A novel Entamoeba histolytica cysteine proteinase, EhCP4, is key for invasive amebiasis and a therapeutic target.
Entamoeba histolytica cysteine proteinases (EhCPs) play a key role in disrupting the colonic epithelial barrier and the innate host immune response during invasion of E. histolytica, the protozoan cause of human amebiasis. EhCPs are encoded by 50 genes, of which ehcp4 (ehcp-a4) is the most up-regulated during invasion and colonization in a mouse cecal model of amebiasis. Up-regulation of ehcp4 in vivo correlated with our finding that co-culture of E. histolytica trophozoites with mucin-producing T84 cells increased ehcp4 expression up to 6-fold. We have expressed recombinant EhCP4, which was autocatalytically activated at acidic pH but had highest proteolytic activity at neutral pH. In contrast to the other amebic cysteine proteinases characterized so far, which have a preference for arginine in the P2 position, EhCP4 displayed a unique preference for valine and isoleucine at P2. This preference was confirmed by homology modeling, which revealed a shallow, hydrophobic S2 pocket. Endogenous EhCP4 localized to cytoplasmic vesicles, the nuclear region, and perinuclear endoplasmic reticulum (ER). Following co-culture with colonic cells, EhCP4 appeared in acidic vesicles and was released extracellularly. A specific vinyl sulfone inhibitor, WRR605, synthesized based on the substrate specificity of EhCP4, inhibited the recombinant enzyme in vitro and significantly reduced parasite burden and inflammation in the mouse cecal model. The unique expression pattern, localization, and biochemical properties of EhCP4 could be exploited as a potential target for drug design.
He
Chen
C
Department of Pathology and Medicine, University of California, San Diego, California 92103-8416, USA.
Nora
George P
GP
Schneider
Eric L
EL
Kerr
Iain D
ID
Hansell
Elizabeth
E
Hirata
Ken
K
Gonzalez
David
D
Sajid
Mohammed
M
Boyd
Sarah E
SE
Hruz
Petr
P
Cobo
Eduardo R
ER
Le
Christine
C
Liu
Wei-Ting
WT
Eckmann
Lars
L
Dorrestein
Pieter C
PC
Houpt
Eric R
ER
Brinen
Linda S
LS
Craik
Charles S
CS
Roush
William R
WR
McKerrow
James
J
Reed
Sharon L
SL
D000562:Amebiasis / Q000469:parasitology*; D000818:Animals; D045744:Cell Line, Tumor; D057056:Cysteine Proteases / Q000737:chemistry* / Q000502:physiology*; D015195:Drug Design; D004748:Entamoeba histolytica / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D008809:Mice, Inbred C3H; D010447:Peptide Hydrolases / Q000737:chemistry; D011480:Protease Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000737:chemistry; D013879:Thioredoxins / Q000737:chemistry
D011480:Protease Inhibitors; D011994:Recombinant Proteins; D013879:Thioredoxins; D057056:Cysteine Proteases; D010447:Peptide Hydrolases