A strong endoplasmic reticulum retention signal in the stem-anchor region of envelope glycoprotein of dengue virus type 2 affects the production of virus-like particles.

Recombinant virus-like particles (VLPs) of flaviviruses have been shown to be produced efficiently by co-expressing the precursor membrane (PrM) and envelope (E) proteins with few exceptions, such as dengue virus type 2 (DENV2). It was reported previously that chimeric DENV2 PrM/E construct containing the stem-anchor region of E protein of Japanese encephalitis virus (JEV) produced VLPs efficiently (Chang, G. J., Hunt, A. R., Holmes, D. A., Springfield, T., Chiueh, T. S., Roehrig, J. T., and Gubler, D. J. 2003. Enhancing biosynthesis and secretion of premembrane and envelope proteins by the chimeric plasmid of dengue virus type 2 and Japanese encephalitis virus. Virology 306, 170-180.). We investigated the mechanisms involved and reported that compared with authentic DENV2 PrM/E-expressing cells, E protein in chimeric DENV2 PrM/E-expressing cells was also present in an endoglycosidase H (endo H)-resistant compartment and has shifted more to the pellets of the soluble fraction. Replacement of the transmembrane and cytoplasmic domains of CD4 with the stem-anchor of DENV2 (CD4D2) or JEV (CD4JEV) rendered the chimeric CD4 retained predominantly in the endoplasmic reticulum (ER). Flow cytometry revealed higher proportion of CD4JEV than CD4D2 expressed on the cell surface. Together, these findings suggested that the stem-anchor of DENV2 contained an ER retention signal stronger than that of JEV, which might contribute to the inefficient production of DENV2 VLPs. Moreover, co-expression of C protein can enhance the production of DENV2 VLPs, suggesting a mechanism of facilitating viral particle formation during DENV2 replication.