Cell adhesion. Competition between nonspecific repulsion and specific bonding

Abstract

We develop a thermodynamic calculus for the modeling of cell adhesion. By means of this approach, we are able to compute the end results of competition between the formation of specific macromolecular bridges and nonspecific repulsion arising from electrostatic forces and osmotic (steric stabilization) forces. Using this calculus also allows us to derive in a straightforward manner the effects of cell deformability, the Young's modulus for stretching of bridges, diffusional mobility of receptors, heterogeneity of receptors, variation in receptor number, and the strength of receptor-receptor binding. The major insight that results from our analysis concerns the existence and characteristics of two phase transitions corresponding, respectively, to the onset of stable cell adhesion and to the onset of maximum cell-cell or cell-substrate contact. We are also able to make detailed predictions of the equilibrium contact area, equilibrium number of bridges, and the cell-cell or cell-substrate separation distance. We illustrate how our approach can be used to improve the analysis of experimental data, by means of two concrete examples.

Dynamics of a Thin Liquid Film with a Surface Chemical Reaction

“…As the surface chemical reaction described here does not affect the hydrodynamic root, the estimation of the dominant wavenumber k max corresponding to v max and of the hydrodynamic rupture time t L (Eq. [25]) remains valid. For K Å 0, k max É 0.5, and t L É 2 (see Figs.…”

“…3): the film height reaches zero at rupture time t L as the minimum of the initial perturbation close to one boundary. The surfactants leave the regions where the film thins t L Å 0(1/v max )ln(a in ), [25] to concentrate at the maxima of h. Complexes are formed at locations of high concentration in receptors. Indeed, when K Å 0, the variables r and c are always in phase.…”

“…[24]), the dominant wavenumber, and the time of rupture (Eq. [25]). As the surface chemical reaction described here does not affect the hydrodynamic root, the estimation of the dominant wavenumber k max corresponding to v max and of the hydrodynamic rupture time t L (Eq.…”

Flexible membranes with anchored polymers

“…The stickers which are anchored in the cell membranes are cell adhesion molecules (CAMs) or receptor/ligand pairs [37,10]. In the absence of such molecules, cell membranes effectively repel one another [16,38].…”

Les récepteurs des entérotoxines bactériennes

“…Pour accéder à un site très proche de la membrane, il semble que le ligand requiert l'induction d'une diffusion latérale des composants masquant la surface. Cette théorie a d'ailleurs été émise pour l'adhésion cellulaire [6]. Le modèle cinétique d'adhésion cellulaire décrit indique que les forces de répulsion impliquées, lors du rapprochement d'une particule, semblent induire une diffusion latérale et une réorganisation des composants de surface permettant alors un attachement de faible énergie.…”