MSc, MD, PhD
Functional characterisation of nutrient membrane transporters
In partnership with the Liverpool School of Tropical Medicine, Department of Parasitology, we are developing a project to study the growth physiology of the malaria parasite Plasmodium falciparum. We are working on innovative methods to analyse and measure growth kinetics using real-time microscopy. Together with transcriptomics and metabolomics we have a long-term plan to describe how the parasite senses the environmental nutrient changes and the consequences of the allocation of resources in response to those changes. Applicable results are expected to show new targets or strategies to inhibit parasite growth and pathogenesis of the malarial infection. In collaboration with Dr Mark McAuley from the University of Chester we are developing a deterministic model for the biosynthesis and usage of folate in microorganism and single cell eukaryotes.
Rapid proliferating eukaryotes have perfected metabolic modes that efficiently convert glucose and specific amino acids into biomass and energy at the required pace. Last decade has brought a change in the paradigm on accelerated cell multiplication. Streamlined metabolic networks and the capacity to support anabolic reactions in a rapid fashion via aerobic fermentative glycolysis and glutaminolysis instead of pursuing the thorough oxidation of the glycolytic carbons via cellular respiration seem to be a precondition for, rather than a consequence of effective proliferative signalling (Salcedo-Sora et al 2014) [http://www.sciencedirect.com/science/article/pii/S147149221400021X].
At the School of Health Sciences we are developing a research theme coordinating efforts to study specific aspects of the metabolism of rapid proliferating eukaryotic cells. The models we use are established cancer cell lines and eukaryotic microorganisms such as the malaria parasitePlasmodium falciparum.
Figure 1: Cancerous cells and microorganisms use glycolysis to fuel their cell growth and multiplication (Salcedo-Sora et al 2014).
Transport across the membranes is a fundamental requirement for any cell. Following a gene-specific approach with encoded protein candidates selected according to their level of similarity to known transporters, we have successfully characterised a number of important transporters (see publications), among them: Two folate transporters of the malaria parasite Plasmodium falciparum, the Calcium/proton antiporter of the same parasite, and a number of plant glutathione transporters. Also, known human and malaria parasite transporters have been described to carry out previously undescribed transport activities such as human solute transporters facilitating the uptake of HIV protease inhibitors and the malaria chloroquine-resistant transporter involvement in glutathione movement across cellular organelles.
Figure 2: Antibodies targeting a folate transporter in the malaria parasite shows this transporter localised in the plasma membrane of P. falciparum (Salcedo-Sora et al 2011).
Folates are essential vitamins due to their role in the making of molecules needed by proliferating cells, chiefly DNA. Thus, the pharmacological inhibition of the enzymes related to the biosynthesis and metabolism of folates have served to treat a wide spectrum of diseases: cancer, inflammatory chronic conditions, and infectious diseases. I have been involved in the characterisation of a number of enzymes involved in the biosynthesis and salvage of folates. Currently, I am collaborating with system biologists and other scientists from more quantitative fields to elucidate a model of the regulatory network of folate biosynthesis. Quantitation of the dynamics of the metabolism of folate vitamins will have applications in the treatment of a variety of pathologies (Salcedo-Sora JE and Ward SA, 2013).
Brenda (Enzyme kinetics) [http://www.brenda-enzymes.info/]
KEGG (Kyoto Encyclopedia of Genes and Genomes) [http://www.genome.jp/kegg/]
PlasmoDB (Plasmodium database) [http://plasmodb.org/plasmo/]
Yeast (S. cerevisiae) database [http://www.yeastgenome.org/]
eQuilibrator (biochemical thermodynamics calculator) [http://equilibrator.weizmann.ac.il/]
Salcedo-Sora JE, Caamano-Gutierrez E, Ward SA, Biagini GA. The proliferating cell hypothesis: a metabolic framework for Plasmodium growth and development. Trends in Parasitology 2014, 30(4): 170-175. [http://www.sciencedirect.com/science/article/pii/S147149221400021X]
Salcedo-Sora JE, Kaniti A, Okpara CE, Stocks PA, Biagini GA, O’Neill PM, Ward SA. PfCRT Mediates Sensitivity of Chloroquine-Resistant P. falciparum to Diamidines. In: Antimalarial Drug Research and Development. Banet AC and Brasier PE (Eds). 2013. Nova Publishers.
Salcedo-Sora JE and Ward SA. The folate metabolic network of Falciparum malaria. Molecular and Biochemical Parasitology 2013, 188(1):51-62.
Patzewitz EM, Salcedo-Sora JE, Wong EH, Sethia S, Stocks PA, Maughan SC, Murray JA, Krishna S, Bray PG, Ward SA, Müller S. Glutathione transport: a new role for PfCRT in chloroquine resistance. Antioxidants & Redox Signalling 2013, 19(7):683-95.
Salcedo-Sora JE, Ward SA, Biagini GA. A yeast expression system for functional and pharmacological studies of the malaria parasite Ca²⁺/H⁺ antiporter. Malaria Journal. 2012, 11:254.
Salcedo-Sora JE, Ochong E, Beveridge S, Johnson D, Nzila A, Biagini GA, Stocks PA, O'Neill PM, Krishna S, Bray PG, Ward SA. The molecular basis of folate salvage in Plasmodium falciparum: characterization of two folate transporters. The Journal of Biological Chemistry 2011, 286(52):44659-68.
Maughan SC, Pasternak M, Cairns N, Kiddle G, Brach T, Jarvis R, Haas F,Nieuwland J, Lim B, Müller C, Salcedo-Sora E, Kruse C, Orsel M, Hell R, Miller AJ, Bray P, Foyer CH, Murray JA, Meyer AJ, Cobbett CS. Plant homologs of the Plasmodium falciparum chloroquine-resistance transporter, PfCRT, are required for glutathione homeostasis and stress responses. Proceedings of the Natural Academy of Sciences USA 2010, 107(5):2331-2336.
Hartkoorn, R.C., Kwan, W.S., Shallcross, V., Chaikan, A., Liptrott, N., Egan, D., Salcedo Sora E., James, C.E., Gibbons, S., Bray, P.G., Back, D.J., Khoo, S.H., Owen, A. HIV protease inhibitors are substrates for OATP1A2, OATP1B1 and OATP1B3 and lopinavir plasma concentrations are influenced by SLCO1B1 polymorphisms. Pharmacogenetics & Genomics 2010, 20(2): 112-120.
Salcedo E., Sims PFG. and Hyde JE. A case for a glycine cleavage complex as part of the folate one-carbon metabolism of the Malaria parasite Plasmodium falciparum and its role in its life cycle. Trends in Parasitology Plasmodium falciparum and its role in its life cycle. Trends in Parasitology 2005, 21(9): 406-411.
Franco-Lara L., Gaitán SL., Filgueira JJ. and Salcedo E. Association of a disease in Fraxinus in Colombia with the presence of Phytoplasmas. Phytopathology 2004, 94(6): S31.
Salcedo, E., Cortese, J., Plowe, C.V., Sims, P.F.G. and Hyde, J.E. A bifunctional dihydrofolate synthetase-folylpolyglutamate synthetase in the human malaria parasite Plasmodium falciparum identified by functional complementation in yeast and bacteria. Molecular and Biochemical Parasitology 2001, 112: 239-252.
Lee, C-S., Salcedo, E., Wang, Q., Wang, P., Sims, P.F.G. and Hyde, J.E. Characterisation of three genes encoding enzymes of the folate biosynthetic pathway in Plasmodium falciparum. Parasitology 2001, 122: 1-13.
Salcedo, E. and Wasserman, M. Optimisation of the electrophoretic separation of ankirin and bands 4.1a and 4.1b of the human erythrocyte. Biomédica. 1993, 13(3): 109-116. (Spanish).