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Molecular sorting in polarized and non-polarized cells: common problems, common solutions
I Mellman1, E Yamamoto, J A Whitney
1Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
Journal of Cell Science. Supplement
|January 1, 1993
Summary
Epithelial cells use discrete targeting signals on membrane proteins for polarized transport. These signals, found in both polarized and non-polarized cells, control protein movement along biosynthetic and endocytic pathways.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Epithelial cells exhibit distinct apical and basolateral membrane domains.
- Maintaining this polarity requires precise trafficking of membrane proteins.
Purpose of the Study:
- To investigate the mechanisms underlying polarized membrane protein distribution in epithelial cells.
- To identify the targeting determinants responsible for protein localization.
Main Methods:
- Analysis of membrane protein cytoplasmic domains for targeting signals.
- Studies in Madin-Darby canine kidney (MDCK) cells to assess protein transport pathways.
- Characterization of signals for basolateral and apical transport.
Main Results:
- Discrete targeting determinants on cytoplasmic domains regulate polarized transport.
- These determinants function in both biosynthetic and endocytic pathways.
- Basolateral signals often involve a tyrosine residue; apical signals are revealed upon basolateral signal inactivation.
- Determinants are not exclusive to polarized cells.
Conclusions:
- Polarized transport relies on a hierarchical set of targeting signals.
- Non-polarized cells may possess similar pathways for constitutive protein transport.
- These conserved mechanisms allow rapid adaptation to polarized phenotypes.