Productive Entry of Foot-and-Mouth Disease Virus via Macropinocytosis Independent of Phosphatidylinositol 3-Kinase

Sci Rep. 2016 Jan 13:6:19294. doi: 10.1038/srep19294.

Abstract

Virus entry is an attractive target for therapeutic intervention. Here, using a combination of electron microscopy, immunofluorescence assay, siRNA interference, specific pharmacological inhibitors, and dominant negative mutation, we demonstrated that the entry of foot-and-mouth disease virus (FMDV) triggered a substantial amount of plasma membrane ruffling. We also found that the internalization of FMDV induced a robust increase in fluid-phase uptake, and virions internalized within macropinosomes colocalized with phase uptake marker dextran. During this stage, the Rac1-Pak1 signaling pathway was activated. After specific inhibition on actin, Na(+)/H(+) exchanger, receptor tyrosine kinase, Rac1, Pak1, myosin II, and protein kinase C, the entry and infection of FMDV significantly decreased. However, inhibition of phosphatidylinositol 3-kinase (PI3K) did not reduce FMDV internalization but increased the viral entry and infection to a certain extent, implying that FMDV entry did not require PI3K activity. Results showed that internalization of FMDV exhibited the main hallmarks of macropinocytosis. Moreover, intracellular trafficking of FMDV involves EEA1/Rab5-positive vesicles. The present study demonstrated macropinocytosis as another endocytic pathway apart from the clathrin-mediated pathway. The findings greatly expand our understanding of the molecular mechanisms of FMDV entry into cells, as well as provide potential insights into the entry mechanisms of other picornaviruses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Animals
  • Caveolins / metabolism
  • Cell Line
  • Cholesterol / metabolism
  • Foot-and-Mouth Disease Virus / physiology*
  • Membrane Lipids / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Pinocytosis*
  • Receptor Protein-Tyrosine Kinases / metabolism
  • Virus Internalization*
  • Virus Replication

Substances

  • Actins
  • Caveolins
  • Membrane Lipids
  • Cholesterol
  • Phosphatidylinositol 3-Kinases
  • Receptor Protein-Tyrosine Kinases