title: Molecular probes for sensing the cholesterol composition of subcellular organelle membranes.
abstract: Neuroendocrine cells contain two types of secretagogue-regulated acidic compartments: secretory granules (SGs) and synaptic-like microvesicles (SLMVs), which can be identified by acidotropic probes such as acridine orange (AO) and DAMP. We investigated the accumulation of these probes in SGs and SLMVs as a function of glucose levels in the culture media using a pancreatic beta-cell line MIN6. AO was accumulated in the low-glucose condition, but not in the high-glucose condition. The AO accumulation correlated well with the SLMV dynamics by glucose and DAMP was localized in the SGs. Because SG membranes are reportedly high in cholesterol, we prepared liposomes with increasing cholesterol levels. AO is well incorporated into liposomes having a 20 to 40 mol% cholesterol composition, whereas DAMP was so in those having over 40 mol% cholesterol levels. Indeed, when cholesterol was depleted from MIN6 SG membranes, DAMP incorporation decreased, instead AO was incorporated. In PC12 cells, AO incorporation into SGs was significant but DAMP incorporation was limited. Consistently, the cholesterol composition was found 37 to 39 mol% in the SG membrane of PC12 cells. We suggest that cholesterol-sensing probes, AO and DAMP, are useful tools for investigating cholesterol compositions in acidic organelle membranes.
authors.affiliation: Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Showa-machi, Maebashi 371-8512, Japan.
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hosaka
authors.forename: Lu
authors.initials: L
authors.lastname: Han
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yokota-Hashimoto
authors.forename: Masayuki
authors.initials: M
authors.lastname: Suda
authors.forename: Dai
authors.initials: D
authors.lastname: Mitsushima
authors.forename: Seiji
authors.initials: S
authors.lastname: Torii
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takeuchi
mesh_terms: D000165:Acridine Orange / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002784:Cholesterol / Q000032:analysis*; D004136:Dinitrobenzenes / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D007425:Intracellular Membranes / Q000737:chemistry*; D007515:Islets of Langerhans; D008081:Liposomes / Q000378:metabolism; D051379:Mice; D015335:Molecular Probes; D015388:Organelles / Q000648:ultrastructure; D016716:PC12 Cells; D051381:Rats; D022142:Secretory Vesicles / Q000737:chemistry
chemical_list: D004136:Dinitrobenzenes; D005456:Fluorescent Dyes; D008081:Liposomes; D015335:Molecular Probes; C042432:3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine; D002784:Cholesterol; D000165:Acridine Orange