Research in my laboratory centers on the characterization of calcium homeostasis and signaling in the apicomplexan parasite Toxoplasma gondii. We are interested in acidic calcium stores and also discovering the molecules responsible for Ca2+ influx into the parasite.
We recently characterized Ca2+ entry in T. gondii and its enhancing effect during the lytic cycle of the parasite. We believe that a voltage gated calcium channel is involved.
We also characterized the vacuolar-H+-pyrophosphatase, which localizes to a novel compartment with similar composition and function to the plat vacuole (named plant-like vacuole or PLV). This organelle stores calcium and is linked to the endosomal system of the parasite and it stores important enzymes used for the maturation of secretory proteins. We are presently studying the function and biogenesis of this organelle and its role in calcium homeostasis.
We are also interested in the isoprenoid pathway of Toxoplasma gondii. Work in collaboration with other laboratories is centered on testing isoprenoid pathway inhibitors against Toxoplasma growth in vitro and in vivio.
Isoprenoids are an extensive group of natural products with diverse structures consisting of various numbers of five carbon isopentenyl disphospate (IPP) units. A central enzyme in the pathway, the farnesyl diphosphate synthases (FPPS) catalyzes the formation of farnesyl diphospate (FPP), a precursor of critical molecules of fundamental biological functions such as dolichols, heme a, cholesterol, farnesylated proteins and others. This enzyme is a validated target for drugs and bisphosphonates, which are specific FPPS inhibitors, inhibit parasite growth in vitro and in vivo. Our findings indicate that T. gondii is able to use isoprenoid intermediates from the host as well as their own supply. Our hypothesis is that the isoprenoid pathway constitutes a major novel target for the treatment of toxoplasmosis and propose a double hit strategy by using a combination of inhibitors against the parasite and host enzymes.
Research Keywords: Toxoplasma gondii, calcium, plant vacuole, phospholipase c, inositol phosphates, isoprenoids, farnesyl diphosphate
- Shuhong L., Vieira, M. A., Zhong, L, Graves, J., and Moreno S.N.J. Cloning, functional expression and co-localization of the vacuolar Ca2+-ATPase with a vacuolar H+-pyrophosphatase to acidocalcisomes of Toxoplasma gondii. (2000) EMBO J. 20, 55-64.
- Rodrigues, C.O., Ruiz, F.A., Rohloff, P., Scott, D.A., and Moreno, S.N.J. Characterization of isolated acidocalcisomes from Toxoplasma gondii tachyzoites reveals a novel pool of hydrolysable polyphosphate. (2002) J. Biol. Chem. 277, 48650-48656.
- Arrizabalaga, G., Ruiz, F., Moreno, S.N.J. and Boothroyd, J.A. Ionophore-resistant mutant of Toxoplasma gondii reveals involvement of a sodium/hydrogen exchanger in calcium regulation. (2004) J. Cell Biol. 165:653-662.
- Luo, S., Ruiz, F.A., and Moreno, S.N.J. The acidocalcisome Ca2+-ATPase (TgA1) of Toxoplasma gondii is required for polyphosphate storage, intracellular calcium homeostasis and virulence. (2005) Mol. Microbiol. 55:1034-1045.
- Docampo, R., de Souza, W., Miranda, K., Rohloff, R., and Moreno, S.N.J. (2005) Acidocalcisomes –conserved from bacteria to man. Nat. Rev. Microbiol. 3:251-261.
- Harper, J.M., Huynh, M.H., Coppens, I., Parussini, F., Moreno, S.N., Carruthers, V.B. A Cleavable Propeptide Influences Toxoplasma Infection by Facilitating the Trafficking and Secretion of the TgMIC2-M2AP Invasion Complex. (2006) Mol. Biol. Cell. 17(10):4551-63.
- Ling Y, Li ZH, Miranda K, Oldfield E, Moreno, S.N.J. The farnesyl diphosphate/geranylgeranyl diphosphate synthase of Toxoplasma gondii is a bifunctional enzyme and the molecular target of bisphosphonates (2007) J. Biol. Chem. 282:30804-16.
- Miranda, K. de Souza, W. Plattner, H. Hentschel, J. Kawazoe, U. and Moreno, SNJ. Acidocalcisomes in Apicomplexan parasites (2008) Exp. Parasitol. Special issue. 118:2-9.
- Miranda, K.#, Pace, D.A.#, Cintron, R., Rodrigues, J.C.F., Fang, J., Smith, A., Rohloff, P., Coelho, E., de Haas, F., de Souza, W., Coppens, I., Sibley, L.D., and Moreno, S.N.J. Characterization of a novel organelle in Toxoplasma gondii with similar composition and function to the plant vacuole. (2010) Mol. Microbiol. 7(6) 1358-1375.
- Nair, S. C., Brooks, C. F., Goodman, C. D., Strurm, A., McFadden, G. I., Sundriyal, S., Anglin, J. L., Song, Y., Moreno, S. N. J., and Striepen, B. (2011) Apicoplast isoprenoid precursor synthesis and the molecular basis of fosmidomycin resistance in Toxoplasma gondii. J. Exp. Med. 208, 1547-59.
- Francia, M.E., Wicher, S., Pace, D.A., Sullivan, J., Moreno, S.N.J., and Arrizabalaga, G. (2011) A Toxoplasma gondii protein with homology to intracellular type Na+/H+ exchangers is important for osmoregulation and invasion. Exp. Cell Res. 317, 1382-1396.
- Rohloff, P., Miranda, K., Rodrigues, J.C.F., Fang, J., Galizzi, M., Plattner, H., Hentschel, J., and Moreno, S.N.J. (2011) Calcium uptake and proton transport by acidocalcisomes of Toxoplasma gondii. PLoS One 6, e18390.
- Rooney, P.J., Ayong, L., Tobin, C.M., Moreno, S.N.J., and Knoll, L.J. (2011) TgVTC2 is involved in polyphosphate accumulation in Toxoplasma gondii. Mol. Biochem. Parasitol. 176, 121-126.
- Li, Z.H., Cintrón R., Koon, N.A., Moreno, S.N.J. (2012) The N-terminus and the chain-length determination domain play a role in the length of the isoprenoid product of the bifunctional Toxoplasma gondii farnesyl diphosphate synthase. Biochemistry 51, 7533-7540.
- Li, Z.H., Ramakrishnan, S., Striepen, B., and Moreno, S.N.J. (2013) Toxoplasma gondii relies on both host and parasite isoprenoids and can be rendered sensitive to atorvastatin. PLoS Pathog. 9, e1003665.
- Moreno, S.N.J., and Docampo, R. (2013) Polyphosphate and its diverse functions in host cells and pathogens. PLoS Pathog. 9(5):e1003230
- Huang, G., Bartlett, P.J., Thomas, A.P., Moreno, S.N.J., and Docampo, R. (2013) Acidocalcisomes of Trypanosoma brucei have an inositol 1,4,5-trisphosphate receptor that is required for growth and infectivity. Proc. Natl. Acad. Sci. U.S.A. 110, 1887-1892.
- Pace, D.A., Mcknight, C.A., Liu, J., Jimenez, V., and Moreno, S.N.J. (2014) Calcium entry in Toxoplasma gondii and its enhancing effect of invasion-linked traits. J. Biol. Chem. 289, 19637-19647.
- Liu, J., Pace, D., Dou, Z., King, T. P., Guidot, D., Carruthers, V. B., and Moreno, S.N.J. (2014) A vacuolar H+-pyrophosphatase (TgVP1) is required for microneme secretion, host cell invasion, and extracellular survival of Toxoplasma gondii. Mol. Microbiol.