Characterization of a novel filarial serine protease inhibitor, Ov-SPI-1, from Onchocerca volvulus, with potential multifunctional roles during development of the parasite.
A novel filarial serine protease inhibitor (SPI) from the human parasitic nematode Onchocerca volvulus, Ov-SPI-1, was identified through the analysis of a molting third-stage larvae expressed sequence tag dataset. Subsequent analysis of the expressed sequence tag datasets of O. volvulus and other filariae identified four other members of this family. These proteins are related to the low molecular weight SPIs originally isolated from Ascaris suum where they are believed to protect the parasite from host intestinal proteases. The two Ov-spi transcripts are up-regulated in the molting larvae and adult stages of the development of the parasite. Recombinant Ov-SPI-1 is an active inhibitor of serine proteases, specifically elastase, chymotrypsin, and cathepsin G. Immunolocalization of the Ov-SPI proteins demonstrates that the endogenous proteins are localized to the basal layer of the cuticle of third-stage, molting third-stage, and fourth-stage larvae, the body channels and multivesicular bodies of third-stage larvae and the processed material found between the two cuticles during molting. In O. volvulus adult worms the Ov-SPI proteins are localized to the sperm and to eggshells surrounding the developing embryos. RNA interference targeting the Ov-spi genes resulted in the specific knockdown of the transcript levels of both Ov-spi-1 and Ov-spi-2, a loss of native proteins, and a significant reduction in both molting and viability of third-stage larvae. We suggest the Ov-SPI proteins play a vital role in nematode molting by controlling the activity of an endogenous serine protease(s). The localization data in adults also indicate that these inhibitors may be involved in other processes such as embryogenesis and spermatogenesis.
Ford
Louise
L
Laboratory of Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York 10021, USA.
Guiliano
David B
DB
Oksov
Yelena
Y
Debnath
Asim K
AK
Liu
Jing
J
Williams
Steven A
SA
Blaxter
Mark L
ML
Lustigman
Sara
S
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D056649:Cathepsin G; D002403:Cathepsins / Q000037:antagonists & inhibitors; D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D018507:Gene Expression Regulation, Developmental; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D007814:Larva / Q000737:chemistry; D008969:Molecular Sequence Data; D017181:Onchocerca volvulus / Q000737:chemistry* / Q000254:growth & development*; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors; D010802:Phylogeny; D021382:Protein Sorting Signals; D012330:RNA, Double-Stranded / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D017385:Sequence Homology; D012697:Serine Endopeptidases; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects
D015801:Helminth Proteins; D021382:Protein Sorting Signals; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D002403:Cathepsins; D012697:Serine Endopeptidases; D002918:Chymotrypsin; C534094:CTSG protein, human; D056649:Cathepsin G; D010196:Pancreatic Elastase