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PLC gamma 1, a possible mediator of T cell receptor function
1Division of Immunogenetics, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
The Journal of Biological Chemistry
|September 5, 1991
Summary
T cell activation triggers phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis via phospholipase C (PLC) gamma 1. This process involves tyrosine phosphorylation of PLC gamma 1, negatively regulated by protein kinase C (PKC) and protein kinase A (PKA).
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- T cell antigen receptor (TCR/CD3) stimulation initiates phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis.
- The specific phospholipase C (PLC) enzyme responsible for this T cell activation-induced PIP2 hydrolysis remains unidentified.
Purpose of the Study:
- To identify the PLC enzyme involved in TCR/CD3-mediated PIP2 hydrolysis in human T cells.
- To investigate the regulatory mechanisms, including phosphorylation, governing PLC activity during T cell activation.
Main Methods:
- Western blotting to detect PLC gamma 1 protein expression and phosphorylation.
- Enzyme assays measuring PLC activity using anti-phosphotyrosine antibodies.
- Calcium (Ca2+) mobilization assays.
- Pharmacological manipulation using forskolin, phorbol ester, and genistein.
Main Results:
- PLC gamma 1 protein is expressed in human T cells and is a phosphoprotein.
- CD3 stimulation induces tyrosine phosphorylation of PLC gamma 1, significantly increasing PLC activity.
- Inhibition of tyrosine kinases with genistein reduces PLC activity and Ca2+ mobilization.
- Pre-treatment with PKC or PKA activators decreases CD3-induced tyrosine phosphorylation of PLC gamma 1 and subsequent PLC activity.
Conclusions:
- CD3 stimulation activates PIP2 hydrolysis through tyrosine phosphorylation of PLC gamma 1.
- Protein kinase C (PKC) and protein kinase A (PKA) negatively regulate this process, suggesting a complex signaling network controlling T cell activation-induced lipid hydrolysis.