Research Article: Functional Analysis of the Cathepsin-Like Cysteine Protease Genes in Adult Brugia malayi Using RNA Interference

Date Published: February 10, 2009

Publisher: Public Library of Science

Author(s): Louise Ford, Jun Zhang, Jing Liu, Sarwar Hashmi, Juliet A. Fuhrman, Yelena Oksov, Sara Lustigman, Paul J. Brindley

Abstract: BackgroundCathepsin-like enzymes have been identified as potential targets for drug or vaccine development in many parasites, as their functions appear to be essential in a variety of important biological processes within the host, such as molting, cuticle remodeling, embryogenesis, feeding and immune evasion. Functional analysis of Caenorhabditis elegans cathepsin L (Ce-cpl-1) and cathepsin Z (Ce-cpz-1) has established that both genes are required for early embryogenesis, with Ce-cpl-1 having a role in regulating in part the processing of yolk proteins. Ce-cpz-1 also has an important role during molting.Methods and FindingsRNA interference assays have allowed us to verify whether the functions of the orthologous filarial genes in Brugia malayi adult female worms are similar. Treatment of B. malayi adult female worms with Bm-cpl-1, Bm-cpl-5, which belong to group Ia of the filarial cpl gene family, or Bm-cpz-1 dsRNA resulted in decreased numbers of secreted microfilariae in vitro. In addition, analysis of the intrauterine progeny of the Bm-cpl-5 or Bm-cpl Pro dsRNA- and siRNA-treated worms revealed a clear disruption in the process of embryogenesis resulting in structural abnormalities in embryos and a varied differential development of embryonic stages.ConclusionsOur studies suggest that these filarial cathepsin-like cysteine proteases are likely to be functional orthologs of the C. elegans genes. This functional conservation may thus allow for a more thorough investigation of their distinct functions and their development as potential drug targets.

Partial Text: Human lymphatic filariasis (LF), caused by the filarial parasites Brugia malayi, Brugia timori and Wuchereria bancrofti, infects 120 million people worldwide, of which 40 million people show chronic disease symptoms ( [1]. The disease is estimated to be responsible for 5.5 million DALYs, and is the second leading cause of permanent and long-term disability worldwide [2]. A further one billion people (18% of the world’s population) are at risk of infection (

Cysteine proteases play important roles in both intracellular and extracellular processes which are important in both development and survival. Cathepsin-like enzymes have been identified as potential targets for drug or vaccine development in many parasites, including filarial nematodes [33],[38], due to as their potential essential roles in feeding [46],[47][48], molting [33],[49], embryogenesis [40],[44] and immune functions [50] (reviewed in [51]). Here we describe the use of RNAi techniques in B. malayi adult females to directly assess the function(s) of the cysteine protease (CP) genes that belong to the CPZ and the group Ia of Bm-CPL protein families.



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