Identification, molecular characterization and subcellular localization of a Theileria annulata parasite protein secreted into the host cell cytoplasm

Abstract

Intracellular leucoproliferative Theileria are unique as eukaryotic organisms that transform the immune cells of their ruminant host. Theileria utilize the uncontrolled proliferation for rapid multiplication and distribution into host daughter cells. The equal distribution of the schizont into the daughter cells is thought to be accomplished by a tight association with the host cell mitotic apparatus. In this study, we describe a highly conserved novel 37 kD Theileria annulata protein (TaSE). TaSE was found to be localized inside the parasite, the parasite membrane and within the host cell cytoplasm. Moreover, it co-localized at distinct points with host cell microtubules, which was especially apparent during mitosis, where co-localization was found with the centromere, the mitotic spindle and the midbody. Association of TaSE with the host cell tubulin network was corroborated by coimmunoprecipitation and transient transfection experiments. This is the first description of a theilerial protein co-localizing and potentially interacting with a host cell protein. The distribution of TaSE during mitosis makes it a protein to consider as playing a potential role for parasite distribution into daughter host cells.

Schizonts of Theileria annulata interact with the microtubuli network of their host cell via the membrane protein TaSP

“…Proteins expressed on the surface of the parasite or which are secreted by the parasite into the host cell cytoplasm are considered candidate proteins playing a potential role in host-parasite interactions. We have previously shown that the secreted parasite protein TaSE interacts with alpha-tubulin, the association being most striking at discrete structures of the tubulin network and the mitotic spindle, such as the spindle poles, the Flemming body, and the centrosome (Schneider et al 2007). Although TaSE could be co-immunoprecipitated with alpha-tubulin, only a fraction of the expressed TaSE was found to interact with alpha-tubulin, indicating that it may also be interacting indirectly with scaffold proteins or with motor proteins and exploiting this association to the parasite's end.…”

“…Recently, we could identify a secretory parasite protein which was shown to interact with alpha-tubulin as demonstrated by confocal microscopy, transient transfection, and immunoprecipitation experiments (Schneider et al 2007). A likely concept for the observation of this association and for further studies was that, since the major part of TaSE did not co-localize with alpha-tubulin and is also a secreted protein, it may not only interact with alphatubulin but indirectly with scaffold proteins or with motor proteins and exploit this association to the parasite's end.…”

Theileria-transformed bovine leukocytes have cancer hallmarks

“…T. annulata recruits endbinding protein 1, a crucial component of host microtubule regulation, to its cell surface via interactions with T. annulata polymorphic piroplasm antigen, p104 [41]. The T. annulata proteins TaSE (T. annulata secretory protein) [42] and the conserved glycosylphosphatidylinositolanchored protein gp34 [43] also localize to host microtubules, although the precise roles of these proteins are not yet well understood. Recent developments in genome-scale technologies have led to the description of human metastasis-suppressor genes with potential for therapy targeting [44].…”

Cellular and molecular interactions between the apicomplexan parasitesPlasmodiumandTheileriaand their host cells

“…The rather minor effects of heterologous expression of single parasite proteins in non-infected cell lines suggested that the transformed phenotype of infected cells is probably induced by many parasite factors rather than by a single dominant transforming parasite protein. Another secreted Theileria protein is TaSE, which appears to co-localize partly with host cell microtubules (Schneider et al, 2007). Theileria parasites are known to closely interact with host cell microtubules during mitosis, allowing passive distribution into both daughter cells and TaSE might be involved in connecting the parasite to host cell tubulin.…”

“…Heterologous expression and subsequent experiments localising TaSE in uninfected cells confirmed the association with tubulin. Localisation of TaSE to the spindle poles and the midbody in Theileria-infected cells and in transfected cells suggested an interaction of the parasite protein with important regulators of mitosis like the Aurora A kinase (Schneider et al, 2007) and it will be a major challenge for the future to prove this hypothesis.…”