Junín virus induces autophagy in human A549 cells

Abstract

Autophagy, a highly regulated degradative process that promotes cellular homeostasis, is increasingly recognised as a fundamental component of the cellular response against viral infection. In this study, we investigated the role of autophagy during Junín virus (JUNV) multiplication using human A549 cells. We found that JUNV infection induces an increment of the LC3-II/LC3-I ratio, an accumulation of punctate pattern in RFP-LC3-transfected cells and the colocalisation of viral nucleoprotein and LC3 protein, suggesting autophagosome formation. JUNV infection also induced the degradation of the autophagy receptor p62, suggesting that complete autophagic flux was triggered. In addition, we showed that inhibition of autophagy with bafilomycin A1 or 3-methyladenine significantly reduces viral multiplication. Moreover, viral yield was increased when autophagy was induced using rapamycin. Furthermore, JUNV infection induced the colocalisation of p62, ATG16, RAB5, RAB7A and LAMP1 with the autophagosomal LC3 protein. That suggests that phagosomes undergo the maturation process during viral infection. Finally, we demonstrated that siRNA experiments targeting essential autophagy genes ( ATG5 , ATG7 and Beclin 1 ) reduce viral protein synthesis and viral yield. Overall, our results indicate that JUNV activates host autophagy machinery enhancing its multiplication.

Differential Immune Responses to Hemorrhagic Fever-Causing Arenaviruses

“…The role of autophagy during arenavirus infection is largely unknown, but recent research has provided evidence of a proviral role for autophagy. Two groups observed that both virulent and attenuated strains of JUNV induce autophagy early in infection [86,87]. Induction of autophagy prior to infection results in increased NP expression [87].…”

“…Two groups observed that both virulent and attenuated strains of JUNV induce autophagy early in infection [86,87]. Induction of autophagy prior to infection results in increased NP expression [87]. The OW MOPV also transiently induces autophagy during the first two days of infection, though LASV does not [88].…”

“…The OW MOPV also transiently induces autophagy during the first two days of infection, though LASV does not [88]. Nevertheless, depleting the essential autophagic vesicle protein ATG5 impairs MOPV, LASV, and JUNV replication [86][87][88], indicating that both OW and NW arenaviruses may utilize components of the autophagy pathway to aid in replication. While ATG5 is the key component in autophagy, there is increasing evidence that ATG5 also plays roles in non-autophagy processes, including negative regulation of RIG-I or MDA5 [89][90][91].…”

“…One group determined that, unlike replication-competent JUNV, UV-inactivated JUNV did not induce autophagy up to 9 hours post-exposure [86]. However, another group observed autophagy induction 24 hours after exposure to UV-inactivated JUNV [87], though it is unclear whether this was virus-driven. Autophagy likely plays a role late in arenavirus infection, as depleting ATG5 reduced extracellular, but not intracellular, LASV and MOPV RNA levels [88].…”

“…MOPV Z, and to a lesser extent LASV Z, interact with the sequestosome 1-like receptors NDP52 and TAX1BP1 [88]. JUNV NP has also been visualized co-localizing with LC3 [87]. However, the biological significance of viral protein interaction with components of autophagy remains unknown.…”