Summary
Dengue virus (DV) infections cause mild dengue fever or severe life-threatening dengue
haemorrhagic fever (DHF)/ dengue shock syndrome (DSS). DV-infected patients have high
plasma concentrations of plasminogen activator inhibitor type I (PAI-1). However,
the mechanism to cause haemorrhage in DV infections remains poorly understood. In
this study, investigation was carried out on the purified recombinant domain III of
the envelope glycoprotein of DV serotypes 2 (EIII) and the signalling pathways of
EIII leading to PAI-1 gene expression were measured by RT-PCR, Western blot, and immunofluorescence
stain. Reporter gene constructs containing serially 5’-deleted sequences of the proximal
human PAI-1 promoter region were constructed and then transfected to Huh7 cells, a
human hepatoma cell line, prior to EIII treatment. EIII increased the PAI-1 mRNA and
protein levels in a dose-dependent manner in Huh7 cells. Results showed that U0126,
an inhibitor of extracellular signal-regulated kinase (ERK) kinase (MEK), almost completely
suppressed EIII-induced PAI-1 expression. The results suggest that the MEK/ERK signalling
pathways mediate the EIII-dependent induction of PAI-1 gene expression via the proximal
promoter region.
Keywords
Flaviviridae - dengue virus type 2 - envelope glycoprotein domain III - plasminogen
activator inhibitor type-1