PLoS Pathog. 7, e1002144. Opti-MEM (Invitrogen), and resuspended in Cytomix buffer (120 mm KCl, 5 mm MgCl2, 0.15 mm CaCl2, 2 mm EGTA, 1.9 mm ATP, 4.7 mm GSH, 25 mm HEPES, 10 mm potassium phosphate buffer, pH 7.6) at 107 cells ml?1. 400 l of the cell suspension was mixed with 10 g of HCV RNA and pulsed at 260 V and 950 microfarads with the Gene Pulser II (Bio-Rad). HCV Production and Infection and Luciferase Analysis Huh7.5 cells were transfected with luciferase reporter HCV Luc-Jc1 as described above on day 1 and plated on 6-well plates. On days 2 and 3, they were transfected with 2 g of plasmids and X-tremeGENE 9 DNA Transfection Reagent (Roche Applied Science). Media were changed on day 4. Supernatants were harvested on days 5 and 6 and used to infect naive Huh7.5 cells overnight. On day 5, aliquots were lysed for Western blot or fixed for immunostaining. On day 6, transfected cells were lysed in 1 lysis buffer (Promega) for luciferase activity measurements. Cells infected with the luciferase reporter viruses were lysed in 1 lysis buffer (Promega). Luciferase activity was measured using the Luciferase Assay System (Promega) on a MonoLight 2010 Luminometer (Pegasus Scientific Inc.). RNA Isolation and Real-time RT-PCR Total cellular RNA was isolated with RNA Stat reagent (TelTest) according to the manufacturer’s protocol and treated with the TURBO DNA-free DNase (Ambion). cDNAs were synthesized with Superscript III reverse transcriptase (Invitrogen) with random hexamer primers. For real-time PCR, we used predesigned 18S rRNA, DGAT1, and DGAT2 Taqman assays (Applied Biosystems). Real-time PCR was performed with a QuantiTect Probe PCR Kit (Qiagen) on a 7900HT Fast Real-time RT-PCR System (Applied Biosystems). Triglyceride Extraction Hepatoma cells in 6-well plates were washed with PBS and incubated with 1 ml of hexane:isopropyl alcohol (3:2) on a vertical shaker at 100 rpm, 3 10 min. The hexane:isopropyl alcohol was evaporated under nitrogen. Lipids were resuspended in 500 l of chloroform with ABBV-4083 1% Triton X-100, dried again, resuspended in 200 l of water, mixed, and quantified with Infinity Triglycerides (Thermo Scientific, TR22421). Statistical Analysis Statistical analyses were performed using unpaired two-tailed Student’s tests. Data in histograms are displayed as the means S.E. RESULTS NS5A Interacts with DGAT1 To determine if DGAT1 has a broader role in HCV infection, we used co-immunoprecipitations (co-IPs) with endogenous DGAT1 and FLAG-tagged HCV proteins in Huh7 hepatoma cells. As expected DGAT1 associates with core. Interestingly, we also detected a new interaction with NS5A but not with E1, NS2, NS3, or NS4B proteins (Fig. 1and 293T cells were transfected with plasmids expressing NS5A-GFP, FLAG-DGAT1, and HA-core. After 24 h, cells were lysed and subjected to Western blotting with -GFP, -core, and -FLAG antibodies. immunoprecipitation was performed with -HA antibody-conjugated agarose and subjected to Western blotting. tandem immunoprecipitations were performed with -FLAG M2 affinity gel and -HA antibody-conjugated agarose. -FLAG M2 affinity gel was eluted with FLAG peptide, and the eluates were incubated with -HA antibody-conjugated agarose. Bound proteins were subjected to Western blotting. The input control was 12% of the whole-cell lysate used for the single immunoprecipitation and 6% of that used for the tandem immunoprecipitation. = 3 independent experiments. Next, we performed sequential co-IPs in the transfected cells described above. First, we immunoprecipitated FLAG-tagged DGAT1 and eluted the associated proteins with an excess of FLAG peptide. We then incubated the eluates with HA beads to immunoprecipitate core and analyzed the double pulldown by Western blotting. We detected NS5A-GFP in cells expressing all three proteins but not in control cells lacking one of the three binding ABBV-4083 partners, showing DGAT1, core, and NS5A form a tripartite complex (Fig. 2and core. We also confirmed our previous findings that DGAT1 inhibition, under normal cell culture conditions, does ABBV-4083 not reduce overall LD content in hepatoma cells, excluding the possibility that the loss of NS5A LD association in response to DGAT1 inhibitors is caused by an overall loss of LDs (Fig. 3epifluorescence microscopy (= 10 m). = 3). = 10 m) and quantification of Huh7-Lunet cells transfected with HCV Jc1 RNA (and and and and and arises directly from NS5A-GFP signal. Cells were analyzed by epifluorescence microscopy in and.(2002) Hepatitis C virus NS5A colocalizes with the core protein on lipid droplets and interacts with apolipoproteins. of infectious viral particles, underscoring the importance of DGAT1-mediated translocation of NS5A to LDs in viral particle production. We propose a model whereby DGAT1 serves as a cellular hub for HCV core and NS5A proteins, guiding both onto the surface of the same subset of LDs, those generated by DGAT1. These results highlight the critical role of DGAT1 as a host factor for HCV infection and as a potential drug target for antiviral therapy. transcription was carried out using the MegaScript T7 kit (Ambion) according to the manufacturer’s protocol. For RNA transfection, Huh7.5 cells were trypsinized, washed once in Opti-MEM (Invitrogen), and resuspended in Cytomix buffer (120 mm KCl, 5 mm MgCl2, 0.15 mm CaCl2, 2 mm EGTA, 1.9 mm ATP, 4.7 mm GSH, 25 mm HEPES, 10 mm potassium phosphate buffer, pH 7.6) at 107 cells ml?1. 400 l of the cell suspension was mixed with 10 g of HCV RNA and pulsed at 260 V and 950 microfarads with the Gene Pulser II (Bio-Rad). HCV Production and Infection and Luciferase Analysis Huh7.5 cells were transfected with luciferase reporter HCV Luc-Jc1 as described above on day 1 and plated on 6-well plates. On days 2 and 3, they were transfected with 2 g of plasmids and X-tremeGENE 9 DNA Transfection Rabbit polyclonal to STAT6.STAT6 transcription factor of the STAT family.Plays a central role in IL4-mediated biological responses.Induces the expression of BCL2L1/BCL-X(L), which is responsible for the anti-apoptotic activity of IL4. Reagent (Roche Applied Science). Media were changed on day 4. Supernatants were harvested on days 5 and 6 and used to infect naive Huh7.5 cells overnight. On day 5, aliquots were lysed for Western blot or fixed for immunostaining. On day 6, transfected cells were lysed in 1 lysis buffer (Promega) for luciferase activity measurements. Cells infected with the luciferase reporter viruses were lysed in 1 lysis buffer (Promega). Luciferase activity was measured using the Luciferase Assay System (Promega) on a MonoLight 2010 Luminometer (Pegasus Scientific Inc.). RNA Isolation and Real-time RT-PCR Total cellular RNA was isolated with RNA Stat reagent (TelTest) according to the manufacturer’s protocol and treated with the TURBO DNA-free DNase (Ambion). cDNAs were synthesized with Superscript III reverse transcriptase (Invitrogen) with random hexamer primers. For real-time PCR, we used predesigned 18S rRNA, DGAT1, and DGAT2 Taqman assays (Applied Biosystems). Real-time PCR was performed with a QuantiTect Probe PCR Kit (Qiagen) on a 7900HT Fast Real-time RT-PCR System (Applied Biosystems). Triglyceride Extraction Hepatoma cells in 6-well plates were washed with PBS and incubated with 1 ml of hexane:isopropyl alcohol (3:2) on a vertical shaker at 100 rpm, 3 10 min. The hexane:isopropyl alcohol was evaporated under nitrogen. Lipids were resuspended in 500 l of chloroform with 1% Triton X-100, dried again, resuspended in 200 l of water, mixed, and quantified with Infinity Triglycerides (Thermo Scientific, TR22421). Statistical Analysis Statistical analyses were performed using unpaired two-tailed Student’s tests. Data in histograms are displayed as the means S.E. RESULTS NS5A Interacts with DGAT1 To determine if DGAT1 has a broader role in HCV infection, we used co-immunoprecipitations (co-IPs) with endogenous DGAT1 and FLAG-tagged HCV proteins in Huh7 hepatoma cells. As expected DGAT1 associates with core. Interestingly, we also detected a new interaction with NS5A but not with E1, NS2, NS3, or NS4B proteins (Fig. 1and 293T cells were transfected with plasmids expressing NS5A-GFP, FLAG-DGAT1, and HA-core. After 24 h, cells were lysed and subjected to Western blotting with -GFP, -core, and -FLAG antibodies. immunoprecipitation was performed with -HA antibody-conjugated agarose and subjected to Western blotting. tandem immunoprecipitations were performed with -FLAG M2 affinity gel and -HA antibody-conjugated agarose. -FLAG M2 affinity gel was eluted with FLAG peptide, and the eluates were incubated with -HA antibody-conjugated agarose. Bound proteins were subjected to Western blotting. The input control was 12% of the whole-cell lysate used for the single immunoprecipitation and 6% of that used for the tandem immunoprecipitation. = 3 independent experiments. Next, we performed sequential co-IPs in the transfected cells described above. First, we immunoprecipitated FLAG-tagged DGAT1 and eluted the associated proteins with an excess of FLAG peptide. We then incubated the eluates with HA beads to immunoprecipitate core and.
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