Subversion of immunoproteasome subunit expression in dengue virus serotype 2-infected HepG2 cells

Infection with all serotypes of dengue virus (DV) results in augmented antigen presentation by MHC class I molecules. However, the upregulation of immunoproteasome subunits only results from infection with two serotypes. This study aims to elucidate changes in the expression of immunoproteasome subunits resulting from infection with DV, particularly DV serotype 2 (DV2).

METHODS:

HepG2 cells were grown in various culture milieu. Total cellular RNA and proteins were extracted and quantified.

RESULTS:

Results demonstrated sequestration of immunoproteasome subunits LMP2 and LMP7 in DV2-infected cells.

CONCLUSIONS:

This study provides insights into the mechanisms underlying immune evasion by DV.

Keywords:
Dengue virus; LMP2; LMP7

Authorship

Chye Sheng Gan

Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia. University of MalayaMalaysiaKuala Lumpur, MalaysiaDepartment of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.

Drug Design and Development Research Group, University of Malaya, Kuala Lumpur, Malaysia. University of MalayaMalaysiaKuala Lumpur, MalaysiaDrug Design and Development Research Group, University of Malaya, Kuala Lumpur, Malaysia.

Pei Jean Lim

Institute of Graduate Studies, University of Malaya, Kuala Lumpur, Malaysia. University of MalayaMalaysiaKuala Lumpur, MalaysiaInstitute of Graduate Studies, University of Malaya, Kuala Lumpur, Malaysia.

Muhammad Fazril Mohamad Razif

Rohana Yusof

Shatrah Othman

Corresponding author: Dr. Shatrah Othman. e-mail: shatraho@um.edu.my

The authors declare that there is no conflict of interest

SCIMAGO INSTITUTIONS RANKINGS

Figures

Figures (3)

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FIGURE 1
Gene expression profiles of LMP2, LMP7, HLA-A, and HLA-B. HepG2 cells were cultured under three different conditions: I) infected with mock infection media (negative control), II) infected with DV2, and III) infected with DV2 and treated with antiviral agent YK73. Cells were incubated for 48 hours; then, total RNA was extracted and RT-qPCR was performed. Average expression of three independent experiments (n = 3) are presented. Error bars are expressed as standard deviation. Values with different symbols are significantly different (at p < 0.05) between groups. DV2: dengue virus type 2; HLA-A: human leukocyte antigen type A; HLA-B: human leukocyte antigen type B; LMP2: low molecular weight polypeptide-2; LMP7: low molecular weight polypeptide-7; RT-qPCR: real time quantitative polymerase chain reaction; RNA: ribonucleic acid.

Thumbnail

FIGURE 2
Protein expression of LMP2 and LMP7 following antiviral treatment. HepG2 cells were infected with DV2, supplemented with or without the antiviral compound, and incubated for 48 hours. Then, cells were harvested and protein lysate was subjected to western blot. A. Western blot of LMP2, LMP7, and β actin. B. The densitometry-quantified intensity of LMP2 and LMP7 bands normalized against that of β actin. Average expression determined by three independent experiments (n = 3) is presented. Error bars are expressed as standard deviation. Values with different symbols are significantly different at p < 0.05 between the groups. DV2: dengue virus type 2; LMP2: low molecular weight polypeptide-2; LMP7: low molecular weight polypeptide-7.

Thumbnail

FIGURE 3
Putative effect of antivirus YK73 on the transformation of the proteasome into the immunoproteasome in DV2-infected cells. Active replication of DV2 prevents efficient transformation of the immunoproteasome by limiting the transcription of both LMP2 and LMP7 genes. The absence of the immunoproteasome results in impaired generation of antigenic peptides, which leads to poor surface presentation of the antigen epitopes. Conversely, increased expression of both LMP2 and LMP7 was observed when virus replication was impeded by the antiviral compound YK73. This finding may indicate the recovery of the host response, which enables the transformation of the immunoproteasome. DV2: dengue virus type 2; LMP2: low molecular weight polypeptide-2; LMP7: low molecular weight polypeptide-7.

FIGURE 1 Gene expression profiles of LMP2, LMP7, HLA-A, and HLA-B. HepG2 cells were cultured under three different conditions: I) infected with mock infection media (negative control), II) infected with DV2, and III) infected with DV2 and treated with antiviral agent YK73. Cells were incubated for 48 hours; then, total RNA was extracted and RT-qPCR was performed. Average expression of three independent experiments (n = 3) are presented. Error bars are expressed as standard deviation. Values with different symbols are significantly different (at p < 0.05) between groups. DV2: dengue virus type 2; HLA-A: human leukocyte antigen type A; HLA-B: human leukocyte antigen type B; LMP2: low molecular weight polypeptide-2; LMP7: low molecular weight polypeptide-7; RT-qPCR: real time quantitative polymerase chain reaction; RNA: ribonucleic acid.

FIGURE 2 Protein expression of LMP2 and LMP7 following antiviral treatment. HepG2 cells were infected with DV2, supplemented with or without the antiviral compound, and incubated for 48 hours. Then, cells were harvested and protein lysate was subjected to western blot. A. Western blot of LMP2, LMP7, and β actin. B. The densitometry-quantified intensity of LMP2 and LMP7 bands normalized against that of β actin. Average expression determined by three independent experiments (n = 3) is presented. Error bars are expressed as standard deviation. Values with different symbols are significantly different at p < 0.05 between the groups. DV2: dengue virus type 2; LMP2: low molecular weight polypeptide-2; LMP7: low molecular weight polypeptide-7.

FIGURE 3 Putative effect of antivirus YK73 on the transformation of the proteasome into the immunoproteasome in DV2-infected cells. Active replication of DV2 prevents efficient transformation of the immunoproteasome by limiting the transcription of both LMP2 and LMP7 genes. The absence of the immunoproteasome results in impaired generation of antigenic peptides, which leads to poor surface presentation of the antigen epitopes. Conversely, increased expression of both LMP2 and LMP7 was observed when virus replication was impeded by the antiviral compound YK73. This finding may indicate the recovery of the host response, which enables the transformation of the immunoproteasome. DV2: dengue virus type 2; LMP2: low molecular weight polypeptide-2; LMP7: low molecular weight polypeptide-7.

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Subversion of immunoproteasome subunit expression in dengue virus serotype 2-infected HepG2 cells

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[1] Corresponding author: Dr. Shatrah Othman. e-mail: shatraho@um.edu.my