Critical Role of HAX-1 in Promoting Avian Influenza Virus Replication in Lung Epithelial Cells

Figure 5

Attenuation of PB1-F2-induced caspase-9 activation by HAX-1. (a) Caspase-9 activity was suppressed by HAX-1 in transfected lung epithelial cells. A549 cells were transfected with plasmids expressing either PB1-F2, HAX-1, or both, and enzymatic activities of caspase-9 in the cell lysates were determined by incubating the lysates with the substrate LEHD-pNA at 37°C for 2 hrs for colorimetric development. The caspase activities were calculated and expressed as relative fold change against the control transfected with a blank plasmid. Expression levels of HAX-1 and PB1-F2 were shown in western blot analysis. (b) Suppression of activated caspase-9 in HAX-1 knockdown cells infected with the H9N2 virus. HAX-1 knockdown or scramble control cells were infected with H9N2 (wt) viruses. Enzymatic activities of caspase-9 in the cell lysates were determined by incubating the lysates with the substrate LEHD-pNA for colorimetric development. Triplicates were performed, and the values of mean ± SD were shown (Student’s t-test, and ; ns: no significance).

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