Investigation of Membrane Order Within Integrin-Mediated Adhesion

[摘要] Integrins are transmembrane adhesion receptors that engage ligands in the extracellular matrix and cytoskeletal proteins to form multi-protein adhesive complexes. These complexes provide a platform for integrin signaling and a mechanical anchor between the cell and its environment. Integrin functionality is hypothesized to be sensitive to cell membrane composition, driven at least in part, by the tendency for the plasma membrane to compartmentalize into ordered and disordered domains resembling coexisting liquid phases observed in model membranes. In particular, past work suggests that adhesions are highly ordered membrane domains and that more integrins in an extended confirmation favor a more ordered membrane environment.This dissertation investigates how integrins associate with membrane order through newly developed super-resolution imaging techniques that are capable of directly observing the local enrichment and depletion of peptide markers of liquid-ordered and disordered domains. I quantify the local membrane environment surrounding β1 integrins by tabulating cross-correlations between antibody labeled β1 integrins and peptide markers. Through the use of conformational specific antibodies, I determine how the conformational state of integrins impacts its local membrane composition and how membrane perturbations alter β1 integrin activity. I find that β1 integrins co-localize with both markers of membrane order and disorder across the plasma membrane. I find that affinity for a membrane ordered probe depends on activation state and that β1 integrins from mature fibrillar adhesive complexes exhibit the strongest preference for membrane order. I determine that adhesions themselves are made up of integrins in at least two different conformational states, and active, extended conformation integrins do not exhibit a strong preference for either phase-like domain composition despite being confined to adhesions. Finally, I demonstrate that perturbing the plasma membrane composition with long-chain n-alcohols robustly affects the activation state of β1 integrins and the formation of adhesive complexes. The structure-function relationship of integrins has broad biological implications contributing to cell viability, growth, and motility. My work indicates that integrin association with membrane order is more subtle than previously proposed and that the subset of integrins in the active, extended conformation is less order preferring than the total integrin population.I show integrin activity is modulated by perturbations of membrane organization, and I conclude that integrin activation is indirectly impacted by membrane order, likely through the regulatory networks responsible for ;;inside-out” signaling.

[发布机构] University of Michigan

[效力级别] Biological Chemistry

[关键词] influence of plasma membrane composition in cell adhesion;Biological Chemistry;Molecular;Cellular and Developmental Biology;Physics;Science (General);Science;Biophysics