After infection with sporozoites of the protozoon Theileria
(Tp) bovine T cells are readily transformed to permanent
growth in vivo and in vitro. Their transformed state
depends on the constant presence of the parasite but membrane signals
remain important. Non-receptor tyrosine kinases play a critical role in
the transduction of membrane signals in haematopoietic cells.
We have investigated Src-family kinases in bovine T cells transformed by
Tp. The T cell receptor-associated tyrosine kinase p60fyn
had high activity in all cell lines tested. In addition, weak phosphorylation
of 2 novel bands was
observed associated with Fyn. In contrast to Fyn, enzymatic activity of
p56lck, which in T cells has an essential role in
signalling, was low. Furthermore, 1 of 3 Tp transformed cell
lines was completely devoid of p56lck indicating that
enzyme is not necessary for the Tp dependent growth of the T cells.
In addition to
p60fyn and p56lck weak enzymatic
activity of 1 splice variant of p53/56lyn
was observed after infection of T cells with Tp. These data show
transformation by Tp influences kinase activity in bovine T cells. However,
they also prove that p56lck does not play an
essential role in the transformation mechanism.