / Q000502:physiology; D016596:Vinculin / Q000378:metabolism; D051316:Wiskott-Aldrich Syndrome Protein / Q000502:physiology
chemical_list: D051377:Actin-Related Protein 2; D000199:Actins; D016169:Lymphocyte Function-Associated Antigen-1; D019269:Phosphatidylinositol 4,5-Diphosphate; D016608:Talin; C495768:Was protein, mouse; D051316:Wiskott-Aldrich Syndrome Protein; C496077:Tln1 protein, mouse; D016596:Vinculin; D018799:Intercellular Adhesion Molecule-1; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase