Poster Presentation Lorne Infection and Immunity 2018

The role of peroxisomes and the ISG viperin in modulation of the MAVS mediated antiviral response (#120)

Michael Beard 1 , Onrudee Khantisittiporn 1 , Byron Shue 1 , Karla Helbig 2 , Nicholas Eyre 1
  1. Research Centre for Infectious Diseases, University of Adelaide, Adelaide, SA, Australia
  2. Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Vic, Australia

The innate response to many positive stranded RNA viruses is facilitated by activation of the pattern recognition receptors RIG-I and MDA-5 that signal via the adaptor protein MAVS. MAVS is localized to the outer mitochondrial membrane and the MAM (mitochondrial associated membrane), a specialized subdomain that physically connects the ER to the mitochondria. However, recently it has been reported that MAVS is also located on and signals from the peroxisome, although the spatial and temporal aspects of MAVS activation from the peroxisome are not well understood. In the course of studying the antiviral ISG Viperin (RSAD2), we observed viperin could significantly augment the cellular response to PolyI:C (Huh-7, HeLa) while was attenuated in MEFs isolated from viperin-/- CRISPR mice. Collectively this suggests that viperin is a positive regulator of innate immune recognition of viral RNA. To gain insight into molecular mechanisms, a yeast two-hybrid assay was employed to identify novel viperin interacting partners. Peroxisomal biogenesis factor 19 (PEX19) a protein important in peroxisome biogenesis was identified and an interaction confirmed by Co-IP and IF. Interestingly, viperin redirected PEX19 (and hence peroxisomes) to the lipid droplet (LD) interface and association with the mitochondria, while a viperin mutant that retained its interaction with PEX19 but not the LD resulted in abrogation of viperin’s ability to augment dsRNA-signaling. Targeted expression of MAVS to either the peroxisome or mitochondria or both revealed that viperin drives a significant increase in IFN expression only in the presence of both mitochondrial and peroxisomal MAVS. Thus, the interaction between viperin and PEX19 plays an important role in positioning the peroxisome within the cell to augment innate immune antiviral signaling. Identification of cellular factors that regulate the innate response is critical to understanding how antiviral networks are integrated into the general cellular infrastructure.