Probing the effect of elevated cholesterol on the mechanical properties of membrane-cytoskeleton by optical tweezers

摘要

The composition of the cell membrane and the surrounding physiological factors determine the nature and dynamics of membrane-cytoskeleton coupling. Mechanical strength of a cell is mainly derived from such coupling. In this article, we investigate the effect of extra cellular cholesterol on the membrane-cytoskelaton connectivity of single cell endothelium and consequent remodeling of its mechanical properties. Using optical tweezers as a force probe, we have measured membrane stiffness (km), membrane microviscosity (ηeff) and the two-dimensional shear modulus (G'(f)) as a function of extracellular cholesterol in the range of 0.1 mM to 6mM. We find that membrane stiffness and shear modulus are dependent on cholesterol-induced membrane-cytoskeletal organization. Further, by disrupting the membrane-cytoskeletal connectivity with Cytochalasin D, an actin delpolymerizing molecule, we recover pure membrane behaviour devoid of any cytoskeleton attachment. However, behaviour of ηeff was found to be unaffected by disruption of membrane-cytoskeleton organization. We infer that cholesterol is playing a distinct role in modulating membrane organization and membrane-cytoskeleton connectivity independently. We further discuss implications of our approach in characterizing cellular mechanics.