Talin 1 and paxillin facilitate distinct steps in rapid VLA-4-mediated adhesion strengthening to vascular cell adhesion molecule 1.
VLA-4 (alpha4beta1) is a key integrin in lymphocytes, interacting with endothelial vascular cell adhesion molecule 1 (VCAM-1) on blood vessels and stroma. To dissect the contribution of the two cytoskeletal VLA-4 adaptor partners paxillin and talin to VLA-4 adhesiveness, we transiently knocked them down in Jurkat T cells and primary resting human T cells by small interfering RNA silencing. Paxillin was required for VLA-4 adhesiveness to low density VCAM-1 under shear stress conditions and was found to control mechanical stability of bonds mediated by the alpha4 subunit but did not affect the integrin affinity or avidity to VCAM-1 in shear-free conditions. Talin 1 maintained VLA-4 in a high affinity conformation, thereby promoting rapid VLA-4 adhesion strengthening to VCAM-1 under both shear stress and shear-free conditions. Talin 1, but not paxillin, was required for VLA-4 to undergo optimal stimulation by the prototypic chemokine, CXCL12, under shear stress conditions. Interestingly, talin 1 and paxillin played the same distinct roles in VLA-4 adhesions of primary T lymphocytes, although VLA-4 affinity to VCAM-1 was at least 200-fold lower in these cells than in Jurkat cells. Collectively, our results suggest that whereas paxillin is a mechanical regulator of VLA-4 bonds generated in the absence of chemokine signals and low VCAM-1 occupancy, talin 1 is a versatile VLA-4 affinity regulator implicated in both spontaneous and chemokine-triggered rapid adhesions to VCAM-1.
Manevich
Eugenia
E
Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
Grabovsky
Valentin
V
Feigelson
Sara W
SW
Alon
Ronen
R
D001808:Blood Vessels / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism; D006801:Humans; D039041:Integrin alpha4beta1 / Q000378:metabolism*; D019169:Jurkat Cells; D051419:Paxillin / Q000172:deficiency / Q000378:metabolism*; D034622:RNA Interference; D033081:Shear Strength; D015398:Signal Transduction; D013314:Stress, Mechanical; D017154:Stromal Cells / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D016608:Talin / Q000172:deficiency / Q000378:metabolism*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D039041:Integrin alpha4beta1; D051419:Paxillin; C518832:TLN1 protein, human; D016608:Talin; D019010:Vascular Cell Adhesion Molecule-1