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Etheridge RD. Protozoan phagotrophy from predators to parasites: An overview of the enigmatic cytostome-cytopharynx complex of Trypanosoma cruzi. J Eukaryot Microbiol 2022; 69:e12896. [PMID: 35175673 PMCID: PMC11110969 DOI: 10.1111/jeu.12896] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 02/14/2022] [Accepted: 02/14/2022] [Indexed: 11/28/2022]
Abstract
Eating is fundamental and from this basic principle, living organisms have evolved innumerable strategies to capture energy and nutrients from their environment. As part of the world's aquatic ecosystems, the expansive family of heterotrophic protozoans uses self-generated currents to funnel prokaryotic prey into an ancient, yet highly enigmatic, oral apparatus known as the cytostome-cytopharynx complex prior to digestion. Despite its near ubiquitous presence in protozoans, little is known mechanistically about how this feeding organelle functions. Intriguingly, one class of these flagellated phagotrophic predators known as the kinetoplastids gave rise to a lineage of obligate parasitic protozoa, the trypanosomatids, that can infect a wide variety of organisms ranging from plants to humans. One parasitic species of humans, Trypanosoma cruzi, has retained this ancestral organelle much like its free-living relatives and continues to use it as its primary mode of endocytosis. In this review, we will highlight foundational observations made regarding the cytostome-cytopharynx complex and examine some of the most pressing questions regarding the mechanistic basis for its function. We propose that T. cruzi has the potential to serve as an excellent model system to dissect the enigmatic process of protozoal phagotrophy and thus enhance our overall understanding of fundamental eukaryotic biology.
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Affiliation(s)
- Ronald Drew Etheridge
- Department of Cellular Biology, Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, USA
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Abstract
Acidocalcisomes are membrane-bounded, electron-dense, acidic organelles, rich in calcium and polyphosphate. These organelles were first described in trypanosomatids and later found from bacteria to human cells. Some of the functions of the acidocalcisome are the storage of cations and phosphorus, participation in pyrophosphate (PPi) and polyphosphate (polyP) metabolism, calcium signaling, maintenance of intracellular pH homeostasis, autophagy, and osmoregulation. Isolation of acidocalcisomes is an important technique for understanding their composition and function. Here, we provide detailed subcellular fractionation protocols using iodixanol gradient centrifugations to isolate high-quality acidocalcisomes from Trypanosoma brucei, which are subsequently validated by electron microscopy, and enzymatic and immunoblot assays with organellar markers.
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Affiliation(s)
- Guozhong Huang
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA.
| | - Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA
- Department of Cellular Biology, University of Georgia, Athens, GA, USA
| | - Roberto Docampo
- Center for Tropical and Emerging Global Diseases, Department of Cellular Biology, University of Georgia, Athens, GA, USA.
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Birge RB, Boeltz S, Kumar S, Carlson J, Wanderley J, Calianese D, Barcinski M, Brekken RA, Huang X, Hutchins JT, Freimark B, Empig C, Mercer J, Schroit AJ, Schett G, Herrmann M. Phosphatidylserine is a global immunosuppressive signal in efferocytosis, infectious disease, and cancer. Cell Death Differ 2016; 23:962-78. [PMID: 26915293 PMCID: PMC4987730 DOI: 10.1038/cdd.2016.11] [Citation(s) in RCA: 460] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 02/06/2023] Open
Abstract
Apoptosis is an evolutionarily conserved and tightly regulated cell death modality. It serves important roles in physiology by sculpting complex tissues during embryogenesis and by removing effete cells that have reached advanced age or whose genomes have been irreparably damaged. Apoptosis culminates in the rapid and decisive removal of cell corpses by efferocytosis, a term used to distinguish the engulfment of apoptotic cells from other phagocytic processes. Over the past decades, the molecular and cell biological events associated with efferocytosis have been rigorously studied, and many eat-me signals and receptors have been identified. The externalization of phosphatidylserine (PS) is arguably the most emblematic eat-me signal that is in turn bound by a large number of serum proteins and opsonins that facilitate efferocytosis. Under physiological conditions, externalized PS functions as a dominant and evolutionarily conserved immunosuppressive signal that promotes tolerance and prevents local and systemic immune activation. Pathologically, the innate immunosuppressive effect of externalized PS has been hijacked by numerous viruses, microorganisms, and parasites to facilitate infection, and in many cases, establish infection latency. PS is also profoundly dysregulated in the tumor microenvironment and antagonizes the development of tumor immunity. In this review, we discuss the biology of PS with respect to its role as a global immunosuppressive signal and how PS is exploited to drive diverse pathological processes such as infection and cancer. Finally, we outline the rationale that agents targeting PS could have significant value in cancer and infectious disease therapeutics.
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Affiliation(s)
- R B Birge
- Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers New Jersey Medical School, 205 South Orange Ave, Newark, NJ 07103, USA
| | - S Boeltz
- Department of Internal Medicine 3-Rheumatology and Immunology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), University Hospital Erlangen, 91054 Erlangen, Germany
| | - S Kumar
- Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers New Jersey Medical School, 205 South Orange Ave, Newark, NJ 07103, USA
| | - J Carlson
- Peregrine Pharmaceuticals, 14282 Franklin Avenue, Tustin, CA 92780, USA
| | - J Wanderley
- Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - D Calianese
- Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers New Jersey Medical School, 205 South Orange Ave, Newark, NJ 07103, USA
| | - M Barcinski
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Rio de Janeiro, Brazil
| | - R A Brekken
- Division of Surgical Oncology, Department of Surgery, Hamon Center for Therapeutic Oncology Research, Dallas, TX 75390-8593, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
| | - X Huang
- Division of Surgical Oncology, Department of Surgery, Hamon Center for Therapeutic Oncology Research, Dallas, TX 75390-8593, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
| | - J T Hutchins
- Peregrine Pharmaceuticals, 14282 Franklin Avenue, Tustin, CA 92780, USA
| | - B Freimark
- Peregrine Pharmaceuticals, 14282 Franklin Avenue, Tustin, CA 92780, USA
| | - C Empig
- Peregrine Pharmaceuticals, 14282 Franklin Avenue, Tustin, CA 92780, USA
| | - J Mercer
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - A J Schroit
- Simmons Cancer Center and the Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390 USA
| | - G Schett
- Department of Internal Medicine 3-Rheumatology and Immunology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), University Hospital Erlangen, 91054 Erlangen, Germany
| | - M Herrmann
- Department of Internal Medicine 3-Rheumatology and Immunology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), University Hospital Erlangen, 91054 Erlangen, Germany
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