Viously described [10]. DRAQ5 was purchased from Biostatus Limited. Hoechst 33258 and wheat

Viously described [10]. DRAQ5 was purchased from Biostatus Limited. Hoechst 33258 and wheat

Viously described [10]. DRAQ5 was purchased from Biostatus Limited. Hoechst 33258 and wheat germ agglutinin (WGA) were purchased from Invitrogen. Bafilomycin A1 (BafA1), cycloheximide, and formaldehyde solution 1317923 (36 ) were from Sigma-Aldrich.Western BlotA549 cells were transfected with 10 nM siRNA for 3 days. Cells were then harvested and subjected to Western blotting. Detection of the ASP-015K ATP6V1B2 and b actin proteins was done with anti-ATP6V1B2 (1:1000 dilution) and anti-b actin (1:3000) antibodies, respectively.IAV Entry AssaysIndirect immunofluorescence techniques were used to detect viral components at different steps of IAV entry. Both confocal laser-scanning and automated high-content fluorescence microscopy were used to acquire the images as described below:A. Virus Internalization ConditionsIAV diluted in infection medium (D-MEM, 50 mM HEPES pH 6.8, 0.2 BSA) at 4uC for 1 h were allowed to bind to siRNAtransfected A549 cells on ice. The cells were then washed with icecold infection medium to remove the unbound virus particles. The bound particles were allowed to internalize at 37uC in a CO2 incubator for different time periods. To prevent the synthesis of new viral proteins in the EE, EA, EF, EU, and EI BTZ043 assays 1 mM cycloheximide was included in the infection medium during IAV binding and internalization. In the EU and EI assays, fresh infection medium containing cycloheximide was exchanged every 2 h post-internalization to ensure optimal efficacy of the drug. For the control of the EA, EF, EU, EI and infection assays, cells were either transfected with siRNA ATP6V1B2 targeting a vATPase subunit, or treated with 50 nM BafA1 during internalization. In both the control samples, acid-exposure of IAV in late endosomes was prevented, and as a consequence of which HA activation and down-stream processes in entry were blocked. The virus amounts used from the stock (2.46105 TCID50 infectious units/ml) in each well of a 24-well or 96-well plate and the detection time point for each assay are summarized in Table S1.B. Entry Assay Techniques1. Binding (EB assay). siRNA-transfected A549 cells were incubated with IAV in infection medium at 4uC for 1 h. Afterwashing 3 times with ice-cold PBS, the cells were fixed with 4 formaldehyde at RT, rewashed and stained with WGA-AF647 in PBS (1:250 dilution) for 30 min at RT. After a further washing step, the cells were incubated with Pinda antibody (1:10000) in blocking solution (BS) (1 BSA, 5 FCS in PBS) for 1 h at RT, washed with PBS, and stained with secondary anti-rabbit IgGAF488 conjugate in BS (1:1000) together with Hoechst 33258 (1:10000) for 1 h at RT. 2. Endocytosis (EE assay). siRNA-transfected cells were incubated with virus in the cold as in B1, and the bound virus allowed to be internalized for different time periods as describe above. After washing, they were fixed, washed with PBS, and the cell membrane was stained with WGA-AF647 in PBS (1:250) for 30 min at RT and washed again to remove unbound WGA-AF647. The epitopes of extracellular HA were blocked overnight at 4uC with Pinda antibody (1:500) in BS, and the cells stained with secondary anti-rabbit IgG-AF594 conjugate in BS (1:1000) for 1 h at RT. After fixation in 4 formaldehyde for 20 min and washing, a permeabilization solution (PS) (0.1 saponin, 1 BSA, 5 FCS in PBS) was added for 30 min followed by incubation with a mouse monoclonal antibody specific for HA1 in PS (1:100) for 2 h at RT. After washing, the cells were incubated wi.Viously described [10]. DRAQ5 was purchased from Biostatus Limited. Hoechst 33258 and wheat germ agglutinin (WGA) were purchased from Invitrogen. Bafilomycin A1 (BafA1), cycloheximide, and formaldehyde solution 1317923 (36 ) were from Sigma-Aldrich.Western BlotA549 cells were transfected with 10 nM siRNA for 3 days. Cells were then harvested and subjected to Western blotting. Detection of the ATP6V1B2 and b actin proteins was done with anti-ATP6V1B2 (1:1000 dilution) and anti-b actin (1:3000) antibodies, respectively.IAV Entry AssaysIndirect immunofluorescence techniques were used to detect viral components at different steps of IAV entry. Both confocal laser-scanning and automated high-content fluorescence microscopy were used to acquire the images as described below:A. Virus Internalization ConditionsIAV diluted in infection medium (D-MEM, 50 mM HEPES pH 6.8, 0.2 BSA) at 4uC for 1 h were allowed to bind to siRNAtransfected A549 cells on ice. The cells were then washed with icecold infection medium to remove the unbound virus particles. The bound particles were allowed to internalize at 37uC in a CO2 incubator for different time periods. To prevent the synthesis of new viral proteins in the EE, EA, EF, EU, and EI assays 1 mM cycloheximide was included in the infection medium during IAV binding and internalization. In the EU and EI assays, fresh infection medium containing cycloheximide was exchanged every 2 h post-internalization to ensure optimal efficacy of the drug. For the control of the EA, EF, EU, EI and infection assays, cells were either transfected with siRNA ATP6V1B2 targeting a vATPase subunit, or treated with 50 nM BafA1 during internalization. In both the control samples, acid-exposure of IAV in late endosomes was prevented, and as a consequence of which HA activation and down-stream processes in entry were blocked. The virus amounts used from the stock (2.46105 TCID50 infectious units/ml) in each well of a 24-well or 96-well plate and the detection time point for each assay are summarized in Table S1.B. Entry Assay Techniques1. Binding (EB assay). siRNA-transfected A549 cells were incubated with IAV in infection medium at 4uC for 1 h. Afterwashing 3 times with ice-cold PBS, the cells were fixed with 4 formaldehyde at RT, rewashed and stained with WGA-AF647 in PBS (1:250 dilution) for 30 min at RT. After a further washing step, the cells were incubated with Pinda antibody (1:10000) in blocking solution (BS) (1 BSA, 5 FCS in PBS) for 1 h at RT, washed with PBS, and stained with secondary anti-rabbit IgGAF488 conjugate in BS (1:1000) together with Hoechst 33258 (1:10000) for 1 h at RT. 2. Endocytosis (EE assay). siRNA-transfected cells were incubated with virus in the cold as in B1, and the bound virus allowed to be internalized for different time periods as describe above. After washing, they were fixed, washed with PBS, and the cell membrane was stained with WGA-AF647 in PBS (1:250) for 30 min at RT and washed again to remove unbound WGA-AF647. The epitopes of extracellular HA were blocked overnight at 4uC with Pinda antibody (1:500) in BS, and the cells stained with secondary anti-rabbit IgG-AF594 conjugate in BS (1:1000) for 1 h at RT. After fixation in 4 formaldehyde for 20 min and washing, a permeabilization solution (PS) (0.1 saponin, 1 BSA, 5 FCS in PBS) was added for 30 min followed by incubation with a mouse monoclonal antibody specific for HA1 in PS (1:100) for 2 h at RT. After washing, the cells were incubated wi.

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