Activation of PI3K, Akt, and ERK during early rotavirus infection leads to V-ATPase-dependent endosomal acidification required for uncoating

PLoS Pathog. 2018 Jan 19;14(1):e1006820. doi: 10.1371/journal.ppat.1006820. eCollection 2018 Jan.

Abstract

The cellular PI3K/Akt and/or MEK/ERK signaling pathways mediate the entry process or endosomal acidification during infection of many viruses. However, their roles in the early infection events of group A rotaviruses (RVAs) have remained elusive. Here, we show that late-penetration (L-P) human DS-1 and bovine NCDV RVA strains stimulate these signaling pathways very early in the infection. Inhibition of both signaling pathways significantly reduced production of viral progeny due to blockage of virus particles in the late endosome, indicating that neither of the two signaling pathways is involved in virus trafficking. However, immunoprecipitation assays using antibodies specific for pPI3K, pAkt, pERK and the subunit E of the V-ATPase co-immunoprecipitated the V-ATPase in complex with pPI3K, pAkt, and pERK. Moreover, Duolink proximity ligation assay revealed direct association of the subunit E of the V-ATPase with the molecules pPI3K, pAkt, and pERK, indicating that both signaling pathways are involved in V-ATPase-dependent endosomal acidification. Acidic replenishment of the medium restored uncoating of the RVA strains in cells pretreated with inhibitors specific for both signaling pathways, confirming the above results. Isolated components of the outer capsid proteins, expressed as VP4-VP8* and VP4-VP5* domains, and VP7, activated the PI3K/Akt and MEK/ERK pathways. Furthermore, psoralen-UV-inactivated RVA and CsCl-purified RVA triple-layered particles triggered activation of the PI3K/Akt and MEK/ERK pathways, confirming the above results. Our data demonstrate that multistep binding of outer capsid proteins of L-P RVA strains with cell surface receptors phosphorylates PI3K, Akt, and ERK, which in turn directly interact with the subunit E of the V-ATPase to acidify the late endosome for uncoating of RVAs. This study provides a better understanding of the RVA-host interaction during viral uncoating, which is of importance for the development of strategies aiming at controlling or preventing RVA infections.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acids / metabolism
  • Animals
  • Caco-2 Cells
  • Capsid Proteins / metabolism*
  • Cattle
  • Cells, Cultured
  • Endosomes / metabolism*
  • Enzyme Activation
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Haplorhini
  • Humans
  • Hydrogen-Ion Concentration
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rotavirus / metabolism
  • Rotavirus / physiology
  • Rotavirus Infections / enzymology
  • Rotavirus Infections / metabolism*
  • Rotavirus Infections / virology
  • Sf9 Cells
  • Signal Transduction
  • Vacuolar Proton-Translocating ATPases / physiology*
  • Virus Uncoating*

Substances

  • Acids
  • Capsid Proteins
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases
  • Vacuolar Proton-Translocating ATPases

Grants and funding

This study was supported by a grant (2017RIA2B3002971) from the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning, a Korea Basic Science Institute grant (C33730), and the Bio-industry Technology Development Program (315021-04) through the Korean Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries (iPET) funded by the Ministry of Agriculture, Food and Rural Affairs, Republic of Korea. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.