Recruitment of EB1, a Master Regulator of Microtubule Dynamics, to the Surface of the Theileria annulata Schizont

Abstract

The apicomplexan parasite Theileria annulata transforms infected host cells, inducing uncontrolled proliferation and clonal expansion of the parasitized cell population. Shortly after sporozoite entry into the target cell, the surrounding host cell membrane is dissolved and an array of host cell microtubules (MTs) surrounds the parasite, which develops into the transforming schizont. The latter does not egress to invade and transform other cells. Instead, it remains tethered to host cell MTs and, during mitosis and cytokinesis, engages the cell's astral and central spindle MTs to secure its distribution between the two daughter cells. The molecular mechanism by which the schizont recruits and stabilizes host cell MTs is not known. MT minus ends are mostly anchored in the MT organizing center, while the plus ends explore the cellular space, switching constantly between phases of growth and shrinkage (called dynamic instability). Assuming the plus ends of growing MTs provide the first point of contact with the parasite, we focused on the complex protein machinery associated with these structures. We now report how the schizont recruits end-binding protein 1 (EB1), a central component of the MT plus end protein interaction network and key regulator of host cell MT dynamics. Using a range of in vitro experiments, we demonstrate that T. annulata p104, a polymorphic antigen expressed on the schizont surface, functions as a genuine EB1-binding protein and can recruit EB1 in the absence of any other parasite proteins. Binding strictly depends on a consensus SxIP motif located in a highly disordered C-terminal region of p104. We further show that parasite interaction with host cell EB1 is cell cycle regulated. This is the first description of a pathogen-encoded protein to interact with EB1 via a bona-fide SxIP motif. Our findings provide important new insight into the mode of interaction between Theileria and the host cell cytoskeleton.

Variation in clinical markers in cattle naturally infected with bovine tropical theileriosis

“…Another significant finding of BTT viz., anemia is contributed to overproduction of cytokines, immune-mediated hemolysis and reactive oxygen species (Nazifi et al 2009;Saleh et al 2011). The T. annulata infected cells undergo clonal expansion resulting in lymphoproliferation or lymphoadenopathy (Woods et al 2013). Cells infected with T. annulata also produce high levels of inflammatory cytokines (Brown et al 1995) which account for all the major clinical symptoms like pyrexia, anaemia, anorexia, muscle wasting and necrosis (Graham et al 2001).…”

Theileria highjacks JNK2 into a complex with the macroschizont GPI (GlycosylPhosphatidylInositol)-anchored surface protein p104

“…The conserved JNK‐binding motif in p104 is distal to the previously described EB1‐binding motif (SKIP) that is located between amino acids 566 and 569 (Woods et al, ). It is highly unlikely therefore that the JNK‐binding motif penetrating peptide competes for EB1‐binding.…”

“…It is highly unlikely therefore that the JNK‐binding motif penetrating peptide competes for EB1‐binding. Furthermore, EB1 colocalizes with p104 on the macroschizont surface in a cell cycle‐dependent manner, being more pronounced during cell division (Woods et al, ). This contrasts with JNK2‐binding to p104 that does not require division of infected macrophages.…”

Theileria-transformed bovine leukocytes have cancer hallmarks

“…Theileria parasites have been shown to have a close association with host microtubules, which play a crucial role in metastasis [40]. 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.…”