Chen, D. V. | Search bioRxiv

bioRxiv2024

Fc-independent SARS-CoV-2 infection-enhancing antibodies decouple N-terminal and receptor-binding domains by cross-linking neighboring spikes

Antibody dependent enhancement (ADE) is a serious concern in vaccine development. The canonical ADE pathways are dependent on the fragment crystallizable (Fc) region of the antibody. In SARS-CoV-2 several antibodies have been discovered that inflict ADE in vitro. These antibodies target the N-terminal domain (NTD) of the SARS-CoV-2 spike protein. We previously proposed that these NTD-targeting infection-enhancing antibodies (NIEAs) cross-link neighboring spike proteins via their NTDs, and that this results in a decoupling between the NTD and receptor binding domain (RBD), facilitating the "RBD down" to "up" transition. In this study we present a combination of molecular dynamics simulations and cryogenic electron microscopy data that, together, demonstrate that NIEAs are indeed able to cross-link neighboring SARS-CoV-2 spike proteins, and that this cross-linking results in a decoupling of the NTD and RBD domains. These findings provide support for an Fc region independent ADE pathway that is not only relevant for SARS-CoV-2 but also for other viruses of which the spike proteins undergo a conformational change upon host cell entry.

molecular biology↗

bioRxiv2018

USP15 participates in HCV propagation through the regulation of viral RNA translation and lipid droplet formation

Hepatitis C virus (HCV) utilizes cellular factors for an efficient propagation. Ubiquitin is covalently conjugated to the substrate to alter its stability or to modulate signal transduction. In this study, we examined the importance of ubiquitination for HCV propagation. We found that inhibition of de-ubiquitinating enzymes (DUBs) or overexpression of non-specific DUBs impaired HCV replication, suggesting that ubiquitination regulates HCV replication. To identify specific DUBs involved in HCV propagation, we set up an RNAi screening against DUBs and successfully identified ubiquitin-specific protease 15 (USP15) as a novel host factor for HCV propagation. Our studies showed that USP15 is involved in translation of HCV RNA and production of infectious HCV particles. In addition, deficiency of USP15 in human hepatic cell lines (Huh7 and Hep3B/miR122 cells) but not in a non-hepatic cell line (293T cells) impaired HCV propagation, suggesting that USP15 participates in HCV propagation through the regulation of hepatocyte-specific functions. Moreover, we showed that loss of USP15 had no effect on innate immune responses in vitro and in vivo. We also found that USP15-deficient Huh7 cells showed reductions in the sizes and numbers of lipid droplets (LDs), and addition of palmitic acids restored the production of infectious HCV particles. Taken together, these data suggest that USP15 participates in HCV propagation by regulating the translation of HCV RNA and formation of LDs.

microbiology↗