Penaeus monodon caspase is targeted by a white spot syndrome virus anti-apoptosis protein

Caspases play a central and evolutionarily conserved role in mediating and executing apoptosis. Here, we report the cloning and characterization of a caspase from Penaeus monodon, Pm caspase. The full-length Pm caspase cDNA is 1386 bp, encoding a polypeptide of 304 amino acids with a calculated molecular mass of 34.3 kDa. BLASTP analysis against the NCBI nr database showed that Pm caspase is similar to insect effector caspases. RT-PCR analysis showed that Pm caspase mRNA is expressed in all examined tissues. When Pm caspase was overexpressed in SF-9 cells, the cells showed apoptotic morphological features including the formation of apoptotic bodies and DNA ladders. The caspase-3 activity of Pm caspase was determined using the recombinant protein purified from Escherichia coli. Both RT-PCR and qRT-PCR analyses showed that the RNA levels of Pm caspase and P monodon inhibitor of apoptosis protein (PmIAP) remained unchanged after white spot syndrome virus (WSSV) infection. We also used Pm caspase to show that WSSV449, an anti-apoptosis protein encoded by WSSV, is a direct caspase inhibitor. (c) 2007 Elsevier Ltd. All rights reserved.