Echinococcus multilocularis infection induces UBE2N suppression via exosomal emu-miR-4989

Highlights

• UBE2N was down-regulated in the liver during E. multilocularis infection.

• UBE2N was further shown to be predominantly expressed in hepatocytes and was also suppressed in response to the infection.

• UBE2N was a target of emu-miR-4989 and exosomal emu-miR-4989 was involved in UBE2N suppression.

• The results provide a clue for further pinpointing a role of UBE2N in the pathogenesis of E. multilocularis.

Abstract

Echinococcus multilocularis metacestodes mainly reside in liver in humans and animals, and cause serious damages. UBE2N was herein shown to be downregulated in response to the infection. UBE2N was further shown to be predominantly expressed in the hepatocytes, which was also significantly downregulated during the infection. UBE2N was a target of emu-miR-4989, which was loaded into the exosomes secreted by parasites. These emu-miR-4989-encapsulating exosomes were internalized by hepatocytes, and induced a significant decrease of relative luciferase activity in the cells transfected with the construct containing a wild type of UBE2N 3’-UTR compared to the control (p < 0.05). These results demonstrate that emu-miR-4989 is involved in the UBE2N inhibition in the hepatocytes during E. multilocularis through exosomes.

Introduction

Alveolar echinococcosis (AE) is a lethal zoonotic disease caused by the metacestode stage of Echinococcus multilocularis, a food-borne zoonotic parasite that is transmitted between wild rodents as an intermediate host and foxes as a definitive host (Kamiya and Sato, 1990). The adult worms reside in the intestine of foxes and produce eggs, which expel with the feces and develop into the larvae in the liver in rodents after consumption of egg-contaminated food or water. When foxes eat these infected rodents, the larvae develop into the adult, thus completing their life cycle (Mackenstedt et al., 2015). Human beings are occasionally infected by eating food or water contaminated by the eggs (Federer et al., 2015). It was reported that the disability adjusted life years caused by AE were estimated to be 687,823 in 2010 (Torgerson et al., 2015). In China, this disease is endemic in the pasture regions of Northwest China, such as Xinjiang, Qinghai, and Gansu (Craig and China, 2006).

UBE2N, also known as Ubc13, is an ubiquitin-conjugating enzyme that is involved in the synthesis of Lys63-linked polyubiquitin chain and plays an important role in inflammatory and immune signal transduction via the interaction with TNF receptor-associated factor 6 (TRAF6) (Hodge et al., 2016). The inhibition of TRAF6 and UBE2N interactions can impede the activation of NF-κB, counteract the signal transduction of NF- κB and prevent the occurrence of autoimmune diseases (Brenke et al., 2018). During the infection of Angiostrongylus cantonensis, UBE2N was found to be involved in the activation of NF-κB and induce eosinophilic meningitis in mice (Zhang et al., 2019). However, the role of UBE2N in the process of E. multilocularis infection is rarely reported.

In this study, we determined the expressional patterns of UBE2N during E. multilocularis infection and unveiled the mechanism by which it was regulated. The current results suggest a potential role of E. multilocularis miR-4989 (emu-miR-4989) in the UBE2N suppression during the infection via exosomes, which will provide a clue to pinpoint the functions of UBE2N in the pathogenesis in future.