Kinetoplasts Play an Important Role in the Drug Responses of Trypanosoma brucei

Agbe, A; Kl, Yielding

doi:10.2307/3284050

Cited by 17 publications

(11 citation statements)

References 11 publications

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“…II. The results in (i) are consistent with a number of experiments over an extended time period by Shapiro and coworkers [29,30] as well as limited studies by Yielding [31] on the importance of the kinetoplast in antiparasitic drug action. There is confusion and disagreement on the importance of the kinetoplast in the older literature due to results with laboratory dyskinetoplastic (Dk) trypanosomes.…”

Section: Biological Mechanism Of Antiparasitic Action Of Dicationic Hsupporting

confidence: 91%

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Dications That Target the DNA Minor Groove: Compound Design and Preparation, DNA Interactions, Cellular Distribution and Biological Activity

Wilson

Nguyen

Tanious³

et al. 2005

CMCACA

159

171

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Fluorescence microscopy of trypanosomes from drug treated mice shows that biologically active heterocyclic diamidines that target the DNA minor groove bind rapidly and specifically to parasite kinetoplast DNA (k-DNA). The observation that the kinetoplast is destroyed, generally within 24 hours, after drug treatment is very important for understanding the biological mechanism, and suggests that the diamidines may be inhibiting some critical opening/closing step of circular k-DNA. Given the uncertainties in the biological mechanism, we have taken an empirical approach to generating a variety of synthetic compounds and DNA minor groove interactions for development of improved and new biological activities. Furamidine, DB75, is a diphenyl-diamidine that has the curvature to match the DNA minor groove as expected in the classical groove interaction model. Surprisingly, a linear diamidine with a nitrogen rich linker has significantly stronger binding than furamidine due to favorable linker and water-mediated DNA interactions. The water interaction is very dependant on compound structure since other linear compounds do not have similar interactions. Change of one phenyl of furamidine to a benzimidazole does not significantly enhance DNA binding but additional conversion of the furan to a thiophene (DB818) yields a compound with ten times stronger binding. Structural analysis shows that DB818 has a very favorable curvature for optimizing minor groove interactions. It is clear that there are many ways for compounds to bind to k-DNA and exert specific effects on kinetoplast replication and/or transcription that are required to obtain an active compound.

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Section: Biological Mechanism Of Antiparasitic Action Of Dicationic Hsupporting

confidence: 91%

“…In a work described above by Wang and Englund [28], RNAi was used to produce a Dk strain that clearly demonstrated the essential role of the kinetoplast for the bloodstream trypanosomes. Additional studies on Dk strains have shown that such strains can be resistant to diamidines [31].…”

Section: Biological Mechanism Of Antiparasitic Action Of Dicationic Hmentioning

confidence: 99%

Dications That Target the DNA Minor Groove: Compound Design and Preparation, DNA Interactions, Cellular Distribution and Biological Activity

Wilson

Nguyen

Tanious³

et al. 2005

CMCACA

159

171

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“…We next addressed the issue of whether this connection would be disturbed by inhibition of kDNA synthesis and if so, what would be the cellular consequences? Acriflavine is an attractive compound for such studies because it is known to have a selective effect on kDNA replication and has well studied effects on mitochondrial DNA in many other cell types (Simpson, 1968;TarragoLitvak et al, 1978;Gillham et al, 1987;Matagne et al, 1989;Agbe and Yielding, 1995). The most striking feature of acriflavine treatment is the rapid rise through 4 and 8 h treatment of a cell type that we term 1K1N (old) and 1K1N (new) ( Figure 5).…”

Section: Flagellum-kinetoplast Structural Linksmentioning

confidence: 99%

A High-OrderTrans-Membrane Structural Linkage Is Responsible for Mitochondrial Genome Positioning and Segregation by Flagellar Basal Bodies in Trypanosomes

Ogbadoyi

Robinson

Gull

2003

MBoC

237

279

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In trypanosomes, the large mitochondrial genome within the kinetoplast is physically connected to the flagellar basal bodies and is segregated by them during cell growth. The structural linkage enabling these phenomena is unknown. We have developed novel extraction/fixation protocols to characterize the links involved in kinetoplast-flagellum attachment and segregation. We show that three specific components comprise a structure that we have termed the tripartite attachment complex (TAC). The TAC involves a set of filaments linking the basal bodies to a zone of differentiated outer and inner mitochondrial membranes and a further set of intramitochondrial filaments linking the inner face of the differentiated membrane zone to the kinetoplast. The TAC and flagellum-kinetoplast DNA connections are sustained throughout the cell cycle and are replicated and remodeled during the periodic kinetoplast DNA S phase. This understanding of the high-order trans-membrane linkage provides an explanation for the spatial position of the trypanosome mitochondrial genome and its mechanism of segregation. Moreover, the architecture of the TAC suggests that it may also function in providing a structural and vectorial role during replication of this catenated mass of mitochondrial DNA. We suggest that this complex may represent an extreme form of a more generally occurring mitochondrion/cytoskeleton interaction. INTRODUCTIONThe African trypanosome Trypanosoma brucei belongs to a large order of pathogenic and free-living flagellated protozoa designated the kinetoplastida. The majority of these organisms possess a single mitochondrion containing a structural mass of proteins and catenated circular DNA molecules, the kinetoplast. The kinetoplast is essential for survival and cyclical transmission of the parasite between mammalian host and tsetse fly. Early light microscope descriptions of trypanosomes recognized the precise location of the kinetoplast in proximity to the base of the flagellum (Robertson, 1912(Robertson, , 1913. The positions of the flagellum and kinetoplast have become the central features in classifying the different life cycle stages of kinetoplastids (Hoare and Wallace, 1966;Vickerman, 1976). Electron microscopy revealed the kinetoplast to be a highly complex disk-shaped structure located within a distended portion of the mitochondrial matrix adjacent to the flagellum basal bodies (Vickerman, 1973). The T. brucei kinetoplast consists of multiple copies of topologically interlocked circular DNA molecules termed maxicircles and minicircles, along with specific kinetoplast proteins. The maxicircle composition of the T. brucei network is 25-50 copies and represents 10% of the network mass (each maxicircle is 20 kb and all have identical DNA sequence). Maxicircles encode the mitochondrial proteins and some guide RNAs (gRNAs), whereas the minicircles are present in several thousand copies (1 kb in length), are heterogeneous in sequence, and encode gRNAs. The gRNAs are essential for the RNA editing process whereby the maxic...

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“…Dyskinetoplastic trypanosomes (24), and T. brucei with ATP synthase γ-subunit mutations (5), display resistance to phenanthridines, including ISM and ethidium bromide, and nonintercalating diamidines, including pentamidine and berenil. These drugs selectively cleave kinetoplast DNA (25).…”

Section: Atp Synthase Uncoupling and Dyskinetoplasty In Cells With Acmentioning

confidence: 99%

Vacuolar ATPase depletion affects mitochondrial ATPase function, kinetoplast dependency, and drug sensitivity in trypanosomes

Baker

Hamilton

Wilkes

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Kinetoplastid parasites cause lethal diseases in humans and animals. The kinetoplast itself contains the mitochondrial genome, comprising a huge, complex DNA network that is also an important drug target. Isometamidium, for example, is a key veterinary drug that accumulates in the kinetoplast in African trypanosomes. Kinetoplast independence and isometamidium resistance are observed where certain mutations in the F 1 -γ-subunit of the two-sector F 1 F o -ATP synthase allow for F o -independent generation of a mitochondrial membrane potential. To further explore kinetoplast biology and drug resistance, we screened a genome-scale RNA interference library in African trypanosomes for isometamidium resistance mechanisms. Our screen identified 14 V-ATPase subunits and all 4 adaptin-3 subunits, implicating acidic compartment defects in resistance; V-ATPase acidifies lysosomes and related organelles, whereas adaptin-3 is responsible for trafficking among these organelles. Independent strains with depleted V-ATPase or adaptin-3 subunits were isometamidium resistant, and chemical inhibition of the V-ATPase phenocopied this effect. While drug accumulation in the kinetoplast continued after V-ATPase subunit depletion, acriflavine-induced kinetoplast loss was specifically tolerated in these cells and in cells depleted for adaptin-3 or endoplasmic reticulum membrane complex subunits, also identified in our screen. Consistent with kinetoplast dispensability, V-ATPase defective cells were oligomycin resistant, suggesting ATP synthase uncoupling and bypass of the normal F o -A6-subunit requirement; this subunit is the only kinetoplast-encoded product ultimately required for viability in bloodstream-form trypanosomes. Thus, we describe 30 genes and 3 protein complexes associated with kinetoplast-dependent growth. Mutations affecting these genes could explain natural cases of dyskinetoplasty and multidrug resistance. Our results also reveal potentially conserved communication between the compartmentalized two-sector rotary ATPases.brucei | mitochondrion | nagana | petite | samorin

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Kinetoplasts Play an Important Role in the Drug Responses of Trypanosoma brucei

Cited by 17 publications

References 11 publications

Dications That Target the DNA Minor Groove: Compound Design and Preparation, DNA Interactions, Cellular Distribution and Biological Activity

Dications That Target the DNA Minor Groove: Compound Design and Preparation, DNA Interactions, Cellular Distribution and Biological Activity

A High-OrderTrans-Membrane Structural Linkage Is Responsible for Mitochondrial Genome Positioning and Segregation by Flagellar Basal Bodies in Trypanosomes

Vacuolar ATPase depletion affects mitochondrial ATPase function, kinetoplast dependency, and drug sensitivity in trypanosomes

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