Identification and Characterization of CD39/Vascular ATP Diphosphohydrolase

doi:10.1074/jbc.271.51.33116

Identification and Characterization of CD39/Vascular ATP Diphosphohydrolase*

From the ^‡ Sandoz Center for Immunobiology, New England Deaconess Hospital, Harvard Medical School, Boston, Massachusetts 02215 and
^§ Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, JIK 2RI Canada

^∥To whom correspondence should be addressed:
New England Deaconess Hospital, Sandoz Center for Immunobiology, 99 Brookline Ave., Boston, MA 02215
. Tel.: 617-632-0881; Fax: 617-632-0880; E-mail: srobson{at}nedhmail.nedh.harvard.edu

Abstract

Vascular ATP diphosphohydrolase (ATPDase) is a plasma membrane-bound enzyme that hydrolyses extracellular ATP and ADP to AMP. Analysis of amino acid sequences available from various mammalian and avian ATPDases revealed their close homology with CD39, a putative B-cell activation marker. We, therefore, isolated CD39 cDNA from human endothelial cells and expressed this in COS-7 cells. CD39 was found to have both immunological identity to, and functional characteristics of, the vascular ATPDase. We also demonstrated that ATPDase could inhibit platelet aggregation in response to ADP, collagen, and thrombin, and that this activity in transfected COS-7 cells was lost following exposure to oxidative stress. ATPDase mRNA was present in human placenta, lung, skeletal muscle, kidney, and heart and was not detected in brain. Multiple RNA bands were detected with the CD39 cDNA probe that most probably represent different splicing products. Finally, we identified an unique conserved motif, DLGGASTQ, that could be crucial for nucleotide binding, activity, and/or structure of ATPDase. Because ATPDase activity is lost with endothelial cell activation, overexpression of the functional enzyme, or a truncated mutant thereof, may prevent platelet activation associated with vascular inflammation.

Footnotes

↵^¶ Recipient of a studentship award from Fonds pour la Formation de Chercheurs et l'Aide a la Recherche du Quebec and from the Heart and Stroke Foundation of Canada.
↵* This work was supported by Sandoz Pharma, Quebec Heart and Stroke Foundation, and the Natural Sciences and Engineering Research Council of Canada. This is manuscript no. 695 from our laboratory. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) S73813[GenBank].
↵¹ The abbreviations used are:

EC

endothelial cell

ATPDase

ATP diphosphohydrolase

mAb

monoclonal antibody

PCR

polymerase chain reaction

FCS

fetal calf serum.
↵² Robson, S. C., Kaczmarck, E., Siegel, J. B., Candinas, D., Koziak, K., Millan, M., Hancock, W. W., and Bach, F. H. (1997) J. Exp. Med., in press.
- Received September 30, 1996.