CD154 (CD40 ligand) expression by activated T cells plays a central role in the immune response. As such, CD154 expression has been implicated as a major target in the treatment of rheumatic diseases and validated by the demonstrated efficacy of CD154 blockade in animal models of Rheumatoid Arthritis and Systemic Lupus Erythematosus. Furthermore, CD154 gene expression is dysregulated in patients with Systemic Lupus Erythematosus. CD 154 (CD40 ligand) expression exhibits a unique pattern of regulation relative to cytokines. These studies have directly implicated CD154 mRNA degradation. We have established that a polypyrimidine-rich region in the 3'UTR of the CD154 mRNA is necessary and sufficient to reduce chimeric reporter gene expression in both cell lines and normal human CD4+ T lymphocytes, thus identifying this region as a cis-acting element. Furthermore, we have identified two proteins that bind to this polypyrimidine-rich region as distinct splice isoforms (PTB, PTB-T) of the PTB gene. This finding suggest that these proteins are trans-acting factors that determine the function of this region in mRNA decay. Overexpression of the novel smaller splice isoform we call PTB-T, consistently inhibits reporter gene expression in a CD154 3'UWR specific manner in normal human CD4+ T lymphocytes and cell lines. ? ? These data suggest the hypothesis that PTB-T interacts with the polypyrimidine-rich region in the CD154 3'UTR to mediate mRNA degradation. We propose to directly test this hypothesis as well as determine the biologic role of PTB-T in the modulation of CD154 mRNA stability. Subsequently, we will identify the pathway(s) by which PTB-T mediates these effects. In this manner, we will functionally delineate the molecular mechanism(s) which regulate CD154 mRNA turnover in vivo and determine their contribution to the unique pattern of CD154 gene regulation as well as the immune response. These studies will generate insights important for the development of approaches that will selectively modulate CD154 expression. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR049834-03
Application #
6923738
Study Section
Special Emphasis Panel (ZRG1-GMA-1 (01))
Program Officer
Gretz, Elizabeth
Project Start
2003-07-01
Project End
2008-06-30
Budget Start
2005-07-01
Budget End
2006-06-30
Support Year
3
Fiscal Year
2005
Total Cost
$344,835
Indirect Cost
Name
Dartmouth College
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
041027822
City
Hanover
State
NH
Country
United States
Zip Code
03755
Jones, Jonathan D; Hamilton, B JoNell; Rigby, William F C (2012) Rituximab mediates loss of CD19 on B cells in the absence of cell death. Arthritis Rheum 64:3111-8
Rigby, William F C; Wu, Yee Ling; Zan, Moe et al. (2012) Increased frequency of complement C4B deficiency in rheumatoid arthritis. Arthritis Rheum 64:1338-44
Nichols, Ralph C; Botson, John; Wang, Xiao Wei et al. (2011) A flexible approach to studying post-transcriptional gene regulation in stably transfected mammalian cells. Mol Biotechnol 48:210-7
Hamilton, B JoNell; Wang, Xiao-Wei; Collins, Jane et al. (2008) Separate cis-trans pathways post-transcriptionally regulate murine CD154 (CD40 ligand) expression: a novel function for CA repeats in the 3'-untranslated region. J Biol Chem 283:25606-16
Rigby, William F C; Roy, Kristen; Collins, Jane et al. (2005) Structure/function analysis of tristetraprolin (TTP): p38 stress-activated protein kinase and lipopolysaccharide stimulation do not alter TTP function. J Immunol 174:7883-93