Abstracts (complete list) - Wissenschaft Online

Anette Brass, Shiyuan Hong, Nicole Schwarz, George Dubyak, Michel Seman, Friedrich
Koch-Nolte, Friedrich Haag
LPS and interferons induce surface expression and activity of
ADP-ribosyltransferase ART2.1 on murine bone marrowderived
macrophages
Nicotinamide adenosine dinucleotide (NAD), a predominantly intracellular metabolite, is
released into the extracellular compartment consequent to cell lysis or by regulated
secretion. Extracellular NAD modulates immune and inflammatory responses by serving
as a substrate for cell surface ADP-ribosyltransferases (ARTs) that transfer ADP-ribose
from NAD to arginine residues on target proteins. In the murine immune system, the
major sources of ART activity are the two ART2 isoforms ART2.1 and ART2.2, which so
far have only been detected on T cells. On these cells, ADP-ribosylation of the P2X7
purinoreceptor leads to activation of the receptor and rapid cell death. ART2.1 differs
from ART2.2 in that it carries an extra disulfide bond, making its activity dependent on
the presence of thiol reducing agents. We now report that bone marrow-derived
macrophages (BMDM) from BALB/c mice up-regulate ART2.1, but not ART2.2, in
response to multiple proinflammatory mediators including agonists for toll-like receptors
(TLR) and type-1/2 interferons. Stimulation of BMDM with LPS, interferon-&Gamma
(IFN-&Gamma) or interferon-&beta (IFN-&beta) induced high expression of ART2.1 as a
GPI-anchored cell surface ecto-enzyme. The catalytic function of the induced cell
surface ART2.1 was strictly dependent on the presence of extracellular thiol reducing
cofactors, suggesting that in vivo activity of ART2.1-expressing macrophages may be
potentiated in hypoxic or ischemic compartments. Consistent with the mutated Art2a
gene in C57BL/6 mice, LPS- or IFN-stimulated BMDM from this strain lacked expression
of cell surface ART2 activity in the presence or absence of extracellular thiol reductants.
In transfection experiments, P2X7 was activated by ART2.1 in the presence of NAD and
reducing agents. Collectively, these findings implicate NAD-dependent ADP-ribosylation
as a potential immunoregulatory mechanism for inflammatory macrophages as well as
for T cells.