Theileria parasites subvert E2F signaling to stimulate leukocyte proliferation

Kyle Tretina,Donald P Knowles,Vishvanath M Nene,Arnab Pain,Marie Chaussepied,Sara Mfarrej,Takaya Sakura,Lindsay Fry,Doron Ginsberg,Claudia A Daubenberger,Gordon Langsley,Joana C Silva,Richard P Bishop,Sally A Madsen-Bouterse,Malak Haidar

doi:10.1038/s41598-020-60939-x

Abstract

Intracellular pathogens have evolved intricate mechanisms to subvert host cell signaling pathways and ensure their own propagation. A lineage of the protozoan parasite genus Theileria infects bovine leukocytes and induces their uncontrolled proliferation causing a leukemia-like disease. Given the importance of E2F transcription factors in mammalian cell cycle regulation, we investigated the role of E2F signaling in Theileria-induced host cell proliferation. Using comparative genomics and surface plasmon resonance, we identified parasite-derived peptides that have the sequence-specific ability to increase E2F signaling by binding E2F negative regulator Retinoblastoma-1 (RB). Using these peptides as a tool to probe host E2F signaling, we show that the disruption of RB complexes ex vivo leads to activation of E2F-driven transcription and increased leukocyte proliferation in an infection-dependent manner. This result is consistent with existing models and, together, they support a critical role of E2F signaling for Theileria-induced host cell proliferation, and its potential direct manipulation by one or more parasite proteins.

Highlights

Uninfected controls[8]; the functional role of E2F signaling in Theileria-induced host cell proliferation has not yet been thoroughly characterized
We discovered a peptide derived from a parasite protein that has the sequence-specific and infection-specific ability to increase host E2F signaling by binding to the Retinoblastoma-1 (RB), a negative regulator of E2F signaling, and thereby contributing to host cell hyper-proliferation
This pipeline was based on the rationale that such peptide motifs have all of the following attributes: (i) are in proteins predicted to be exposed to the host, (ii) are present in host-transforming Theileria species (T. parva and T. annulata), and (iii) are found in proteins that are expressed in the schizont life-cycle stage based on RNA-seq data

Summary

Introduction

Uninfected controls[8]; the functional role of E2F signaling in Theileria-induced host cell proliferation has not yet been thoroughly characterized. We leveraged a comparative genomics approach to predict parasite protein sequences that are potentially involved in the Theileria-induced transformation of host leukocytes. We discovered a peptide derived from a parasite protein that has the sequence-specific and infection-specific ability to increase host E2F signaling by binding to the Retinoblastoma-1 (RB), a negative regulator of E2F signaling, and thereby contributing to host cell hyper-proliferation. Cumulative evidence to date demonstrates the critical role of the RB/E2F signaling axis in Theileria host cell proliferation, and suggests a mechanism by which one or more parasite proteins could manipulate E2F signaling

Methods

Results

Conclusion