title: Role of cholesterol in developing T-tubules: analogous mechanisms for T-tubule and caveolae biogenesis.
abstract: Recent work has suggested that caveolae biogenesis and transverse-tubule (T-tubule) formation in muscle cells share similar underlying features. We compared the properties of caveolin-1 (cav-1)-positive caveolae, in epithelial cells, with caveolin-3 (cav-3)-positive precursor T-tubules, in differentiating C2C12 muscle cells, using the cholesterol-binding drug, Amphotericin B (AmphB). Treatment of MDCK epithelial cells with acute high doses or chronic low doses of AmphB caused a loss of surface caveolae and the rapid redistribution of cav-1, and exogenously expressed cav-3, from the cell surface into modified endosomes. This effect was reversible and specific, as the GPI-anchored protein, alkaline phosphatase, was largely unaffected by the treatment unless it had been previously partitioned into caveolar domains. In differentiating C2C12 mouse myotubes, AmphB also caused a complete redistribution of cav-3 from precursor T-tubule elements into enlarged endosomes, morphologically very similar to those seen in MDCK cells. This was accompanied by redistribution of a T-tubule marker and a dramatic reduction in the extent of surface-connected tubular elements. We propose that cholesterol-enriched glycolipid 'raft' domains are involved in the formation and maintenance of diverse membrane systems including caveolae and the T-tubule system of muscle.
authors.affiliation: Centre for Microscopy and Microanalysis, Department of Physiology and Pharmacology and Centre for Molecular and Cellular Biology, University of Queensland, Queensland, 4072, Australia.
authors.forename: A J
authors.initials: AJ
authors.lastname: Carozzi
authors.forename: E
authors.initials: E
authors.lastname: Ikonen
authors.forename: M R
authors.initials: MR
authors.lastname: Lindsay
authors.forename: R G
authors.initials: RG
authors.lastname: Parton
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D021941:Caveolae / Q000378:metabolism*; D051242:Caveolin 1; D051244:Caveolin 3; D022461:Caveolins / Q000378:metabolism; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D011992:Endosomes / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005372:Filipin / Q000378:metabolism; D051379:Mice; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009132:Muscles / Q000166:cytology* / Q000378:metabolism*; D013997:Time Factors
chemical_list: C495541:Cav1 protein, mouse; C495548:Cav3 protein, mouse; D051242:Caveolin 1; D051244:Caveolin 3; D022461:Caveolins; D003432:Cross-Linking Reagents; D000666:Amphotericin B; D005372:Filipin; D002784:Cholesterol; D000469:Alkaline Phosphatase