Nicotinic acetylcholine receptor at the cell membrane is stabilized by cholesterol

KELLNER, R.; BAIER, J.; WILLIG, K.I.; BORRONI, V.; GARBUS, I.; HELL, S.W.; BARRANTES, F.J.

Montevideo, Uruguay

Congreso; 6th Int. Conference of Biological Physics, 5th Southern Cone Biophysical Congress & 34th Annual Meeting of the Argentinean Biophysical Society; 2007

The effect of cholesterol (Chol) on acetylcholine receptor (AChR) supramolecular organization has been studied by a combination of approaches using the clonal cell line CHO-K1/A5, a mammalian cell line stably expressing adult murine AChR. Acute (30 min, 37ºC) exposure to methyl-beta-cyclodextrin (CDx), commonly used as a diagnostic tool of endocytic mechanisms, dramatically accelerated AChR internalization from the cell surface. From a functional point of view, gain-of-function changes were observed in single-channel recordings upon Chol depletion. Wide-field and confocal microscopy disclosed AChR submicron-sized (240-280 nm) domains that remain stable over a period of hours at the cell membrane. Stimulated emission depletion (STED) fluorescence microscopy resolved the domains into AChR "nanoclusters" with a peak size distribution of ~55 nm. CDx-mediated Chol depletion resulted in a smaller number of nanoclusters with larger size, and changes in nanocluster distribution on larger scales (0.5 - 3.5 microns). Chol content at the plasmalemma may thus modulate cell-surface organization and stability of receptor domains, and fine-tune receptor channel function to temporarily compensate for acute AChR loss from the cell surface.