Modulation of α-enolase post-translational modifications by dengue virus: increased secretion of the basic isoforms in infected hepatic cells

PLoS One. 2014 Aug 29;9(8):e88314. doi: 10.1371/journal.pone.0088314. eCollection 2014.


Hepatic cells are major sites of dengue virus (DENV) replication and liver injury constitutes a characteristic of severe forms of dengue. The role of hepatic cells in dengue pathogenesis is not well established, but since hepatocytes are the major source of plasma proteins, changes in protein secretion by these cells during infection might contribute to disease progression. Previously, we showed that DENV infection alters the secretion pattern of hepatic HepG2 cells, with α-enolase appearing as one of the major proteins secreted in higher levels by infected cells. ELISA analysis demonstrated that DENV infection modulates α-enolase secretion in HepG2 cells in a dose-dependent manner, but has no effect on its gene expression and on the intracellular content of the protein as assessed by PCR and western blot analyses, respectively. Two-dimensional western blots showed that both intracellular and secreted forms of α-enolase appear as five spots, revealing α-enolase isoforms with similar molecular weights but distinct isoeletric points. Remarkably, quantification of each spot content revealed that DENV infection shifts the isoform distribution pattern of secreted α-enolase towards the basic isoforms, whereas the intracellular protein remains unaltered, suggesting that post-translational modifications might be involved in α-enolase secretion by infected cells. These findings provide new insights into the mechanisms underlying α-enolase secretion by hepatic cells and its relationship with the role of liver in dengue pathogenesis. In addition, preliminary results obtained with plasma samples from DENV-infected patients suggest an association between plasma levels of α-enolase and disease severity. Since α-enolase binds plasminogen and modulates its activation, it is plausible to speculate the association of the increase in α-enolase secretion by infected hepatic cells with the haemostatic dysfunction observed in dengue patients including the promotion of fibrinolysis and vascular permeability alterations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Dengue Virus / physiology*
  • Hep G2 Cells
  • Hepatocytes / enzymology*
  • Hepatocytes / pathology
  • Hepatocytes / virology
  • Humans
  • Isoenzymes / metabolism
  • Phosphopyruvate Hydratase / metabolism*
  • Protein Processing, Post-Translational*
  • Virus Replication / physiology*


  • Isoenzymes
  • Phosphopyruvate Hydratase

Grants and funding

This work was supported by Conselho Nacional de Desenvolvimento Cientıfico e Tecnológico (CNPq,, grant numbers 550114/2010-6 and 550137/2010-6); Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ,, grant numbers E-26/102.919/2011 and E-26/110.636/2012); National Institute of Science and Technology in Dengue (INCT-Dengue,; and International Research Staff Exchange Scheme (FP7-PEOPLE IRSES), project MEMPEPACROSS (grant number FP7-HEALTH-F3–2008-223414). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.