The functional identification, biochemical purification and cloning of a novel cytosolic serine protease, QPP (Quiescent Proline di-Peptidase), which prevents quiescent lymphocytes from undergoing programmed cell death (PCD) forms the basis for the working hypothesis that apoptosis is blocked in resting lymphocytes by an active mechanism. QPP seems to be essential for the survival of resting T and B cells, because specific inhibition of this enzyme leads to activation of cellular caspases and PCD. The goals of this proposal are to substantiate these intriguing observations and to define the apoptosis pathway in G/o lymphocytes. I. to directly analyze the role of QPP in lymphocyte, a dominant negative (DN) variant will be constructed by mutating its catalytic site(s) such that it still binds its specific substrate, but no longer cleaves it. Wild type and DN QPP constructs will be expressed in vitro in cell lines and primary T cells, as well as in vivo by the use of the RAG-2 blastocyst ES complementation system. II. To understand the functional significance of QPP in the protection of lymphocytes from PCD, its physiological substrate(s) has to be identified. Two approaches will be used: i) rDN QPP protein as affinity matrix to extract the substrate from lymphocyte lysate; and ii) the yeast-two hybrid system with the DN QPP as bait for screening a lymphocyte cDNA library. The proteins identified by these methods will be verified as substrates of QPP by their susceptibility to cleavage by wild type enzyme, followed by N- terminal sequence analysis. III. Preliminary data indicate that the caspase cascade initiated in quiescent lymphocytes by blocking QPP differs significantly from other well characterized apoptotic pathways in these cells, such as irradiation- or Fas-induced PCD. Radioactively labeled zVADfmk, an irreversible caspase inhibitor, will be used as an active site-directed affinity reagent, in conjunction with 2D gel analysis, to identify the caspase(s) involved. IV. All cells tested so far contain a protease activity that resembles QPP in its blots, namely, a band of 1.7 kB that is expressed in all tissues and a band of 2.5 kB that is seen mainly in lymphoid cells and pancreas. Furthermore, the sequencing of QPP ESTs revealed clones that contain internal sequence gaps. Thus, it will be determined whether this enzyme is differentially spliced and/of differentially modified in a tissue specific manner. Taken together, these studies will provide new insights into the maintenance of homeostasis of resting lymphocytes in the immune system.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI043469-03
Application #
6362360
Study Section
Immunobiology Study Section (IMB)
Program Officer
Deckhut Augustine, Alison M
Project Start
1999-03-01
Project End
2003-02-28
Budget Start
2001-03-01
Budget End
2003-02-28
Support Year
3
Fiscal Year
2001
Total Cost
$293,098
Indirect Cost
Name
Tufts University
Department
Pathology
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02111
Mele, Deanna A; Sampson, James F; Huber, Brigitte T (2011) Th17 differentiation is the default program for DPP2-deficient T-cell differentiation. Eur J Immunol 41:1583-93
Danilov, Alexey V; Danilova, Olga V; Brown, Jennifer R et al. (2010) Dipeptidyl peptidase 2 apoptosis assay determines the B-cell activation stage and predicts prognosis in chronic lymphocytic leukemia. Exp Hematol 38:1167-77
Mele, Deanna A; Bista, Pradeep; Baez, Diana Velez et al. (2009) Dipeptidyl peptidase 2 is an essential survival factor in the regulation of cell quiescence. Cell Cycle 8:2425-34
Rockwell, Karen R; Huber, Brigitte T (2009) Biologically distinct conformations of Bcl-x can be resolved using 2D isoelectric focusing. Mol Immunol 46:1605-12
Danilova, Olga V; Tai, Albert K; Mele, Deanna A et al. (2009) Neurogenin 3-specific dipeptidyl peptidase-2 deficiency causes impaired glucose tolerance, insulin resistance, and visceral obesity. Endocrinology 150:5240-8
Bista, Pradeep; Mele, Deanna A; Baez, Diana Velez et al. (2008) Lymphocyte quiescence factor Dpp2 is transcriptionally activated by KLF2 and TOB1. Mol Immunol 45:3618-23
Danilova, Olga; Li, Bei; Szardenings, A Katrin et al. (2007) Synthesis and activity of a potent, specific azabicyclo[3.3.0]-octane-based DPP II inhibitor. Bioorg Med Chem Lett 17:507-10
Danilov, Alexey V; Klein, Andreas K; Lee, Henry J et al. (2005) Differential control of G0 programme in chronic lymphocytic leukaemia: a novel prognostic factor. Br J Haematol 128:472-81
Denis, Maria C; Huber, Brigitte T (2003) Native and recombinant interleukin-2, two functionally distinct molecules. Mol Immunol 40:279-86
Seward, Robert J; von Haller, Priska D; Aebersold, Ruedi et al. (2003) Phosphorylation of the pro-apoptotic protein Bim in lymphocytes is associated with protection from apoptosis. Mol Immunol 39:983-93

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