Positive-stranded RNA viruses, such as hepatitis C virus (HCV), assemble their viral replication complexes by remodeling host intracellular membranes to a membranous web. The precise composition of these replication complexes and the detailed mechanisms by which they are formed are incompletely understood. Here we show that the human immunity-related GTPase M (IRGM), known to contribute to autophagy, plays a previously unrecognized role in this process. We show that IRGM is localized at the Golgi apparatus and regulates the fragmentation of Golgi membranes in response to HCV infection, leading to colocalization of Golgi vesicles with replicating HCV. Our results show that IRGM controls phosphorylation of GBF1, a guanine nucleotide exchange factor for Arf-GTPases, which normally operates in Golgi membrane dynamics and vesicle coating in resting cells. We also find that HCV triggers IRGM-mediated phosphorylation of the early autophagy initiator ULK1, thereby providing mechanistic insight into the role of IRGM in HCV-mediated autophagy. Collectively, our results identify IRGM as a key Golgi-situated regulator that links intracellular membrane remodeling by autophagy and Golgi fragmentation with viral replication.HCV | Golgi fragmentation | autophagy | IRGM | membranous web H epatitis C virus (HCV) is a positive-sense RNA virus in the family Flaviviridae that is a major cause of chronic liver disease. All positive-strand RNA viruses studied until now, including HCV, replicate their genomes in association with cellular membrane rearrangements. In this process, viruses remodel intracellular membranes [e.g., of mitochondria, endoplasmic reticulum (ER), and plasma membrane] to generate membrane structures such as single-or double-membrane vesicles that contribute to viral replication complexes (VRCs). HCV replication takes place at a unique subcellular compartment, the membranous web (MW), which has been proposed to be derived from the ER (1, 2). The HCV MW has a complex morphology consisting of clusters of single-, double-, and multimembrane vesicles and probably includes autophagosomes and lipid droplets (1, 3, 4). Recent findings reveal that the MW is produced by distinct HCV nonstructural (NS) proteins acting through sequential interaction with several host factors, such as the virus-targeted phosphatidylinositol-4 kinase III α (PI4KIIIα) (2, 3), but the full spectrum of host components and precise membrane composition that supports HCV replication are not fully defined.Autophagy is an evolutionarily conserved cellular mechanism that involves intracellular membrane trafficking and degradation to maintain cell homeostasis. Viruses, including HCV, have been reported to exploit autophagy for replication purposes (4-6), but the mechanism by which this exploitation occurs is largely unknown. De novo synthesis of autophagosomes is a complex process that involves the formation of a phagophore membrane and its elongation. Initiation of autophagy is regulated by the mammalian target of rapamycin complex 1 (mTORC1), which neg...

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In this paper we model credit spreads on contingent convertible bonds (CoCos) in the Norwegian financial bond market, using a Merton style option model approach. We examine whether the Merton risk default model provides a good measure of CoCo-bond prices. We find that this model, although favoured by its simplicity, is overly sensitive to changes in the volatility of firm asset values, and fails to account for liquidity premiums. We further ask if CoCo prices account for the prepayment risk that are unique to these hybrid equity-like capital instruments. Analogously we ask if CoCo-bonds offer cheap funding for banks relative to equity capital. We find no evidence that bond markets underprices the CoCo-risk of the trial banks. Still we find that CoCos offer cheap funding for banks relative to issuing equity capital. In addition, CoCos offer capital cushion for banks when most needed.