AJP - Gastrointestinal and Liver Physiology, Vol 269, Issue 5 613-G627, Copyright © 1995 by American Physiological Society
Mucin gene structure and expression: protection vs. adhesion
B. J. Van Klinken, J. Dekker, H. A. Buller and A. W. Einerhand
Academic Medical Center, Amsterdam, The Netherlands.
The cloning of mucin cDNAs brought about by the application of molecular
biology and molecular analyses constitutes a major step in understanding
mucin structure and function. Here two classes of mucins are described:
epithelium-associated and endothelium/leukocyte-associated mucins, which
have thus far been described separately in the literature. The epithelial
mucins are generally believed to play a role in cytoprotection. The
endothelial and leukocyte class of mucins are adhesion molecules involved
in lymphocyte homing and lymphocyte activation or are part of the adhesion
cascade that plays a role in the initiation of inflammation. Mucins in
general contain many threonine and serine residues, which are extensively
O-glycosylated. Due to this profound glycosylation, mucins have a
filamentous conformation. By virtue of their extended filamentous, and
often negatively charged, structure, mucins can act as a barrier protecting
the cell. However, when an opposing cell has specific receptors for mucins,
adhesion can override the barrier function. Therefore, mucins may be
powerful two-edged swords: they are both protective and adhesive.
