Assoc. Prof Heinrich Hoppe Research
Malaria parasite cell biology
Malaria is caused by protozoan parasites that are transmitted to humans by Anopheles mosquitoes and cause disease through the cyclical invasion, modification and destruction of host red blood cells. Plasmodium falciparum is the parasite species predominantly responsible for global malaria morbidity and mortality. It can be routinely maintained in continuous in vitro cultures, which has significantly aided research aimed at revealing the cell biological properties of the organism, as well as efforts to discover novel therapeutics against it. However, many aspects of its fundamental biology remain superficially characterized. An example is its principal feeding mechanism, the ingestion of host red blood cell cytoplasm by endocytosis. The general topology and organization of the endocytic process and pathway have been reasonably well described, but its detailed features and molecular mechanisms remain largely unknown.
An ongoing interest of the group is to explore the molecular mechanism of red blood cell endocytosis by characterizing parasite homologues of proteins known to be involved in endocytosis in other cell types. The principal approach is to create transgenic parasites expressing GFP/mCherry fusion constructs of the proteins of interest and determining their sub-cellular localization in the parasite by epifluorescence, confocal and electron microscopy. A supporting approach is to express humanized versions of the malaria proteins fused to GFP in mammalian cells and determining their localization and effects on the cells.
Malaria parasite expressing ARF-GFP
HeLa cell expressing malaria ARF fused to GFP
Implementing bioassays for drug screening
Driven by the menace of drug resistance, poor efficacy, cost and side-effects there is a persistent need to discover novel synthetic and natural compounds for infectious diseases drug development programmes. Numerous South African academic research groups are engaged in this pursuit, and Rhodes University is no exception. A common bottleneck in these projects is rapid, reliable access to bioassays for testing compounds produced by synthetic and natural product chemists. The award of an MRC SA University Flagship Programme grant has enabled us to establish a bioassay group to implement and routinely perform a selection of assays to support drug discovery projects in the departments of Chemistry, Biochemistry & Microbiology and Pharmacy. Assays being introduced include whole cell assays and assays using recombinant enzymes produced in-house:
- Malaria parasite (Plasmodium falciparum) blood stages
- Cytotoxicity (human cell lines)
- Trypanosoma brucei
- Mycobacterium tuberculosis
- HIV reverse transcriptase
- HIV protease
- HIV integrase
- P. falciparum DOXP reductoisomerase
In addition to the standard assays described above, another activity of the group is to develop protein-protein interaction assays for drug screening. With the decline of new chemical entities entering the pharmaceutical marketplace, new types of drug targets are being explored and protein-protein interactions are likely to become increasingly prominent in this regard. We are establishing assays that can quantitate particular protein-protein interactions in live cells for the purposes of research and compound screening, notably FRET (fluorescence resonance energy transfer), BRET (bioluminescence resonance energy transfer) and mammalian 2-hybrid assays. The model we are using for developing these assays is the interaction between the malaria parasite chaperone Pfhsp90 and its co-chaperone PfHop. Hsp90 is currently being pursued as a prominent drug target in cancer drug discovery and disrupting its interaction with binding partners (e.g. Hop) is thought to be one avenue for targeting its function in cancer cells and protozoan pathogens.
The standard cell-based assays provide information on a compound’s efficacy (i.e. active dose), but little or no indication of the rate of action of the compounds (i.e. how rapidly they act on cells). We are developing rate of action assays for antimalarial drugs using fluorescent vitality probes, ATP measurements and transgenic luciferase parasites to address this issue.
Dividing malaria parasite stained with trypan blue
Lab group (2015)
Dumisani Mnkandhla (Res. Assist.)
Michelle Isaacs (Res. Assist.)
Dustin Laming (MSc, upgrading to PhD)
Travis Basson (MSc)
Tarryn Swart (MSc, upgrading to PhD)
Leigh-Anne Derry (MSc)
Greg Woolf (MSc)
Lynn Wambua (BSc Hons)
Amira Damji (BSc Hons)
h-index (ISI Web of Science) : 18
- Zininga T., O.J. Pooe, I. Achilonu, H. Hoppe, E. Prinsloo, H.W. Dirr & A. Shonhai. 2015. Overexpression, purification and characterization of the Plasmodium falciparum Hsp70-z (PfHsp70-z). Plos One (accepted)
- Kramer A.H., A.L. Edkins, H.C. Hoppe & E. Prinsloo. 2015. Dynamic mitochondrial localization of STAT3 in the cellular adipogenesis model. J Cell Biochem 116: 1232-40
- Kadye R., A.H. Kramer, J. Joos-Vandewalle, M. Parsons, Z. Njengele, H. Hoppe & E. Prinsloo. 2014. Guardian of the furnace: mitochondria, TRAP1, ROS and stem cell maintenance. IUBMB Life 66:42-45.
- Paraskevopolous J.N., P.J. Smith, H.C. Hoppe, D. Chopra, T. Govender, H.G. Kruger & G.E.M. Maguire. 2013. Terpyridyl complexes as antimalarial agents. SA Journal of Chemistry 66:80-85
- Combrinck J.M., T.E. Mabotha, K.K. Ncokazi, M.A. Ambele, D. Taylor, P.J. Smith, H.C. Hoppe & T.J. Egan 2013. Insights into the role of heme in the mechanism of action of antimalarials. ACS Chemical Biology 8:133-137
- DePonte M., H.C Hoppe, M. Lee, A.G. Maier, D Richard, M. Rug, T. Spielman & J.M. Przyborski. 2012. Wherever I may roam: Protein and membrane trafficking in the malaria parasite. Molecular and Biochemical Parasitology 186:95-116
- Khan T., A.C. van Brummelen, C.J. Parkinson & H.C. Hoppe*. 2012. ATP and luciferase assays to determine the rate of drug action in in vitro cultures of Plasmodium falciparum. Malaria Journal 11:369
- Campos, W.R., P.P. Catarino & H.C. Hoppe. 2012. New frontiers in ethnomedicine: exploring the Angolan indigenous pharmacopeia for antimalarial drugs. Drug Discovery Today 17:651-653
- Gravestock, D., A.L. Rousseau, A.C.U. Lourens, H.C. Hoppe, L.A. Nkabinde & M.L. Bode. 2012. Novel branched isocyanides as useful building blocks in the Passerini-amine deprotection-acyl migration (PADAM) synthesis of potential HIV-1 protease inhibitors. Tetrahedron Letters 53:3225-3229.
- Rossouw, C.L., A. Chetty, F.S. Moolman, R. Anandjiwala, L. Birkoltz, H.C. Hoppe & D.T. Mancama. 2012. Thermo-responsive non-woven scaffolds for “smart” 3D culture. Biotechnology and Bioengineering 109:2147-2158.
- Bode, M.L., D. Gravestock, S.S. Moleele, C.W. van der Westhuyzen, S.C. Pelley, P.A. Steenkamp, H.C. Hoppe, T. Khan & L.A. Nkabinde. 2011. Imidazo[1,2-a]pyridine-3-amines as potential HIV-1 non-nucleoside reverse transcriptase inhibitors. Bioorganic and Medicinal Chemistry 19:4227-4237.
- Feng, T-S, E.M. Guantai, M.J. Nell, C. Medlin, K. Ncokazi, T.J. Egan, H.C. Hoppe* & K. Chibale. 2011. Effects of highly active novel artemisinin-chloroquinoline hybrid compounds on B-hematin formation, parasite morphology and endocytosis in Plasmodium falciparum. Biochemical Pharmacology 82: 236-247.
- Feng, T-S, E.M. Guantai, M.J. Nell, C.E.J. van Rensburg, H.C. Hoppe & K. Chibale. 2011. Antiplasmodial and antitumor activity of dihydroartemisinin analogs derived via the aza-Michael addition reaction. Bioorganic and Medicinal Chemistry Letters 21: 2882-86
- Botha, M., A.N. Chiang, P.G. Needham, L.L. Stephens, H.C. Hoppe, S. Külzer, J.M. Przyborski, K. Lingelbach, P Wipf, J.L. Brodsky, A. Shonhai & G.L. Blatch. 2011. Plasmodium falciparum encodes a single cytosolic type I Hsp40 that functionally interacts with Hsp70 and is upregulated by heat shock. Cell Stress and Chaperones 16: 389-401
- Coetzee, J., S. Cronje, L. Dobrzanska, H.G. Raubenheimer, M.J. Nell, C.E.J. van Rensburg & H.C. Hoppe. 2011. First N-heterocycliv ylideneamine gold(I) complexes: characterisation and screening for antitumour and antimalarial activity. Dalton Transactions 40: 1471-83
- Vaid, A., R. Ranjan, G. Verma, W.A. Smythe, H.C. Hoppe & P. Sharma. 2010. PfPI3K, a phosphatidylinositol-3 kinase in Plasmodium falciparum, is exported to the host erythrocyte and is involved in haemoglobin trafficking. Blood 115:2500-07
- Toomey, D., H.C. Hoppe, M.P. Brennan, K.B. Nolan & A.J. Chubb. 2009. Genomes2Drugs: identifies target proteins and lead drugs from transcriptome data. PLoS ONE 4(7):e6195
- Birkholtz, L-M., G. Blatch, T.L. Coetzer, H.C. Hoppe, E. Human, J. Morris, Z. Ngcete, L. Oldfield, R. Roth, A. Shonhai, L. Stephens & A.I. Louw. 2008. Heterologous expression of plasmodial proteins for structural studies and functional annotation. Malaria J. 7:197
- Pesce, E.-R., P. Acharya, U. Tatu, W.S. Nicoll, A. Shonhai, H.C. Hoppe & G.L. Blatch. 2008. The Plasmodium falciparum heat shock protein 40, Pfj4, associates with heat shock protein 70 and shows similar heat induction and localization patterns. Int J Biochem Cell Biol 40: 2914-26
- Roberts, L., T. Egan, K.A. Joiner & H.C. Hoppe *. 2008. Differential effects of quinoline anti-malarials on endocytosis in Plasmodium falciparum. Antimicrob Agents Chemother 52: 1840-1842.
- Smythe, W.A., K.A. Joiner & H.C. Hoppe.* 2008. Actin is required for endocytic trafficking in the malaria parasite Plasmodium falciparum. Cellular Microbiol 10: 1079-1085
Last Modified :Thu, 25 Jun 2015 14:55:55 SAST