Multiple Membrane Tethers Probed By Atomic Force Microscopy

¹ University of Missouri-Columbia
² University of Missouri - Columbia
³ University of Indiana-Bloomington
⁴ University of Sherbrooke

^* To whom correspondence should be addressed. E-mail: michel.grandbois{at}usherbrooke.ca.

Submitted on December 16, 2004
Revised on January 20, 2005
Accepted on 9 September 2005

	Abstract

Using the atomic force microscope (AFM) to locally probe the cell membrane we observed the formation of multiple tethers, thin nanotubes - each requiring a similar pulling force - as reproducible features within force profiles recorded on individual cells. Forces obtained with Chinese Hamster Ovary (CHO) cells, a malignant human brain tumor cell line (HB), and human endothelial cells (EA hy926) were found to be 28±10 pN, 29±9 pN, and 29±10 pN, respectively, independent of the nature of attachment to the cantilever. The rather large variation of the tether pulling forces measured at several locations on individual cells indicates that some degree of heterogeneity exists in the membrane properties over a morphologically homogeneous cell. Measurement of the summary lengths of the simultaneously extracted tethers provides a measure of the size of the available reservoir and indicates that multiply extracted tethers are interdependent and associated through a common membrane reservoir. As expected, partial disruption of the actin cytoskeleton and removal of the hyaluronan backbone of the glycocalyx were observed to result in a marked decrease (30-50%) in the magnitude and a significant sharpening of the force distribution indicating reduced heterogeneity of membrane properties. Taken together our results clearly demonstrate the ability of the plasma membrane to produce multiple interdependent tethers, a process that could play an important role in the mechanical association of cells with their environment.

Key Words: atomic force microscopy, cytoskeleton, force spectroscopy, glycocalyx, membrane mechanics, membrane tether

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