The feline calicivirus leader of the capsid protein causes survivin and XIAP downregulation and apoptosis

Calicivirus infection causes intrinsic apoptosis, leading to viral propagation in the host. During murine norovirus infection, a reduction in the anti-apoptotic protein survivin has been documented. Here we report that in feline calicivirus infection, a downregulation of the anti-apoptotic proteins survivin and XIAP occur, which correlates with the translocation of the pro-apoptotic protein Smac/DIABLO from the mitochondria to the cytoplasm and the activation of caspase-3. Inhibition of survivin degradation by lactacystin treatment caused a delay in apoptosis progression, reducing virus release, without affecting virus production. However, the overexpression of survivin caused a negative effect in viral progeny production. Overexpression of the leader of the capsid protein (LC), but not of the protease-polymerase NS6/7, results in the downregulation of survivin and XIAP, caspase activation and mitochondrial damage. These results indicate that LC is responsible for the induction of apoptosis in transfected cells and most probably in FCV infection.