Abstract
BackgroundTheileria annulata is a protozoan parasite that can infect and transform bovine B cells, macrophages, and dendritic cells. The mechanism of the transformation is still not well understood, and some parasite molecules have been identified, which contribute to cell proliferation by regulating host signaling pathways. Subtelomeric variable secreted proteins (SVSPs) of Theileria might affect the host cell phenotype, but its function is still not clear. Therefore, in the present study, we explored the interactions of SVSP454 with host cell proteins to investigate the molecular mechanism of T. annulata interaction with host cells.MethodsThe transcription level of an SVSP protein from T. annulata, SVSP454, was analyzed between different life stages and transformed cell passages using qRT-PCR. Then, SVSP454 was used as a bait to screen its interacting proteins from the bovine B cell cDNA library using a yeast two-hybrid (Y2H) system. The potential interacting proteins of host cells with SVSP454 were further identified by using a coimmunoprecipitation (Co-IP) and bimolecular fluorescence complementation (BiFC) assays.ResultsSVSP454 was transcribed in all three life stages of T. annulata but had the highest transcription during the schizont stage. However, the transcription level of SVSP454 continuously decreased as the cultures passaged. Two proteins, Bos Taurus coiled-coil domain 181 (CCDC181) and Bos Taurus mitochondrial ribosomal protein L30 (MRPL30), were screened. The proteins CCDC181 and MRPL30 of the host were further identified to directly interact with SVSP454.ConclusionIn the present study, SVSP454 was used as a bait plasmid, and its prey proteins CCDC181 and MRPL30 were screened out by using a Y2H system. Then, we demonstrated that SVSP454 directly interacted with both CCDC181 and MRPL30 by Co-IP and BiFC assays. Therefore, we speculate that SVSP454-CCDC181/SVSP454MRPL30 is an interacting axis that regulates the microtubule network and translation process of the host by some vital signaling molecules. Identification of the interaction of SVSP454 with CCDC181 and MRPL30 will help illustrate the transformation mechanisms induced by T. annulata.Graphic abstract
Highlights
Theileria annulata is a protozoan parasite that can infect and transform bovine B cells, macrophages, and dendritic cells
We demonstrated that SVSP454 interacts with both CCDC181 and mitochondrial ribosomal protein L30 (MRPL30) using a coimmunoprecipitation (Co-IP) assay
The results showed that the sizes of the colonies for the SVSP454 bait plasmid grown on the SDO and SDO/X plates were similar to those of the colonies with the empty vector incubated on the same plates (Fig. 5a)
Summary
Theileria annulata is a protozoan parasite that can infect and transform bovine B cells, macrophages, and dendritic cells. Theileria annulata together with T. parva are referred to as “transforming species” for their ability to induce the uncontrolled proliferation of infected cells [2]. The target cells of these two T. species are different, where T. annulata mainly infects B cells, macrophages and dendritic cells, while T. parva invades T and B lymphocytes. Infection of both parasites could cause acute lymphoproliferative disease, which shares some clinical characteristics with human leukemias [3]. The transformation induced by T. annulata is reversible, once the cells are treated with a theilericidal drug, they lose cancer-like characteristics and undergo the programmed apoptosis [7]
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