Title

ART2, a T cell surface mono-ADP-ribosyltransferase, generates extracellular poly(ADP-ribose)

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Biochemistry and Molecular Pharmacology; Department of Medicine

Date

8-26-2006

Document Type

Article

Medical Subject Headings

ADP Ribose Transferases; Adenosine Diphosphate Ribose; Animals; Catalysis; Cell Membrane; Cell Survival; Models, Molecular; Phosphoric Diester Hydrolases; Poly Adenosine Diphosphate Ribose; Protein Binding; Protein Structure, Tertiary; Rats; Recombinant Proteins; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Structural Homology, Protein; T-Lymphocytes

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

NAD functions in multiple aspects of cellular metabolism and signaling through enzymes that covalently transfer ADP-ribose from NAD to acceptor proteins, thereby altering their function. NAD is a substrate for two enzyme families, mono-ADP-ribosyltransferases (mARTs) and poly(ADP-ribose) polymerases (PARPs), that covalently transfer an ADP-ribose monomer or polymer, respectively, to acceptor proteins. ART2, a mART, is a phenotypic marker of immunoregulatory cells found on the surface of T lymphocytes, including intestinal intraepithelial lymphocytes (IELs). We have shown that the auto-ADP-ribosylation of the ART2.2 allelic protein is multimeric. Our backbone structural alignment of ART2 (two alleles of the rat art2 gene have been reported, for simplicity, the ART2.2 protein investigated in this study will be referred to as ART2) and PARP suggested that multimeric auto-ADP-ribosylation of ART2 may represent an ADP-ribose polymer, rather than multiple sites of mono-ADP-ribosylation. To investigate this, we used highly purified recombinant ART2 and demonstrated that ART2 catalyzes the formation of an ADP-ribose polymer by sequencing gel and by HPLC and MS/MS mass spectrometry identification of PR-AMP, a breakdown product specific to poly(ADP-ribose). Furthermore, we identified the site of ADP-ribose polymer attachment on ART2 as Arg-185, an arginine in a crucial loop of its catalytic core. We found that endogenous ART2 on IELs undergoes multimeric auto-ADP-ribosylation more efficiently than ART2 on peripheral T cells, suggesting that these distinct lymphocyte populations differ in their ART2 surface topology. Furthermore, ART2.2 IELs are more resistant to NAD-induced cell death than ART2.1 IELs that do not have multimeric auto-ADP-ribosylation activity. The data suggest that capability of polymerizing ADP-ribose may not be unique to PARPs and that poly(ADP-ribosylation), an established nuclear activity, may occur extracellularly and modulate cell function.

Rights and Permissions

Citation: J Biol Chem. 2006 Nov 3;281(44):33363-72. Epub 2006 Aug 24. Link to article on publisher's site

Comments

Medical student Alan Morrison participated in this study as part of the Senior Scholars research program.

Related Resources

Link to article in PubMed

PubMed ID

16931513