CD5, a lymphocyte-specific cell-surface molecule, can provide the accessory signals necessary to permit antigen receptor (CD3/Ti)-mediated activation of resting peripheral T lymphocytes. Signal transduction by CD3/Ti involves the hydrolysis of membrane polyphosphoinositides (PPI) with the generation of inositol phosphates (InsPs) and diacylglycerol. We observe that perturbation of CD5 substantially augments CD3/Ti- mediated generations of InsPs and allows an otherwise transient InsP response to be sustained. In the absence of other stimuli, perturbation of CD5 does not change InsP levels but does have selective effects on phosphatidylinositol phosphate (PIP) and bisphosphate (PIP2). These observations suggest that CD5 may increase the activity of either the PI kinase, or the PIP kinase, thereby increasing the levels of PPI and augmenting CD3/Ti- induced generation of InsPs. To test this hypothesis, the effects of stimulating CD5 and CD3/Ti, individually and in combination, on the mass of PI, PIP, PIP2, and diacylglycerol will be examined. Using membranes prepared from T cells, we will determine whether stimulation of CD5 enhances the incorporation of 32p from (32p) ATP into PIP and PIP2 and whether guanine nucleotides can regulate this process. The possibilities that CD5 is physically associated with a PI/PIP kinase and that CD5 can functionally interact with PI/PIP kinases will be examined using immunoprecitated CD5 and partially purified PI and PIP kinase preparations. By transfecting non-lymphoid cells with the CD5 gene, we will determine whether CD5 can regulate PPI levels in non-lymphoid cells and whether CD5 can augment InsP generation by receptors other than CD3/Ti. Because the the cytoplasmic domain of CD5 contains three tyrosine residues, we will determine whether tyrosine phosphorylation of CD5 occurs during T cell activation. If so, phenylalanine will be substituted for tyrosine, and the consequences of this substitution on the ability of CD5 to regulate PPI will be determined. The general aims of these studies are to understand the molecular mechanisms by which CD5 regulates PIP and PIP2 and to provide insights into the regulation of inositol phospholipid metabolism during T cell activation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI026644-04
Application #
3140483
Study Section
Special Emphasis Panel (SRC (64))
Project Start
1988-08-01
Project End
1993-07-31
Budget Start
1991-08-01
Budget End
1992-07-31
Support Year
4
Fiscal Year
1991
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Medicine
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Sadra, Ali; Cinek, Tomas; Imboden, John B (2004) Translocation of CD28 to lipid rafts and costimulation of IL-2. Proc Natl Acad Sci U S A 101:11422-7
Chikuma, Shunsuke; Imboden, John B; Bluestone, Jeffrey A (2003) Negative regulation of T cell receptor-lipid raft interaction by cytotoxic T lymphocyte-associated antigen 4. J Exp Med 197:129-35
Cinek, T; Sadra, A; Imboden, J B (2000) Cutting edge: tyrosine-independent transmission of inhibitory signals by CTLA-4. J Immunol 164:8-May
Sadra, A; Cinek, T; Imboden, J B (2000) Multiple probing of an immunoblot membrane using a non-block technique: advantages in speed and sensitivity. Anal Biochem 278:235-7
Sadra, A; Cinek, T; Arellano, J L et al. (1999) Identification of tyrosine phosphorylation sites in the CD28 cytoplasmic domain and their role in the costimulation of Jurkat T cells. J Immunol 162:1966-73
Barz, C; Nagel, T; Truitt, K E et al. (1998) Mutational analysis of CD28-mediated costimulation of Jun-N-terminal kinase and IL-2 production. J Immunol 161:5366-72
Truitt, K E; Nagel, T; Suen, L F et al. (1996) Structural requirements for CD28-mediated costimulation of IL-2 production in Jurkat T cells. J Immunol 156:4539-41
Truitt, K E; Shi, J; Gibson, S et al. (1995) CD28 delivers costimulatory signals independently of its association with phosphatidylinositol 3-kinase. J Immunol 155:4702-10
Truitt, K E; Hicks, C M; Imboden, J B (1994) Stimulation of CD28 triggers an association between CD28 and phosphatidylinositol 3-kinase in Jurkat T cells. J Exp Med 179:1071-6
Truitt, K E; Mills, G B; Turck, C W et al. (1994) SH2-dependent association of phosphatidylinositol 3'-kinase 85-kDa regulatory subunit with the interleukin-2 receptor beta chain. J Biol Chem 269:5937-43

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