Identification of a novel interaction between Theileria Prohibitin (TaPHB-1) and bovine RUVBL-1

Bovine tropical theileriosis causes huge economic loss worldwide. It is a tick borne disease of bovine caused by the parasite Theileria annulata. T. annulata is an intracellular parasite that belongs to the phylum Apicomplexa.The sporozoites of T. annulata re released by the tick into the bloodstream of the host during the blood meal that invades bovine B cells, macrophages, or monocytes. This infection leads to the transformation of the host cells and brings cancer-like phenotype in the host cells. The parasite proteins play a vital role in the transformation of the host cell. However, the parasite factors involved in the host cell transformation are not well explored. Previously, Ta PIN1, a peptidyl-prolyl isomerase of T. annulata, was shown to be secreted to the host cytosol and play a role in the host cell transformation. The present study was carried out to explore the parasite-host interactions that may play an important role in the host cell transformation. We identified the parasite proteins that are expressed in the schizont stage with a signal peptide. We narrow down our search to a parasite prohibitin. The in silico analysis of T. annulata prohibitin (TA04375, Ta PHB-1) showed that Ta PHB-1 shares homology with the mammalian prohibitin 1. With the localization experiments, we confirmed that Ta PHB-1 is exported to the parasite surface and also to the host cell cytosol. Further, we observed that the localization of host prohibitin differs in the parasite-infected cells and could not be reverted back by the elimination of the parasite in the infected cells. We found through the yeast-two-hybrid studies that bovine RUVBL1 (BoRUVBL-1) interacts with Ta PHB-1. The interaction between BoRUVBL1 and Ta PHB-1 was predominantly observed on the parasite surface in the infected bovine cells. The interaction was further confirmed with immunoprecipitation and LC-MS/MS analysis. Further, the LC-MS/MS based Ta PHB-1 interactome study reveals that it interacts with proteins that regulate actin cytoskeleton organization, protein folding, mRNA processing, and metabolic processes. Our finding suggests that the parasite releases prohibitin protein into the cytoplasm of the host cell where it interacts with the host RUVBL-1. This finding has implications not only in the understanding of Theileria parasite biology in greater depth but also in the cancer biology where previously differential localization of prohibitin proteins was observed but its interaction partner was not known. ### Competing Interest Statement The authors have declared no competing interest.