Molecular and functional analyses of CD25 as a target for ADP-ribosylation on CD4+/CD25+ regulatory T cells
Final Report Abstract
NAD+-dependent ADP-ribosylation, a posttranslational protein modification, is best known as the pathogenic mechanism of bacterial toxins. ART2.2, a toxin-related arginine-specific ADP- ribosyltransferase, is expressed as a GPI-anchored, raft-associated ecto-enzyme by murine Foxp3+CD4+CD25+ regulatory T cells (Tregs). During inflammation, NAD+ is released from damaged cells, allowing ART2.2 to ADP-ribosylate other raft-associated membrane proteins. In this project we identified CD25 as a major target of ART2.2 and showed that ART2.2 ADP-ribosylates CD25 at an arginine doublet (R35 R36) within the IL-2 binding region. ADP-ribosylation of CD25 inhibits binding of IL-2, phosphorylation of STAT-5, and IL-2-dependent proliferation. Our results indicate that ADP-ribosylation of CD25 acts synergistically with ART2-catalyzed ADP-ribosylation of P2X7 to inhibit Tregs. Indeed, incubation of Tregs with NAD+ in vitro inhibits the capacity of these cells to suppress the proliferation of responder T cells. Systemic injections of NAD+ also suppressed Treg functions in vivo, resulting in more efficient anti-tumor responses. Our study elucidates an as-yet-unrecognized mechanism to tune IL-2 signaling and to inhibit Tregs by ADP-ribosylation of cell surface proteins. We propose that NAD+ represent a new type of danger signal, liberated at sites of inflammation by dying cells, that can inhibit Treg function to unleash effectors T cell activation and functions.
Publications
- Extracellular NAD and ATP: Partners in immune cell modulation. Purinergic Signal. 2007 Mar;3(1-2): 71-81
Haag F, Adriouch S, Braß A, Jung C, Möller S, Scheuplein F, Bannas P, Seman M, Koch-Nolte F
- Characterisation of the R276A gain-of-function mutation in the ectodomain of murine P2X7. Purinergic Signal. 2009 Jun;5 (2):151-61
Adriouch S, Scheuplein F, Bähring R, Seman M, Boyer O, Koch-Nolte F, Haag F
- NAD+ and ATP released from injured cells induce P2X7-dependent shedding of CD62L and externalization of phosphatidylserine by murine T cells. J Immunol. 2009 Mar 1;182(5):2898-908
Scheuplein F, Schwarz N, Adriouch S, Krebs C, Bannas P, Rissiek B, Seman M, Haag F, Koch-Nolte F
- "Extracellular NAD+ shapes the Foxp3+ regulatory T cell compartment through the ART2- P2X7 pathway". J Exp Med. 207:2561-8. 2010
Hubert S, Rissiek B, Klages K, Huehn J, Sparwasser T, Haag F, Koch-Nolte F, Boyer O, Seman M, Adriouch S
