Recent work in our lab has demonstrated that Fas ligand (FasL or CD95L), best known for delivering a death signal through its interaction with Fas, is also capable of positive reverse signaling. Thus, CD8+ T cells lacking functional FasL exhibit depressed antigen-specific proliferation relative to their FasL+ counterparts, and FasIgG fusion proteins can inhibit the response of wildtype CD8+ cells. These findings place FasL among the growing number of tumor necrosis factor superfamily members capable of bipolar signaling -- both of delivering signals through their receptors and of transducing signals inward upon ligand binding. The first goal of the proposed experiments is to explore the nature of FasL-mediated costimulation by investigating what regions of the FasL molecule are required and whether binding of FasL to molecules other than Fas can initiate reverse signaling. The second overall goal is to determine the in vivo relevance of this reverse signaling, both for mature peripheral T cells and for developing thymocytes.
The Specific Aims are as follows:
Specific Aim 1 : To determine whether the cytoplasmic tail of FasL is required for reverse signaling, to pinpoint critical residues in this domain, and to identify associated molecules.
Specific Aim 2 : To explore the in vivo role of FasL signaling in the regulation of CD8+ T cell responses and intrathymic T cell differentiation.
Specific Aim 3 : To continue to investigate FasL-mediated costimulation induced by a molecule other than Fas, and to identify and characterize this molecule by expression cloning.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI044130-02
Application #
6170702
Study Section
Special Emphasis Panel (ZRG1-ALY (02))
Program Officer
Ridge, John P
Project Start
1999-07-15
Project End
2004-06-30
Budget Start
2000-07-01
Budget End
2001-06-30
Support Year
2
Fiscal Year
2000
Total Cost
$215,122
Indirect Cost
Name
University of Washington
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
135646524
City
Seattle
State
WA
Country
United States
Zip Code
98195
Stranges, Peter B; Watson, Jessica; Cooper, Cristie J et al. (2007) Elimination of antigen-presenting cells and autoreactive T cells by Fas contributes to prevention of autoimmunity. Immunity 26:629-41
Sun, Mingyi; Lee, Shinhee; Karray, Saoussen et al. (2007) Cutting edge: two distinct motifs within the Fas ligand tail regulate Fas ligand-mediated costimulation. J Immunol 179:5639-43
Sun, Mingyi; Ames, Kristina T; Suzuki, Ivy et al. (2006) The cytoplasmic domain of Fas ligand costimulates TCR signals. J Immunol 177:1481-91
Boursalian, Tamar E; Golob, Jonathan; Soper, David M et al. (2004) Continued maturation of thymic emigrants in the periphery. Nat Immunol 5:418-25
Ali, Mohamed; Weinreich, Michael; Balcaitis, Stephanie et al. (2003) Differential regulation of peripheral CD4+ T cell tolerance induced by deletion and TCR revision. J Immunol 171:6290-6
Boursalian, Tamar E; Fink, Pamela J (2003) Mutation in fas ligand impairs maturation of thymocytes bearing moderate affinity T cell receptors. J Exp Med 198:349-60
Suzuki, I; Fink, P J (2000) The dual functions of fas ligand in the regulation of peripheral CD8+ and CD4+ T cells. Proc Natl Acad Sci U S A 97:1707-12
Suzuki, I; Martin, S; Boursalian, T E et al. (2000) Fas ligand costimulates the in vivo proliferation of CD8+ T cells. J Immunol 165:5537-43