Evidence for the involvement of tyrosine kinase ZAP 70 in nuclear retinoid receptor-dependent transactivation in T lymphocytes.
Retinoic acid receptors (RARs) and retinoid X receptors (RXRs) are transcription factors that control diverse cellular functions during development and homeostasis. The biochemical role of these proteins in T lymphocytes is not well known. Here we have studied the role of protein-tyrosine kinase ZAP 70, a key enzyme involved in the proximal signaling events during T cell activation, in the modulation of RXRE- and RARE-dependent activation in T lymphocytes. Surprisingly, ZAP 70-negative Jurkat T cells showed considerable loss of both RXRE- and RARE-mediated transactivation as compared with wild type Jurkat cells. In addition, ZAP 70-negative cells failed to exhibit normal protein kinase C and calcineurin-induced transcriptional activity. ZAP 70-negative cells that were reconstituted with active ZAP 70 regained the transactivation function, whereas cells expressing kinase-dead form of ZAP 70 failed to do so. Defective transcriptional activation was also observed in actively proliferating human peripheral blood T lymphocytes in which RNA interference was used to induce loss of ZAP 70 expression. In addition, an Lck-deficient Jurkat cell line that cannot efficiently activate ZAP 70 was also found defective in RXRE-mediated transcription. Finally, RNA interference-induced loss of ZAP 70 or Lck protein in Jurkat cells resulted in significant decrease in the RXRE-dependent activation. Together, these results suggest a novel functional role for ZAP 70 in nuclear receptor-driven transactivation in T lymphocytes.
Ishaq
Mohammad
M
Laboratory of Molecular Cell Biology, SAIC, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA. mishaq@nih.gov
DeGray
Gerald
G
Natarajan
Ven
V
D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D047488:Retinoid X Receptors / Q000502:physiology*; D013601:T-Lymphocytes / Q000201:enzymology* / Q000502:physiology; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000378:metabolism*
D047488:Retinoid X Receptors; D051746:ZAP-70 Protein-Tyrosine Kinase