Intracellular Theileria annulata Promote Invasive Cell Motility through Kinase Regulation of the Host Actin

The intracellular, protozoan Theileria species parasites are the only eukaryotes known to transform another eukaryotic cell. One consequence of this parasite-dependent transformation is the acquisition of motile and invasive properties of parasitized cells in vitro and their metastatic dissemination in the animal, which causes East Coast Fever (T. parva) or Tropical Theileriosis (T. annulata). These motile and invasive properties of infected host cells are enabled by parasite-dependent, poorly understood F-actin dynamics that control host cell membrane protrusions. Herein, we dissected functional and structural alterations that cause acquired motility and invasiveness of T. annulata-infected cells, to understand the molecular basis driving cell dissemination in Tropical Theileriosis. We found that chronic induction of TNFa by the parasite contributes to motility and invasiveness of parasitized host cells. We show that TNFa does so by specifically targeting expression and function of the host proto-oncogenic ser/thr kinase MAP4K4. Blocking either TNFa secretion or MAP4K4 expression dampens the formation of polar, F-actin-rich invasion structures and impairs cell motility in 3D. We identified the F-actin binding ERM family proteins as MAP4K4 downstream effectors in this process because TNFa-induced ERM activation and cell invasiveness are sensitive to MAP4K4 depletion. MAP4K4 expression in infected cells is induced by TNFa-JNK signalling and maintained by the inhibition of translational repression, whereby both effects are parasite dependent. Thus, parasite-induced TNFa promotes invasive motility of infected cells through the activation of MAP4K4, an evolutionary conserve