Abstract
Carboxypeptidase M (CPM) is a GPI anchored enzyme that plays a role in kallikrein-kinin system. CPM catalytic domain hydrolyzes Lys or Arg from C-terminal peptides (i.e., bradykinin and kallidin), generating B1 receptor agonist, as des-Arg9-BK. It is known that CPM and kinin B1 receptors are co-localized in plasma membrane microdomains, where they interact with each other, facilitating the receptor signaling. Enzyme-receptor interactions in membrane microdomains are not well understood, especially from the enzyme's point of view. In this context, this study becomes crucial, considering the ectoenzymes role, like CPM, in kallikrein-kinin system. The hormonal function of this system depends on circulating levels of its agonists, whose local availability is controlled by the enzymes which are close to their receptors. Therefore, we hypothesize that CPM-kinin B1 receptors interaction might also affect the enzyme activity, by using the fluorescent substrate dansyl-Ala-Arg. For this purpose, we will study two different kind of cell system: first, primary culture of endothelial cells from both wildtype and kinin receptors knockout mice; second, an artificial system, by using HUVEC cells transfected only with CPM and both CPM and B1 or B2 receptor. We will also evaluate the kinin receptor antagonists' effect on CPM activity and NO production by endothelial cells. This work will contribute not only to better understanding of kallikrein-kinin system in general, but also locally, by studying the CPM-kinin receptors interaction and its result in endothelial function. (AU)
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