passages.id: 8051172__text
passages.type: abstract
passages.text: ZAP-70 tyrosine kinase, CD45, and T cell receptor involvement in UV- and H2O2-induced T cell signal transduction. 
  Several mammalian responses to UV irradiation, including the activation of NF-kappa B, are believed to involve tyrosine phosphorylation. UV irradiation and H2O2 treatment of T lymphocytes induce protein tyrosine phosphorylation and Ca2+ signals similar to those observed following biological stimulation. We have examined the role of cell surface molecules in these responses. Normal T lymphocytes whose surface expression of CD3 was depleted showed impaired UV-induced tyrosine phosphorylation and Ca2+ signals. Similarly, Jurkat T cell lines deficient in CD3 or CD45 expression also gave impaired UV responses. However, all these cell types still gave strong Ca2+ and tyrosine phosphorylation responses to H2O2. The T cell tyrosine kinase ZAP-70 was found to be highly responsive to UV and H2O2 treatment. ZAP-70 responsiveness to UV required expression of both CD3 and CD45, whereas only CD3 was required for the response to H2O2. UV-induced activation of NF-kappa B was blocked by CD3 depletion, indicating the importance of such cell surface molecules in biological responses to UV. In nonlymphoid cells, the epidermal growth factor receptor displayed increased tyrosine phosphorylation within seconds of UV irradiation. These results suggest that UV-induced signal transduction is mediated via cell surface receptors that normally respond to biological stimulation, whereas H2O2 is able to partially bypass this requirement. 