title: Beta 1/beta 3 integrin ligation is uncoupled from ERK1/ERK2 activation in cytotoxic T lymphocytes.
abstract: beta 3 integrins mediate fibronectin binding and enhanced activation of cytotoxic T lymphocytes (CTL). The intracellular signals initiated by beta 3 integrins in lymphocytes are not well characterized, but in many cell types, beta 1 integrin ligation activates mitogen-activated protein (MAP) kinases. In the present study, we find that fibronectin can synergize with very low levels of CD3 stimulation to activate the extracellular signal-regulated kinase (ERK)1 and ERK2 MAP kinases but that fibronectin alone induces no detectable MAP kinase activation in CTL. Surprisingly, antibodies to beta1 or beta 3 integrins were also unable to stimulate MAP kinase activation, suggesting that although beta 1 integrins are capable of stimulating MAP kinase activation in other cells, they cannot do so in CTL. In CTL, phosphorylation of proline-rich tyrosine kinase 2 downstream of integrin stimulation did not result in recruitment of the adaptor protein Grb2. Additionally, we examined the role of MAP kinases in regulating integrin-mediated adhesion. Anti-CD3-triggered adhesion to fibronectin was largely insensitive to the MAP kinase kinase inhibitor PD98059. Triggered cell-spreading on fibronectin was inhibited by PD98059 but not by U0126. In summary, ligation of beta 3 integrin by antibodies or fibronectin or of beta1 integrin by monoclonal antibodies fails to activate ERK MAP kinases, but integrin ligation synergizes with T cell receptor stimulation upstream of MAP kinases.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Canada.
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Puente
authors.forename: Hanne L
authors.initials: HL
authors.lastname: Ostergaard
mesh_terms: D000818:Animals; D017252:CD3 Complex / Q000378:metabolism; D002448:Cell Adhesion; D004789:Enzyme Activation; D005353:Fibronectins / Q000494:pharmacology; D019012:Integrin beta1 / Q000378:metabolism*; D039661:Integrin beta3 / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology*
chemical_list: D017252:CD3 Complex; D005353:Fibronectins; D019012:Integrin beta1; D039661:Integrin beta3; D011948:Receptors, Antigen, T-Cell; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases