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Newly synthesized canalicular ABC transporters are directly targeted from the Golgi to the hepatocyte apical domain in rat liver.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2000 May 26; Vol. 275 (21), pp. 15917-25. - Publication Year :
- 2000
-
Abstract
- Newly synthesized canalicular ectoenzymes and a cell adhesion molecule (cCAM105) have been shown to traffic from the Golgi to the basolateral plasma membrane, from where they transcytose to the apical bile canalicular domain. It has been proposed that all canalicular proteins are targeted via this indirect route in hepatocytes. We studied the membrane targeting of rat canalicular proteins by in vivo [(35)S]methionine metabolic labeling followed by preparation of highly purified Golgi membranes and canalicular (CMVs) and sinusoidal/basolateral (SMVs) membrane vesicles and subsequent immunoprecipitation. In particular, we compared membrane targeting of newly synthesized canalicular ABC (ATP-binding cassette) transporters MDR1, MDR2, and SPGP (sister of P-glycoprotein) with that of cCAM105. Significant differences were observed in metabolic pulse-chase labeling experiments with regard to membrane targeting of these apical proteins. After a chase time of 15 min, cCAM105 appeared exclusively in SMVs, peaked at 1 h, and progressively declined thereafter. In CMVs, cCAM105 was first detected after 1 h and subsequently increased for 3 h. This findings confirm the transcytotic targeting of cCAM105 reported in earlier studies. In contrast, at no time point investigated were MDR1, MDR2, and SPGP detected in SMVs. In CMVs, MDR1 and MDR2 appeared after 30 min, whereas SPGP appeared after 2 h of labeling. In Golgi membranes, each of the ABC transporters peaked at 30 min and was virtually absent thereafter. These data suggest rapid, direct targeting of newly synthesized MDR1 and MDR2 from the Golgi to the bile canaliculus and transient sequestering of SPGP in an intracellular pool en route from the Golgi to the apical plasma membrane. This study provides biochemical evidence for direct targeting of newly synthesized apical ABC transporters from the Golgi to the bile canaliculus in vivo.
- Subjects :
- ATP-Binding Cassette Transporters biosynthesis
Animals
Asialoglycoprotein Receptor
Biomarkers
Cell Membrane metabolism
Coatomer Protein analysis
Intracellular Membranes metabolism
Male
Precipitin Tests
Rats
Rats, Sprague-Dawley
Receptors, Cell Surface metabolism
ATP-Binding Cassette Transporters metabolism
Bile Canaliculi metabolism
Golgi Apparatus metabolism
Liver metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 275
- Issue :
- 21
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 10748167
- Full Text :
- https://doi.org/10.1074/jbc.M909875199