Publikationsdatenbank

Molecular mechanisms of Theileria annulata host cell transformation and drug resistance (2025)

Art

Hochschulschrift

Autor

Tajeri, Shahin (WE 13)

Quelle

Berlin: Mensch und Buch Verlag, 2025 — V, 103 Seiten

ISBN: 978-3-96729-290-9

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/48382

Kontakt

Institut für Parasitologie und Tropenveterinärmedizin

Robert-von-Ostertag-Str. 7-13
14163 Berlin
+49 30 838 62310
parasitologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

In tropical theileriosis of cattle, the major driver of pathology is the transformation of host macrophagesby the intracellular apicomplexan parasite Theileria annulata. In Theileria-transformed leukocytes, several oncogene-associated signaling pathways including Activator Protein 1 (AP-1) and NF-κB, are constitutively activated in a parasite-dependent manner. These pathways are essential for proliferation, dissemination and resistance to apoptosis in infected cells. The exact mechanisms employed by Theileria to constitutively activate these pathways is not fully known. Taking other Apicomplexans such as Toxoplasma gondii and Plasmodium falciparum as models, Theileria might achieve this via secretion of effector proteins. Here we studied the contribution of a secreted T. annulata effector protein Ta9 to the transcriptional de-regulation of bovine macrophage genes by performing RNA-seq on macrophages that stably expressed Ta9. Ta9 was previously shown to be capable of stimulating AP-1-driven transcription when introduced into human HEK cells in luciferase reporter assays. RNA-seq analysis revealed that Ta9 affected the expression of 560 (400 upregulated and 160 downregulated) bovine genes that included oncogenes, tumor suppressor genes and inflammation-associated genes previously known or hypothesized to be involved in the pathogenesis of tropical theileriosis. Example genes include FRA1, IL-6, TGFß1, TNFɑ, MMP2 and the proto-oncogene haematopoetic cell kinase (HCK). We further characterized the contribution of HCK to the Theileria-induced leukocyte transformation by using a selective HCK inhibitor (A419219) in cell proliferation and transformation (soft agar colony formation) assays. HCK belongs to the SRC family of non-receptor tyrosine kinases that is constitutively active in T. parvatransformed B cells and contributes to AP-1-driven transcription (similar to Ta9). This raised the possibility that Ta9 might do so by augmenting HCK signaling. Indeed, Ta9-mediated upregulation of hck (as detected first by RNA-seq) was confirmed by qRT-PCR and the increase in protein levels by immunofluorescence (IF). Furthermore, Ta9-expressing cells grew membrane protrusions and microspikes. These results were consistent with Ta9 potentially augmenting HCK activity in the cells and treatment of T. annulata-infected macrophages with A419219 negatively impacted on the parasite-dependent transformed phenotype. A419219 could also block proliferation of sheep leukocytes transformed by another acutely pathogenic Theileria species, T. lestoquardi. Buparvaquone is currently the only drug in the market to treat T. annulata, T. lestoquardi and T. parva infections, however resistance is spreading worldwide and the need to for a drug to replace buparvaquone is rising. Due to the therapeutic effect that HCK inhibition showed against T.annulata- and T. lestoquardi-transformed leukocytes in our hands, as a parallel part of this project we generated buparvaquone-resistant T. annulata parasites and tested whether A419219 could block the proliferation of macrophages that harbored resistant parasites. As expected, A419219 was equally effective against macrophages containing buparvaquone-resistant parasites. Past studies have reported susceptibility of T. parva transformed leukocytes to Src kinase inhibitors and herein we have extended that reports to T. annulata and T. lestoquardi infections and to buparvaquone-resistant T. annulata parasites. Therefore, the ensemble highlights the importance of Src kinases as potential targets for the consideration in the development of the next generation of therapies against theileriosis.