Abstract
BackgroundAmoebiasis, caused by Entamoeba histolytica infection, is a global public health problem. However, available drugs to treat amoebiasis are currently limited, and no effective vaccine exists. Therefore, development of new preventive measures against amoebiasis is urgently needed.Methodology/Principal findingsHere, to develop new drugs against amoebiasis, we focused on E. histolytica adenosine 5′-phosphosulfate kinase (EhAPSK), an essential enzyme in Entamoeba sulfolipid metabolism. Fatty alcohol disulfates and cholesteryl sulfate, sulfolipids synthesized in Entamoeba, play important roles in trophozoite proliferation and cyst formation. These processes are closely associated with clinical manifestation and severe pathogenesis of amoebiasis and with disease transmission, respectively. We validated a combination approach of in silico molecular docking analysis and an in vitro enzyme activity assay for large scale screening. Docking simulation ranked the binding free energy between a homology modeling structure of EhAPSK and 400 compounds. The 400 compounds were also screened by a 96-well plate-based in vitro APSK activity assay. Among fifteen compounds identified as EhAPSK inhibitors by the in vitro system, six were ranked by the in silico analysis as having high affinity toward EhAPSK. Furthermore, 2-(3-fluorophenoxy)-N-[4-(2-pyridyl)thiazol-2-yl]-acetamide, 3-phenyl-N-[4-(2-pyridyl)thiazol-2-yl]-imidazole-4-carboxamide, and auranofin, which were identified as EhAPSK inhibitors by both in silico and in vitro analyses, halted not only Entamoeba trophozoite proliferation but also cyst formation. These three compounds also dose-dependently impaired the synthesis of sulfolipids in E. histolytica.Conclusions/SignificanceHence, the combined approach of in silico and in vitro-based EhAPSK analyses identified compounds that can be evaluated for their effects on Entamoeba. This can provide leads for the development of new anti-amoebic and amoebiasis transmission-blocking drugs. This strategy can also be applied to identify specific APSK inhibitors, which will benefit research into sulfur metabolism and the ubiquitous pathway terminally synthesizing essential sulfur-containing biomolecules.
Highlights
Amoebiasis, a parasitic disease, causes high morbidity and mortality; approximately 50 million cases of disease and 40,000–70,000 deaths annually [1]
To develop new drugs against amoebiasis, we focused on E. histolytica adenosine 50-phosphosulfate kinase (EhAPSK), an essential enzyme in sulfur metabolism
An E. histolytica adenosine 50phosphosulfate kinase (EhAPSK)-based combination approach of computer-based in silico and laboratory-based in vitro analyses enabled us to screen 400 chemicals, from which we identified 15 that inhibit EhAPSK activity
Summary
Amoebiasis, a parasitic disease, causes high morbidity and mortality; approximately 50 million cases of disease and 40,000–70,000 deaths annually [1]. Typical symptoms of this disease include diarrhea, dysentery, fever, and abdominal pains, which are diagnosed as intestinal manifestations. Patients sometimes develop extra-intestinal amoebiasis with amoebic liver abscess being most commonly diagnosed. Together with these obvious clinical cases, a high occurrence of asymptomatic patients who unconsciously spread the disease makes amoebiasis a global public health problem. Available drugs to treat amoebiasis are currently limited, and no effective vaccine exists. Development of new preventive measures against amoebiasis is urgently needed.
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