The Cytoplasmic Domains of a β1 Integrin Mediate Polarization in Madin-Darby Canine Kidney Cells by Selective Basolateral Stabilization*
Abstract
In Madin-Darby canine kidney cells, newly synthesized apical and basolateral membrane proteins are generally transported directly to their respective cell surface domain due to targeting determinants that mediate sorting in the Golgi complex. In several basolateral membrane proteins, these targeting determinants reside in the cytoplasmic domains. We show here that basolateral expression of the human α5β1 integrin in stably transfected Madin-Darby canine kidney cells is also mediated by the cytoplasmic domains. Distinct regions in both cytoplasmic domains were found to be sufficient to mediate basolateral expression independently from one another. Unexpectedly, newly synthesized wild-type α5β1 and basolaterally expressed chimeras containing the cytoplasmic domain of either α5or β1 were integrated into both cell surface domains, preferentially apically, during biosynthesis. The apical pools of wild-type integrin and chimeric subunits were found to become quickly degraded, whereas the basolateral pools were stabilized. Thus, the cytoplasmic domains of the α5β1 integrin are independently sufficient to mediate sorting by selective basolateral stabilization.
Footnotes
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↵* This research was supported by the Swiss National Science Foundation and the Canton de Genève.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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↵‡ These authors contributed equally to this work.
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↵§ Recipient of a fellowship from the Swiss Talents in Academic Research and Teaching program of the Swiss National Science Foundation. To whom correspondence should be addressed: Dept. of Cell Biology, University of Geneva, Sciences III, 30, Quai Ernest-Ansermet, 1211 Genève-4, Switzerland. Tel.: 41-22-702-6729; Fax: 41-22-781-1747; E-mail: Matter{at}cellbio.unige.ch.
- Abbreviations:
- MDCK
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Madin-Darby canine kidney
- HRP
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horseradish peroxidase
- PAGE
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polyacrylamide gel electrophoresis.
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- Received August 13, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
