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 (k_m), membrane microviscosity (η_eff ) and the two-dimensional shear modulus (G′(f)) as a function of extracellular cholesterol in the range of 0.1mM to 6mM. We find that membrane stiffness and shear modulus are dependent on cholesterol-induced membrane-cytoskeletal organization. Further, by disrupting the membranecytoskeletal connectivity with Cytochalasin D, an actin delpolymerizing molecule, we recover pure membrane behaviour devoid of any cytoskeleton attachment. However, behaviour of η_eff 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.

Date Published: 2 September 2010
PDF: 13 pages
Proc. SPIE 7762, Optical Trapping and Optical Micromanipulation VII, 77621K (2 September 2010); doi: 10.1117/12.860464

Published in SPIE Proceedings Vol. 7762:
Optical Trapping and Optical Micromanipulation VII
Kishan Dholakia; Gabriel C. Spalding, Editor(s)