The strategy is promising for targeting new therapies for neglected tropical diseases
Researchers of INCT of the Open Access Medicinal Chemistry Center based at the Center for Medicinal Chemistry (CQMED) at Unicamp, advanced the study of a protein that occurs in two organisms that cause neglected tropical diseases. This is the Brugia malay, one of the worms that cause elephantiasis (lymphatic filariasis), and Leishmania major, which causes cutaneous leishmaniasis. The study's target protein, deoxyhypusine synthase (DHS), is related to basic cell functioning processes and is unprecedented as a drug target. The search for inhibitors of these processes is one of the most successful paths towards the development of effective medicines to treat these diseases. O study was published on October 22nd in the scientific journal PLOS Neglected Tropical Diaseases.
One of the strategies for discovering new drugs is based on the identification of molecular targets, often a protein with enzymatic activity, and the development of inhibitors to interrupt the biochemical processes involved in the disease. This approach based on specific and potent inhibitors is the first step towards developing sophisticated, more effective drugs with fewer side effects. The time between the discovery of new drugs and their arrival on pharmacy shelves is estimated at 12 to 15 years and the investment could reach US$2,5 billion. When it comes to Neglected Tropical Diseases (NTDs) this situation is accentuated. There is a great lack of medicines developed specifically for the treatment of these diseases and, often, the side effects are not negligible.
Two neglected diseases in urgent need of new treatments are leishmaniasis, caused by parasites Leishmania, and elephantiasis, caused by nematodes Wuchereria bancrofti, Brugia malay e timori witch. “Current treatments for the three main clinical manifestations of leishmaniasis (cutaneous, mucocutaneous and visceral) have serious side effects and many are currently ineffective due to the emergence of resistance. For lymphatic filariasis, eradication efforts have been hampered by the inability of current medications to kill adult worms,” the authors explain in the article. Currently, there are approximately 70 million people infected with filarial worms and up to 1,6 million new cases of leishmaniasis each year.
In the study published by the group of Brazilians, two important advances are recorded in understanding how these diseases work and finding possible medicines. The first refers to the standardization of a protein study platform for protozoa Leishmania major. The system was based on yeast cells that were genetically modified to produce the protein deoxyhypusine synthase (DHS) from Leishmania major. The researchers found that the modified yeasts began to depend on this enzyme to survive, as is the case with the protozoan itself. The next step is to search for known molecules to test which ones will prevent the proliferation of yeast with the protozoan DHS gene. “The standardization of the platform for studying the DHS protein of Leishmania major based on yeast is fundamental, as until now there had been no success using conventional techniques in obtaining this enzyme from other sources”, explains Suelen Silva, PhD candidate in the Biotechnology Program at Unesp in Araraquara, CNPq scholarship holder and the first author of the article.
The other advance described in the article is the determination of the three-dimensional structure of the DHS protein from the elephantiasis worm, whose cell viability depends on the proper functioning of this enzyme. “Although the DHS proteins are similar, each organism has its own characteristics. It is these particularities that interest us. That's where we're going to insert an inhibitor. Otherwise, our inhibitor could target, for example, the host's protein simultaneously and we would lose specificity for the parasite”, explains co-author Angélica Klippel, PhD student in the Biosciences and Biotechnology Applied to Pharmacy Program at Unesp in Araraquara and a FAPESP scholarship holder. Unraveling the three-dimensional structure of the molecule makes it possible to design specific inhibitors for this protein. With this structure, researchers investigate the best sites on the molecule where an inhibitor could bind.
However, as the authors point out in the article, the fact of identifying a gene, being successful in cellular assays, describing the three-dimensional structure of the protein and finding a potent inhibitor under controlled laboratory conditions does not automatically mean that the inhibitor will work within the human host. “It’s a long journey, but each successful step is a victory”, explains Rafael Couñago, co-author of the study and main researcher at the Centro que Química Medicinal (CQMED) that hosts the INCT.
“In this sense, the use of a yeast platform that is useful for the rapid large-scale screening of new inhibitors of these enzymes could contribute fundamentally to the development of possible new drugs”, highlights professor Cleslei Zanelli, from the Faculty of Sciences Pharmacists from Unesp in Araraquara, main researcher at INCT and co-author of the study.
In addition to the DHS enzymes from filariasis and leishmaniasis pathogens, INCT researchers are also studying the structure of the DHS protein from other species that cause neglected diseases. With this study, the authors hope to facilitate the identification and development of new DHS inhibitors that can be used to validate these enzymes as targets for therapeutic interventions against DHS infections. Brugia malay e Leishmania major.
The research is part of the INCT thematic project on Open Access Medicinal Chemistry, which is located at Center for Medicinal Chemistry (CQMED) from Unicamp and is financed by Fapesp, CNPq and CAPES. INCT's main mission is to foster partnerships between researchers from different research centers to investigate little-studied proteins and thus increase the impact of discoveries. “It’s a win-win model. Collaborating researchers benefit from our structure and know-how of our team of researchers fully dedicated to biochemistry, cellular, molecular and structural biology and medicinal chemistry. And we learned a lot from the challenges that these collaborations bring us”, explains Counãgo.
Researchers from the Center for Molecular Biology and Genetic Engineering (CBMEG) and the Institute of Biology, both at Unicamp, also participated.
Article: Silva SF, Klippel AH, Ramos PZ, Santiago AdS, Valentini SR, Bengtson MH, et al. (2020) Structural characteristics and development of an assay platform of the parasite target deoxyhypusine synthesis of Brugia malay and Leishmania major. PLoS Negl Trop Dis 14(10): e0008762.
