Molecular Mechanism Of Host Factor UBXN11 Regulating Influenza Virus Replication

Highly pathogenic avian influenza virus(HPAIV)not only seriously endangers the healthy development of the poultry industry,but also poses a major threat to human public health security.In addition to the use of vaccines to prevent and control influenza,antiviral drugs are also widely used in the treatment of influenza in clinical practice.Currently,anti-influenza drugs are mainly designed to target NA and M2 proteins.In recent years,influenza virus strains resistant to the above antiviral drugs are constantly emerging.Therefore,it is urgent to develop new broad-spectrum and efficient antiviral drugs.Effective replication of influenza virus in host cells depends on the participation of a large number of host factors.Screening host factors that have important effects on influenza virus replication and elucidating their molecular mechanisms can provide potential targets for the development of novel antiinfluenza drugs.Previously,we used high throughput genome-wide siRNA library screening to identify the host factors that are critical for the replication of influenza virus.One of such host factors is ubiquitin regulatory domain X 11(UBXN11),which is also called UBXD5 or Socius.In the present study,we focused on the molecular mechanisms of host factor UBXN11 protein regulating influenza virus replication.We found that siRNA knockdown of UBXN11 expression significantly inhibited the replication of influenza virus.By using retroviral-mediated system,we established a UBXN11-overexpressing A549 cell line.We found that overexpression of UBXN11 dramatically promoted the replication of influenza virus.Together,our results indicate that UBXN11 plays a positive regulatory role in the replication process of influenza virus.By using laser confocal microscopy,we found that the nuclear export process of viral ribonucleoprotein(vRNP)complex was significantly inhibited when the expression of UBXN11 was knocked down by siRNA.By contrast,the nuclear export of vRNP was accelerated when UBXN11 was overexpressed.Co-immunoprecipitation(Co-IP)experiment showed that UBXN11 did not interact with protein components of the classical CRM1 nuclear export pathway.However,UBXN11 could interact with viral HA protein,leading to enhanced membrane accumulation of HA protein.Further study showed that both HA and UBXN11 could activate the phosphorylation of ERK1/2.Importantly,the interaction between UBXN11 and HA enhanced the phosphorylation of ERK protein,thereby triggering the activation of MAPK signaling cascade and inducing the export of vRNP complex.This study revealed the molecular mechanism by which the host factor UBXN11 promotes the membrane accumulation of HA protein and activates the MAPK signaling pathway to induce vRNP export from nucleus to cytoplasm.The results enrich our understanding of how host factors regulate influenza virus replication and provide potential targets for the development of new anti-influenza drugs.