Tec kinases regulate TCR-mediated recruitment of signaling molecules and integrin-dependent cell adhesion

T cells deficient in the Tec kinases Itk or Itk and Rlk exhibit defective TCR-stimulated proliferation, IL-2 production, and activation of phospholipase C-γ. Evidence also implicates Tec kinases in actin cytoskeleton regulation, which is necessary for cell adhesion and formation of the immune synapse in T lymphocytes. In this study we show that Tec kinases are required for TCR-mediated up-regulation of adhesion via the LFA-1 integrin. We also demonstrate that the defect in adhesion is associated with defective clustering of LFA-1 and talin at the site of interaction of Rlk^-/-Itk ^-/- and Itk^-/- T cells with anti-TCR-coated beads. Defective recruitment of Vav1, protein kinase Cθ, and Pyk2 was also observed in Rlk^-/-Itk^-/- and Itk^-/- T cells. Stimulation with ICAM-2 in conjunction with anti-TCR-coated beads enhanced polarization of Vav1, protein kinase Cθ, and Pyk2 in wild-type cells, demonstrating a role for integrins in potentiating the recruitment of signaling molecules in T cells. Increased recruitment of signaling molecules was most pronounced under conditions of low TCR stimulation. Under these suboptimal TCR stimulation conditions, ICAM-2 could also enhance the recruitment of signaling molecules in Itk^-/-, but not Rlk^-/-Itk^-/- T cells. Thus, Tec kinases play key roles in regulating TCR-mediated polarization of integrins and signaling molecules to the site of TCR stimulation as well as the up-regulation of integrin adhesion.