Raft Recruitment Processes and Oligomerization State of Integrins Studied in Polymer-Tethered Single and Double Bilayer Systems

Abstract

Specific lipid environments are increasingly recognized as a crucial factor affecting membrane protein function in plasma membranes. Unfortunately, this topic has remained elusive, due to the challenging characterization of small and transient plasma membrane heterogeneities. To overcome this impasse, we present an experimental model membrane platform based on polymer-supported single and double bilayers containing stable raft-mimicking domains into which transmembrane proteins are incorporated (αvβ3 and α5β1 integrins). This flexible platform lets us probe the effect of native ligands in domain-specific protein sequestration and protein oligomerization state. Here we show significant ligand-induced changes in integrin sequestering. Remarkably, preliminary results indicate that integrins do not change their oligomerization state on the addition of ligands in lipid environments with varying concentrations of cholesterol. These results strongly suggest that ligands induce changes to integrin conformation and/or dynamics without inducing changes in integrin oligomerization state, and in fact these ligand-induced conformational changes impact protein-lipid interactions.