Dengue virus induces PCSK9 expression to alter antiviral responses and disease outcomes
Esther Shuyi Gan, … , Eng Eong Ooi, Sophie Yacoub
Esther Shuyi Gan, … , Eng Eong Ooi, Sophie Yacoub
Published July 9, 2020
Citation Information: J Clin Invest. 2020;130(10):5223-5234. https://doi.org/10.1172/JCI137536.
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Research Article Infectious disease

Dengue virus induces PCSK9 expression to alter antiviral responses and disease outcomes

Abstract

Dengue virus (DENV) infection requires cholesterol as a proviral factor, although statin treatment did not show antiviral efficacy in patients with dengue. Here, we show that DENV infection manipulated cholesterol metabolism in cells residing in low-oxygen microenvironments (hypoxia) such as in the liver, spleen, and lymph nodes. DENV infection induced expression of proprotein convertase subtilisin/kexin type 9 (PCSK9), which reduces low-density lipoprotein receptor (LDLR) recycling and hence cholesterol uptake. We found that, whereas LDLR uptake would have distributed cholesterol throughout the various cell compartments, de novo cholesterol synthesis enriched this lipid in the endoplasmic reticulum (ER). With cholesterol enrichment in the ER, ER-resident STING and type I IFN (IFN) activation was repressed during DENV infection. Our in vitro findings were further supported by the detection of elevated plasma PCSK9 levels in patients with dengue with high viremia and increased severity of plasma leakage. Our findings therefore suggest that PCSK9 plays a hitherto unrecognized role in dengue pathogenesis and that PCSK9 inhibitors could be a suitable host-directed treatment for patients with dengue.

Authors

Esther Shuyi Gan, Hwee Cheng Tan, Duyen Huynh Thi Le, Trieu Trung Huynh, Bridget Wills, Nabil G. Seidah, Eng Eong Ooi, Sophie Yacoub

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Figure 2

PCSK9 augments DENV infection and dampens the antiviral effect of statins.

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PCSK9 augments DENV infection and dampens the antiviral effect of statin...
(A) SREBP2 mRNA levels in uninfected and infected hypoxic Huh7 cells 24 hpi. (B) MFI of LDLR in uninfected and infected hypoxic Huh7 cells 24 hpi as assessed by flow cytometry. (C) MFI of DIL-LDL in uninfected and infected hypoxic Huh7 cells 24 hpi as assessed by flow cytometry. (D) Levels of secreted PCSK9 in uninfected and infected hypoxic Huh7 cells 24 hpi. (E) MFI of LDL in uninfected, infected, and alirocumab-treated (Ali) hypoxic Huh7 cells 24 hpi as assessed by flow cytometry. (F and G) Plaque titers in hypoxic Huh7 cells treated with or without alirocumab 24 (F) and 48 (G) hpi. (H) mRNA expression of SREBP2 in hypoxic Huh7 cells 6 hpi. Cells were cultured without (black) or with supplementation of 400 ng/mL PCSK9 (purple) 24 hours before DENV2 infection. (I and J) Plaque titers in hypoxic Huh7 cells 24 (G) and 48 (H) hpi with DENV2 infection. Cells were cultured without (black), with supplementation of 400 ng/mL PCSK9 (purple), or with PCSK9 with increasing doses of alirocumab (orange) for 24 hours before DENV2 infection. (K) EC50 values of hypoxic (red) and normoxic (blue) Huh7 cells 48 hpi with DENV2 infection with varying doses of simvastatin. Cells were cultured without (dark blue, dark red) or with supplementation of 400 ng/mL PCSK9 (light blue, light red) 24 hours before DENV2 infection. Experiments were replicated 3 times, with a minimum of 3 biological replicates. Representative data from 1 of these 3 independent experiments are shown. Data in A–K represent the mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by unpaired t test (A–D and F–H) and 1-way ANOVA corrected for multiple comparisons (E and I–K).