title: Transient cholesterol effects on nicotinic acetylcholine receptor cell-surface mobility.
abstract: To what extent do cholesterol-rich lipid platforms modulate the supramolecular organization of the nicotinic acetylcholine receptor (AChR)? To address this question, the dynamics of AChR particles at high density and its cholesterol dependence at the surface of mammalian cells were studied by combining total internal reflection fluorescence microscopy and single-particle tracking. AChR particles tagged with a monovalent ligand, fluorescent α-bungarotoxin (αBTX), exhibited two mobile pools: i) a highly mobile one undergoing simple Brownian motion (16%) and ii) one with restricted motion (∼50%), the rest being relatively immobile (∼44%). Depletion of membrane cholesterol by methyl-α-cyclodextrin increased the fraction of the first pool to 22% and 33% after 15 and 40 min, respectively; the pool undergoing restricted motion diminished from 50% to 44% and 37%, respectively. Monoclonal antibody binding results in AChR crosslinking-internalization after 2 h; here, antibody binding immobilized within minutes ∼20% of the totally mobile AChR. This proportion dramatically increased upon cholesterol depletion, especially during the initial 10 min (83.3%). Thus, antibody crosslinking and cholesterol depletion exhibited a mutually synergistic effect, increasing the average lifetime of cell-surface AChRs∼10 s to ∼20 s. The instantaneous (microscopic) diffusion coefficient D2-4 of the AChR obtained from the MSD analysis diminished from ∼0.001 µm2 s(-1) to ∼0.0001-0.00033 µm2 s(-1) upon cholesterol depletion, ∼30% of all particles falling into the stationary mode. Thus, muscle-type AChR exhibits heterogeneous motional regimes at the cell surface, modulated by the combination of intrinsic (its supramolecular organization) and extrinsic (membrane cholesterol content) factors.
authors: Laboratory of Molecular Neurobiology, Biomedical Research Institute, Pontifical Catholic University of Argentina (UCA) and National Scientific and Technical Research Council of Argentina (CONICET), Buenos Aires, Argentina.
authors: Gonzalo
authors: G
authors: Almarza
authors: Laboratory of Molecular Neurobiology, Biomedical Research Institute, Pontifical Catholic University of Argentina (UCA) and National Scientific and Technical Research Council of Argentina (CONICET), Buenos Aires, Argentina.
authors: Francisco
authors: F
authors: Sánchez
authors: Laboratory of Molecular Neurobiology, Biomedical Research Institute, Pontifical Catholic University of Argentina (UCA) and National Scientific and Technical Research Council of Argentina (CONICET), Buenos Aires, Argentina.
authors: Francisco J
authors: FJ
authors: Barrantes
mesh_terms: D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D003412:Cricetulus; D008856:Microscopy, Fluorescence; D057054:Molecular Imaging / Q000379:methods; D066329:Protein Aggregates; D021381:Protein Transport; D011978:Receptors, Nicotinic / Q000378:metabolism*
chemical_list: D066329:Protein Aggregates; D011978:Receptors, Nicotinic; D002784:Cholesterol