Glycolipid-independent Sorting of a Secretory Glycoprotein to the Apical Surface of Polarized Epithelial Cells*
- ‡ To whom correspondence should be addressed: Institut für Biochemie der J. Gutenberg-Universität, Becherweg 30, 55099 Mainz, Germany. Tel.: 49-6131-395839; Fax: 49-6131-395138.
Abstract
Proteins attached to the membrane by a glycosylphosphatidylinositol (GPI)-anchor cluster together with glycolipids in detergent-insoluble complexes at the site of sorting in the trans-Golgi network. This process has been shown to be critical for the targeting of these proteins to the apical cell surface in polarized epithelial cells. We show in this study that gp80 (clusterin), an apically secreted glycoprotein, is not included in detergent-insoluble complexes in Madin-Darby canine kidney cells. Furthermore in Fisher rat thyroid cells, which target GPI-anchored proteins preferentially to the basolateral cell surface, gp80 is secreted apically. Together these results suggest that this secretory glycoprotein and GPI-linked proteins use different mechanisms to reach the apical membrane.
Footnotes
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↵* This work was supported by the Deutsche Forschungsgemeinschaft and by the Fonds der Chemischen Industrie in cooperation with the “Bundesministerium für Bildung und Forschung.” The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- MDCK
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Madin-Darby canine kidney
- FRT
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Fisher rat thyroid
- GPI
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glycosylphosphatidylinositol
- GSL
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glycosphingolipid
- PI-PLC
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phosphatidylinositol-dependent phospholipase C
- PAGE
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polyacrylamide gel electrophoresis
- TGN
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trans-Golgi network
- Chaps
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3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid.
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- Received March 5, 1996.
- Revision received April 12, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
