[Frontiers in Bioscience 14, 1088-1098, January 1, 2009]

Epithelial cell surface polarity: the early steps

Lene N. Nejsum1, W. James Nelson1

1Departments of Biology, and Molecular and Cellular Physiology, The James H. Clark Center, Bio-X Program, Stanford University, 318 Campus Drive E200, Stanford, CA 94305-5430

TABLE OF CONTENTS

1. Abstract
2. Epithelial cell and tissue functions
3. Regulation of protein sorting in polarized epithelial cells
4. Initial establishment of cell polarity
5. Establishment of the lateral targeting patch upon initial cell-cell adhesion
6. Conclusions
7. Acknowledgements
8. References

1. ABSTRACT

Establishment and maintenance of epithelial cell surface polarity is of vital importance for the correct function of transporting epithelia. To maintain normal cell function, the distribution of apical and basal-lateral proteins is highly regulated and defects in expression levels or plasma membrane targeting can have severe consequences. It has been shown recently that initiation of cell-surface polarity occurs immediately upon cell-cell contact, and requires components of the lateral targeting patch, the Exocyst and the lateral SNARE complex to specify delivery of basolateral proteins to the site of cell-cell adhesion. The Exocyst and SNARE complex are present in the cytoplasm in single epithelial cells before adhesion. Upon initial cell-cell adhesion, E-cadherin accumulates at the forming contact between cells. Shortly hereafter, components of the lateral targeting patch, the Exocyst and the lateral SNARE complex, co-localize with E-cadherin at the forming contact, where they function in specifying the delivery of basal-lateral