title: Vesicular and nonvesicular transport of phosphatidylcholine in polarized HepG2 cells.
abstract: We have investigated the transport and canalicular enrichment of fluorescent phosphatidylcholine (PC) in HepG2 cells using the fluorescent analogs of PC C6-NBD-PC and beta-BODIPY-PC. Fluorescent PC was efficiently transported to the biliary canaliculus (BC) and became enriched on the lumenal side of the canalicular membrane as shown for C6-NBD-PC. Some fluorescent PC was transported in vesicles to a subapical compartment (SAC) or apical recycling compartment (ARC) in polarized HepG2 cells as shown by colocalization with fluorescent sphingomyelin (C6-NBD-SM) and fluorescent transferrin, respectively. Extensive trafficking of vesicles containing fluorescent PC between the basolateral domain, the SAC/ARC and the BC as well as endocytosis of PC analogs from the canalicular membrane were found. Evidence for nonvesicular transport included enrichment of the PC-analog beta-BODIPY-PC in the BC (t1/2 = 3.54 min) prior to its accumulation in the SAC/ARC (t1/2 = 18.5 min) at 37 degrees C. Transport of fluorescent PC to the canalicular membrane also continued after disruption of the actin or microtubule cytoskeleton and at 2 degrees C. These results indicate that: (i) a nonvesicular transport pathway significantly contributes to the canalicular enrichment of PC in hepatocytic cells, and (ii) vesicular transport of fluorescent PC occurs from both membrane domains via the SAC/ARC.
authors: Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, Institut für Biologie/Biophysik, Invalidenstr. 43, D-10115 Berlin, Germany.
authors: D
authors: D
authors: Wüstner
authors: S
authors: S
authors: Mukherjee
authors: F R
authors: FR
authors: Maxfield
authors: P
authors: P
authors: Müller
authors: A
authors: A
authors: Herrmann
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000378:metabolism; D001647:Bile Acids and Salts / Q000378:metabolism; D001648:Bile Canaliculi / Q000166:cytology / Q000378:metabolism; D001693:Biological Transport, Active; D001896:Boron Compounds / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D003599:Cytoskeleton / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010713:Phosphatidylcholines / Q000378:metabolism*; D013109:Sphingomyelins / Q000378:metabolism; D013997:Time Factors; D014168:Transferrin / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001647:Bile Acids and Salts; D001896:Boron Compounds; D005452:Fluoresceins; D005456:Fluorescent Dyes; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D014168:Transferrin; C090312:cholylglycylamidofluorescein; C044745:1-palmitoyl-2-(6-(N-(7-nitrobenz)-2-oxa-1,3-diazol-4-yl)aminocaproyl)phosphatidylcholine; C081708:N-(N-(7-nitro-2,1,3-benzoxadiazol-4-yl)-epsilon-aminohexanoyl)sphingosylphosphorylcholine; D009327:4-Chloro-7-nitrobenzofurazan