Christelle Guyot1, Bruno Stieger. 1. Division of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland.
Abstract
BACKGROUND & AIMS: Canalicular phosphatidylcholine and cholesterol secretion requires the coordinate action of the ATP binding cassette transporters: the bile salt export pump (Bsep) for bile salts (BS) and the phosphatidylcholine translocator multidrug resistance protein 2 (Mdr2). After their secretion, phosphatidylcholine and BS form mixed micelles acting as acceptors for canalicular cholesterol. We have shown that the canalicular liver plasma membrane (cLPM) contains lipid raft enriched in sphingomyelin and cholesterol. As BS have detergent properties and their concentration in the canaliculus is very high, we tested the hypothesis that the canalicular membrane contains BS resistant microdomains. METHODS: Isolated cLPMs were extracted at 4°C with different BS or detergents and subjected to flotation in sucrose step gradients followed by Western blotting and lipid composition analysis. RESULTS: Incubating cLPMs with increasing taurocholate concentrations revealed the presence of BS resistant microdomains. These microdomains were found with different BS in the presence and absence of lipids and contained the raft markers reggie-1/-2 and caveolin-1 and canalicular transporters Bsep, Mrp2, and Abcg5, the latter independent of the presence of lipids. BS resistant microdomains contain mainly cholesterol, phosphatidylcholine, and phosphatidylethanolamine. Extraction of cLPMs with a mixture of different BS similar to rat bile revealed a comparable microdomain composition. CONCLUSIONS: cLPM contains BS resistant microdomains potentially protecting the cLPM against the detergent action of BS. Combination of different BS has no synergistic effect on microdomain composition.
BACKGROUND & AIMS: Canalicular phosphatidylcholine and cholesterol secretion requires the coordinate action of the ATP binding cassette transporters: the bile salt export pump (Bsep) for bile salts (BS) and the phosphatidylcholine translocator multidrug resistance protein 2 (Mdr2). After their secretion, phosphatidylcholine and BS form mixed micelles acting as acceptors for canalicular cholesterol. We have shown that the canalicular liver plasma membrane (cLPM) contains lipid raft enriched in sphingomyelin and cholesterol. As BS have detergent properties and their concentration in the canaliculus is very high, we tested the hypothesis that the canalicular membrane contains BS resistant microdomains. METHODS: Isolated cLPMs were extracted at 4°C with different BS or detergents and subjected to flotation in sucrose step gradients followed by Western blotting and lipid composition analysis. RESULTS: Incubating cLPMs with increasing taurocholate concentrations revealed the presence of BS resistant microdomains. These microdomains were found with different BS in the presence and absence of lipids and contained the raft markers reggie-1/-2 and caveolin-1 and canalicular transporters Bsep, Mrp2, and Abcg5, the latter independent of the presence of lipids. BS resistant microdomains contain mainly cholesterol, phosphatidylcholine, and phosphatidylethanolamine. Extraction of cLPMs with a mixture of different BS similar to rat bile revealed a comparable microdomain composition. CONCLUSIONS:cLPM contains BS resistant microdomains potentially protecting the cLPM against the detergent action of BS. Combination of different BS has no synergistic effect on microdomain composition.
Authors: Elizabeth S Moore; Erin K Daugherity; David I Karambizi; Bethany P Cummings; Erica Behling-Kelly; Deanna M W Schaefer; Teresa L Southard; Joseph W McFadden; Robert S Weiss Journal: J Biol Chem Date: 2019-08-21 Impact factor: 5.157
Authors: Patricio Godoy; Nicola J Hewitt; Ute Albrecht; Melvin E Andersen; Nariman Ansari; Sudin Bhattacharya; Johannes Georg Bode; Jennifer Bolleyn; Christoph Borner; Jan Böttger; Albert Braeuning; Robert A Budinsky; Britta Burkhardt; Neil R Cameron; Giovanni Camussi; Chong-Su Cho; Yun-Jaie Choi; J Craig Rowlands; Uta Dahmen; Georg Damm; Olaf Dirsch; María Teresa Donato; Jian Dong; Steven Dooley; Dirk Drasdo; Rowena Eakins; Karine Sá Ferreira; Valentina Fonsato; Joanna Fraczek; Rolf Gebhardt; Andrew Gibson; Matthias Glanemann; Chris E P Goldring; María José Gómez-Lechón; Geny M M Groothuis; Lena Gustavsson; Christelle Guyot; David Hallifax; Seddik Hammad; Adam Hayward; Dieter Häussinger; Claus Hellerbrand; Philip Hewitt; Stefan Hoehme; Hermann-Georg Holzhütter; J Brian Houston; Jens Hrach; Kiyomi Ito; Hartmut Jaeschke; Verena Keitel; Jens M Kelm; B Kevin Park; Claus Kordes; Gerd A Kullak-Ublick; Edward L LeCluyse; Peng Lu; Jennifer Luebke-Wheeler; Anna Lutz; Daniel J Maltman; Madlen Matz-Soja; Patrick McMullen; Irmgard Merfort; Simon Messner; Christoph Meyer; Jessica Mwinyi; Dean J Naisbitt; Andreas K Nussler; Peter Olinga; Francesco Pampaloni; Jingbo Pi; Linda Pluta; Stefan A Przyborski; Anup Ramachandran; Vera Rogiers; Cliff Rowe; Celine Schelcher; Kathrin Schmich; Michael Schwarz; Bijay Singh; Ernst H K Stelzer; Bruno Stieger; Regina Stöber; Yuichi Sugiyama; Ciro Tetta; Wolfgang E Thasler; Tamara Vanhaecke; Mathieu Vinken; Thomas S Weiss; Agata Widera; Courtney G Woods; Jinghai James Xu; Kathy M Yarborough; Jan G Hengstler Journal: Arch Toxicol Date: 2013-08-23 Impact factor: 5.153