Highly pathogenic avian influenza A virus H5N1 non-structural protein 1 is associated with apoptotic activation of the intrinsic mitochondrial pathway

Bian, Qian; Lu, Jing; Zhang, Li; Chi, Ying; Li, Yan; Guo, Hongxiong

As demonstrated in Fig. 4 , NS1 together with STS induced the release of cytochrome c from the mitochondria to the cytosol. It is known that cytochrome c release from the mitochondria to the cytosol is a signal for apoptosis (19) . This implies the possibility of NS1 protein being associated with apoptosis by activating the intrinsic pathway through cytochrome c. In order to confirm this, MMP was initially detected by JC-1 staining. Normal cells stained with JC-1 emitted mitochondrial orange-red fluorescence with a slight green fluorescence, whereas the ratio of orange-red and green fluorescence was inverted when cell apoptosis was induced by NS1 protein. As shown in Fig. 5 , in comparison with the empty vector transfected cells group, NS1 transfected cells significantly initiated apoptosis with STS (the ratio of fluorescence intensity at 555/488 nm was ~1.00; P<0.05). However, without STS treatment, the NS1-expressing NCI-H292 cells have no significant difference with the empty vector.