Activation of a Neospora caninum EGFR-Like Kinase Facilitates Intracellular Parasite Proliferation.

Yanhui Yu,Pengtao Gong,Guojiang Li,Jianhua Li,Xiaoxia Jin,Xichen Zhang

doi:10.3389/fmicb.2017.01980

Abstract

The Apicomplexan parasite Neospora caninum, an obligate intracellular protozoan, causes serious diseases in a number of mammalian species, especially in cattle. Infection with N. caninum is associated with abortions in both dairy and beef cattle worldwide which have a major economic impact on the cattle industry. However, the mechanism by which N. caninum proliferates within host cells is poorly understood. Epidermal growth factor receptor (EGFR) is a protein kinase ubiquitously expressed, present on cell surfaces in numerous species, which has been confirmed to be essential in signal transduction involved in cell growth, proliferation, survival, and many other intracellular processes. However, the presence of EGFR in N. caninum and its role in N. caninum proliferation remain unclear. In the present study, we identified a putative EGFR-like kinase in N. caninum, which could be activated in tachyzoites by infection or treatment with rNcMIC3 [containing four epidermal growth factor (EGF) domains] or human EGF. Blockade of EGFR-like in tachyzoites by AG1478 significantly reduced parasite proliferation in host cells. Our data suggested that the activation of tachyzoite EGFR-like might facilitate the intracellular proliferation of N. caninum.

Highlights

Neospora caninum, classified in the phylum Apicomplexa (Dubey et al, 2002), infects a variety of mammalian species with a worldwide distribution which results in severe protozoosis–Neosporosis (Dubey, 2003)
We found that N. caninum possessed a putative Epidermal growth factor receptor (EGFR)-like protein in tachyzoites which could be activated by N. caninum infection or by recombinant NcMIC3 and human epidermal growth factor (EGF)
In order to determine the expression of parasite EGFR, protein extracts from N. caninum tachyzoites and HEK293 cells were subject to immunoblot using monoclonal antibodies (mAb) against EGFR and β-actin, respectively

Summary

Introduction

Neospora caninum, classified in the phylum Apicomplexa (Dubey et al, 2002), infects a variety of mammalian species with a worldwide distribution which results in severe protozoosis–Neosporosis (Dubey, 2003). Infection with N. caninum mainly leads to abortions and stillbirths in pregnant herds and neuromuscular disorders in newborns which cause huge economic losses in the animal husbandry, especially in the cattle production. N. caninum is regarded as the main cause of abortions in dairy cattle throughout the world (Reichel and Ellis, 2008; Dubey and Schares, 2011). The process of host cells infection by N. caninum includes adhesion, invasion, parasitophorous vacuole formation, and polypide growth. Replication of N. caninum in host cells leads to cell lysis, which results in the release of parasites to invade neighboring cells to repeat the life cycle and establish infection (Innes et al, 2005; Dubey et al, 2007). The mechanism by which N. caninum proliferates within host cells is not fully elucidated

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