This program addresses the grand challenge of investigating how proteins function within the constrained two-dimensional microenvironments of adhesive contacts between cell membranes. We propose to develop a multiscale computational and experimental framework that predicts both molecular scale protein dynamics at intermembrane contacts and ensemble average intermembrane binding kinetics. The results will have broad impact for investigations of adhesion proteins within complex microenvironments that have, until now, been largely inaccessible.
This program addresses the grand challenge of quantitatively interrogating protein interactions within the constrained two-dimensional (2D) adhesive contacts between cells. Adhesion proteins are essential for the organization of all multicellular organisms, and for numerous biological processes critical to life. Their functions are linked not only to their binding affinities (bond energies), but also to their organization within adhesion zones. However, it is a major challenge to study adhesion proteins in their native context because they function at buried interfaces, which are experimentally difficult to access. The broad goal of this research program is to develop a multiscale computational and experimental framework that quantitatively predicts both molecular scale protein dynamics and ensemble-average receptor binding kinetics at intermembrane contacts. Our approach will integrate empirically derived molecular parameters in a computational algorithm that will quantitatively simulate protein behavior in 2D environments of increasing complexity. These studies use cadherins as model adhesion proteins, because both theory and experiment suggest that 2D confinement alters the assembly of cadherin adhesions in ways that affect tissue physiology. In Aim 1 we will develop a kinetic Monte Carlo algorithm to quantitatively predict single molecule tracking measurements of cadherin diffusion, binding rates and clustering on planar lipid bilayers. Under Aim 2, single molecule tracking measurements and simulations will test the hypothesis that 2D protein confinement within adhesion zones alters molecular-scale protein binding rates and diffusivities relative to proteins on unconfined membranes. In Aim 3 we extend the simulations to connect molecular scale dynamics (in Aims 1 and 2) to macroscale measurements of ensemble-average intermembrane (cell) binding kinetics. If successful, our approach and findings will have broad significance for studies of proteins within adhesive contacts that have, until now, been experimentally and computationally challenging to study.