The src-related protein tyrosine kinase p56(lck) is thought to be important in regulating maturation and functional responsiveness of T cells and thymocytes. In the present studies we report that expression of p56(lck) is suppressed during apoptosis. Using primary cultures of rat thymocytes, we found that agents that are effective in inducing apoptosis, including okadaic acid, dexamethasone, and antibodies to the CD3 receptor, also deplete cells of p56(lck). This process is rapid, occurring within 24 h, and is not due to cytotoxicity. Inhibition of DNA fragmentation in apoptotic cells with the endonuclease inhibitor ZnCl2 failed to prevent depletion of p56(lck), suggesting that it was not a consequence of the DNA degradation process. Using the thymic lymphoma cell line LSTRA, apoptosis was also associated with cellular depletion of p56(lck) In contrast to thymocytes, this process required 48-72 h possibly because these cells overexpress p56(lck). Although at this time we are uncertain as to the precise role of p56(lck) in the process of apoptosis, our results indicate that changes in the expression of this protein in thymocytes is an important marker of programmed cell death.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy
- Cell Biology
- DNA degradation
- Protein tyrosine