The Landfear laboratory studies the cell and molecular biology and biochemistry of single cell parasites, both Leishmania species and African trypanosomes (Trypanosoma brucei). These two related parasites cause devastating diseases, leishmaniasis (estimated 12 million people infected) and African sleeping sickness, primarily in the developing world. Because these parasites are very distant from higher eukaryotes on an evolutionary scale, they display many intriguing and unusual biological features and present fascinating systems for exploring cell and molecular biology. In addition, the current drugs for both parasites are far from optimal, and there is an urgent need to discover new leads for development of more potent and less toxic therapies. Hence, our research covers both basic biology and novel drug development for these important parasites. 

experience within the parasitophorous vacuole. There are robust molecular genetic tools to study these parasites and the functions of specific genes and proteins. 

African trypanosomes live in the gut and salivary glands of tsetse fly vectors and in the bloodstream of the mammalian host (Figure 2). 

Three of the major projects of the laboratory dealing with Leishmania and trypanosomes are outlined below. 

A major discovery in biology was that the small (76 amino acid) protein ubiquitin could be covalently attached to specific lysine residues on many cellular proteins and could thus modify their activities. A principal, albeit not exclusive, function of ubiquitination is to target the modified proteins for proteolytic degradation, thus determining which proteins are stable and which are removed from cells under various physiological conditions. Intriguingly, the ubiquitin modification pathway itself is subject to regulation by a process in which another ubiquitin-related protein, NEDD8, is covalently attached to one subunit (the cullin protein) of the so-called E3 ubiquitin ligase enzymes that attach ubiquitin to its substrate proteins. Once NEDD8 is attached to a cullin, the E3 enzyme is activated to ubiquitinate its substrates, and thus neddylation (the covalent attachment of NEDD8 to proteins) ultimately controls the composition of the cellular proteome. Hence, a major area of study is the neddylation pathway, which itself contains 3 enzymes, E1, E2, and E3, that activate NEDD8 and ultimately attach it to cullins (Figure 5). Neddylation is of major biomedical importance, as overactive neddylation is a dysregulation associated with many cancers, and inhibiting the overactive neddylation pathway is being pursued actively for anti-cancer therapies. 

Project 3: Using Phenotypic Screening to Discover Novel Compounds for Anti-leishmanial Drug Development

One approach to drug discovery is to target a specific biological pathway that has been demonstrated to be essential for the parasite, as in Project 2 above. An alternative approach is to carry out large-scale screens of compound libraries to identify small molecules with potent activity against the parasite, a method referred to as ‘phenotypic screening’. The initial ‘hits’ from a phenotypic screen can then be explored for those with the greatest potential for drug development.

We have engaged in two separate collaborative projects that initiated with such phenotypic screens. The first project is a collaboration with the laboratory of Dr. Kip Guy, mentioned in Project 2, and the second is a collaboration with Dr. Jane Kelly (Portland State University, pharmaceutical chemistry). Intriguingly, the collaboration with the Guy laboratory led to discovery of two completely different small molecules that inhibit the same critical biosynthetic pathway in Leishmania parasites. Both compounds cause extensive changes in the parasite metabolome, demonstrating the core importance of this pathway for parasite metabolism. This discovery involved yet another collaboration with Dr. Mike Barrett (University of Glasgow, metabolomics) to identify the pathway that is targeted by these two compounds. Efforts are now underway to both explore the biochemical pathway and to optimize the two initial lead compounds for drug development. Another collaboration with Dr. Kelly’s laboratory has exploited a group of structurally related natural product derived compounds that have demonstrated efficacy against malaria parasites. Many of these compounds show potent activity against Leishmania parasites, and we are now exploring improved derivatives of the initial hits to identify analogs that have efficacy against Leishmania parasites in a murine model of infection. Ultimately, we plan to identify the target or targets of these compounds to allow both the development of novel anti-parasitic drugs and an exploration of the relevant pathway.

Relevant Publications:

Ortiz, D., Guiguemde, W.A., Hammill, J.T., Carrillo. A.K., Chen, Y., Connelly, M., Stalheim, K., Elya, C., Johnson, A., Min, J., Shelat, A., Smithson, D.C., Yang, L., Zhu, F., Guy, R.K., Landfear, S.M. Discovery of novel, orally bioavailable, antileishmanial compounds using phenotypic screening. PLoS Negl. Trop. Dis. 11:e0006157 (2017). 

Hammill, J.T., Sviripa, V.M., Kril, L.M., Ortiz, D., Fargo, C.M., Kim, H.S., Chen, Y., Rector, J., Rice, A.L., Domagalska, M.A., Begley, K.L., Liu, C., Rangnekar, V.M., Dujardin, J.-C., Watt, D.S., Landfear, S.M., and Guy, R.K. Amino-substituted 3‑aryl- and 3‑heteroarylquinolines as potential antileishmanial agents. J. Med. Chem. 64:12152-12162 (2021). 

Kancharla, P., Li, Y., Yeluguri, M. Dodean, R.A., Reynolds, K.A., and Kelly, J.X. Total synthesis and antimalarial activity of 2-(p-hydroxybenzyl)-prodigiosins, isoheptylprodigiosin, and geometric isomers of tambjamine MYP1 isolated from marine bacteria. J. Med. Chem. 64:8739-8754 (2021)