Volume 8 Issue 1, March 1998: 33-39
ORIGINAL ARTICLES
Trichosanthin inhibits T cell activation by interfering with the recruitment of ZAP-70 to CD3 zeta chain.
Hong J, Fu SL, Shen ZY, Lu PH, Chou KY.
Shanghai Institute of Immunology, Shanghai Second Medical University, China
Correspondence: Chou KY(my@shsmu.edu.cn)
Plant protein Trichosanthin (Tk) has been shown in our previous experiments to suppress antigenic response of T cells. Here we explored its inhibitory mechanisms on the proliferation of human Jurkat leukemia T cell triggered by anti-CD3 McAb. By examination of tyrosine phosphorylation of cell lysate, we were able to show that Tk could interfere with the PTK-related activity in the TCR/CD3-initiated signal transduction in addition to blocking the phosphorylation of PKC. As shown in our experiment, the expression intensity of ZAP-70, a kind of protein tyrosine kinase, was not changed but its phosphorylation could be inhibited. When physical link between CD3 zeta chain and ZAP-70 was further examined by using coimmunoprecipitation after pluse-treatment of the cell line with Tk, the anti-CD3 McAb-induced recruitment of ZAP-70 to CD3 zeta chain was observed to be blocked in some extent. This may account for, at least in part, how Trichosanthin was able to inhibit the TCR-triggered T cell proliferation.
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