Engagement of T-cell receptor (TcR)/CD3 complexes on T-cells rapidly provokes tyrosine phosphorylation of cellular proteins, which is thought to be an essential step to the following events of T-cell activation. p56lck, a member of src-related, non-receptor type protein tyrosine kinases, is expressed predominantly in lymphocytes. Accumulating data suggest that p56lck is one of the kinases responsible for TcR-mediated protein tyrosine phosphorylation. To investigate the role of p56lck in TcR-signaling in detail, we injected anti-Lck monoclonal antibody (mAb), MOL171 or MOL294, both specfically suppress Lck kinase activity in vitro, into Jurkat T-cells by the erythrocyte-ghost procedure in order to block the activity of p56lck. In Jurkat cells injected with anti-Lck mAb, intracellular Ca2+ mobilization induced by TcR-stimulation was markedly reduced in comparison with control mouse IgG-injected samples. This block of Ca2+ influx seems to be specific for TcR-signaling because anti-Lck mAb-injection did not cause significant suppression of phytohaemagglutinin-induced Ca2+ increase. Furthermore, injection of anti-Lck mAb inhibited TcR-mediated protein tyrosine phosphorylation of 100 kDa protein and phospholipase Cγ1. These results confirm that p56lck is an indispensable element of TcR-signaling and p100 and phospholipase Cγ1 are strongly presumed to be candidates for substrates for p56lck.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology