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SUMMARY OF RESEARCH
Target identification for ParasiticTropical Diseases Drug Discovery.
Our lab is interested in exploiting unique aspects of parasitic protozoa metabolism as drug targets for the discovery of new treatments. Kinetoplastid and apicomplexan parasites comprise a group of protozoans responsible for diseases with a serious impact in human health and the socioeconomic growth of developing countries. We actively participate in international consortia together with pharma industry in order to implement a multidisciplinary approach towards drug discovery. Our main focus is nucleotide metabolism and we have identified several unique druggable enzymes that perform essential functions in kinetoplastids. Many nucleoside analogs are already approved for the treatment of patients with cancer or viral diseases. Of particular interest is pyrimidine metabolism where several enzymes are essential for parasite viability. Thus, inhibition of thymidylate (dTMP) biosynthesis severely diminishes the viability of parasitic protozoa. We have characterized several enzymes specifically involved in the formation of dTTP (dUTPase, thymidine kinase, thymidylate kinase) and have shown that depletion results in decreased deoxythymidine triphosphate (dTTP) levels and the so-called thymineless death. In this process the ratio of deoxyuridine triphosphate (dUTP) versus dTTP in the cellular nucleotide pool has a crucial role. A high dUTP/dTTP ratio leads to uracil misincorporation into DNA, the activation of DNA repair pathways, DNA fragmentation and eventually cell death. We are interested in how all these processes take place in parasitic protozoa. In addition we continue to explore the properties, biological function and druggability of additional enzymes involved in nucleotide metabolism.
Carbohydrate-binding agents for the treatment of trypanosomal diseases.
Another area of interest is the exploitation of carbohydrate-binding agents as antitrypanosomals. This is a new approach based on the use of compounds that bind to parasite surface glycans and that lead to rapid killing of trypanosomes. As an example, pradimicin and its derivatives are non-peptidic carbohydrate-binding agents that adhere to the carbohydrate moiety of the parasite surface glycoproteins inducing parasite lysis. Notably, pradimicin S has good pharmaceutical properties and enables cure of an acute form of sleeping sickness in mice. By inducing resistance in vitro we have established that the composition of the sugars attached to the variant surface glycoproteins are critical to the mode of action of pradimicins and play an important role in infectivity. We are currently exploring the potential of this class of compounds in the treatment of other parasitic diseases.
Phenotype-driven novel methodologies for screening using high throughput formats in antiprotozoan drug discovery.
We also have ongoing collaborations with medicinal chemists and the MEDINA foundation in the area of drug discovery through phenotypic screening. MEDINA has one of the biggest collections in the world of microbial natural products. The collection holds 190,000 strains of filamentous fungi, actinomycetes and bacteria, and has contributed to some of the most important discoveries of recent decades in natural product drug discovery. Together we have established an HTS platform for phenotypic screening of the collection. As a result of screening against Plasmodium and trypanosomes, many novel compounds with antiparasitic activities that include known and novel microbial natural products have been identified.
Role of the human NTP pyrophosphatase DCTPP1 in nucleotide homoeostasis
In order to keep the dNTP pool in balance, the synthesis and degradation of DNA precursors must be precisely regulated. Catabolic activities that convert deoxynucleoside triphosphates into their monophosphate form are involved in this process. Human cells possess an all-α-NTP (nucleoside triphosphate) pyrophosphatase named DCTPP1 which is structurally related to trypanosomal dUTPases. We have performed studies in order to evaluate the role of DCTPP1 in the size and composition of dNTP pools and genetic stability. We are extensively characterizing its properties and have established that DCTPP1 has a central role in the balance of dCTP and the metabolism of deoxycytidine analogues, thus contributing to the preservation of genome integrity and to the mode of action of nucleoside analogues used in cancer chemotherapy.
FUNDING AGENCIES LAST 5 YEARS
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