Lipid metabolism at the host-parasite interface
A long-standing goal in the lab is to identify host cellular processes needed to support successful infection of mammalian host cells by T. cruzi amastigotes. To this end, we performed a genome-scale functional screen using RNA interference to silence host gene expression that was instrumental in revealing cellular processes in mammalian host cells that influence intracellular T. cruzi growth . Host lipid metabolism was identified among several key metabolic processes predicted to support intracellular parasite infection. To probe this further, unbiased lipidomics analyses were performed to characterize lipid class and fatty acid signatures of isolated intracellular T. cruzi amastigotes and their cognate mammalian host cells . Our analysis revealed evidence for the scavenging of host triacylglycerides (TG) by intracellular amastigotes, which provides an exogenous source of fatty acids to facilitate parasite proliferation. Given that T. cruzi amastigotes express the enzymes needed for de novo fatty acid and lipid synthesis [eg. 3], it is likely that the parasite strikes a balance between synthesis and scavenging, and that this balance is impacted by local metabolic parameters. Studies in the lab are aimed at understanding the mechanistic basis for fatty acid/TG scavenging by T. cruzi amastigotes and the extent to which intracellular parasites rely on de novo fatty acid synthesis. A range of molecular genetic (shRNA, CRISPR/Cas9), biochemical and cell biological approaches are employed to investigate this parasite-host relationship.
- Caradonna K.L., Engel, J.C., Jacobi, D., Lee, C-H., Burleigh, B.A. 2013. Host metabolism regulates intracellular growth of Trypanosoma cruzi. Cell Host & Microbe 13, 108–117.
- Gazos-Lopes, F*., Martin, J.L*., Dumoulin, P.C., Burleigh, B.A. 2017. Host triacylglycerol fatty acids shape the lipidome of intracellular trypanosomes and modulate their growth. PLoS Pathogens, 13(12):e1006800. doi: 10.1371/journal.ppat.1006800. PMID: 29281741 *equal contribution
- Li, Y. Shah-Simpson, S., Okrah, K., Belew, A.T., Choi, J., Caradonna, K.L., Padmanabhan, P.Temanni, M. R., Corrada Bravo, H. El-Sayed, N.M. and B. A. Burleigh. 2016. Transcriptome remodeling in Trypanosoma cruzi and human cells during intracellular Infection. PLoS Pathogens 12(4):e1005511. doi: 10.1371/journal.ppat.1005511.
Metabolic flexibility and the impact of environment on intracellular T. cruzi growth and susceptibility to drugs.
The ability of T. cruzi to colonize diverse tissue and cell types in vivo suggests a capacity for metabolic flexibility and adaptation. Few studies have considered the impact of the immediate metabolic environment on the growth and survival of intracellular T. cruzi amastigotes. We have demonstrated that metabolic perturbation in mammalian host cells induced by altering gene expression , or through the manipulation of exogenous nutrients [4,5] or addition of small molecule inhibitors of metabolism [4,5] can have profound and reversible effects on amastigote proliferation and the susceptibility of parasites to drugs (unpublished). Our goal is to determine whether T. cruzi amastigotes undergo metabolic reprogramming in response to changing environmental conditions and how altered host cellular environment impacts the ability to eliminate intracellular parasites.
- Shah-Simpson, S., Lentini, G., Dumoulin, P.C., Burleigh, B.A. 2017. Modulation of host central carbon metabolism and in situ glucose uptake by intracellular Trypanosoma cruzi amastigotes. PLoS Pathogens, Nov 27;13(11):e1006747. doi: 10.1371/journal.ppat.1006747. PMID:29176805
- Dumoulin, P.C. and Burleigh, B.A. 2018. Stress-induced proliferation and cell cycle plasticity of intracellular T. cruzi amatigotes. mBio. 9(4). pii: e00673-18. doi: 10.1128/mBio.00673-18. PMID:29991586
Dissecting the physical and functional basis of T. cruzi amastigote flagellum-host mitochondrial interactions.
Unlike many intracellular pathogens, T. cruzi amastigotes replicate in the host cell cytosol, providing an opportunity for direct interaction with host subcellular structures. We have little information regarding the potential physical and biochemical interactions that are occurring between T. cruzi amastigotes and their host cells, but it has been long appreciated that the parasites are not randomly distributed throughout the host cell cytoplasm. Instead, amastigotes tend to cluster near the host cell nucleus. This juxtanuclear positioning of the parasite is established very early in the infection process  prior to the disruption of the parasitophorous vacuole and the first parasite duplication event . As amastigotes undergo binary fission every ~10 hr (this varies with parasite strain and particular growth condition) they remain clustered and their distribution is influenced by cell shape.
We have also recently discovered that the amastigotes establish close physical contact with host mitochondria using the distal portion of their short flagellum [7; inset Fig]. The purpose of this parasite-host organelle interaction is currently unknown but likely serves some key metabolic function for the parasite and/or as a mechanism for the parasite to influence innate immune or apoptotic functions in the host cell. Importantly, these observations indicate that the T. cruzi amastigote flagellum, long considered an inert remnant of the much longer motile flagellum of the invasive trypomastigote stage of the parasite, has a functional role inside the host cell. Efforts in the lab are currently focused on mapping the surface proteome of the amastigote flagellum to identify candidate proteins involved in mediating interactions with host mitochondria and identifying the functional role of this interaction.
- Zhao, X., Kumar, P., Shah-Simpson, S., Caradonna, K.L., Galjart, N., Teygong, C., Blader, I., Wittmann, T., Burleigh, B.A. 2013. Regulation of Trypanosoma cruzi infection by the host microtubule plus-end binding protein CLASP1. Cellular Microbiology 15:571-584.
- Lentini, G., Dos Santos Pacheco, N., B. A. Burleigh. 2017. Targeting host mitochondria: a role for the Trypanosoma cruzi amastigote flagellum. Cellular Microbiology. doi: 10.1111/ cmi.12807. PMID: 29119655.