DENV up-regulates the HMG-CoA reductase activity through the impairment of AMPK phosphorylation: A potential antiviral target

Abstract

Dengue is the most common mosquito-borne viral disease in humans. Changes of lipid-related metabolites in endoplasmic reticulum of dengue virus (DENV) infected cells have been associated with replicative complexes formation. Previously, we reported that DENV infection inhibits HMGCR phosphorylation generating a cholesterol-enriched cellular environment in order to favor viral replication. In this work, using enzymatic assays, ELISA, and WB we found a significant higher activity of HMGCR in DENV infected cells, associated with the inactivation of AMPK. AMPK activation by metformin declined the HMGCR activity suggesting that AMPK inactivation mediates the enhanced activity of HMGCR. A reduction on AMPK phosphorylation activity was observed in DENV infected cells at 12 and 24 hpi. HMGCR and cholesterol co-localized with viral proteins NS3, NS4A and E, suggesting a role for HMGCR and AMPK activity in the formation of DENV replicative complexes. Furthermore, metformin and lovastatin (HMGCR inhibitor) altered this co-localization as well as replicative complexes formation supporting that active HMGCR is required for replicative complexes formation. In agreement, metformin prompted a significant dose-dependent antiviral effect in DENV infected cells, while compound C (AMPK inhibitor) augmented the viral genome copies and the percentage of infected cells. The PP2A activity, the main modulating phosphatase of HMGCR, was not affected by DENV infection. These data demonstrate that the elevated activity of HMGCR observed in DENV infected cells is mediated through AMPK inhibition and not by increase in PP2A activity. Interestingly, the inhibition of this phosphatase showed an antiviral effect in an HMGCR-independent manner. These results suggest that DENV infection increases HMGCR activity through AMPK inactivation leading to higher cholesterol levels in endoplasmic reticulum necessary for replicative complexes formation. This work provides new information about the mechanisms involved in host lipid metabolism during DENV replicative cycle and identifies new potential antiviral targets for DENV replication.

Perturbation of Intracellular Cholesterol and Fatty Acid Homeostasis During Flavivirus Infections

“…In mammalian cells, HMGCR activity is suppressed by cholesterol imported through receptor-mediated endocytosis of low density lipoproteins (54). Dengue infection inhibits phosphorylation of HMGCR at an inactivating site, generating a cholesterol-rich environment in the process (55,56). This was further corroborated through inactivation of AMPK and a subsequent increase in HMGCR activity, respectively (56).…”

“…Dengue infection inhibits phosphorylation of HMGCR at an inactivating site, generating a cholesterol-rich environment in the process (55,56). This was further corroborated through inactivation of AMPK and a subsequent increase in HMGCR activity, respectively (56). In comparison, West Nile virus infection has a more direct impact on intracellular cholesterol distribution.…”

The Dengue Virus Nonstructural Protein 1 (NS1) Is Secreted from Mosquito Cells in Association with the Intracellular Cholesterol Transporter Chaperone Caveolin Complex

“…NS1 lipid cargo indicates high requirements of cholesterol and triglycerides in infected cells (6). In hepatic cells, DENV infection induces an increase in the activity of cholesterol biosynthesis enzymes (49). The results showing lipid droplet decay during CCC inhibition in mosquito cells suggest an association between NS1 and LD during its traffic.…”

The dengue virus non-structural protein 1 (NS1) is secreted from mosquito cells in association with the intracellular cholesterol transporter chaperone caveolin complex

“…NS1 lipid cargo indicates high requirements of cholesterol and triglycerides in infected cells [6]. In hepatic cells, DENV infection induces an increase in the activity of cholesterol biosynthesis enzymes [48]. The results showing lipid droplet decay during CCC inhibition in mosquito cells, suggest a possible association between NS1 and LD during its traffic.…”