MOLECULAR BASIS FOR THE DYNAMIC STRENGTH OF THE INTEGRIN ₄₁/VCAM-1 INTERACTION

¹ University of Miami
² University of Manchester
³ Celltech Group
⁴ Univ. of Miami School of Med.

^* To whom correspondence should be addressed. E-mail: vmoy{at}newssun.med.miami.edu.

Submitted on May 10, 2004
Revised on August 1, 2004
Accepted on 24 August 2004

	Abstract

Intercellular adhesion mediated by integrin ₄₁ and vascular cell adhesion molecule-1 (VCAM-1) plays a crucial role in both the rolling and firm attachment of leukocytes onto the vascular endothelium. Essential to the ₄₁/VCAM-1 interaction is its mechanical strength that allows the complex to resist the large shear forces imposed by the bloodstream. Herein we employed single molecule dynamic force spectroscopy (DFS) to investigate the dynamic strength of the ₄₁/VCAM-1 complex. Our force measurements revealed that the dissociation of the ₄₁/VCAM-1 complex involves overcoming at least two activation potential barriers: a steep inner barrier and a more elevated outer barrier. The inner barrier grants the complex the tensile strength to withstand large pulling forces (>50 pN) and was attributed to the ionic interaction between the chelated Mg²⁺ ion at the N-terminal A domain of the ₁ subunit of ₄₁ and the carboxyl group of Asp-40 of VCAM-1 through the use of site-directed mutations. In general, additional mutations within the C-D loop of domain 1 of VCAM-1 suppressed both inner and outer barriers of the ₄₁/VCAM-1 complex, while a mutation at Asp-143 of domain 2 of VCAM-1 resulted in the suppression of outer barrier, but not the inner barrier. In contrast, the outer barrier of ₄₁/VCAM-1 complex was stabilized by integrin activation. Together, these findings provide a structural explanation for the functionally-relevant kinetic properties of the ₄₁/VCAM-1 interaction.

Key Words: AFM, cell adhesion, force spectrosopy, integrins, ligand-receptor interaction

This article has been cited by other articles:

				S. Liang and C. Dong Integrin VLA-4 enhances sialyl-Lewisx/a-negative melanoma adhesion to and extravasation through the endothelium under low flow conditions Am J Physiol Cell Physiol, September 1, 2008; 295(3): C701 - C707. [Abstract] [Full Text] [PDF]

				J. Schmitz, M. Benoit, and K.-E. Gottschalk The Viscoelasticity of Membrane Tethers and Its Importance for Cell Adhesion Biophys. J., August 1, 2008; 95(3): 1448 - 1459. [Abstract] [Full Text] [PDF]

				J. Helenius, C.-P. Heisenberg, H. E. Gaub, and D. J. Muller Single-cell force spectroscopy J. Cell Sci., June 1, 2008; 121(11): 1785 - 1791. [Abstract] [Full Text] [PDF]

				J. te Riet, A. W. Zimmerman, A. Cambi, B. Joosten, S. Speller, R. Torensma, F. N. van Leeuwen, C. G. Figdor, and F. de Lange Distinct kinetic and mechanical properties govern ALCAM-mediated interactions as shown by single-molecule force spectroscopy J. Cell Sci., November 15, 2007; 120(22): 3965 - 3976. [Abstract] [Full Text] [PDF]

				M. H. Abdulreda and V. T. Moy Atomic Force Microscope Studies of the Fusion of Floating Lipid Bilayers Biophys. J., June 15, 2007; 92(12): 4369 - 4378. [Abstract] [Full Text] [PDF]

				R. Alon, S. W. Feigelson, E. Manevich, D. M. Rose, J. Schmitz, D. R. Overby, E. Winter, V. Grabovsky, V. Shinder, B. D. Matthews, et al. {alpha}4{beta}1-dependent adhesion strengthening under mechanical strain is regulated by paxillin association with the {alpha}4-cytoplasmic domain J. Cell Biol., December 19, 2005; 171(6): 1073 - 1084. [Abstract] [Full Text] [PDF]

				D. J. Brockwell, G. S. Beddard, E. Paci, D. K. West, P. D. Olmsted, D. A. Smith, and S. E. Radford Mechanically Unfolding the Small, Topologically Simple Protein L Biophys. J., July 1, 2005; 89(1): 506 - 519. [Abstract] [Full Text] [PDF]