A schizont-derived protein, TpSCOP, is involved in the activation of NF-kappaB in Theileria parva-infected lymphocytes.

Theileria parva is a tick-transmitted intracellular protozoan parasite that causes East Coast fever, a fatal bovine lymphoproliferative disease. The molecular mechanisms that underlie host cell transformation by T. parva schizonts have been studied extensively, and it is known that the nuclear factor-kappa B (NF-kappaB) is activated in schizont-infected cells, making T. parva-transformed cells resistant to apoptosis. However, the mechanism by which the parasite triggers the activation of NF-kappaB remains enigmatic. In the present study, we biochemically characterized a novel protein, which we termed TpSCOP (T. parvaschizont-derived cytoskeleton-binding protein), which is expressed in the schizont stage of T. parva. TpSCOP was shown to interact with F-actin in vitro. Expression of TpSCOP in a murine lymphocytic cell line resulted in the activation of NF-kappaB signaling pathways, leading to apoptosis resistance. The activation of mitogen-activated protein kinase (MAPK), including extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), was also detected. Furthermore, the introduction of TpSCOP into T. parva-infected cells also enhanced the activation of NF-kappaB. This is the first report to demonstrate that a parasite-derived molecule has the ability to activate the host NF-kappaB pathway. Based on these results, TpSCOP likely plays an important role in apoptosis inhibition during Theileria infection.