Interleukin-2 induces β₂-integrin-dependent signal transduction involving the focal adhesion kinase-related protein B (fakB)

Abstract

ABSTRACT␤ 2 integrin molecules are involved in a multitude of cellular events, including adhesion, migration, and cellular activation. Here, we studied the inf luence of ␤ 2 integrins on interleukin-2 (IL-2)-mediated signal transduction in human CD4؉ T cell lines obtained from healthy donors and a leukocyte adhesion deficiency (LAD) patient. We show that IL-2 induces tyrosine phosphorylation of a 125-kDa protein and homotypic adhesion in ␤ 2 integrin (CD18)-positive but not in ␤ 2 -integrin-negative T cells. EDTA, an inhibitor of integrin adhesion, blocks IL-2-induced tyrosine phosphorylation of the 125-kDa protein but not other proteins in ␤ 2 -integrin-positive T cells. Likewise, a ␤ 2 integrin (CD18) antibody selectively inhibits induction of the 125-kDa phosphotyrosine protein, whereas cytokine-mediated tyrosine phosphorylation of other proteins is largely unaffected. Immunoprecipitation experiments indicate that the IL-2-induced 125-kDa phosphotyrosine protein is the focal adhesion kinase-related protein B (fakB). Thus, IL-2 induces strong tyrosine phosphorylation of fakB in ␤ 2 -integrinpositive but not in ␤ 2 -integrin-negative T cells, and CD18 mAb selectively blocks IL-2-induced fakB-tyrosine phosphorylation in ␤ 2 -integrin-positive T cells. In parallel experiments, IL-2 does not induce or augment tyrosine phosphorylation of p125 FAK . In conclusion, our data indicate that IL-2 induces ␤ 2 -integrin-dependent signal transduction events involving the tyrosine kinase substrate fakB.Interleukin-2 (IL-2) plays a crucial role in the differentiation and clonal expansion of T lymphocytes. The cytokine exerts its biological effect through specific IL-2 receptors expressed on T lymphocytes. Various combinations of three distinct chains (␣, ␤, and ␥) form three classes of IL-2 receptors (reviewed in ref. 1). Low-affinity IL-2 receptors consist of IL-2R␣, intermediate-affinity receptors contain IL-2R␤ and IL-2R␥, and high-affinity receptors contain all three chains. The IL-2R␣ chain has a short cytoplasmic tail consisting of only 13 amino acids, and the function of this chain appears to be limited to increasing the affinity of IL-2 binding (2). In contrast, it is likely that both IL-2R␤ and -␥ chains function in IL-2 signal transduction, because deletion of the cytoplasmic tails of these chains abolishes IL-2-induced signaling (reviewed in ref.3).Although IL-2R subunits do not appear to contain protein tyrosine kinase (PTK) domains within their cytoplasmic tails, a variety of data are consistent with an important role for PTKs in IL-2 signaling. Thus, IL-2 can induce tyrosine kinase activity (4) and is known to cause tyrosine phosphorylation of a number of substrates, including transcription factors such as . Furthermore, IL-2Rs associate noncovalently with tyrosine kinases belonging to the src family (e.g., p56 lck ) and Janus kinases (Jak1 and Jak3) (refs. 9-11, reviewed in ref. 3). Serine͞threonine kinases such as Raf-1 and MAP kinase, the lipid kinase phosphatidylinositol 3-kinase, and the protein phosphatas...

A critical role for elastin signaling in vascular morphogenesis and disease

“…Fibulin 5 interacts directly with elastin, and serves as a ligand for cell-surface integrins. Integrins require extracellular divalent cations to bind their matrix ligands, and low doses of chelators such as EDTA block these cell-matrix interactions (Brockdorff et al, 1998). As expected, control experiments demonstrated that integrin mediated migration of vascular smooth muscle cells to collagen was EDTA sensitive (Fig.…”

szlig 2 integrin signaling in leukocytes

“…FAK (23)(24)(25), as well as the focal adhesion kinase-related protein B (fakB) (26,27) and PYk2 (28,29) have been implicated. However, the precise mechanisms by which β2 integrins initiate activation of these tyrosine kinases are unknown.…”

Human NK Cells Lyse Organ-Specific Endothelial Cells: Analysis of Adhesion and Cytotoxic Mechanisms

“…EDTA, which is known as a chelator of different divalent cations (18,34), is able to bind both calcium and magnesium ions with almost the same affinity at neutral pH: log K ϭ 7.27 and log K ϭ 5.37, respectively; whereas EGTA in the presence of Mg 2ϩ is suitable for demonstrating calcium cation involvement alone (due to its higher association constant for calcium: log K ϭ 6.68 compared with magnesium log K ϭ 1.61 at pH 7) (35). -dependent lectins were not involved in NKL2/OSEC recognition, whereas integrins, which are the main adhesion molecules, of which activity is Mg 2ϩ dependent, might participate to NKL2 adhesion to organo-selective ECs.…”