Coxsackievirus can exploit LC3 in both autophagy-dependent and -independent manners in vivo

Abstract

RNA viruses modify intracellular membranes to produce replication scaffolds. In pancreatic cells, coxsackievirus B3 (CVB3) hijacks membranes from the autophagy pathway, and in vivo disruption of acinar cell autophagy dramatically delays CVB3 replication. This is reversed by expression of GFP-LC3, indicating that CVB3 may acquire membranes from an alternative, autophagy-independent, source(s). Herein, using 3 recombinant CVB3s (rCVB3s) encoding different proteins (proLC3, proLC3^G120A, or ATG4B^C74A), we show that CVB3 is, indeed, flexible in its utilization of cellular membranes. When compared with a control rCVB3, all 3 viruses replicated to high titers in vivo, and caused severe pancreatitis. Most importantly, each virus appeared to subvert membranes in a unique manner. The proLC3 virus produced a large quantity of LC3-I which binds to phosphatidylethanolamine (PE), affording access to the autophagy pathway. The proLC3^G120A protein cannot attach to PE, and instead binds to the ER-resident protein SEL1L, potentially providing an autophagy-independent source of membranes. Finally, the ATG4B^C74A protein sequestered host cell LC3-I, causing accumulation of immature phagophores, and massive membrane rearrangement. Taken together, our data indicate that some RNA viruses can exploit a variety of different intracellular membranes, potentially maximizing their replication in each of the diverse cell types that they infect in vivo.

Keywords:

• autophagy
• coxsackievirus
• enterovirus
• ER
• ERAD
• LC3
• membranes
• pancreas
• RNA virus
• SEL1L

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We thank Drs. Noburu Mizushima (Tokyo Medical and Dental University) and Herbert W. “Skip” Virgin (Washington University) for providing Atg5^f/f mice; Dr. Eric P. Sandgren (University of Wisconsin-Madison) for providing EL-Cre transgenic mice; and Dr. Karin Klingel (University Hospital Tübingen) for providing antibodies against VP1. We thank Dr. G Suizdak and LT Hoang of the Scripps Center for Metabolomics and Mass Spectrometry.

Funding

This work was supported by NIH R01 awards AI103218, AI114615 and AI110621 (to J.L.W.). This is manuscript number 28047 from the Scripps Research Institute.