This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vitte, J. Articles by Pierres, A. Search for Related Content PubMed PubMed Citation Articles by Vitte, J. Articles by Pierres, A.

ß-1 Integrin-Mediated Adhesion May Be Initiated by Multiple Incomplete Bonds, Thus Accounting for the Functional Importance of Receptor Clustering

Laboratoire d'Immunologie, Institut National de la Sante et de la Recherche Medicale U600, Centre National de la Recherche Scientifique FRE2059, Hôpital de Ste-Marguerite, Marseille, France

Correspondence: Address reprint requests to Professor Pierre Bongrand, Tel.: +33-491-26-03-31; Fax: +33-491-75-73-28; E-mail: bongrand{at}marseille.inserm.fr.

The regulation of cell integrin receptors involves modulation of membrane expression, shift between different affinity states, and topographical redistribution on the cell membrane. Here we attempted to assess quantitatively the functional importance of receptor clustering. We studied ß-1 integrin-mediated attachment of THP-1 cells to fibronectin-coated surfaces under low shear flow. Cells displayed multiple binding events with a half-life of the order of 1 s. The duration of binding events after the first second after arrest was quantitatively accounted for by a model assuming the existence of a short-time intermediate binding state with 3.6 s^–1 dissociation rate and 1.3 s^–1 transition frequency toward a more stable state. Cell binding to surfaces coated with lower fibronectin densities was concluded to be mediated by single molecular interactions, whereas multiple bonds were formed <1 s after contact with higher fibronectin surface densities. Cell treatment with microfilament inhibitors or a neutral antiintegrin antibody decreased bond number without changing aforementioned kinetic parameters whereas a function enhancing antibody increased the rate of bond formation and/or the lifetime of intermediate state. Receptor aggregation was induced by treating cells with neutral antiintegrin antibody and antiimmunoglobulin antibodies. A semiquantitative confocal microscopy study suggested that this treatment increased between 40% and 100% the average number of integrin receptors located in a volume of 0.045 µm³ surrounding each integrin. This aggregation induced up to 2.7-fold increase of the average number of bonds. Flow cytometric analysis of fluorescent ligand binding showed that THP-1 cells displayed low-affinity ß-1 integrins with a dissociation constant in the micromolar range. It is concluded that the initial step of cell adhesion was mediated by multiple incomplete bonds rather than a single equilibrium-state ligand receptor association. This interpretation accounts for the functional importance of integrin clustering.

This article has been cited by other articles:

				A. Pierres, A.-M. Benoliel, D. Touchard, and P. Bongrand How Cells Tiptoe on Adhesive Surfaces before Sticking Biophys. J., May 15, 2008; 94(10): 4114 - 4122. [Abstract] [Full Text] [PDF]

				G. Knoner, B. E. Rolfe, J. H. Campbell, S. J. Parkin, N. R. Heckenberg, and H. Rubinsztein-Dunlop Mechanics of Cellular Adhesion to Artificial Artery Templates Biophys. J., October 15, 2006; 91(8): 3085 - 3096. [Abstract] [Full Text] [PDF]

				F. Zhang, W. D. Marcus, N. H. Goyal, P. Selvaraj, T. A. Springer, and C. Zhu Two-dimensional Kinetics Regulation of {alpha}L{beta}2-ICAM-1 Interaction by Conformational Changes of the {alpha}L-Inserted Domain J. Biol. Chem., December 23, 2005; 280(51): 42207 - 42218. [Abstract] [Full Text] [PDF]