Thrombospondin-1 is a potent suppressor of T cell activation via its receptor CD47. However, the precise mechanism for this inhibition remains unclear. Because H2S is an endogenous potentiator of T cell activation and is necessary for full T cell activation, we hypothesized that thrombospondin-1 signaling through CD47 inhibits T cell activation by antagonizing H2S signaling. Primary T cells from thrombospondin-1 null mice were more sensitive to H2S-dependent activation assessed by proliferation and induction of interleukin-2 and CD69 mRNAs. Exogenous thrombospondin-1 inhibited H2S responses in wild type and thrombospondin-1 null T cells but enhanced the same responses in CD47 null T cells. Fibronectin, which shares integrin and glycosaminoglycan binding properties with thrombospondin-1 but not CD47 binding, did not inhibit H2S signaling. A CD47-binding peptide derived from thrombospondin-1 inhibited H2S-induced activation, whereas two other functional sequences from thrombospondin-1 enhanced H2S signaling. Therefore, engaging CD47 is necessary and sufficient for thrombospondin-1 to inhibit H2S-dependent T cell activation. H2S stimulated T cell activation by potentiating MEK-dependent ERK phosphorylation, and thrombospondin-1 inhibited this signaling in a CD47-dependent manner. Thrombospondin-1 also limited activation-dependent T cell expression of the H2S biosynthetic enzymes cystathionine beta-synthase and cystathionine gamma-lyase, thereby limiting the autocrine role of H2S in T cell activation. Thus, thrombospondin-1 signaling through CD47 is the first identified endogenous inhibitor of H2S signaling and constitutes a novel mechanism that negatively regulates T cell activation.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Investigator-Initiated Intramural Research Projects (ZIA)
Project #
1ZIASC009174-25
Application #
8763693
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
25
Fiscal Year
2013
Total Cost
$472,910
Indirect Cost
Name
National Cancer Institute Division of Clinical Sciences
Department
Type
DUNS #
City
State
Country
Zip Code
Miller, Thomas W; Soto-Pantoja, David R; Schwartz, Anthony L et al. (2015) CD47 Receptor Globally Regulates Metabolic Pathways That Control Resistance to Ionizing Radiation. J Biol Chem 290:24858-74
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Soto-Pantoja, David R; Stein, Erica V; Rogers, Natasha M et al. (2013) Therapeutic opportunities for targeting the ubiquitous cell surface receptor CD47. Expert Opin Ther Targets 17:89-103
Miller, Thomas W; Wang, Evelyn A; Gould, Serge et al. (2012) Hydrogen sulfide is an endogenous potentiator of T cell activation. J Biol Chem 287:4211-21
Roberts, David D; Miller, Thomas W; Rogers, Natasha M et al. (2012) The matricellular protein thrombospondin-1 globally regulates cardiovascular function and responses to stress via CD47. Matrix Biol 31:162-9
Roberts, David D (2011) Activate Rac to rescue new vessels. Blood 117:1444-5

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