It is now widely recognized that lipid heterogeneities, such as lipid rafts, may have a profound influence on protein functionality by causing lipid domain-induced membrane protein sequestration in biological membranes. Nonetheless, the underlying factors of protein sequestration regulation remain elusive mainly due to the small size and transient character of lipid heterogeneities in the plasma membrane. To address this challenge, recently we introduced a complementary method of protein sequestration analysis in a polymer-supported lipid bilayer system with coexisting micron-sized liquid-ordered (lo) and liquid-disordered (ld) phase separations. This method, involving combined confocal fluorescence spectroscopy, photon counting histogram (PCH) analysis, and epifluorescence microscopy, was successfully applied to explore the roles of native ligands and membrane asymmetry on integrin sequestration and oligomerization state in well-defined lipid environments without artificial crosslinkers. Here we utilize this model membrane platform to investigate lipid packing density and hydrophobic matching as potential regulatory factors of integrin (av�3 and a5�1) sequestration. Specifically, the role of lipid packing density on integrin sequestration was determined by systematically modifying the cholesterol content in lipid mixtures with lo-ld phase separations. In contrast, the impact of hydrophobic matching between transmembrane regions of membrane proteins and hydrophobic bilayer regions was studied by altering the hydrophobic mismatch conditions between lo and ld domains. Experimental results will be discussed, which highlight the potential importance of lipid packing and hydrophobic thickness as critical parameters of membrane protein sequestration regulation in biological membranes.

Influence of lipid packing density and hydrophobic thickness on integrin sequestration in raft-mimicking lipid mixtures

246th National Meeting (2013)

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