Roberto Docampo Archives - Page 4 of 5 - Center for Tropical and Emerging Global Diseases

UGA researchers join team of 100+ scientists to develop genetic tools for marine protists

Donna Huber on April 30, 2020

Roberto Docampo and colleagues at the University of Georgia’s Center for Tropical and Emerging Global Diseases have joined with 53 other lab groups to develop tools to genetically manipulate marine protists, a microscopic single-cell organism that plays an important ecological role in marine ecosystems. Their results were recently published in Nature Methods.

Protists aid in sequestering carbon dioxide, serve as a food source for many organisms (including humans), and cause the toxic red tides that have plagued Florida beaches in recent years. However, little is known about their cellular biology or evolutionary history, and no model organisms exist for this group. Protists are a highly diverse collection of species, and the inability to genetically modify a large majority of them has been a major hurdle to their study. A few protists, such as some parasitic protists which have an impact on human or animal health, have protocols, but they are not highly representative of the broader kingdom.

Funded by a $8 million grant from the Gordon and Betty Moore Foundation, researchers for the first time were able to develop protocols for transfection, or the introduction of foreign DNA, and gene expression in 13 species. They were also able to build on the tools already developed for eight other species. While they could not develop a universal protocol for genetic transfection for all protists due to their vast diversity, they were able to provide what the researchers are calling a synthetic “Transformation Roadmap.”

Docampo collaborated with Virginia Edgcomb and her lab at the Woods Hole Oceanographic Institute to develop genetic tools that would allow successful transfection of genes into Bodo saltans.

Bodo saltans is a unicellular organism found in marine and freshwater habitats. It belongs in the Discoba group which also includes the clinically significant parasitic protists Trypanosoma cruzi, Trypanosoma brucei, and Leishmania . Docampo and his team of researchers have been at the forefront of developing the genetic modification tool CRISPR/Cas9 for Trypanosoma cruzi, the causative agent of Chagas Disease.

“The development of tools to genetically modify [B. saltans] will be essential for the study of its biology and for the understanding of the evolution of the adaptions of trypanosomatids to parasitism,” said Docampo, Barbara and Sanford Orkin – GRA Eminent Scholar in Emerging Diseases and Cellular and professor in the Franklin College of Arts and Sciences department of cellular biology.

B. saltans, like the other protists in this study, will serve as a model organism for related protists that may be difficult to culture in the laboratory or in which protocols are unsuccessful. This study is not only a step toward closing the knowledge gap in the biology and evolution of this diverse kingdom of organisms but will also aid in the advancement of protisan biotechnology. Marine protists are an untapped resource and their study could reveal mechanisms and drug therapies to treat human and animal diseases.

The study is available online: Faktorová, D., Nisbet, R.E.R., Fernández Robledo, J.A. et al. Genetic tool development in marine protists: emerging model organisms for experimental cell biology. Nat Methods (2020). https://doi.org/10.1038/s41592-020-0796-x

Noelia Lander receives research award

Donna Huber on April 9, 2020

Noelia Lander, a cellular biologist and postdoctoral researcher in Roberto Docampo‘s laboratory, has received the 2020 Postdoctoral Award from the UGA Research Foundation.

Lander has used her research to advance understanding of a dangerous parasite affecting millions of people worldwide. She adapted the CRISPR/Cas9 genome-editing system for the study of Trypanosoma cruzi, a human parasite that causes Chagas disease. In widely cited research, she proved the usefulness of this new gene-editing system and its range of applications in T. cruzi, which historically had been difficult to manipulate. Dozens of Chagas molecular biology labs worldwide use her CRISPR/Cas9 strategy to study the parasite’s proteins, characterize its metabolic pathways, understand its biology and search for new chemotherapeutic targets. More recently, she has used her system to study protein function and calcium signaling in T. cruzi. She has trained laboratory personnel and students in scientific research and is currently conducting the mentored phase of an NIH Pathway to Independence Award.

Created in 2011, Postdoctoral Research Awards recognize the remarkable contributions of postdoctoral research scholars to the UGA research enterprise. The UGA Research Foundation funds up to two awards a year to current scholars.

Genetic tool development in marine protists: emerging model organisms for experimental cell biology

Donna Huber on April 6, 2020

Diverse microbial ecosystems underpin life in the sea. Among these microbes are many unicellular eukaryotes that span the diversity of the eukaryotic tree of life. However, genetic tractability has been limited to a few species, which do not represent eukaryotic diversity or environmentally relevant taxa. Here, we report on the development of genetic tools in a range of protists primarily from marine environments. We present evidence for foreign DNA delivery and expression in 13 species never before transformed and for advancement of tools for eight other species, as well as potential reasons for why transformation of yet another 17 species tested was not achieved. Our resource in genetic manipulation will provide insights into the ancestral eukaryotic lifeforms, general eukaryote cell biology, protein diversification and the evolution of cellular pathways.

Roberto Docampo and several of his lab members are co-authors of this study.

Faktorová, D., Nisbet, R.E.R., Fernández Robledo, J.A. et al. Genetic tool development in marine protists: emerging model organisms for experimental cell biology. Nat Methods (2020). https://doi.org/10.1038/s41592-020-0796-x

Multi-target heteroleptic palladium bisphosphonate complexes

Donna Huber on March 30, 2020

Bisphosphonates are the most commonly prescribed drugs for the treatment of osteoporosis and other bone illnesses. Some of them have also shown antiparasitic activity. In search of improving the pharmacological profile of commercial bisphosphonates, our group had previously developed first row transition metal complexes with N-containing bisphosphonates (NBPs). In this work, we extended our studies to heteroleptic palladium–NBP complexes including DNA intercalating polypyridyl co-ligands (NN) with the aim of obtaining potential multi-target species. Complexes of the formula [Pd(NBP)₂(NN)]·2NaCl·xH₂O with NBP = alendronate (ale) or pamidronate (pam) and NN = 1,10 phenanthroline (phen) or 2,2′-bipyridine (bpy) were synthesized and fully characterized. All the obtained compounds were much more active in vitro against T. cruzi (amastigote form) than the corresponding NBP ligands. In addition, complexes were nontoxic to mammalian cells up to 50–100 µM. Compounds with phen as ligand were 15 times more active than their bpy analogous. Related to the potential mechanism of action, all complexes were potent inhibitors of two parasitic enzymes of the isoprenoid biosynthetic pathway. No correlation between the anti-T. cruzi activity and the enzymatic inhibition results was observed. On the contrary, the high antiparasitic activity of phen-containing complexes could be related to their ability to interact with DNA in an intercalative-like mode. These rationally designed compounds are good candidates for further studies and good leaders for future drug developments.

Micaella Cipriani, Santiago Rostán, Ignacio León, Zhu-Hong Li, Jorge S. Gancheff, Ulrike Kemmerling, Claudio Olea Azar, Susana Etcheverry, Roberto Docampo, Dinorah Gambino & Lucía Otero. J Biol Inorg Chem. 2020 Mar 30. doi: 10.1007/s00775-020-01779-y.

CRISPR/Cas9 Technology Applied to the Study of Proteins Involved in Calcium Signaling in Trypanosoma cruzi

Donna Huber on March 28, 2020

Chagas disease is a vector-borne tropical disease affecting millions of people worldwide, for which there is no vaccine or satisfactory treatment available. It is caused by the protozoan parasite Trypanosoma cruzi and considered endemic from North to South America. This parasite has unique metabolic and structural characteristics that make it an attractive organism for basic research. The genetic manipulation of T. cruzi has been historically challenging, as compared to other pathogenic protozoans. However, the use of the prokaryotic CRISPR/Cas9 system for genome editing has significantly improved the ability to generate genetically modified T. cruzi cell lines, becoming a powerful tool for the functional study of proteins in different stages of this parasite’s life cycle, including infective trypomastigotes and intracellular amastigotes. Using the CRISPR/Cas9 method that we adapted to T. cruzi, it has been possible to perform knockout, complementation and in situ tagging of T. cruzi genes. In our system we cotransfect T. cruzi epimastigotes with an expression vector containing the Cas9 sequence and a single guide RNA, together with a donor DNA template to promote DNA break repair by homologous recombination. As a result, we have obtained homogeneous populations of mutant epimastigotes using a single resistance marker to modify both alleles of the gene. Mitochondrial Ca²⁺ transport in trypanosomes is critical for shaping the dynamics of cytosolic Ca²⁺ increases, for the bioenergetics of the cells, and for viability and infectivity. In this chapter we describe the most effective methods to achieve genome editing in T. cruzi using as example the generation of mutant cell lines to study proteins involved in calcium homeostasis. Specifically, we describe the methods we have used for the study of three proteins involved in the calcium signaling cascade of T. cruzi: the inositol 1,4,5-trisphosphate receptor (TcIP₃R), the mitochondrial calcium uniporter (TcMCU) and the calcium-sensitive pyruvate dehydrogenase phosphatase (TcPDP), using CRISPR/Cas9 technology as an approach to establish their role in the regulation of energy metabolism.

Noelia Lander, Miguel A. Chiurillo, Roberto Docampo. Methods Mol Biol. 2020;2116:177-197. doi: 10.1007/978-1-0716-0294-2_13.

Isolation and Characterization of Acidocalcisomes from Trypanosomatids

Donna Huber on March 28, 2020

Acidocalcisomes are membrane-bounded, electron-dense, acidic organelles, rich in calcium and polyphosphate. These organelles were first described in trypanosomatids and later found from bacteria to human cells. Some of the functions of the acidocalcisome are the storage of cations and phosphorus, participation in pyrophosphate (PP_i) and polyphosphate (polyP) metabolism, calcium signaling, maintenance of intracellular pH homeostasis, autophagy, and osmoregulation. Isolation of acidocalcisomes is an important technique for understanding their composition and function. Here, we provide detailed subcellular fractionation protocols using iodixanol gradient centrifugations to isolate high-quality acidocalcisomes from Trypanosoma brucei, which are subsequently validated by electron microscopy, and enzymatic and immunoblot assays with organellar markers.

Guozhong Huang, Silvia N. J. Moreno, Roberto Docampo. Methods Mol Biol. 2020;2116:673-688. doi: 10.1007/978-1-0716-0294-2_40.

The Mitochondrial Calcium Uniporter Interacts with Subunit c of the ATP Synthase of Trypanosomes and Humans

Donna Huber on March 17, 2020

Mitochondrial Ca²⁺ transport mediated by the uniporter complex (MCUC) plays a key role in the regulation of cell bioenergetics in both trypanosomes and mammals. Here we report that Trypanosoma brucei MCU (TbMCU) subunits interact with subunit c of the mitochondrial ATP synthase (ATPc), as determined by coimmunoprecipitation and split-ubiquitin membrane-based yeast two-hybrid (MYTH) assays. Mutagenesis analysis in combination with MYTH assays suggested that transmembrane helices (TMHs) are determinants of this specific interaction. In situ tagging, followed by immunoprecipitation and immunofluorescence microscopy, revealed that T. brucei ATPc (TbATPc) coimmunoprecipitates with TbMCUC subunits and colocalizes with them to the mitochondria. Blue native PAGE and immunodetection analyses indicated that the TbMCUC is present together with the ATP synthase in a large protein complex with a molecular weight of approximately 900 kDa. Ablation of the TbMCUC subunits by RNA interference (RNAi) significantly increased the AMP/ATP ratio, revealing the downregulation of ATP production in the cells. Interestingly, the direct physical MCU-ATPc interaction is conserved in Trypanosoma cruzi and human cells. Specific interaction between human MCU (HsMCU) and human ATPc (HsATPc) was confirmed in vitro by mutagenesis and MYTH assays and in vivo by coimmunoprecipitation. In summary, our study has identified that MCU complex physically interacts with mitochondrial ATP synthase, possibly forming an MCUC-ATP megacomplex that couples ADP and P_i transport with ATP synthesis, a process that is stimulated by Ca²⁺ in trypanosomes and human cells.

IMPORTANCE The mitochondrial calcium uniporter (MCU) is essential for the regulation of oxidative phosphorylation in mammalian cells, and we have shown that in Trypanosoma brucei, the etiologic agent of sleeping sickness, this channel is essential for its survival and infectivity. Here we reveal that that Trypanosoma brucei MCU subunits interact with subunit c of the mitochondrial ATP synthase (ATPc). Interestingly, the direct physical MCU-ATPc interaction is conserved in T. cruzi and human cells.

Guozhong Huang, Roberto Docampo. mBio. 2020 Mar 17;11(2). pii: e00268-20. doi: 10.1128/mBio.00268-20.

A CRISPR/Cas9-riboswitch-Based Method for Downregulation of Gene Expression in Trypanosoma cruzi

Donna Huber on February 27, 2020

Few genetic tools were available to work with Trypanosoma cruzi until the recent introduction of the CRISPR/Cas9 technique for gene knockout, gene knock-in, gene complementation, and endogenous gene tagging. Riboswitches are naturally occurring self-cleaving RNAs (ribozymes) that can be ligand-activated. Results from our laboratory recently demonstrated the usefulness of the glmS ribozyme from Bacillus subtilis, which has been shown to control reporter gene expression in response to exogenous glucosamine, for gene silencing in Trypanosoma brucei. In this work we used the CRISPR/Cas9 system for endogenously tagging T. cruzi glycoprotein 72 (TcGP72) and vacuolar proton pyrophosphatase (TcVP1) with the active (glmS) or inactive (M9) ribozyme. Gene tagging was confirmed by PCR and protein downregulation was verified by western blot analyses. Further phenotypic characterization was performed by immunofluorescence analysis and quantification of growth in vitro. Our results indicate that the method was successful in silencing the expression of both genes without the need of glucosamine in the medium, suggesting that T. cruzi produces enough levels of endogenous glucosamine 6-phosphate to stimulate the glmS ribozyme activity under normal growth conditions. This method could be useful to obtain knockdowns of essential genes in T. cruzi and to validate potential drug targets in this parasite.

Noelia Lander, Teresa Cruz-Bustos, and Roberto Docampo. Front Cell Infect Microbiol. 2020 Feb 27;10:68. doi: 10.3389/fcimb.2020.00068. eCollection 2020.

Synthesis and in vitro evaluation of new 5-substituted 6-nitroimidazooxazoles as antikinetoplastid agents

Donna Huber on February 14, 2020

In continuation of our pharmacomodulation work on the nitroimidazooxazole series, we report the synthesis of new 5-substituted 6-nitroimidazooxazole derivatives. Our aim was to evaluate how functionalization of the 5-position of the 6-nitroimidazooxazole scaffold affects antileishmanial and antitrypanosomal in vitro activities. Twenty-one original compounds were synthesized and evaluated for their in vitro antileishmanial (L. donovani) and antitrypanosomal (T. cruzi) properties. Pallado-catalyzed cross-coupling reactions were used to introduce an aryl or ethynyl aryl substituent in 5-position from a 5-brominated-6-nitroimidazooxazole starting product. Unfortunately, the first series of compounds bearing an aryl group in 5-position presented limited in vitro activities against L. donovani and T. cruzi, with IC₅₀ > 10 μM (vs 0.18 μM and 2.31 μM for the reference drugs amphotericin B and benznidazole respectively). Interestingly, the second series of compounds bearing an ethynyl aryl substituent in 5-position showed more promising, particularly against T. cruzi. Compounds 6a, 6b, 6c, 6g and 6h had better activity than the reference drug benznidazole (0.92 μM ≤ IC₅₀ ≤ 2.18 μM vs IC₅₀ = 2.31 μM), whereas the non-functionalized 2-methyl-6-nitro-2,3-dihydroimidazo [2,1-b]oxazole 2 was not active against T. cruzi (IC₅₀ > 10 μM).

Fanny Mathias, AnitaCohen, Youssef Kabri, Núria Waddington Negrão, Maxime D.Crozet, RobertoDocampo, Nadine Azas, Patrice Vanelle. Eur J Med Chem. 2020 Feb 14;191:112146. doi: 10.1016/j.ejmech.2020.112146

Functional analysis and importance for host cell infection of the Ca2+-conducting subunits of the mitochondrial calcium uniporter of Trypanosoma cruzi

Donna Huber on May 15, 2019

We report here that Trypanosoma cruzi, the etiologic agent of Chagas disease, possesses two unique paralogs of the mitochondrial calcium uniporter complex TcMCU subunit that we named TcMCUc, and TcMCUd. The predicted structure of the proteins indicates that, as that predicted for the TcMCU and TcMCUb paralogs, they are composed of two helical membrane-spanning domains, and contain a WDXXEPXXY motif. Overexpression of each gene led to a significant increase in mitochondrial Ca²⁺ uptake while knockout (KO) of either TcMCUc or TcMCUd led to a loss of mitochondrial Ca²⁺ uptake, without affecting the mitochondrial membrane potential. TcMCUc-KO and TcMCUd-KO epimastigotes exhibited reduced growth rate in low glucose medium and alterations in their respiratory rate, citrate synthase activity and AMP/ATP ratio, while trypomastigotes had reduced ability to efficiently infect host cells and replicate intracellularly as amastigotes. By gene complementation of KO cell lines or by a newly developed knock-in approach we also studied the importance of critical amino acid residues of the four paralogs on mitochondrial Ca²⁺ uptake. In conclusion, the results predict a hetero-oligomeric structure for the T. cruzi MCU complex, with structural and functional differences, as compared to those in the mammalian complex.

Miguel A. Chiurillo, Noelia Lander, Mayara S. Bertolini, Anibal E. Vercesi, and Roberto Docampo. 2019. Mol Biol Cell.; mbcE19030152. doi: 10.1091/mbc.E19-03-0152

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