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González JEH, Salas-Sarduy E, Alvarez LH, Valiente PA, Arni RK, Pascutti PG. Three Decades of Targeting Falcipains to Develop Antiplasmodial Agents: What have we Learned and What can be Done Next? Curr Med Chem 2024; 31:2234-2263. [PMID: 37711130 DOI: 10.2174/0929867331666230913165219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 05/06/2023] [Accepted: 07/25/2023] [Indexed: 09/16/2023]
Abstract
Malaria is a devastating infectious disease that affects large swathes of human populations across the planet's tropical regions. It is caused by parasites of the genus Plasmodium, with Plasmodium falciparum being responsible for the most lethal form of the disease. During the intraerythrocytic stage in the human hosts, malaria parasites multiply and degrade hemoglobin (Hb) using a battery of proteases, which include two cysteine proteases, falcipains 2 and 3 (FP-2 and FP-3). Due to their role as major hemoglobinases, FP-2 and FP-3 have been targeted in studies aiming to discover new antimalarials and numerous inhibitors with activity against these enzymes, and parasites in culture have been identified. Nonetheless, cross-inhibition of human cysteine cathepsins remains a serious hurdle to overcome for these compounds to be used clinically. In this article, we have reviewed key functional and structural properties of FP-2/3 and described different compound series reported as inhibitors of these proteases during decades of active research in the field. Special attention is also paid to the wide range of computer-aided drug design (CADD) techniques successfully applied to discover new active compounds. Finally, we provide guidelines that, in our understanding, will help advance the rational discovery of new FP-2/3 inhibitors.
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Affiliation(s)
- Jorge Enrique Hernández González
- Multiuser Center for Biomolecular Innovation, IBILCE/UNESP, São José do Rio Preto, SP, Brazil
- Department of Pharmaceutical Sciences, UZA II, University of Vienna, Vienna, 1090, Austria
| | - Emir Salas-Sarduy
- Instituto de Investigaciones Biotecnológicas Dr. Rodolfo Ugalde, Universidad Nacional de San Martín, CONICET, San Martín, Buenos Aires, Argentina
- Escuela de Bio y Nanotecnología (EByN), Universidad de San Martín (UNSAM), San Martín, Buenos Aires, Argentina
| | | | - Pedro Alberto Valiente
- Donnelly Centre for Cellular & Biomolecular Research, University of Toronto, Toronto, Canada
| | | | - Pedro Geraldo Pascutti
- Laboratório de Modelagem e Dinâmica Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, RJ, Brazil
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2
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Argüello-García R, Carrero JC, Ortega-Pierres MG. Extracellular Cysteine Proteases of Key Intestinal Protozoan Pathogens-Factors Linked to Virulence and Pathogenicity. Int J Mol Sci 2023; 24:12850. [PMID: 37629029 PMCID: PMC10454693 DOI: 10.3390/ijms241612850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 08/07/2023] [Accepted: 08/08/2023] [Indexed: 08/27/2023] Open
Abstract
Intestinal diseases caused by protistan parasites of the genera Giardia (giardiasis), Entamoeba (amoebiasis), Cryptosporidium (cryptosporidiosis) and Blastocystis (blastocystosis) represent a major burden in human and animal populations worldwide due to the severity of diarrhea and/or inflammation in susceptible hosts. These pathogens interact with epithelial cells, promoting increased paracellular permeability and enterocyte cell death (mainly apoptosis), which precede physiological and immunological disorders. Some cell-surface-anchored and molecules secreted from these parasites function as virulence markers, of which peptide hydrolases, particularly cysteine proteases (CPs), are abundant and have versatile lytic activities. Upon secretion, CPs can affect host tissues and immune responses beyond the site of parasite colonization, thereby increasing the pathogens' virulence. The four intestinal protists considered here are known to secrete predominantly clan A (C1- and C2-type) CPs, some of which have been characterized. CPs of Giardia duodenalis (e.g., Giardipain-1) and Entamoeba histolytica (EhCPs 1-6 and EhCP112) degrade mucin and villin, cause damage to intercellular junction proteins, induce apoptosis in epithelial cells and degrade immunoglobulins, cytokines and defensins. In Cryptosporidium, five Cryptopains are encoded in its genome, but only Cryptopains 4 and 5 are likely secreted. In Blastocystis sp., a legumain-activated CP, called Blastopain-1, and legumain itself have been detected in the extracellular medium, and the former has similar adverse effects on epithelial integrity and enterocyte survival. Due to their different functions, these enzymes could represent novel drug targets. Indeed, some promising results with CP inhibitors, such as vinyl sulfones (K11777 and WRR605), the garlic derivative, allicin, and purified amoebic CPs have been obtained in experimental models, suggesting that these enzymes might be useful drug targets.
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Affiliation(s)
- Raúl Argüello-García
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México City 07360, Mexico;
| | - Julio César Carrero
- Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), México City 04510, Mexico
| | - M. Guadalupe Ortega-Pierres
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México City 07360, Mexico;
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3
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Previti S, Ettari R, Di Chio C, Legac J, Bogacz M, Zimmer C, Schirmeister T, Rosenthal PJ, Zappalà M. Influence of amino acid size at the P3 position of N-Cbz-tripeptide Michael acceptors targeting falcipain-2 and rhodesain for the treatment of malaria and human african trypanosomiasis. Bioorg Chem 2023; 137:106587. [PMID: 37163812 DOI: 10.1016/j.bioorg.2023.106587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 04/18/2023] [Accepted: 05/01/2023] [Indexed: 05/12/2023]
Abstract
In recent decades, several structure-activity relationship (SAR) studies provided potent inhibitors of the cysteine proteases falcipain-2 (FP-2) and rhodesain (RD) from Plasmodium falciparum and Trypanosoma brucei rhodesiense, respectively. Whilst the roles of the warhead and residues targeting the P1 and P2 pockets of the proteases were extensively investigated, the roles of the amino acids occupying the S3 pocket were not widely assessed. Herein we report the synthesis and biological evaluation of a set of novel Michael acceptors bearing amino acids of increasing size at the P3 site (1a-g/2a-g, SPR20-SPR33) against FP-2, RD, P. falciparum, and T. brucei. Overall, the Michael acceptors bearing small amino acids at the P3 site exhibited the most potent inhibitory properties towards FP-2. In contrast, analogues with bulky residues at the P3 position were very potent rhodesain inhibitors. In cell based assays, single-digit micromolar EC50 values against the two protozoa were observed. These findings can be a starting point for the development of peptide-based FP-2 and RD inhibitors.
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Affiliation(s)
- Santo Previti
- Department of Chemical, Biological, Pharmaceutical, and Environmental Sciences, University of Messina, Viale Stagno d'Alcontres 31, 98166 Messina, Italy.
| | - Roberta Ettari
- Department of Chemical, Biological, Pharmaceutical, and Environmental Sciences, University of Messina, Viale Stagno d'Alcontres 31, 98166 Messina, Italy
| | - Carla Di Chio
- Department of Chemical, Biological, Pharmaceutical, and Environmental Sciences, University of Messina, Viale Stagno d'Alcontres 31, 98166 Messina, Italy
| | - Jenny Legac
- Department of Medicine, University of California, San Francisco, CA 94143, United States
| | - Marta Bogacz
- Institute of Organic Chemistry & Macromolecular Chemistry, Friedrich-Schiller-University of Jena, 07743 Jena, Germany
| | - Collin Zimmer
- Institute of Pharmaceutical and Biomedical Sciences, University of Mainz, 55128 Mainz, Germany
| | - Tanja Schirmeister
- Institute of Pharmaceutical and Biomedical Sciences, University of Mainz, 55128 Mainz, Germany
| | - Philip J Rosenthal
- Department of Medicine, University of California, San Francisco, CA 94143, United States
| | - Maria Zappalà
- Department of Chemical, Biological, Pharmaceutical, and Environmental Sciences, University of Messina, Viale Stagno d'Alcontres 31, 98166 Messina, Italy
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4
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Rojas-Pirela M, Kemmerling U, Quiñones W, Michels PAM, Rojas V. Antimicrobial Peptides (AMPs): Potential Therapeutic Strategy against Trypanosomiases? Biomolecules 2023; 13:biom13040599. [PMID: 37189347 DOI: 10.3390/biom13040599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 03/19/2023] [Accepted: 03/20/2023] [Indexed: 03/29/2023] Open
Abstract
Trypanosomiases are a group of tropical diseases that have devastating health and socio-economic effects worldwide. In humans, these diseases are caused by the pathogenic kinetoplastids Trypanosoma brucei, causing African trypanosomiasis or sleeping sickness, and Trypanosoma cruzi, causing American trypanosomiasis or Chagas disease. Currently, these diseases lack effective treatment. This is attributed to the high toxicity and limited trypanocidal activity of registered drugs, as well as resistance development and difficulties in their administration. All this has prompted the search for new compounds that can serve as the basis for the development of treatment of these diseases. Antimicrobial peptides (AMPs) are small peptides synthesized by both prokaryotes and (unicellular and multicellular) eukaryotes, where they fulfill functions related to competition strategy with other organisms and immune defense. These AMPs can bind and induce perturbation in cell membranes, leading to permeation of molecules, alteration of morphology, disruption of cellular homeostasis, and activation of cell death. These peptides have activity against various pathogenic microorganisms, including parasitic protists. Therefore, they are being considered for new therapeutic strategies to treat some parasitic diseases. In this review, we analyze AMPs as therapeutic alternatives for the treatment of trypanosomiases, emphasizing their possible application as possible candidates for the development of future natural anti-trypanosome drugs.
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Ibezim A, Ofokansi MN, Ndukwe X, Chiama CS, Obi BC, Isiogugu ON, Ikechukwu PE, Onwuka AM, Ihim SA, Asegbeloyin JN, Nwodo NJ. Evaluation of anti-malarial potency of new pyrazole-hydrazine coupled to Schiff base derivatives. Malar J 2022; 21:243. [PMID: 35996135 PMCID: PMC9396901 DOI: 10.1186/s12936-022-04266-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 08/10/2022] [Indexed: 11/10/2022] Open
Abstract
Background The search for pharmacologically effective agents among molecules bearing multiple functionalities is commonly practiced. In continuation of the search for new anti-malarial agents, new pyrazole-hydrazine coupled Schiff-base derivatives previously synthesized were screened for anti-malarial property. Methods Here, in vivo prophylactic and curative activities of the compounds were assessed while their binding affinity for falcipain-2, a crucial enzyme in Plasmodium survival, was done using computational techniques. Results The two derivatives (BepINH and BepBeH) respectively led to a significant (p < 0.05) reduction in parasitaemia count (0.76 ± 1.11 and 0.79 ± 1.19) at day 3 post-treatment relative to the negative control (16.37 ± 1.25). For the prophylactic study, it was observed that the highest parasitaemia suppression level of 95.35% and 95.17% for BepINH and BepBeH at 15 mg/kg was slightly comparable to that obtained for ACT-Lonart (99.38%). In addition, their haematological profiles indicate that they are potentially beneficial in suppressing haemolytic damage to RBC, thereby protecting the body against infection-induced anaemia. Docking calculations on the derivatives toward the Plasmodium falciparum falcipain-2 revealed that they favourably interacted with a binding affinity higher than that of a known cocrystallized inhibitor. Conclusion This study confirms the relevance of multi-functional molecules in the search for new and effective anti-plasmodial agent and lay the foundation for further development of these compound series to potent anti-plasmodial agent that interacts with falcipain-2. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04266-8.
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Affiliation(s)
- Akachukwu Ibezim
- Department of Pharmaceutical and Medicinal Chemistry, University of Nigeria, Nsukka, Nigeria.
| | - Martha N Ofokansi
- Department of Pharmacology and Toxicology, University of Nigeria, Nsukka, Nigeria.
| | - Xavier Ndukwe
- Department of Pharmaceutical and Medicinal Chemistry, University of Nigeria, Nsukka, Nigeria
| | - Chidera S Chiama
- Department of Pharmaceutical and Medicinal Chemistry, University of Nigeria, Nsukka, Nigeria
| | - Bonaventure C Obi
- Department of Pharmacology and Toxicology, University of Nigeria, Nsukka, Nigeria
| | - Ogechukwu N Isiogugu
- Department of Pharmacology and Toxicology, University of Nigeria, Nsukka, Nigeria
| | - Peter E Ikechukwu
- Department of Pharmacology and Toxicology, University of Nigeria, Nsukka, Nigeria
| | - Akachukwu M Onwuka
- Department of Pharmacology and Toxicology, University of Nigeria, Nsukka, Nigeria
| | - Stella A Ihim
- Department of Science Laboratory, University of Nigeria, Nsukka, Nigeria
| | - Jonnie N Asegbeloyin
- Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Nigeria
| | - Ngozi J Nwodo
- Department of Pharmaceutical and Medicinal Chemistry, University of Nigeria, Nsukka, Nigeria
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6
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Computer-Aided Design of Peptidomimetic Inhibitors of Falcipain-3: QSAR and Pharmacophore Models. Sci Pharm 2021. [DOI: 10.3390/scipharm89040044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In this work, antiparasitic peptidomimetics inhibitors (PEP) of falcipain-3 (FP3) of Plasmodium falciparum (Pf) are proposed using structure-based and computer-aided molecular design. Beginning with the crystal structure of PfFP3-K11017 complex (PDB ID: 3BWK), three-dimensional (3D) models of FP3-PEPx complexes with known activities ( IC50exp) were prepared by in situ modification, based on molecular mechanics and implicit solvation to compute Gibbs free energies (GFE) of inhibitor-FP3 complex formation. This resulted in a quantitative structure–activity relationships (QSAR) model based on a linear correlation between computed GFE (ΔΔGcom) and the experimentally measured IC50exp. Apart from the structure-based relationship, a ligand-based quantitative pharmacophore model (PH4) of novel PEP analogues where substitutions were directed by comparative analysis of the active site interactions was derived using the proposed bound conformations of the PEPx. This provided structural information useful for the design of virtual combinatorial libraries (VL), which was virtually screened based on the 3D-QSAR PH4. The end results were predictive inhibitory activities falling within the low nanomolar concentration range.
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7
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Ettari R, Previti S, Di Chio C, Zappalà M. Falcipain-2 and Falcipain-3 Inhibitors as Promising Antimalarial Agents. Curr Med Chem 2021; 28:3010-3031. [PMID: 32744954 DOI: 10.2174/0929867327666200730215316] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 07/01/2020] [Accepted: 07/11/2020] [Indexed: 11/22/2022]
Abstract
Malaria remains a serious problem in global public health, particularly widespread in South America and in tropical regions of Africa and Asia. Chemotherapy is actually the only way to treat this poverty-related disease, since an effective vaccine is not currently available. However, the onset of resistance to the most common antimalarial drugs sometimes makes the current therapeutic regimen problematic. Therefore, the identification of new targets for a new drug discovery process is an urgent priority. In this context, falcipain-2 and falcipain- 3 of P. falciparum represent the key enzymes in the life-cycle of the parasite. Both falcipain- 2 and falcipain-3 are involved in hemoglobin hydrolysis, an essential pathway to provide free amino acids for the parasite metabolic needs. In addition, falcipain-2 is involved in cleaving ankirin and band 4.1 protein, which are cytoskeletal elements essential for the stability of the red cell membrane. This review article is focused on the most recent and effective inhibitors of falcipain-2 and falcipain-3, with particular attention to peptide, peptidomimetic or nonpeptide inhibitors, which targeted one or both the malarial cysteine proteases, endowed with a consistent activity against P. falciparum.
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Affiliation(s)
- Roberta Ettari
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
| | - Santo Previti
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
| | - Carla Di Chio
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
| | - Maria Zappalà
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
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8
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Singh A, Kalamuddin M, Maqbool M, Mohmmed A, Malhotra P, Hoda N. Quinoline carboxamide core moiety-based compounds inhibit P. falciparumfalcipain-2: Design, synthesis and antimalarial efficacy studies. Bioorg Chem 2020; 108:104514. [PMID: 33280833 DOI: 10.1016/j.bioorg.2020.104514] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 09/07/2020] [Accepted: 11/19/2020] [Indexed: 12/11/2022]
Abstract
Targeting Falcipain-2 (FP2) for the development of antimalarials is a promising and established concept in antimalarial drug discovery and development. FP2, a member of papain-family cysteine protease of the malaria parasite Plasmodium falciparum holds an important role in hemoglobin degradation pathway. A new series of quinoline carboxamide-based compounds was designed, synthesized and evaluated for antimalarial activity. We integrated molecular hybridization strategy with in-silico drug design to develop FP2 inhibitors. In-vitro results of FP2 inhibition by Qs17, Qs18, Qs20 and Qs21 were found to be in low micromolar range with IC50 4.78, 7.37, 2.14 and 2.64 µM, respectively. Among the 25 synthesized compounds, four compounds showed significant antimalarial activities. These compounds also depicted morphological and food-vacuole abnormalities much better than that of E-64, an established FP2 inhibitor. Overall these aromatic substituted quinoline carboxamides can serve as promising leads for the development of novel antimalarial agents.
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Affiliation(s)
- Anju Singh
- Drug Design and Synthesis Lab., Department of Chemistry, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India
| | - Md Kalamuddin
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Mudasir Maqbool
- Drug Design and Synthesis Lab., Department of Chemistry, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India
| | - Asif Mohmmed
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Pawan Malhotra
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India.
| | - Nasimul Hoda
- Drug Design and Synthesis Lab., Department of Chemistry, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India.
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9
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Peptidyl Fluoromethyl Ketones and Their Applications in Medicinal Chemistry. Molecules 2020; 25:molecules25174031. [PMID: 32899354 PMCID: PMC7504820 DOI: 10.3390/molecules25174031] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 12/29/2022] Open
Abstract
Peptidyl fluoromethyl ketones occupy a pivotal role in the current scenario of synthetic chemistry, thanks to their numerous applications as inhibitors of hydrolytic enzymes. The insertion of one or more fluorine atoms adjacent to a C-terminal ketone moiety greatly modifies the physicochemical properties of the overall substrate, especially by increasing the reactivity of this functionalized carbonyl group toward nucleophiles. The main application of these peptidyl α-fluorinated ketones in medicinal chemistry relies in their ability to strongly and selectively inhibit serine and cysteine proteases. These compounds can be used as probes to study the proteolytic activity of the aforementioned proteases and to elucidate their role in the insurgence and progress on several diseases. Likewise, if the fluorinated methyl ketone moiety is suitably connected to a peptidic backbone, it may confer to the resulting structure an excellent substrate peculiarity and the possibility of being recognized by a specific subclass of human or pathogenic proteases. Therefore, peptidyl fluoromethyl ketones are also currently highly exploited for the target-based design of compounds for the treatment of topical diseases such as various types of cancer and viral infections.
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10
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Rosenthal PJ. Falcipain cysteine proteases of malaria parasites: An update. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2020; 1868:140362. [DOI: 10.1016/j.bbapap.2020.140362] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 01/04/2020] [Accepted: 01/07/2020] [Indexed: 02/06/2023]
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Vieira RP, Santos VC, Ferreira RS. Structure-based Approaches Targeting Parasite Cysteine Proteases. Curr Med Chem 2019; 26:4435-4453. [PMID: 28799498 DOI: 10.2174/0929867324666170810165302] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/18/2017] [Accepted: 07/18/2017] [Indexed: 12/17/2022]
Abstract
Cysteine proteases are essential hydrolytic enzymes present in the majority of organisms, including viruses and unicellular parasites. Despite the high sequence identity displayed among these proteins, specific structural features across different species grant distinct functions to these biomolecules, frequently related to pathological conditions. Consequently, their relevance as promising targets for potential specific inhibitors has been highlighted and occasionally validated in recent decades. In this review, we discuss the recent outcomes of structure-based campaigns aiming the discovery of new inhibitor prototypes against cruzain and falcipain, as alternative therapeutic tools for Chagas disease and malaria treatments, respectively. Computational and synthetic approaches have been combined on hit optimization strategies and are also discussed herein. These rationales are extended to additional tropical infectious and neglected pathologies, such as schistosomiasis, leishmaniasis and babesiosis, and also to Alzheimer's Disease, a widespread neurodegenerative disease poorly managed by currently available drugs and recently linked to particular physiopathological roles of human cysteine proteases.
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Affiliation(s)
- Rafael Pinto Vieira
- Departamento de Bioquimica e Imunologia, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil.,CAPES Foundation, Ministry of Education of Brazil, 70040-020 Brasília, DF, Brazil
| | - Viviane Corrêa Santos
- Departamento de Bioquimica e Imunologia, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
| | - Rafaela Salgado Ferreira
- Departamento de Bioquimica e Imunologia, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
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12
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Gupta P, Mehrotra S, Sharma A, Chugh M, Pandey R, Kaushik A, Khurana S, Srivastava N, Srivastava T, Deshmukh A, Panda A, Aggarwal P, Bhavesh NS, Bhatnagar RK, Mohmmed A, Gupta D, Malhotra P. Exploring Heme and Hemoglobin Binding Regions of Plasmodium Heme Detoxification Protein for New Antimalarial Discovery. J Med Chem 2017; 60:8298-8308. [PMID: 28949547 DOI: 10.1021/acs.jmedchem.7b00089] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Hemoglobin degradation/hemozoin formation, essential steps in the Plasmodium life cycle, are targets of existing antimalarials. The pathway still offers vast possibilities to be explored for new antimalarial discoveries. Here, we characterize heme detoxification protein, PfHDP, a major protein involved in hemozoin formation, as a novel drug target. Using in silico and biochemical approaches, we identified two heme binding sites and a hemoglobin binding site in PfHDP. Treatment of Plasmodium falciparum 3D7 parasites with peptide corresponding to the hemoglobin binding domain in PfHDP resulted in food vacuole abnormalities similar to that seen with a cysteine protease inhibitor, E-64 (I-1). Screening of compounds that bound the modeled PfHDP structure in the heme/hemoglobin-binding pockets from Maybridge Screening Collection identified a compound, ML-2, that inhibited parasite growth in a dose-dependent manner, thus paving the way for testing its potential as a new drug candidate. These results provide functional insights into the role of PfHDP in Hz formation and further suggest that PfHDP could be an important drug target to combat malaria.
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Affiliation(s)
- Priya Gupta
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Sonali Mehrotra
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Anil Sharma
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Monika Chugh
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Rajan Pandey
- Translational Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Abhinav Kaushik
- Translational Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Sachin Khurana
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Neha Srivastava
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Tarushikha Srivastava
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Arunaditya Deshmukh
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India.,Centre for Biotechnology, Maharishi Dayanand University Rohtak , Haryana 123401, India
| | - Ashutosh Panda
- Department of Microbiology, All India Institute of Medical Sciences , New Delhi 110029, India
| | - Priyanka Aggarwal
- Transcriptional Regulation Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Neel Sarovar Bhavesh
- Transcriptional Regulation Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Raj K Bhatnagar
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Asif Mohmmed
- Parasite Cell Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Dinesh Gupta
- Translational Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Pawan Malhotra
- Malaria Biology Group, International Centre for Genetic Engineering and Biotechnology , Aruna Asaf Ali Marg, New Delhi 110067, India
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13
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Bacherikov VA, Chittiboyina AG, Avery MA. Design, Synthesis, and Biological Evaluation of Peptidomimetic N-Substituted Cbz-4-Hyp-Hpa-Amides as Novel Inhibitors of Plasmodium falciparum. Chem Biodivers 2017; 14. [PMID: 28498611 DOI: 10.1002/cbdv.201700037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Accepted: 05/08/2017] [Indexed: 11/10/2022]
Abstract
A new series of peptidomimetic N-substituted Cbz-4-Hyp-Hpa-amides were designed, synthesized, and evaluated for inhibition of the Plasmodium falciparum. Substituents on the N-atom of the amide group were selected alkyl-, allyl-, aryl-, 2-hydroxyethyl-, 2-cyanoethyl-, cyanomethyl-, 2-hydroxyethyl-, 2,2-diethoxyethyl-, or 2-ethoxy-2-oxoethylamino groups, and about of 40 new compounds were synthesized and evaluated for antiplasmodial activity in vitro. Antimalarial activity has been investigated as for the final peptide mimetics, and their immediate predecessors, carrying TBDMS or TBDPS protecting groups on 4-hydroxyproline residue and 18 derivatives exhibited toxicity against P. falciparum. Of these agents, compound 23e was shown to have potent antimalarial activity with IC50 528 ng/ml.
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Affiliation(s)
- Valeriy A Bacherikov
- Department of Medicinal Chemistry and Biology, Odessa Medical Institute, International Humanitarian University, Fontanskaya road, 33, Odessa, 65009, Ukraine
| | - Amar G Chittiboyina
- National Center for Natural Products Research, University of Mississippi, Oxford, MS, 38677, USA.,Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, Oxford, MS, 38677, USA
| | - Mitchell A Avery
- National Center for Natural Products Research, University of Mississippi, Oxford, MS, 38677, USA.,Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, Oxford, MS, 38677, USA
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14
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Vijayaraghavan S, Mahajan S. Docking, synthesis and antimalarial activity of novel 4-anilinoquinoline derivatives. Bioorg Med Chem Lett 2017; 27:1693-1697. [PMID: 28318947 DOI: 10.1016/j.bmcl.2017.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 02/27/2017] [Accepted: 03/02/2017] [Indexed: 11/25/2022]
Abstract
A series of 4-anilinoquinoline triazine derivatives were designed, synthesized and screened for in vivo antimalarial activity against a chloroquine-sensitive strain of Plasmodium berghei. The compounds were further subjected to in vitro antimalarial activity against chloroquine-resistant W2 strain of Plasmodium falciparum and β-haematin inhibition studies. All the compounds exhibited in vivo antimalarial activity better than that shown by the standard drug, chloroquine. Twelve out of fifteen compounds showed better inhibition than that of chloroquine against chloroquine-resistant W2 strain of Plasmodium falciparum. Ten compounds showed β-haematin inhibition, better than that of chloroquine, with IC50 values in the range of 18-25µM. One compound, 3k, was found to be better than artemisinin against W2 strain of Plasmodium falciparum and also displayed the best β-haematin inhibitory activity, thereby becoming eligible to be explored as a potential lead for antimalarial chemotherapy.
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Affiliation(s)
- Shilpa Vijayaraghavan
- Department of Pharmaceutical Chemistry, C.U. Shah College of Pharmacy, S.N.D.T. Women's University, Sir Vithaldas Vidyavihar, Santacruz (W), Mumbai 400049, India.
| | - Supriya Mahajan
- Department of Pharmaceutical Chemistry, C.U. Shah College of Pharmacy, S.N.D.T. Women's University, Sir Vithaldas Vidyavihar, Santacruz (W), Mumbai 400049, India
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15
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Musyoka TM, Kanzi AM, Lobb KA, Bishop ÖT. Analysis of non-peptidic compounds as potential malarial inhibitors against Plasmodial cysteine proteases via integrated virtual screening workflow. J Biomol Struct Dyn 2016; 34:2084-101. [PMID: 26471975 PMCID: PMC5035544 DOI: 10.1080/07391102.2015.1108231] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 10/08/2015] [Indexed: 10/22/2022]
Abstract
Falcipain-2 (FP-2) and falcipain-3 (FP-3), haemoglobin-degrading enzymes in Plasmodium falciparum, are validated drug targets for the development of effective inhibitors against malaria. However, no commercial drug-targeting falcipains has been developed despite their central role in the life cycle of the parasites. In this work, in silico approaches are used to identify key structural elements that control the binding and selectivity of a diverse set of non-peptidic compounds onto FP-2, FP-3 and homologues from other Plasmodium species as well as human cathepsins. Hotspot residues and the underlying non-covalent interactions, important for the binding of ligands, are identified by interaction fingerprint analysis between the proteases and 2-cyanopyridine derivatives (best hits). It is observed that the size and chemical type of substituent groups within 2-cyanopyridine derivatives determine the strength of protein-ligand interactions. This research presents novel results that can further be exploited in the structure-based molecular-guided design of more potent antimalarial drugs.
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Affiliation(s)
- Thommas M. Musyoka
- Research Unit in Bioinformatics (RUBi), Department of Biochemistry and Microbiology, Rhodes University, Grahamstown, South Africa
| | - Aquillah M. Kanzi
- Research Unit in Bioinformatics (RUBi), Department of Biochemistry and Microbiology, Rhodes University, Grahamstown, South Africa
- Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
| | - Kevin A. Lobb
- Research Unit in Bioinformatics (RUBi), Department of Biochemistry and Microbiology, Rhodes University, Grahamstown, South Africa
- Department of Chemistry, Rhodes University, Grahamstown, South Africa
| | - Özlem Tastan Bishop
- Research Unit in Bioinformatics (RUBi), Department of Biochemistry and Microbiology, Rhodes University, Grahamstown, South Africa
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16
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Sinha S, Singh A, Medhi B, Sehgal R. Systematic Review: Insight into Antimalarial Peptide. Int J Pept Res Ther 2016. [DOI: 10.1007/s10989-016-9512-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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17
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Allosteric regulation of the Plasmodium falciparum cysteine protease falcipain-2 by heme. Arch Biochem Biophys 2015; 573:92-9. [PMID: 25791019 DOI: 10.1016/j.abb.2015.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/22/2015] [Accepted: 03/09/2015] [Indexed: 11/20/2022]
Abstract
During the erythrocytic cycle of Plasmodium falciparum malaria parasites break down host hemoglobin, resulting in the release of free heme (ferriprotoporphyrin IX). Heme is a generator of free radicals that cause oxidative stress, but it is detoxified by crystallization into hemozoin inside the food vacuole. We evaluated the interaction of heme and heme analogues with falcipain-2, a P. falciparum food vacuole cysteine protease that plays a key role in hemoglobin digestion. Heme bound to falcipain-2 with a 1:1 stoichiometry, and heme inhibited falcipain-2 activity against both human hemoglobin and chromogenic peptide substrates through a noncompetitive-like mechanism. A series of porphyrin analogues was screened for inhibition of falcipain-2, demonstrating a minor contribution of iron to heme-falcipain-2 interaction, and revealing dependence on both propionic and vinyl groups for inhibition of falcipain-2 by heme. Docking and molecular dynamics simulation unveiled a novel, inducible heme-binding moiety in falcipain-2 adjacent to the catalytic site. Kinetic data suggested that the noncompetitive-like inhibition was substrate inhibition induced by heme. Collectively these data suggest that binding of heme to falcipain-2 may limit the accumulation of free heme in the parasite food vacuole, providing a means of heme detoxification in addition to crystallization into hemozoin.
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18
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Sinha S, Medhi B, Sehgal R. Challenges of drug-resistant malaria. ACTA ACUST UNITED AC 2014; 21:61. [PMID: 25402734 PMCID: PMC4234044 DOI: 10.1051/parasite/2014059] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Accepted: 10/23/2014] [Indexed: 01/09/2023]
Abstract
Over the past six decades, the drug resistance of Plasmodium falciparum has become an issue of utmost concern. Despite the remarkable progress that has been made in recent years in reducing the mortality rate to about 30% with the scaling-up of vector control, introduction of artemisinin-based combination therapies and other malaria control strategies, the confirmation of artemisinin resistance on the Cambodia–Thailand border threatened all the previous success. This review addresses the global scenario of antimalarial resistance and factors associated with it, with the main emphasis on futuristic approaches like nanotechnology and stem cell therapy that may impede resistant malaria, along with novel medications which are preparing to enter the global antimalarial market. These novel studies are likely to escalate over the coming years and will hopefully help to reduce the burden of malaria.
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Affiliation(s)
- Shweta Sinha
- Department of Medical Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India
| | - Bikash Medhi
- Department of Pharmacology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India
| | - Rakesh Sehgal
- Department of Medical Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India
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19
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Weldon DJ, Shah F, Chittiboyina AG, Sheri A, Chada RR, Gut J, Rosenthal PJ, Shivakumar D, Sherman W, Desai P, Jung JC, Avery MA. Synthesis, biological evaluation, hydration site thermodynamics, and chemical reactivity analysis of α-keto substituted peptidomimetics for the inhibition of Plasmodium falciparum. Bioorg Med Chem Lett 2014; 24:1274-9. [PMID: 24507921 DOI: 10.1016/j.bmcl.2014.01.062] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 01/21/2014] [Indexed: 11/29/2022]
Abstract
A new series of peptidomimetic pseudo-prolyl-homophenylalanylketones were designed, synthesized and evaluated for inhibition of the Plasmodium falciparum cysteine proteases falcipain-2 (FP-2) and falcipain-3 (FP-3). In addition, the parasite killing activity of these compounds in human blood-cultured P. falciparum was examined. Of twenty-two (22) compounds synthesized, one peptidomimetic comprising a homophenylalanine-based α-hydroxyketone linked Cbz-protected hydroxyproline (39) showed the most potency (IC50 80 nM against FP-2 and 60 nM against FP-3). In silico analysis of these peptidomimetic analogs offered important protein-ligand structural insights including the role, by WaterMap, of water molecules in the active sites of these protease isoforms. The pseudo-dipeptide 39 and related compounds may serve as a promising direction forward in the design of competitive inhibitors of falcipains for the effective treatment of malaria.
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Affiliation(s)
- David J Weldon
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States; School of Pharmacy, Department of Pharmaceutical Sciences, Loma Linda University, Loma Linda, CA 92350, United States
| | - Falgun Shah
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States
| | - Amar G Chittiboyina
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States; National Center for Natural Products Research, University of Mississippi, University, MS 38677, United States
| | - Anjaneyulu Sheri
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States
| | - Raji Reddy Chada
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States
| | - Jiri Gut
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, CA 94143, United States
| | - Philip J Rosenthal
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, CA 94143, United States
| | - Develeena Shivakumar
- Schrodinger, Inc., 120 West 45th Street, 17th Floor, New York, NY 10036, United States
| | - Woody Sherman
- Schrodinger, Inc., 120 West 45th Street, 17th Floor, New York, NY 10036, United States
| | - Prashant Desai
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States
| | - Jae-Chul Jung
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States
| | - Mitchell A Avery
- School of Pharmacy, Department of Medicinal Chemistry, University of Mississippi, University, MS 38677, United States; National Center for Natural Products Research, University of Mississippi, University, MS 38677, United States.
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20
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Ndao M, Nath-Chowdhury M, Sajid M, Marcus V, Mashiyama ST, Sakanari J, Chow E, Mackey Z, Land KM, Jacobson MP, Kalyanaraman C, McKerrow JH, Arrowood MJ, Caffrey CR. A cysteine protease inhibitor rescues mice from a lethal Cryptosporidium parvum infection. Antimicrob Agents Chemother 2013; 57:6063-73. [PMID: 24060869 PMCID: PMC3837922 DOI: 10.1128/aac.00734-13] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 09/16/2013] [Indexed: 02/06/2023] Open
Abstract
Cryptosporidiosis, caused by the protozoan parasite Cryptosporidium parvum, can stunt infant growth and can be lethal in immunocompromised individuals. The most widely used drugs for treating cryptosporidiosis are nitazoxanide and paromomycin, although both exhibit limited efficacy. To investigate an alternative approach to therapy, we demonstrate that the clan CA cysteine protease inhibitor N-methyl piperazine-Phe-homoPhe-vinylsulfone phenyl (K11777) inhibits C. parvum growth in mammalian cell lines in a concentration-dependent manner. Further, using the C57BL/6 gamma interferon receptor knockout (IFN-γR-KO) mouse model, which is highly susceptible to C. parvum, oral or intraperitoneal treatment with K11777 for 10 days rescued mice from otherwise lethal infections. Histologic examination of untreated mice showed intestinal inflammation, villous blunting, and abundant intracellular parasite stages. In contrast, K11777-treated mice (210 mg/kg of body weight/day) showed only minimal inflammation and no epithelial changes. Three putative protease targets (termed cryptopains 1 to 3, or CpaCATL-1, -2, and -3) were identified in the C. parvum genome, but only two are transcribed in infected mammals. A homology model predicted that K11777 would bind to cryptopain 1. Recombinant enzymatically active cryptopain 1 was successfully targeted by K11777 in a competition assay with a labeled active-site-directed probe. K11777 exhibited no toxicity in vitro and in vivo, and surviving animals remained free of parasites 3 weeks after treatment. The discovery that a cysteine protease inhibitor provides potent anticryptosporidial activity in an animal model of infection encourages the investigation and development of this biocide class as a new, and urgently needed, chemotherapy for cryptosporidiosis.
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Affiliation(s)
- Momar Ndao
- National Reference Centre for Parasitology, Research Institute of the McGill University Health Center, Montreal, Canada
| | - Milli Nath-Chowdhury
- National Reference Centre for Parasitology, Research Institute of the McGill University Health Center, Montreal, Canada
| | - Mohammed Sajid
- Center for Discovery and Innovation in Parasitic Diseases and Department of Pathology, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California, USA
- Leiden University Medical Center, Leiden, Netherlands
| | - Victoria Marcus
- Department of Pathology, McGill University Health Centre, Montreal General Hospital, Montreal, Canada
| | - Susan T. Mashiyama
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Judy Sakanari
- Center for Discovery and Innovation in Parasitic Diseases and Department of Pathology, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California, USA
| | - Eric Chow
- Center for Discovery and Innovation in Parasitic Diseases and Department of Pathology, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California, USA
| | - Zachary Mackey
- Center for Discovery and Innovation in Parasitic Diseases and Department of Pathology, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California, USA
| | - Kirkwood M. Land
- Center for Discovery and Innovation in Parasitic Diseases and Department of Pathology, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California, USA
- Department of Biological Sciences, University of the Pacific, Stockton, California, USA
| | - Matthew P. Jacobson
- Departments of Pharmaceutical Sciences
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Chakrapani Kalyanaraman
- Departments of Pharmaceutical Sciences
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA
| | - James H. McKerrow
- Center for Discovery and Innovation in Parasitic Diseases and Department of Pathology, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California, USA
| | - Michael J. Arrowood
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Conor R. Caffrey
- Center for Discovery and Innovation in Parasitic Diseases and Department of Pathology, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California, USA
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21
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Mugumbate G, Newton AS, Rosenthal PJ, Gut J, Moreira R, Chibale K, Guedes RC. Novel anti-plasmodial hits identified by virtual screening of the ZINC database. J Comput Aided Mol Des 2013; 27:859-71. [PMID: 24158745 DOI: 10.1007/s10822-013-9685-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/12/2013] [Indexed: 01/16/2023]
Abstract
Increased resistance of Plasmodium falciparum to most available drugs challenges the control of malaria. Studies with protease inhibitors have suggested important roles for the falcipain family of cysteine proteases. These enzymes act in concert with other proteases to hydrolyze host erythrocyte hemoglobin in the parasite food vacuole. In order to find potential new antimalarial drugs, we screened in silico the ZINC database using two different protocols involving structure- and ligand-based methodologies. Our search identified 19 novel low micromolar inhibitors of cultured chloroquine resistant P. falciparum. The most active compound presented an IC50 value of 0.5 μM against cultured parasites and it also inhibited the cysteine protease falcipain-2 (IC50 = 25.5 μM). These results identify novel classes of antimalarials that are structurally different from those currently in use and which can be further derivatized to deliver leads suitable for optimisation.
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Affiliation(s)
- Grace Mugumbate
- Department of Chemistry, University of Cape Town, Rondebosch, 7701, South Africa
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22
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Marques AF, Esser D, Rosenthal PJ, Kassack MU, Lima LMTR. Falcipain-2 inhibition by suramin and suramin analogues. Bioorg Med Chem 2013; 21:3667-73. [PMID: 23680445 DOI: 10.1016/j.bmc.2013.04.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 04/09/2013] [Accepted: 04/17/2013] [Indexed: 10/26/2022]
Abstract
Falcipain-2 is a cysteine protease of the malaria parasite Plasmodium falciparum that plays a key role in the hydrolysis of hemoglobin, a process that is required by intraerythrocytic parasites to obtain amino acids. In this work we show that the polysulfonated napthylurea suramin is capable of binding to falcipain-2, inhibiting its catalytic activity at nanomolar concentrations against both synthetic substrates and the natural substrate hemoglobin. Kinetic measurements suggest that the inhibition occurs through an noncompetitive allosteric mechanism, eliciting substrate inhibition. Smaller suramin analogues and those with substituted methyl groups also showed inhibition within the nanomolar range. Our results identify the suramin family as a potential starting point for the design of falcipain-2 inhibitor antimalarials that act through a novel inhibition mechanism.
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Affiliation(s)
- Adriana Fonseca Marques
- Laboratory for Pharmaceutical Biotechnology, School of Pharmacy, Federal University of Rio de Janeiro, CCS, Bss34, Ilha do Fundão, 21941-590 Rio de Janeiro, RJ, Brazil
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23
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Pillai AD, Addo R, Sharma P, Nguitragool W, Srinivasan P, Desai SA. Malaria parasites tolerate a broad range of ionic environments and do not require host cation remodelling. Mol Microbiol 2013; 88:20-34. [PMID: 23347042 DOI: 10.1111/mmi.12159] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2013] [Indexed: 11/29/2022]
Abstract
Malaria parasites grow within erythrocytes, but are also free in host plasma between cycles of asexual replication. As a result, the parasite is exposed to fluctuating levels of Na(+) and K(+) , ions assumed to serve important roles for the human pathogen, Plasmodium falciparum. We examined these assumptions and the parasite's ionic requirements by establishing continuous culture in novel sucrose-based media. With sucrose as the primary osmoticant and K(+) and Cl(-) as the main extracellular ions, we obtained parasite growth and propagation at rates indistinguishable from those in physiological media. These conditions abolish long-known increases in intracellular Na(+) via parasite-induced channels, excluding a requirement for erythrocyte cation remodelling. We also dissected Na(+) , K(+) and Cl(-) requirements and found that unexpectedly low concentrations of each ion meet the parasite's demands. Surprisingly, growth was not adversely affected by up to 148 mM K(+) , suggesting that low extracellular K(+) is not an essential trigger for erythrocyte invasion. At the same time, merozoite egress and invasion required a threshold ionic strength, suggesting critical electrostatic interactions between macromolecules at these stages. These findings provide insights into transmembrane signalling in malaria and reveal fundamental differences between host and parasite ionic requirements.
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Affiliation(s)
- Ajay D Pillai
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
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24
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Zhang L, Fourches D, Sedykh A, Zhu H, Golbraikh A, Ekins S, Clark J, Connelly MC, Sigal M, Hodges D, Guiguemde A, Guy RK, Tropsha A. Discovery of novel antimalarial compounds enabled by QSAR-based virtual screening. J Chem Inf Model 2013; 53:475-92. [PMID: 23252936 DOI: 10.1021/ci300421n] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Quantitative structure-activity relationship (QSAR) models have been developed for a data set of 3133 compounds defined as either active or inactive against P. falciparum. Because the data set was strongly biased toward inactive compounds, different sampling approaches were employed to balance the ratio of actives versus inactives, and models were rigorously validated using both internal and external validation approaches. The balanced accuracy for assessing the antimalarial activities of 70 external compounds was between 87% and 100% depending on the approach used to balance the data set. Virtual screening of the ChemBridge database using QSAR models identified 176 putative antimalarial compounds that were submitted for experimental validation, along with 42 putative inactives as negative controls. Twenty five (14.2%) computational hits were found to have antimalarial activities with minimal cytotoxicity to mammalian cells, while all 42 putative inactives were confirmed experimentally. Structural inspection of confirmed active hits revealed novel chemical scaffolds, which could be employed as starting points to discover novel antimalarial agents.
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Affiliation(s)
- Liying Zhang
- The Laboratory for Molecular Modeling, Eshelman School of Pharmacy, CB# 7568, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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25
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Dou Z, Coppens I, Carruthers VB. Non-canonical maturation of two papain-family proteases in Toxoplasma gondii. J Biol Chem 2012; 288:3523-34. [PMID: 23250753 DOI: 10.1074/jbc.m112.443697] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Proteases regulate key events during infection by the pervasive intracellular parasite Toxoplasma gondii. Understanding how parasite proteases mature from an inactive zymogen to an active enzyme is expected to inform new strategies for blocking their actions. Herein, we show that T. gondii cathepsin B protease (TgCPB) does not undergo self-maturation but instead requires the expression of a second papain-family cathepsin protease, TgCPL. Using recombinant enzymes we also show that TgCPL is capable of partially maturing TgCPB in vitro. Consistent with this interrelationship, antibodies with validated specificity detected TgCPB in the lysosome-like vacuolar compartment along with TgCPL. Our findings also establish that TgCPB does not localize to the rhoptries as previously reported. Accordingly, rhoptry morphology and rhoptry protein maturation are normal in TgCPB knock-out parasites. Finally, we show that although maturation of TgCPL is independent of TgCPB, it may involve an additional protease(s) in conjunction with self-maturation.
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Affiliation(s)
- Zhicheng Dou
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
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26
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Expression, characterization, and cellular localization of knowpains, papain-like cysteine proteases of the Plasmodium knowlesi malaria parasite. PLoS One 2012; 7:e51619. [PMID: 23251596 PMCID: PMC3520923 DOI: 10.1371/journal.pone.0051619] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 11/02/2012] [Indexed: 01/09/2023] Open
Abstract
Papain-like cysteine proteases of malaria parasites degrade haemoglobin in an acidic food vacuole to provide amino acids for intraerythrocytic parasites. These proteases are potential drug targets because their inhibitors block parasite development, and efforts are underway to develop chemotherapeutic inhibitors of these proteases as the treatments for malaria. Plasmodium knowlesi has recently been shown to be an important human pathogen in parts of Asia. We report expression and characterization of three P. knowlesi papain-like proteases, termed knowpains (KP2-4). Recombinant knowpains were produced using a bacterial expression system, and tested for various biochemical properties. Antibodies against recombinant knowpains were generated and used to determine their cellular localization in parasites. Inhibitory effects of the cysteine protease inhibitor E64 were assessed on P. knowlesi culture to validate drug target potential of knowpains. All three knowpains were present in the food vacuole, active in acidic pH, and capable of degrading haemoglobin at the food vacuolar pH (≈5.5), suggesting roles in haemoglobin degradation. The proteases showed absolute (KP2 and KP3) to moderate (KP4) preference for peptide substrates containing leucine at the P2 position; KP4 preferred arginine at the P2 position. While the three knowpains appear to have redundant roles in haemoglobin degradation, KP4 may also have a role in degradation of erythrocyte cytoskeleton during merozoite egress, as it displayed broad substrate specificity and was primarily localized at the parasite periphery. Importantly, E64 blocked erythrocytic development of P. knowlesi, with enlargement of food vacuoles, indicating inhibition of haemoglobin hydrolysis and supporting the potential for inhibition of knowpains as a strategy for the treatment of malaria. Functional expression and characterization of knowpains should enable simultaneous screening of available cysteine protease inhibitor libraries against knowpains for developing broadly effective compounds active against multiple human malaria parasites.
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27
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Mane UR, Gupta RC, Nadkarni SS, Giridhar RR, Naik PP, Yadav MR. Falcipain inhibitors as potential therapeutics for resistant strains of malaria: a patent review. Expert Opin Ther Pat 2012; 23:165-87. [DOI: 10.1517/13543776.2013.743992] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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28
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Pérez-Picaso L, Olivo HF, Argotte-Ramos R, Rodríguez-Gutiérrez M, Rios MY. Linear and cyclic dipeptides with antimalarial activity. Bioorg Med Chem Lett 2012; 22:7048-51. [PMID: 23084276 DOI: 10.1016/j.bmcl.2012.09.094] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 09/20/2012] [Accepted: 09/25/2012] [Indexed: 11/30/2022]
Abstract
Several natural and synthetic polypeptides possess important antimalarial activity. Shorter peptides with potent antimalarial activity have also been described, among them linear di-, tri-, tetra- and pentapeptides and their cyclic analogs. In an attempt to find dipeptides with antimalarial activities we show that linear and cyclic dipeptides, the latter known as diketopiperazines, still retain the fundamental core to preserve antimalarial activity. Thirteen linear dipeptides and ten diketopiperazines were investigated. Eight linear dipeptides showed IC(50) values between 2.78 and 7.07 μM, while eight diketopiperazines were also active with IC(50) values between 2.26 and 4.26 μM on Plasmodium berghei schizont cultures.
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Affiliation(s)
- Lemuel Pérez-Picaso
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos 62209, Mexico
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29
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Shah F, Gut J, Legac J, Shivakumar D, Sherman W, Rosenthal PJ, Avery MA. Computer-aided drug design of falcipain inhibitors: virtual screening, structure-activity relationships, hydration site thermodynamics, and reactivity analysis. J Chem Inf Model 2012; 52:696-710. [PMID: 22332946 DOI: 10.1021/ci2005516] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Falcipains (FPs) are hemoglobinases of Plasmodium falciparum that are validated targets for the development of antimalarial chemotherapy. A combined ligand- and structure-based virtual screening of commercial databases was performed to identify structural analogs of virtual screening hits previously discovered in our laboratory. A total of 28 low micromolar inhibitors of FP-2 and FP-3 were identified and the structure-activity relationship (SAR) in each series was elaborated. The SAR of the compounds was unusually steep in some cases and could not be explained by a traditional analysis of the ligand-protein interactions (van der Waals, electrostatics, and hydrogen bonds). To gain further insights, a statistical thermodynamic analysis of explicit solvent in the ligand binding domains of FP-2 and FP-3 was carried out to understand the roles played by water molecules in binding of these inhibitors. Indeed, the energetics associated with the displacement of water molecules upon ligand binding explained some of the complex trends in the SAR. Furthermore, low potency of a subset of FP-2 inhibitors that could not be understood by the water energetics was explained in the context of poor chemical reactivity of the reactive centers of these compounds. The present study highlights the importance of considering energetic contributors to binding beyond traditional ligand-protein interactions.
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Affiliation(s)
- Falgun Shah
- Department of Medicinal Chemistry, School of Pharmacy, University of Mississippi, University, Mississippi 38677, USA
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30
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Moneriz C, Mestres J, Bautista JM, Diez A, Puyet A. Multi-targeted activity of maslinic acid as an antimalarial natural compound. FEBS J 2011; 278:2951-61. [PMID: 21689375 DOI: 10.1111/j.1742-4658.2011.08220.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Most drugs against malaria that are available or under development target a single process of the parasite infective cycle, favouring the appearance of resistant mutants which are easily spread in areas under chemotherapeutic treatments. Maslinic acid (MA) is a low toxic natural pentacyclic triterpene for which a wide variety of biological and therapeutic activities have been reported. Previous work revealed that Plasmodium falciparum erythrocytic cultures were inhibited by MA, which was able to hinder the maturation from ring to schizont stage and, as a consequence, prevent the release of merozoites and the subsequent invasion. We show here that MA effectively inhibits the proteolytic processing of the merozoite surface protein complex, probably by inhibition of PfSUB1. In addition, MA was also found to inhibit metalloproteases of the M16 family by a non-chelating mechanism, suggesting the possible hindrance of plasmodial metalloproteases belonging to that family, such as falcilysin and apicoplast peptide-processing proteases. Finally, in silico target screening was used to search for other potential binding targets that may have remained undetected. Among the targets identified, the method recovered two for which experimental activity could be confirmed, and suggested several putative new targets to which MA could have affinity. One of these unreported targets, phospholipase A2, was shown to be partially inhibited by MA. These results suggest that MA may behave as a multi-targeted drug against the intra-erythrocytic cycle of Plasmodium, providing a new tool to investigate the synergistic effect of inhibiting several unrelated processes with a single compound, a new concept in antimalarial research.
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Affiliation(s)
- Carlos Moneriz
- Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain
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31
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Ojha PK, Roy K. Exploring molecular docking and QSAR studies of plasmepsin-II inhibitor di-tertiary amines as potential antimalarial compounds. MOLECULAR SIMULATION 2011. [DOI: 10.1080/08927022.2010.548384] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Probir Kumar Ojha
- a Drug Theoretics and Cheminformatics Laboratory, Division of Medicinal and Pharmaceutical Chemistry, Department of Pharmaceutical Technology , Jadavpur University , Kolkata, India
| | - Kunal Roy
- a Drug Theoretics and Cheminformatics Laboratory, Division of Medicinal and Pharmaceutical Chemistry, Department of Pharmaceutical Technology , Jadavpur University , Kolkata, India
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32
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Affiliation(s)
- P Olliaro
- UNDP/World Bank /WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland
| | - D Wirth
- UNDP/World Bank /WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland
- Harvard School of Tropical Public Health, Boston MA, USA
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33
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Affiliation(s)
- Robert G Ridley
- F. Hoffmann-La Roche, Pharmaceuticals Division, Pharma Research, CH-4070 Basel, Switzerland
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34
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Shah F, Mukherjee P, Gut J, Legac J, Rosenthal PJ, Tekwani BL, Avery MA. Identification of novel malarial cysteine protease inhibitors using structure-based virtual screening of a focused cysteine protease inhibitor library. J Chem Inf Model 2011; 51:852-64. [PMID: 21428453 DOI: 10.1021/ci200029y] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Malaria, in particular that caused by Plasmodium falciparum , is prevalent across the tropics, and its medicinal control is limited by widespread drug resistance. Cysteine proteases of P. falciparum , falcipain-2 (FP-2) and falcipain-3 (FP-3), are major hemoglobinases, validated as potential antimalarial drug targets. Structure-based virtual screening of a focused cysteine protease inhibitor library built with soft rather than hard electrophiles was performed against an X-ray crystal structure of FP-2 using the Glide docking program. An enrichment study was performed to select a suitable scoring function and to retrieve potential candidates against FP-2 from a large chemical database. Biological evaluation of 50 selected compounds identified 21 diverse nonpeptidic inhibitors of FP-2 with a hit rate of 42%. Atomic Fukui indices were used to predict the most electrophilic center and its electrophilicity in the identified hits. Comparison of predicted electrophilicity of electrophiles in identified hits with those in known irreversible inhibitors suggested the soft-nature of electrophiles in the selected target compounds. The present study highlights the importance of focused libraries and enrichment studies in structure-based virtual screening. In addition, few compounds were screened against homologous human cysteine proteases for selectivity analysis. Further evaluation of structure-activity relationships around these nonpeptidic scaffolds could help in the development of selective leads for antimalarial chemotherapy.
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Affiliation(s)
- Falgun Shah
- Department of Medicinal Chemistry, School of Pharmacy, University of Mississippi , University, Mississippi 38677, USA
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35
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Moon SU, Kang JM, Kim TS, Kong Y, Sohn WM, Na BK. Plasmodium vivax: collaborative roles for plasmepsin 4 and vivapains in hemoglobin hydrolysis. Exp Parasitol 2011; 128:127-32. [PMID: 21334328 DOI: 10.1016/j.exppara.2011.02.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 12/08/2010] [Accepted: 02/14/2011] [Indexed: 01/16/2023]
Abstract
Plasmepsins, a family of aspartic proteases of Plasmodium species, are known to participate in a wide variety of cellular processes essential for parasite survival. Therefore, the plasmepsins of malaria parasites have been recognized as attractive antimalarial drug targets. Although the plasmepsins of P. falciparum have been extensively characterized, the plasmepsins of P. vivax are currently not well known. To expand our understanding of the plasmepsins of P. vivax, we characterized plasmepsin 4 of P. vivax (PvPM4). The bacterially expressed recombinant PvPM4 was insoluble, but it was easily refolded into a soluble protein. The processing of PvPM4 into a mature enzyme occurred through autocatalytic activity under acidic conditions in a pepstatin A-sensitive manner, in which process a portion of prodomain was essential for correct folding. PvPM4 could hydrolyze native human hemoglobin at acidic pHs, but preferred denatured hemoglobin as a substrate. PvPM4 acted synergistically with vivapain-2 and vivapain-3, cysteine proteases of P. vivax, in the hydrolysis of hemoglobin. The vivapains also mediated processing of PvPM4 into a mature enzyme. These results collectively suggest that PvPM4 is an active hemoglobinase of P. vivax that works collaboratively with vivapains to enhance the parasite's ability to hydrolyze hemoglobin.
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Affiliation(s)
- Sung-Ung Moon
- Department of Parasitology, Brain Korea 21 Biomedical Center, and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 660-751, Republic of Korea
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36
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Dou Z, Carruthers VB. Cathepsin proteases in Toxoplasma gondii. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 712:49-61. [PMID: 21660658 DOI: 10.1007/978-1-4419-8414-2_4] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cysteine proteases are important for the growth and survival of apicomplexan parasites that infect humans. The apicomplexan Toxoplasma gondii expresses five members of the C1 family of cysteine proteases, including one cathepsin L-like (TgCPL), one cathepsin B-like (TgCPB) and three cathepsin C-like (TgCPC1, 2 and 3) proteases. Recent genetic, biochemical and structural studies reveal that cathepsins function in microneme and rhoptry protein maturation, host cell invasion, replication and nutrient acquisition. here, we review the key features and roles of T. gondii cathepsins and discuss the therapeutic potential for specific inhibitor development.
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Affiliation(s)
- Zhicheng Dou
- Department of Microbiology and Immunology, University of Michigan School of Medicine, Ann Arbor, Michigan, USA
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37
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Shah F, Wu Y, Gut J, Pedduri Y, Legac J, Rosenthal PJ, Avery MA. Design, synthesis and biological evaluation of novel benzothiazole and triazole analogs as falcipain inhibitors. MEDCHEMCOMM 2011. [DOI: 10.1039/c1md00129a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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38
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Rosenthal PJ. Falcipains and other cysteine proteases of malaria parasites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 712:30-48. [PMID: 21660657 DOI: 10.1007/978-1-4419-8414-2_3] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A number of cysteine proteases of malaria parasites have been described and many more are suggested by analysis of the Plasmodium falciparum genome sequence. The best characterized of these proteases are the falcipains, a family of four papain-family enzymes. Falcipain-2 and falcipain-3 act in concert with other proteases to hydrolyze host erythrocyte hemoglobin in the parasite food vacuole. Disruption of the falcipain-2 gene led to a transient block in hemoglobin hydrolysis and parasites with increased sensitivity to protease inhibitors. Disruption of the falcipain-3 gene was not possible, strongly suggesting that this protease is essential for erythrocytic parasites. Disruption of the falcipain-1 gene did not alter development in erythrocytes, but led to decreased production of oocysts in mosquitoes. other papain-family proteases predicted by the genome sequence include dipeptidyl peptidases, a calpain homolog and serine-repeat antigens (SERAs). Dipeptidyl aminopeptidase 1 appears to be essential and localized to the food vacuole, suggesting a role in hemoglobin hydrolysis. Dipeptidyl aminopeptidase 3 appears to play a role in the rupture of erythrocytes by mature parasites. the P. falciparum calpain homolog gene could not be disrupted, suggesting that the protein is essential and a role in the parasite cell cycle has been suggested. Nine P. falciparum SERAs have cysteine protease motifs, but in some the active site cys is replaced by a Ser. Gene disruption studies suggested that SERA-5 and SERA-6 are essential. activation of SERA-5 by a serine protease seems to be required for merozoite egress from the erythrocyte. New drugs for malaria are greatly needed and cysteine proteases represent potential drug targets. cysteine protease inhibitors have demonstrated potent antimalarial effects and the optimization and testing of falcipain inhibitor antimalarials is underway.
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Affiliation(s)
- Philip J Rosenthal
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, California, USA.
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39
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Abstract
Malaria, particularly that one caused by Plasmodium falciparum, remains a serious health problem in Africa, South America, and many parts of Asia where it afflicts about 500 million people and is responsible for the death of more than one million children each year. The main reasons for the persistence of malaria are the emergence of resistance to common antimalarial drugs, inadequate control of mosquito vectors, and the lack of effective vaccines. Therefore, the identification and characterization of new targets for antimalarial chemotherapy are of urgent priority. This review is focused on inhibitors of falcipain-2, a cysteine protease from P. falciparum, which represents one of the most promising targets for antimalarial drug design. Falcipain-2 is a key enzyme in the life cycle of P. falciparum since it degrades hemoglobin, at the early trophozoite stage, and cleaves ankyrin and protein 4.1, the cytoskeletal elements vital to the stability of red cell membrane, at the schizont stage. The main classes of falcipain-2 inhibitors are peptides or peptidomimetics bearing the most popular pharmacophores of cysteine protease inhibitors, such as vinyl sulfones, halomethyl ketones, and aldehydes. Furthermore, many other chemotypes have been identified as inhibitors of falcipain-2, such as isoquinolines, thiosemicarbazones, and chalcones. These inhibitors represent all classes, which, to the best of our knowledge, have been disclosed in journal articles to date.
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Affiliation(s)
- Roberta Ettari
- Dipartimento Farmaco-Chimico, University of Messina, Messina, Italy.
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40
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Pillai AD, Pain M, Solomon T, Bokhari AAB, Desai SA. A cell-based high-throughput screen validates the plasmodial surface anion channel as an antimalarial target. Mol Pharmacol 2010; 77:724-33. [PMID: 20101003 DOI: 10.1124/mol.109.062711] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The plasmodial surface anion channel (PSAC) is an unusual small-conductance ion channel induced on erythrocytes infected with plasmodia, including parasites responsible for human malaria. Although broadly available inhibitors produce microscopic clearance of parasite cultures at high concentrations and suggest that PSAC is an antimalarial target, they have low affinity for the channel and may interfere with other parasite activities. To address these concerns, we developed a miniaturized assay for PSAC activity and carried out a high-throughput inhibitor screen. Approximately 70,000 compounds from synthetic and natural product libraries were screened, revealing inhibitors from multiple structural classes including two novel and potent heterocyclic scaffolds. Single-channel patch-clamp studies indicated that these compounds act directly on PSAC, further implicating a proposed role in transport of diverse solutes. A statistically significant correlation between channel inhibition and in vitro parasite killing by a family of compounds provided chemical validation of PSAC as a drug target. These new inhibitors should be important research tools and may be starting points for much-needed antimalarial drugs.
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Affiliation(s)
- Ajay D Pillai
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852-8132, USA
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41
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Pérez-Picaso L, Velasco-Bejarano B, Aguilar-Guadarrama AB, Argotte-Ramos R, Rios MY. Antimalarial activity of ultra-short peptides. Molecules 2009; 14:5103-14. [PMID: 20032878 PMCID: PMC6254971 DOI: 10.3390/molecules14125103] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 12/08/2009] [Accepted: 12/08/2009] [Indexed: 11/29/2022] Open
Abstract
Ultra-short peptides 1-9 were designed and synthesized with phenylalanine, ornithine and proline amino acid residues and their effect on antimalarial activity was analyzed. On the basis of the IC50 data for these compounds, the effects of nature, polarity, and amino acid sequence on Plasmodium berghei schizont cultures were analyzed too. Tetrapeptides Phe-Orn-Phe-Orn (4) and Lys-Phe-Phe-Orn (5) showed a very important activity with IC50 values of 3.31 and 2.57 μM, respectively. These two tetrapeptides are candidates for subsequent in vivo assays and SARS investigations.
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Affiliation(s)
- Lemuel Pérez-Picaso
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col. Chamilpa, 62209 Cuernavaca, Morelos, México
| | - Benjamín Velasco-Bejarano
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col. Chamilpa, 62209 Cuernavaca, Morelos, México
| | - A. Berenice Aguilar-Guadarrama
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col. Chamilpa, 62209 Cuernavaca, Morelos, México
| | - Rocío Argotte-Ramos
- Instituto Nacional de Salud Pública, Centro de Investigación Sobre Enfermedades Infecciosas (CISEI), Avenida Universidad 655, Col. Santa María Ahuacatitlán, 62100 Cuernavaca, Morelos, México
| | - María Yolanda Rios
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col. Chamilpa, 62209 Cuernavaca, Morelos, México
- Authors to whom correspondence should be addressed; E-Mail: ; Tel.: +52-777-329-7000 ext. 6024; Fax: +52-777-329-7997
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42
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Li H, Huang J, Chen L, Liu X, Chen T, Zhu J, Lu W, Shen X, Li J, Hilgenfeld R, Jiang H. Identification of Novel Falcipain-2 Inhibitors as Potential Antimalarial Agents through Structure-Based Virtual Screening. J Med Chem 2009; 52:4936-40. [DOI: 10.1021/jm801622x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Honglin Li
- School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Jin Huang
- School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Lili Chen
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Xiaofeng Liu
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Tong Chen
- School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Jin Zhu
- School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Weiqiang Lu
- School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Xu Shen
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Jian Li
- School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
| | - Rolf Hilgenfeld
- Institute of Biochemistry, Center for Structural and Cell Biology in Medicine, University of Lübeck, Lübeck 23538, Germany
| | - Hualiang Jiang
- School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
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43
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Subramanian S, Hardt M, Choe Y, Niles RK, Johansen EB, Legac J, Gut J, Kerr ID, Craik CS, Rosenthal PJ. Hemoglobin cleavage site-specificity of the Plasmodium falciparum cysteine proteases falcipain-2 and falcipain-3. PLoS One 2009; 4:e5156. [PMID: 19357776 PMCID: PMC2663817 DOI: 10.1371/journal.pone.0005156] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 03/10/2009] [Indexed: 11/18/2022] Open
Abstract
The Plasmodium falciparum cysteine proteases falcipain-2 and falcipain-3 degrade host hemoglobin to provide free amino acids for parasite protein synthesis. Hemoglobin hydrolysis has been described as an ordered process initiated by aspartic proteases, but cysteine protease inhibitors completely block the process, suggesting that cysteine proteases can also initiate hemoglobin hydrolysis. To characterize the specific roles of falcipains, we used three approaches. First, using random P1 – P4 amino acid substrate libraries, falcipain-2 and falcipain-3 demonstrated strong preference for cleavage sites with Leu at the P2 position. Second, with overlapping peptides spanning α and β globin and proteolysis-dependent 18O labeling, hydrolysis was seen at many cleavage sites. Third, with intact hemoglobin, numerous cleavage products were identified. Our results suggest that hemoglobin hydrolysis by malaria parasites is not a highly ordered process, but rather proceeds with rapid cleavage by falcipains at multiple sites. However, falcipain-2 and falcipain-3 show strong specificity for P2 Leu in small peptide substrates, in agreement with the specificity in optimized small molecule inhibitors that was identified previously. These results are consistent with a principal role of falcipain-2 and falcipain-3 in the hydrolysis of hemoglobin by P. falciparum and with the possibility of developing small molecule inhibitors with optimized specificity as antimalarial agents.
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Affiliation(s)
- Shoba Subramanian
- Department of Medicine, Division of Infectious Diseases, University of California San Francisco, San Francisco, California, United States of America
| | - Markus Hardt
- Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, California, United States of America
| | - Youngchool Choe
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Richard K. Niles
- Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, California, United States of America
| | - Eric B. Johansen
- Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, California, United States of America
| | - Jennifer Legac
- Department of Medicine, Division of Infectious Diseases, University of California San Francisco, San Francisco, California, United States of America
| | - Jiri Gut
- Department of Medicine, Division of Infectious Diseases, University of California San Francisco, San Francisco, California, United States of America
| | - Iain D. Kerr
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America
| | - Charles S. Craik
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Philip J. Rosenthal
- Department of Medicine, Division of Infectious Diseases, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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Plasmodium chabaudi: expression of active recombinant chabaupain-1 and localization studies in Anopheles sp. Exp Parasitol 2009; 122:97-105. [PMID: 19292986 DOI: 10.1016/j.exppara.2009.03.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 02/17/2009] [Accepted: 03/02/2009] [Indexed: 11/20/2022]
Abstract
Plasmodium cysteine proteases have been shown to be immunogenic and are being used as malaria potential serodiagnostic markers and vaccine targets. Genes encoding two Plasmodium chabaudi cysteine proteases chabaupain-1 (CP-1) and chabaupain-2 (CP-2) were identified and further expressed in Escherichia coli. Solubilisation of recombinant CP-1 and CP-2 was achieved by decreasing the temperature of induction. Anopheles gambiae tissues infected with Plasmodium were analyzed by Western blotting using the anti-CP-1 antibody showing that CP-1 is only present in the A. gambiae midguts being absent from other infected mosquito biological material. Anti-CP-1 anti-serum recognized a 30 kDa band in P. chabaudi, Plasmodium berghei and Plasmodium yoelii lysates but does not recognize the recombinant CP-2 extracts suggesting high antibody specificity.
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45
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Zhu J, Chen T, Liu J, Ma R, Lu W, Huang J, Li H, Li J, Jiang H. 2-(3,4-dihydro-4-oxothieno[2,3-d]pyrimidin-2-ylthio) acetamides as a new class of falcipain-2 inhibitors. 3. design, synthesis and biological evaluation. Molecules 2009; 14:785-97. [PMID: 19223827 PMCID: PMC6253991 DOI: 10.3390/molecules14020785] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 01/18/2009] [Accepted: 02/13/2009] [Indexed: 12/04/2022] Open
Abstract
The cysteine protease falcipain-2 (FP-2) of Plasmodium falciparum is a principal cysteine protease and an essential hemoglobinase of erythrocytic P. falciparum trophozoites, making it become an attractive target enzyme for developing anti-malarial drugs. In this study, a series of novel small molecule FP-2 inhibitors have been designed and synthesized based on compound 1, which was identified by using structure-based virtual screening in conjunction with an enzyme inhibition assay. All compounds showed high inhibitory effect against FP-2 with IC(50)s of 1.46-11.38 microM, and the inhibitory activity of compound 2a was ~2 times greater than that of prototype compound 1. The preliminary SARs are summarized and should be helpful for future inhibitor design, and the novel scaffold presented here, with its potent inhibitory activity against FP-2, also has potential application in discovery of new anti-malarial drugs.
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Affiliation(s)
- Jin Zhu
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Tong Chen
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Jie Liu
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Ruoqun Ma
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Weiqiang Lu
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Jin Huang
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Honglin Li
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Jian Li
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
| | - Hualiang Jiang
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, P.R. China
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Zhu J, Chen T, Chen L, Lu W, Che P, Huang J, Li H, Li J, Jiang H. 2-amido-3-(1H-indol-3-yl)-N-substituted-propanamides as a new class of falcipain-2 inhibitors. 1. Design, synthesis, biological evaluation and binding model studies. Molecules 2009; 14:494-508. [PMID: 19158658 PMCID: PMC6253880 DOI: 10.3390/molecules14010494] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2008] [Revised: 01/11/2009] [Accepted: 01/13/2009] [Indexed: 11/16/2022] Open
Abstract
The Plasmodium falciparum cysteine protease falcipain-2 (FP-2) is an important cysteine protease and an essential hemoglobinase of erythrocytic P. falciparum trophozoites. The discovery of new FP-2 inhibitors is now a hot topic in the search for potential malaria treatments. In this study, a series of novel small molecule FP-2 inhibitors have been designed and synthesized based on three regional optimizations of the lead (R)-2-phenoxycarboxamido-3-(1H-indol-3-yl)-N-benzylpropanamide(1), which was identified using structure-based virtual screening in conjunction with surface plasmon resonance (SPR)-based binding assays. Four compounds--1, 2b, 2k and 2l--showed moderate FP-2 inhibition activity, with IC(50) values of 10.0-39.4 microM, and the inhibitory activity of compound 2k was approximately 3-fold better than that of the prototype compound 1 and may prove useful for the development of micromolar level FP-2 inhibitors. Preliminary SAR data was obtained, while molecular modeling revealed that introduction of H-bond donor or/and acceptor atoms to the phenyl ring moiety in the C region would be likely to produce some additional H-bond interactions, which should consequently enhance molecular bioactivity.
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Affiliation(s)
- Jin Zhu
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
| | - Tong Chen
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
| | - Lili Chen
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, P.R. China; E-Mail: (L. C.)
| | - Weiqiang Lu
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
| | - Peng Che
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
| | - Jin Huang
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
| | - Honglin Li
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
| | - Jian Li
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
| | - Hualiang Jiang
- School of Pharmacy, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, P.R. China. E-Mails: (J. Z.); (T. C.); (W. L.); (P. C.); (H. J.)
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, P.R. China; E-Mail: (L. C.)
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Yadav MR, Shinde AK, Chouhan BS, Giridhar R, Menard R. Peptidomimetic 2-cyanopyrrolidines as potent selective cathepsin L inhibitors. J Enzyme Inhib Med Chem 2008; 23:190-7. [PMID: 18343903 DOI: 10.1080/14756360701504842] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Cathepsins have been found to have important physiological roles. The implication of cathepsin L in various types of cancers is well established. In a search for selective cathepsin L inhibitors as anticancer agents, a series of 2-cyanoprrolidine peptidomimetics, carrying a nitrile group as warhead, were designed. Two series of compounds, one with a benzyl moiety and a second with an isobutyl moiety at P(2) position of the enzyme were synthesized. The synthesized compounds were evaluated for inhibitory activity against human cathepsin L and cathepsin B. Although, none of the compounds showed promising inhibitory activity, (E)N-{(S)1-[(S)2-cyano-1-pyrrolidinecarbonyl]-3-methylbutyl}-2,3-diphenylacrylamide (24) with an isobutyl moiety at P(2) was found to show selectivity as a cathepsin L inhibitor (Ki 5.3 microM for cathepsin L and Ki > 100 microM for cathepsin B). This compound could act as a new lead for the further development of improved inhibitors within this inhibitor type.
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Affiliation(s)
- Mange R Yadav
- Pharmacy Department, Faculty of Technology and Engineering, The M S University of Baroda, Vadodara, India.
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48
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Verissimo E, Berry N, Gibbons P, Cristiano MLS, Rosenthal PJ, Gut J, Ward SA, O’Neill PM. Design and synthesis of novel 2-pyridone peptidomimetic falcipain 2/3 inhibitors. Bioorg Med Chem Lett 2008; 18:4210-4. [DOI: 10.1016/j.bmcl.2008.05.068] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2008] [Revised: 05/15/2008] [Accepted: 05/16/2008] [Indexed: 12/01/2022]
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49
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Fasciola gigantica: Evaluation of the effect of phenyl vinyl sulfone in vitro. Exp Parasitol 2008; 119:125-34. [DOI: 10.1016/j.exppara.2008.01.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 12/19/2007] [Accepted: 01/03/2008] [Indexed: 11/17/2022]
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50
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Changes in the plasmodial surface anion channel reduce leupeptin uptake and can confer drug resistance in Plasmodium falciparum-infected erythrocytes. Antimicrob Agents Chemother 2008; 52:2346-54. [PMID: 18443109 DOI: 10.1128/aac.00057-08] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cysteine protease inhibitors kill malaria parasites and are being pursued for development as antimalarial agents. Because they have multiple targets within bloodstream-stage parasites, workers have assumed that resistance to these inhibitors would not be acquired easily. In the present study, we used in vitro selection to generate a parasite resistant to growth inhibition by leupeptin, a broad-profile cysteine and serine protease inhibitor. Resistance was not associated with upregulation of cysteine protease activity, reduced leupeptin sensitivity of this activity, or expression level changes for putative cysteine or serine proteases in the parasite genome. Instead, it was associated with marked changes in the plasmodial surface anion channel (PSAC), an ion channel on infected erythrocytes that functions in nutrient and bulky organic solute uptake. Osmotic fragility measurements, electrophysiological recordings, and leupeptin uptake studies revealed selective reductions in organic solute permeability via PSAC, altered single-channel gating, and reduced inhibitor affinity. These changes yielded significantly reduced leupeptin uptake and could fully account for the acquired resistance. PSAC represents a novel route for the uptake of bulky hydrophilic compounds acting against intraerythrocytic parasite targets. Drug development based on such compounds should proceed cautiously in light of possible resistance development though the selection of PSAC mutants.
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