title: Cholesterol regulates volume-sensitive osmolyte efflux from human SH-SY5Y neuroblastoma cells following receptor activation.
abstract: The ability of cholesterol to modulate receptor-mediated increases in the volume-dependent release of the organic osmolyte, taurine, has been examined. Depletion of cholesterol from SH-SY5Y neuroblastoma by preincubation of the cells with 5 mM methyl-beta-cyclodextrin (CD) for 10 min resulted in a 40 to 50% reduction in cholesterol and an enhancement of the ability of proteinase-activated receptor (PAR) 1, muscarinic cholinergic receptor (mAChR), and sphingosine 1-phosphate receptor to stimulate taurine efflux, when monitored under hypoosmotic conditions. Basal (swelling-induced) release of taurine was also enhanced by cholesterol depletion, but less markedly. Both basal- and receptor-mediated increases in taurine efflux were mediated via a volume-sensitive organic osmolyte and anion channel in control and cholesterol-depleted cells. Studies with the PAR-1 and mAChR receptor subtypes indicated that the stimulatory effect of CD pretreatment could be reversed by incubation of the cells with either CD/cholesterol or CD/5-cholesten-3alpha-ol donor complexes and that cholesterol depletion increased agonist efficacy, but not potency. The ability of cholesterol depletion to promote the PAR-1 receptor-mediated stimulation of osmolyte release was most pronounced under conditions of isotonicity or mild hypotonicity. In contrast to CD pretreatment, preincubation of the cells with cholesterol oxidase, a condition under which lipid microdomains are also disrupted, had no effect on either basal- or receptor-stimulated taurine efflux. Taken together, the results suggest that cholesterol regulates receptor-mediated osmolyte release via its effects on the biophysical properties of the plasma membrane, rather than its presence in lipid microdomains.
authors.affiliation: University of Michigan, Molecular and Behavioral Neuroscience Institute, 5039 Biomedical Science Research Building, Ann Arbor, MI 48109-2200, USA.
authors.forename: Tooba A
authors.initials: TA
authors.lastname: Cheema
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Fisher
mesh_terms: D045744:Cell Line, Tumor; D048429:Cell Size; D002784:Cholesterol / Q000502:physiology*; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology*; D044463:Receptor, PAR-1 / Q000378:metabolism*; D013654:Taurine / Q000378:metabolism*
chemical_list: D044463:Receptor, PAR-1; D013654:Taurine; D002784:Cholesterol