Biochemistry and Physiopathology of Extracellular Nucleotides and Ectonucleotidases

Our laboratory studies the functions of extracellular nucleotides, the receptors by which they trigger their actions and the enzymes at the cell surface that hydrolyze them. In mammals, extracellular nucleotides act on all systems by causing a variety of physiological responses. The cells release these molecules under various conditions such as cell lysis, shear stress and cell activation. For example, platelets store nucleotides in secretory granules and release them by exocytosis during aggregation. Once released, nucleotides exert their actions primarily via P2 receptors. The extracellular concentration of nucleotides is modulated by enzymes located at the cell surface called ectonucleotidases. They convert triphospho- (e.g. ATP) and diphosphonucleosides (e.g. ADP) into nucleoside monophosphates (e.g. AMP). The Nucleoside Triphosphate Diphosphohydrolases (NTPDases) represent an important family of ectonucleotidase. The AMP produced is then converted into adenosine by the ecto-5’-nucleotidase. In turn, adenosine activates P1 receptors initiating cellular responses often opposite to those elicited by ATP. This complex system allows a tight regulation of the physiological effects associated with these molecules.

The research of our laboratory focuses on the following projects:

Characterization of mammalian NTPDases

We have recently identified and purified a new NTPDase member that is strongly expressed in the biliary canaliculi of hepatocytes. One of our projects is to clone the gene that codes for this enzyme and to generate the tools to study its properties and functions. We are also involved in the identification and characterization of other NTPDases.

Roles of extracellular nucleotides and NTPDases in inflammation, and in cardiovascular and hepatic functions.

By modulating the levels of nucleotides at the cell surface, NTPDases control various biological functions. Our objective is to test some of these functions using cellular and animal models. In inflammation, we are particularly interested in neutrophil and macrophage pathophysiology. In the cardiovascular system, we primarily study thrombosis and haemostasis as well as vascular tonicity. Finally, we also focus on nucleotide salvage and fibrosis in the liver.

These research projects are supported by the Canadian Institutes of Health Research (CIHR), the “Fonds de la Recherche en Santé du Québec” (FRSQ; Funds for health research of Quebec) and The Arthritis Society of Canada (TAS).

Few Representative Publications

Sévigny, J., Sundberg, C., Braun, N., Guckelberger, O., Csizmadia, E., Qawi, I., Imai, M., Zimmermann, H., and Robson, S.C. 2002. Differential catalytic properties and vascular topography of murine nucleoside triphosphate diphosphohydrolase 1 (NTPDase1) and NTPDase2 have implications for thromboregulation. Blood 99:2801-2809.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11929769&dopt=Abstract

Dranoff, J.A., Kruglov, E.A., Robson, S.C., Braun, N., Zimmermann, H., and Sévigny, J. 2002. The ecto-nucleoside triphosphate diphosphohydrolase NTPDase2/CD39L1 is expressed in a novel functional compartment within the liver. Hepatology 36:1135-1144.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12395323&dopt=Abstract

Mizumoto, N., Kumamoto, T., Robson, S.C., Sévigny, J., Matsue, H., Enjyoji, K., and Takashima, A. 2002. CD39 is the dominant Langerhans cell-associated ecto-NTPDase: Modulatory roles in inflammation and immune responsiveness. Nat. Med. 8:358-365.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11927941&dopt=Abstract

Sévigny, J., Robson, S.C., Waelkens, E., Csizmadia, E., Smith, R.N., and Lemmens, R. 2000. Identification and characterization of a novel hepatic canalicular ATP diphosphohydrolase. J. Biol. Chem. 275:5640-5647.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10681547&dopt=Abstract

Enjyoji, K., Sévigny, J., Lin, Y., Frenette, P.S., Christie, P.D., Schulte am Esch II, J., Imai, M., Edelberg, J.M., Rayburn, H., Lech, M., Beeler, D.L., Csizmadia, E., Wagner, D.D., Robson, S.C., and Rosenberg, R.D. 1999. Targeted disruption of cd39/ATP diphosphohydrolase results in disordered hemostasis and thromboregulation. Nat. Med. 5:1010-1017.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10470077&dopt=Abstract

(updated July 2003)