Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2018-2019)

Background: Vital organs are lined by a specialized layer made up by epithelial cells. These create a protective barrier and regulate transport of substances through the layer, vital for healthy organ functions. A key structural component of epithelial layers are the cell-cell contacts, which consist of a large number of proteins. Among the many proteins residing at the contact sites are the claudins, a family of small proteins, that are responsible for regulating selective transport across the layer. Research in the past years also pointed out that the function of claudins is more widespread as they can affect cell growth and cell movement. Interestingly, many conditions, e.g. inflammation can alter the amount of claudin proteins in the cells, which has huge functional consequences. Thus, it is very important to understand how the cells control amounts of their claudins.
In our previous studies supported by NSERC, we showed that two claudins, claudin-2 and 3 are affected similarly by inflammation: initially the level of these claudins increases, and later it drops. Amounts of a given protein is determined by the balance of production and elimination via break down, and we found that for claudin-2, both production and elimination are affected by inflammation. We also showed that both of these claudins play important roles in changes in barrier functions during inflammation, and cell movement. These studies provided exciting new observations, and started to explain regulation, but large gaps in our knowledge remain. Therefore, the overall objective of this program is to define regulation of claudin-2 and 3, that reside in the intercellular junctions and affect many epithelial functions.
Approach: We propose that localization of claudin-2 and 3 within the cells (e.g. at the cell-cell contacts, or other areas of the cells) determines their elimination, and thus their levels. Therefore, we will first ask how the localization of these claudins is controlled, and what factors induce delocalization from contact sites (project 1). Next, we will determine how these proteins are broken down and test what determines the rate of elimination (project 2). Finally, we will test how factors that control claudin localization and break down affect barrier functions. All studies will be performed in cultured epithelial cells using a variety of state of the art cell biology methods.
Significance: Claudins have key roles in determining healthy functions of epithelial cells. This program will allow fundamental new insights and lay the foundation for studies into how claudins can cause disease.