Cholesterol depletion activates rapid Internalization of AChR domains at the cell membrane.

BAIER JAVIER,; VIRGINA BORRONI,; THORSTEN LANG,; BONINI IDA,; MICHAEL WHITE,; GARBUS INGRID,; BARRANTES FRANCISCO,

Rosario

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

CHOLESTEROL DEPLETION ACTIVATES RAPID INTERNALIZATION OF AChR DOMAINS AT THE CELL MEMBRANE Baier C. J.; Borroni V.; Lang T.; Bonini I.; White M. M.; Garbus I. ; Barrantes F. J. UNESCO Chair Biophys & Mol Neurobiol/INIBIBB, 8000 B. Blanca, Argentina * E-mail: cjbaier@criba.edu.ar Novel effects of cholesterol on nicotinic acetylcholine receptors (AChR) cell-surface stability and function (single-channel behavior) are reported. AChR are shown to occur in the form of diffraction-limited (240-280 nm) domains that remain stable at the cell-surface membrane of CHO-K1/A5 cells over a period of hours. Acute (30 min, 37°C) exposure to methyl-β-cyclodextrin, commonly used as a diagnostic tool of endocytic mechanisms, is shown here to enhance AChR internalization kinetics in the receptor-expressing clonal cell line. This treatment drastically reduced (~50%) the number of plasma membrane domains and accelerated internalization (t1/2 decreased from 1.5 to 0.5 h). In addition, cholesterol depletion produced ion channel gain-offunction of the remaining cell-surface AChR, whereas cholesterol enrichment had the opposite effect. Homeostatic control of cholesterol content at the plasmalemma may thus modulate cellsurface organization and stability of receptor domains, and fine tune receptor channel function to temporarily compensate for acute AChR loss from the cell surface. * Collaborative work with Max-Planck Inst. biophys. Chem., Göttingen, Germany (T.L.) and Drexel Univers. College of Med., Philadelphia, USA (M.M.W.)