Article

Tissue specificity of a baculovirus-expressed, basement membrane-degrading protease in larvae of Heliothis virescens.

Department of Entomology, Iowa State University, 418 Science II, Ames, IA 50011-3222, USA.
Tissue and Cell (Impact Factor: 1.05). 01/2008; 39(6):431-43. DOI: 10.1016/j.tice.2007.08.003
Source: PubMed

ABSTRACT ScathL is a cathepsin L-like cysteine protease from the flesh fly, Sarcophaga peregrina, which digests components of the basement membrane during insect metamorphosis. A recombinant baculovirus (AcMLF9.ScathL) expressing ScathL kills larvae of the tobacco budworm Heliothis virescens significantly faster than the wild type virus and triggers melanization and tissue fragmentation shortly before death. The tissue fragmentation was assumed to be a direct consequence of basement membrane degradation by ScathL. The goal of this study was to investigate the tissue specificity of ScathL when expressed by AcMLF9.ScathL using light, transmission and scanning electron microscopy. Baculovirus expression of ScathL resulted in damage to the basement membrane overlying the midgut, fat body and muscle fibers in larvae infected with AcMLF9.ScathL, but not in larvae infected with the control virus AcMLF9.ScathL.C146A or wild type virus AcMNPV C6. Injection of recombinant ScathL and high levels of baculovirus-mediated expression of ScathL resulted in complete loss of the gut. Extensive damage to the basement membrane mediated by ScathL likely resulted in loss of viability of the underlying tissue and subsequent death of the insect. These results confirm the conclusion of an earlier study (Philip, J.M.D., Fitches, E., Harrison, R.L., Bonning, B.C., Gatehouse, J.A., 2007. Characterisation of functional and insecticidal properties of a recombinant cathepsin L-like proteinase from flesh fly (Sarcophaga peregrina), which plays a role in differentiation of imaginal discs. Insect Biochem. Mol. Biol. 37, 589-600) of the remarkable specificity of this protease.

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    • "Interestingly, it has been shown that a recombinant baculovirus expressing the S. peregrina cathepsin L (SCathL) induces melanization of larvae (Harrison and Bonning, 2001). In this case, melanization was not directly activated by SCathL but was postulated to be induced by the SCathL-dependent degradation of the basement membrane and recruitment of hemocytes at the sites of injury, because damaged tissues are most probably recognized as non-self (Tang et al., 2007; Li et al., 2008). "
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