The Src kinase p56(lck) up-regulates VLA-4 integrin affinity. Implications for rapid spontaneous and chemokine-triggered T cell adhesion to VCAM-1 and fibronectin.
In circulating lymphocytes, the VLA-4 integrin preexists in multiple affinity states that mediate spontaneous tethering, rolling, and arrest on its endothelial ligand, vascular cell adhesion molecule-1 (VCAM-1). The regulation and function of VLA-4 affinity in lymphocytes has never been elucidated. We show here that p56(lck), the major Src kinase in T cells, is a key regulator of high affinity VLA-4. This high affinity is essential for the rapid development of firm adhesion of resting T cells to VCAM-1 and to their extracellular matrix ligand, fibronectin. Lck-regulated VLA-4 function does not require intact TCR nor several key components of the TCR signaling pathway, including ZAP-70 and SLP-76. Furthermore, stimulation of p56(lck) by the phosphatase inhibitor, pervanadate, triggers firm VLA-4-dependent adhesion to VCAM-1. Although Lck is not required for chemokine receptor signaling to mitogen-activated protein kinase, the presence of Lck-regulated high affinity VLA-4 also facilitates firm adhesion triggered by the chemokine, SDF-1, at short-lived contacts. Surprisingly, bond formation rates, ability to tether cells to VLA-4 ligand, and VLA-4 tether bond stability under shear flow are not affected by VLA-4 affinity or Lck activity. Thus, the ability of high affinity VLA-4 to arrest cells on VCAM-1 under flow arises from instantaneous post-ligand strengthening rather than from increased kinetic stability of individual VLA-4 bonds. These results suggest that p56(lck) maintains high affinity VLA-4 on circulating lymphocytes, which determines their ability to strengthen VLA-4 adhesion and rapidly respond to proadhesive chemokine signals at endothelial sites.
Feigelson
S W
SW
Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel.
Grabovsky
V
V
Winter
E
E
Chen
L L
LL
Pepinsky
R B
RB
Yednock
T
T
Yablonski
D
D
Lobb
R
R
Alon
R
R
D015153:Blotting, Western; D002448:Cell Adhesion / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004727:Endothelium / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D039041:Integrin alpha4beta1; D016023:Integrins / Q000378:metabolism*; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D007700:Kinetics; D008024:Ligands; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D016201:Receptors, Lymphocyte Homing / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D015854:Up-Regulation; D014638:Vanadates / Q000494:pharmacology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
D004791:Enzyme Inhibitors; D005353:Fibronectins; D039041:Integrin alpha4beta1; D016023:Integrins; D007376:Interleukin-2; D008024:Ligands; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1; C076715:pervanadate; D019000:Phosphotyrosine; D014638:Vanadates; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)