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1.
Cells ; 13(20)2024 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-39451256

RESUMO

Apolipoprotein-L1 (APOL1) is a membrane-interacting protein induced by inflammation, which confers human resistance to infection by African trypanosomes. APOL1 kills Trypanosoma brucei through induction of apoptotic-like parasite death, but two T. brucei clones acquired resistance to APOL1, allowing them to cause sleeping sickness. An APOL1 C-terminal sequence alteration, such as occurs in natural West African variants G1 and G2, restored human resistance to these clones. However, APOL1 unfolding induced by G1 or G2 mutations enhances protein hydrophobicity, resulting in kidney podocyte dysfunctions affecting renal filtration. The mechanism involved in these dysfunctions is debated. The ability of APOL1 to generate ion pores in trypanosome intracellular membranes or in synthetic membranes was provided as an explanation. However, transmembrane insertion of APOL1 strictly depends on acidic conditions, and podocyte cytopathology mainly results from secreted APOL1 activity on the plasma membrane, which occurs under non-acidic conditions. In this review, I argue that besides inactivation of APOL3 functions in membrane dynamics (fission and fusion), APOL1 variants induce inflammation-linked podocyte toxicity not through pore formation, but through plasma membrane disturbance resulting from increased interaction with cholesterol, which enhances cation channels activity. A natural mutation in the membrane-interacting domain (N264K) abrogates variant APOL1 toxicity at the expense of slightly increased sensitivity to trypanosomes, further illustrating the continuous mutual adaptation between host and parasite.


Assuntos
Apolipoproteína L1 , Nefropatias , Tripanossomíase Africana , Humanos , Tripanossomíase Africana/parasitologia , Apolipoproteína L1/metabolismo , Apolipoproteína L1/genética , Nefropatias/metabolismo , Nefropatias/patologia , Nefropatias/genética , Animais , Trypanosoma brucei brucei/metabolismo , Podócitos/metabolismo , Podócitos/patologia
2.
Mol Biol Cell ; 35(11): br22, 2024 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-39382839

RESUMO

Trypanosoma brucei is a human and animal pathogen that depends on flagellar motility for transmission and infection. The trypanosome flagellum is built around a canonical "9+2" axoneme, containing nine doublet microtubules (DMTs) surrounding two singlet microtubules. Each DMT contains a 13-protofilament A-tubule and a 10-protofilament B-tubule, connected to the A-tubule by a conserved, non-tubulin inner junction (IJ) filament made up of alternating PACRG and FAP20 subunits. Here we investigate FAP20 in procyclic form T. brucei. A FAP20-NeonGreen fusion protein localized to the axoneme as expected. Surprisingly, FAP20 knockdown led to a catastrophic failure in flagellum assembly and concomitant lethality. This differs from other organisms, where FAP20 is required for normal flagellum motility, but generally dispensable for flagellum assembly and viability. Transmission electron microscopy demonstrates failed flagellum assembly in FAP20 mutants is associated with a range of DMT defects and defective assembly of the paraflagellar rod, a lineage-specific flagellum filament that attaches to DMT 4-7 in trypanosomes. Our studies reveal a lineage-specific requirement for FAP20 in trypanosomes, offering insight into adaptations for flagellum stability and motility in these parasites and highlighting pathogen versus host differences that might be considered for therapeutic intervention in trypanosome diseases.


Assuntos
Axonema , Flagelos , Proteínas de Protozoários , Trypanosoma brucei brucei , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/fisiologia , Flagelos/metabolismo , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Axonema/metabolismo , Microtúbulos/metabolismo
3.
ACS Synth Biol ; 13(10): 3344-3353, 2024 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-39292964

RESUMO

Phosphatidylinositol (PI) and its phosphorylated derivatives are of paramount importance in cellular functions and diseases. Understanding their diverse roles is, however, challenged by difficulties in synthesis and labeling techniques. In this proof-of-concept study, we demonstrate that PI can be straightforwardly de novo-synthesized and deuterium (2H)-labeled in Escherichia coli by genomic insertion of PI synthase from Trypanosoma brucei under constitutive synthetic promoter proD. Insertion into loci atpi-gidB and ybb revealed PI accumulation of 41% and 34% (mol/mol), respectively, when cultivated with glycerol as the sole carbon source. Growth of the atpi-gidB-PIS strain in deuterium-labeled (2H) substrates D2O, D8-glycerol, and D6-myo-inositol achieved PI deuteration of 90%, PE deuteration of 95%, and total fatty acids|fatty acid (FA) deuteration of 97%. This study offers an alternative convenient route to chemical and enzymatic labeling synthesis of PI; more excitingly, this work also, in principle, opens a door for tailoring the FA profile of deuterated PI/PE for task-specific application by repurposing FA biosynthesis pathways.


Assuntos
Deutério , Escherichia coli , Fosfatidilinositóis , Escherichia coli/genética , Escherichia coli/metabolismo , Deutério/química , Fosfatidilinositóis/metabolismo , Fosfatidilinositóis/biossíntese , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/genética , Fosfolipídeos/biossíntese , Fosfolipídeos/metabolismo , Fosfolipídeos/química , Ácidos Graxos/biossíntese , Ácidos Graxos/metabolismo
4.
Int J Biol Macromol ; 280(Pt 4): 135510, 2024 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-39304044

RESUMO

Peroxisomal protein import has been identified as a valid target in trypanosomiases, an important health threat in Central and South America. The importomer is built of multiple peroxins (Pex) and structural characterization of these proteins facilitates rational inhibitor development. We report crystal structures of the Trypanosoma brucei and T. cruzi tetratricopeptide repeat domain (TPR) of the cytoplasmic peroxisomal targeting signal 1 (PTS1) receptor Pex5. The structure of the TPR domain of TbPex5 represents an apo-form of the receptor which, together with the previously determined structure of the complex of TbPex5 TPR and PTS1 demonstrate significant receptor dynamics associated with signal peptide recognition. The structure of the complex of TPR domain of TcPex5 with PTS1 provided in this study details the molecular interactions that guide signal peptide recognition at the atomic level in the pathogenic species currently perceived as the most relevant among Trypanosoma. Small - angle X - ray scattering (SAXS) data obtained in solution supports the crystallographic findings on the compaction of the TPR domains of TbPex5 and TcPex5 upon interaction with the cargo.


Assuntos
Receptor 1 de Sinal de Orientação para Peroxissomos , Domínios Proteicos , Receptor 1 de Sinal de Orientação para Peroxissomos/metabolismo , Receptor 1 de Sinal de Orientação para Peroxissomos/química , Trypanosoma brucei brucei/metabolismo , Modelos Moleculares , Proteínas de Protozoários/química , Proteínas de Protozoários/metabolismo , Espalhamento a Baixo Ângulo , Peroxissomos/metabolismo , Ligação Proteica , Sequência de Aminoácidos , Trypanosoma cruzi/metabolismo , Cristalografia por Raios X , Receptores Citoplasmáticos e Nucleares/química , Receptores Citoplasmáticos e Nucleares/metabolismo
5.
Curr Biol ; 34(20): 4803-4812.e3, 2024 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-39321796

RESUMO

The acquisition of mitochondria was imperative for initiating eukaryogenesis and thus is a characteristic feature of eukaryotic cells.1,2 The parasitic protist Trypanosoma brucei contains a singular mitochondrion with a unique mitochondrial genome, termed the kinetoplast DNA (kDNA).3 Replication of the kDNA occurs during the G1 phase of the cell cycle, prior to the start of nuclear DNA replication.4 Although numerous proteins have been functionally characterized and identified as vital components of kDNA replication and division, the molecular mechanisms governing this highly precise process remain largely unknown.5,6 One division-related and morphologically characteristic structure that remains most enigmatic is the "nabelschnur," an undefined, filament-resembling structure observed by electron microscopy between segregating daughter kDNA networks.7,8,9 To date, only one protein, TbLAP1, an M17 family leucyl aminopeptidase metalloprotease, is known to localize to the nabelschnur.9 While screening proteins from the T. brucei MitoTag project,10 we identified a previously uncharacterized protein with an mNeonGreen signal localizing to the kDNA as well as forming a point of connection between dividing kDNAs. Here, we demonstrate that this kDNA-associated protein, named TbNAB70, indeed localizes to the nabelschnur and plays an essential role in the segregation of newly replicated kDNAs and subsequent cytokinesis in T. brucei.


Assuntos
DNA de Cinetoplasto , Proteínas de Protozoários , Trypanosoma brucei brucei , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/metabolismo , DNA de Cinetoplasto/metabolismo , DNA de Cinetoplasto/genética , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Replicação do DNA
6.
Nat Commun ; 15(1): 8113, 2024 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-39285175

RESUMO

Although genome-wide polycistronic transcription places major emphasis on post-transcriptional controls in trypanosomatids, messenger RNA cis-regulatory untranslated regions (UTRs) have remained largely uncharacterised. Here, we describe a genome-scale massive parallel reporter assay coupled with 3'-UTR-seq profiling in the African trypanosome and identify thousands of regulatory UTRs. Increased translation efficiency was associated with dosage of adenine-rich poly-purine tracts (pPuTs). An independent assessment of native UTRs using machine learning based predictions confirmed the robust correspondence between pPuTs and positive control, as did an assessment of synthetic UTRs. Those 3'-UTRs associated with upregulated expression in bloodstream-stage cells were also enriched in uracil-rich poly-pyrimidine tracts, suggesting a mechanism for developmental activation through pPuT 'unmasking'. Thus, we describe a cis-regulatory UTR sequence 'code' that underpins gene expression control in the context of a constitutively transcribed genome. We conclude that thousands of UTRs post-transcriptionally reprogram gene expression profiles in trypanosomes.


Assuntos
Regiões 3' não Traduzidas , RNA Mensageiro , Trypanosoma brucei brucei , RNA Mensageiro/metabolismo , RNA Mensageiro/genética , Regiões 3' não Traduzidas/genética , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/metabolismo , Regulação da Expressão Gênica , RNA de Protozoário/genética , RNA de Protozoário/metabolismo , Processamento Pós-Transcricional do RNA , Trypanosoma/genética , Trypanosoma/metabolismo , Genoma de Protozoário
7.
Sci Adv ; 10(36): eadq2950, 2024 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-39231220

RESUMO

Eukaryotic cilia and flagella are essential for cell motility and sensory functions. Their biogenesis and maintenance rely on the intraflagellar transport (IFT). Several cargo adapters have been identified to aid IFT cargo transport, but how ciliary cargos are discharged from the IFT remains largely unknown. During our explorations of small GTPases ARL13 and ARL3 in Trypanosoma brucei, we found that ODA16, a known IFT cargo adapter present exclusively in motile cilia, is a specific effector of ARL3. In the cilia, active ARL3 GTPases bind to ODA16 and dissociate ODA16 from the IFT complex. Depletion of ARL3 GTPases stabilizes ODA16 interaction with the IFT, leading to ODA16 accumulation in cilia and defects in axonemal assembly. The interactions between human ODA16 homolog HsDAW1 and ARL GTPases are conserved, and these interactions are altered in HsDAW1 disease variants. These findings revealed a conserved function of ARL GTPases in IFT transport of motile ciliary components, and a mechanism of cargo unloading from the IFT.


Assuntos
Fatores de Ribosilação do ADP , Cílios , Proteínas de Protozoários , Trypanosoma brucei brucei , Humanos , Fatores de Ribosilação do ADP/metabolismo , Fatores de Ribosilação do ADP/genética , Axonema/metabolismo , Transporte Biológico , Cílios/metabolismo , Flagelos/metabolismo , Ligação Proteica , Transporte Proteico , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Trypanosoma brucei brucei/metabolismo
8.
Open Biol ; 14(9): 240128, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39255848

RESUMO

Cilia are antenna-like organelles protruding from the surface of many cell types in the human body. Defects in ciliary structure or function often lead to diseases that are collectively called ciliopathies. Cilia and flagella-associated protein 410 (CFAP410) localizes at the basal body of cilia/flagella and plays essential roles in ciliogenesis, neuronal development and DNA damage repair. It remains unknown how its specific basal body location is achieved. Multiple single amino acid mutations in CFAP410 have been identified in patients with various ciliopathies. One of the mutations, L224P, is located in the C-terminal domain (CTD) of human CFAP410 and causes severe spondylometaphyseal dysplasia, axial (SMDAX). However, the molecular mechanism for how the mutation causes the disorder remains unclear. Here, we report our structural studies on the CTD of CFAP410 from three distantly related organisms, Homo sapiens, Trypanosoma brucei and Chlamydomonas reinhardtii. The crystal structures reveal that the three proteins all adopt the same conformation as a tetrameric helical bundle. Our work further demonstrates that the tetrameric assembly of the CTD is essential for the correct localization of CFAP410 in T. brucei, as the L224P mutation that disassembles the tetramer disrupts its basal body localization. Taken together, our studies reveal that the basal body localization of CFAP410 is controlled by the CTD and provide a mechanistic explanation for how the mutation L224P in CFAP410 causes ciliopathies in humans.


Assuntos
Corpos Basais , Trypanosoma brucei brucei , Humanos , Sequência de Aminoácidos , Corpos Basais/metabolismo , Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/metabolismo , Cílios/metabolismo , Cristalografia por Raios X , Modelos Moleculares , Mutação , Multimerização Proteica , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/química , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/genética
9.
J Cell Biol ; 223(11)2024 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-39196069

RESUMO

Kinetochores form the interface between chromosomes and spindle microtubules and are thus under tight control by a complex regulatory circuitry. The Aurora B kinase plays a central role within this circuitry by destabilizing improper kinetochore-microtubule attachments and relaying the attachment status to the spindle assembly checkpoint. Intriguingly, Aurora B is conserved even in kinetoplastids, a group of early-branching eukaryotes which possess a unique set of kinetochore proteins. It remains unclear how their kinetochores are regulated to ensure faithful chromosome segregation. Here, we show in Trypanosoma brucei that Aurora B activity controls the metaphase-to-anaphase transition through phosphorylation of the divergent Bub1-like protein KKT14. Depletion of KKT14 overrides the metaphase arrest resulting from Aurora B inhibition, while expression of non-phosphorylatable KKT14 delays anaphase onset. Finally, we demonstrate that re-targeting Aurora B to the outer kinetochore suffices to promote mitotic exit but causes extensive chromosome missegregation in anaphase. Our results indicate that Aurora B and KKT14 are involved in an unconventional circuitry controlling cell cycle progression in trypanosomes.


Assuntos
Anáfase , Aurora Quinase B , Segregação de Cromossomos , Cinetocoros , Proteínas de Protozoários , Trypanosoma brucei brucei , Aurora Quinase B/metabolismo , Aurora Quinase B/genética , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/enzimologia , Cinetocoros/metabolismo , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Fosforilação , Fuso Acromático/metabolismo , Fuso Acromático/genética , Microtúbulos/metabolismo , Microtúbulos/genética
10.
PLoS Biol ; 22(8): e3002449, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39146359

RESUMO

Protein import and genome replication are essential processes for mitochondrial biogenesis and propagation. The J-domain proteins Pam16 and Pam18 regulate the presequence translocase of the mitochondrial inner membrane. In the protozoan Trypanosoma brucei, their counterparts are TbPam16 and TbPam18, which are essential for the procyclic form (PCF) of the parasite, though not involved in mitochondrial protein import. Here, we show that during evolution, the 2 proteins have been repurposed to regulate the replication of maxicircles within the intricate kDNA network, the most complex mitochondrial genome known. TbPam18 and TbPam16 have inactive J-domains suggesting a function independent of heat shock proteins. However, their single transmembrane domain is essential for function. Pulldown of TbPam16 identifies a putative client protein, termed MaRF11, the depletion of which causes the selective loss of maxicircles, akin to the effects observed for TbPam18 and TbPam16. Moreover, depletion of the mitochondrial proteasome results in increased levels of MaRF11. Thus, we have discovered a protein complex comprising TbPam18, TbPam16, and MaRF11, that controls maxicircle replication. We propose a working model in which the matrix protein MaRF11 functions downstream of the 2 integral inner membrane proteins TbPam18 and TbPam16. Moreover, we suggest that the levels of MaRF11 are controlled by the mitochondrial proteasome.


Assuntos
Replicação do DNA , DNA Mitocondrial , Proteínas de Protozoários , Trypanosoma brucei brucei , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/genética , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Mitocôndrias/metabolismo , Mitocôndrias/genética , Evolução Molecular
11.
Front Immunol ; 15: 1441131, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39114668

RESUMO

Haptoglobin is a plasma protein of mammals that plays a crucial role in vascular homeostasis by binding free haemoglobin released from ruptured red blood cells. Trypanosoma brucei can exploit this by internalising haptoglobin-haemoglobin complex to acquire host haem. Here, we investigated the impact of haptoglobin deficiency (Hp-/-) on T. brucei brucei infection and the parasite´s capacity to internalise haemoglobin in a Hp-/- mouse model. The infected Hp-/- mice exhibited normal disease progression, with minimal weight loss and no apparent organ pathology, similarly to control mice. While the proteomic profile of mouse sera significantly changed in response to T. b. brucei, no differences in the infection response markers of blood plasma between Hp-/- and control Black mice were observed. Similarly, very few quantitative differences were observed between the proteomes of parasites harvested from Hp-/- and Black mice, including both endogenous proteins and internalised host proteins. While haptoglobin was indeed absent from parasites isolated from Hp-/-mice, haemoglobin peptides were unexpectedly detected in parasites from both Hp-/- and Black mice. Combined, the data support the dispensability of haptoglobin for haemoglobin internalisation by T. b. brucei during infection in mice. Since the trypanosomes knock-outs for their haptoglobin-haemoglobin receptor (HpHbR) internalised significantly less haemoglobin from Hp-/- mice compared to those isolated from Black mice, it suggests that T. b. brucei employs also an HpHbR-independent haptoglobin-mediated mode for haemoglobin internalisation. Our study reveals a so-far hidden flexibility of haemoglobin acquisition by T. b. brucei and offers novel insights into alternative haemoglobin uptake pathways.


Assuntos
Haptoglobinas , Hemoglobinas , Camundongos Knockout , Trypanosoma brucei brucei , Tripanossomíase Africana , Animais , Camundongos , Modelos Animais de Doenças , Haptoglobinas/genética , Haptoglobinas/metabolismo , Hemoglobinas/metabolismo , Camundongos Endogâmicos C57BL , Proteômica/métodos , Trypanosoma brucei brucei/metabolismo , Tripanossomíase Africana/parasitologia , Tripanossomíase Africana/imunologia , Masculino , Feminino
12.
J Biol Chem ; 300(9): 107657, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39128729

RESUMO

Damage to the genetic material of the cell poses a universal threat to all forms of life. The DNA damage response is a coordinated cellular response to a DNA break, key to which is the phosphorylation signaling cascade. Identifying which proteins are phosphorylated is therefore crucial to understanding the mechanisms that underlie it. We have used stable isotopic labeling of amino acids in cell culture-based quantitative phosphoproteomics to profile changes in phosphorylation site abundance following double stranded DNA breaks, at two distinct loci in the genome of the single cell eukaryote Trypanosoma brucei. Here, we report on the T. brucei phosphoproteome following a single double-strand break at either a chromosome internal or subtelomeric locus, specifically the bloodstream form expression site. We detected >6500 phosphorylation sites, of which 211 form a core set of double-strand break responsive phosphorylation sites. Along with phosphorylation of canonical DNA damage factors, we have identified two novel phosphorylation events on histone H2A and found that in response to a chromosome internal break, proteins are predominantly phosphorylated, while a greater proportion of proteins dephosphorylated following a DNA break at a subtelomeric bloodstream form expression site. Our data represent the first DNA damage phosphoproteome and provides novel insights into repair at distinct chromosomal contexts in T. brucei.


Assuntos
Fosfoproteínas , Proteínas de Protozoários , Trypanosoma brucei brucei , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/genética , Fosfoproteínas/metabolismo , Fosfoproteínas/genética , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Fosforilação , Dano ao DNA , Proteômica/métodos , Proteoma/metabolismo , Quebras de DNA de Cadeia Dupla , Reparo do DNA , Histonas/metabolismo
13.
Mol Biol Cell ; 35(9): br16, 2024 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-39024276

RESUMO

The outer dynein arm (ODA) is a large, multimeric protein complex essential for ciliary motility. The composition and assembly of ODA are best characterized in the green algae Chlamydomonas reinhardtii, where individual ODA subunits are synthesized and preassembled into a mature complex in the cytosol prior to ciliary import. The single-cellular parasite Trypanosoma brucei contains a motile flagellum essential for cell locomotion and pathogenesis. Similar to human motile cilia, T. brucei flagellum contains a two-headed ODA complex arranged at 24 nm intervals along the axonemal microtubule doublets. The subunit composition and the preassembly of the ODA complex in T. brucei, however, have not been investigated. In this study, we affinity-purified the ODA complex from T. brucei cytoplasmic extract. Proteomic analyses revealed the presence of two heavy chains (ODAα and ODAß), two intermediate chains (IC1and IC2) and several light chains. We showed that both heavy chains and both intermediate chains are indispensable for flagellar ODA assembly. Our study also provided biochemical evidence supporting the presence of a cytoplasmic, preassembly pathway for T. brucei ODA.


Assuntos
Axonema , Citoplasma , Dineínas , Flagelos , Proteínas de Protozoários , Trypanosoma brucei brucei , Trypanosoma brucei brucei/metabolismo , Flagelos/metabolismo , Citoplasma/metabolismo , Axonema/metabolismo , Dineínas/metabolismo , Proteínas de Protozoários/metabolismo , Microtúbulos/metabolismo , Proteômica/métodos , Cílios/metabolismo
14.
Proc Natl Acad Sci U S A ; 121(29): e2403188121, 2024 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-38990950

RESUMO

The kinetoplastid parasite, Trypanosoma brucei, undergoes a complex life cycle entailing slender and stumpy bloodstream forms in mammals and procyclic and metacyclic forms (MFs) in tsetse fly hosts. The numerous gene regulatory events that underlie T. brucei differentiation between hosts, as well as between active and quiescent stages within each host, take place in the near absence of transcriptional control. Rather, differentiation is controlled by RNA-binding proteins (RBPs) that associate with mRNA 3' untranslated regions (3'UTRs) to impact RNA stability and translational efficiency. DRBD18 is a multifunctional T. brucei RBP, shown to impact mRNA stability, translation, export, and processing. Here, we use single-cell RNAseq to characterize transcriptomic changes in cell populations that arise upon DRBD18 depletion, as well as to visualize transcriptome-wide alterations to 3'UTR length. We show that in procyclic insect stages, DRBD18 represses expression of stumpy bloodstream form and MF transcripts. Additionally, DRBD18 regulates the 3'UTR lengths of over 1,500 transcripts, typically promoting the use of distal polyadenylation sites, and thus the inclusion of 3'UTR regulatory elements. Remarkably, comparison of polyadenylation patterns in DRBD18 knockdowns with polyadenylation patterns in stumpy bloodstream forms shows numerous similarities, revealing a role for poly(A) site selection in developmental gene regulation, and indicating that DRBD18 controls this process for a set of transcripts. RNA immunoprecipitation supports a direct role for DRBD18 in poly(A) site selection. This report highlights the importance of alternative polyadenylation in T. brucei developmental control and identifies a critical RBP in this process.


Assuntos
Regiões 3' não Traduzidas , Estágios do Ciclo de Vida , Proteínas de Protozoários , Proteínas de Ligação a RNA , Trypanosoma brucei brucei , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/metabolismo , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Proteínas de Ligação a RNA/metabolismo , Proteínas de Ligação a RNA/genética , Estágios do Ciclo de Vida/genética , Regiões 3' não Traduzidas/genética , Animais , Transcriptoma , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Poli A/metabolismo , Poli A/genética , Poliadenilação
15.
Nucleic Acids Res ; 52(16): 9867-9885, 2024 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-38967000

RESUMO

Mitochondrial transcripts in Trypanosoma brucei require extensive uridine insertion/deletion RNA editing to generate translatable open reading frames. The RNA editing substrate binding complex (RESC) serves as the scaffold that coordinates the protein-protein and protein-RNA interactions during editing. RESC broadly contains two modules termed the guide RNA binding complex (GRBC) and the RNA editing mediator complex (REMC), as well as organizer proteins. How the protein and RNA components of RESC dynamically interact to facilitate editing is not well understood. Here, we examine the roles of organizer proteins, RESC8 and RESC14, in facilitating RESC dynamics. High-throughput sequencing of editing intermediates reveals an overlapping RESC8 and RESC14 function during editing progression across multiple transcripts. Blue native PAGE analysis demonstrates that RESC14 is essential for incorporation of RESC8 into a large RNA-containing complex, while RESC8 is important in recruiting a smaller ribonucleoprotein complex (RNP) to this large complex. Proximity labeling shows that RESC14 is important for stable RESC protein-protein interactions, as well as RESC-RECC associations. Together, our data support a model in which RESC14 is necessary for assembly of editing competent RESC through recruitment of an RNP containing RESC8, GRBC and gRNA to REMC and mRNA.


Assuntos
Proteínas de Protozoários , Edição de RNA , RNA de Protozoário , Proteínas de Ligação a RNA , Trypanosoma brucei brucei , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/metabolismo , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Proteínas de Ligação a RNA/metabolismo , Proteínas de Ligação a RNA/genética , RNA de Protozoário/metabolismo , RNA de Protozoário/genética , RNA Guia de Cinetoplastídeos/genética , RNA Guia de Cinetoplastídeos/metabolismo , RNA Mensageiro/metabolismo , RNA Mensageiro/genética , Ligação Proteica , Ribonucleoproteínas/metabolismo , Ribonucleoproteínas/genética
16.
Open Biol ; 14(6): 240025, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38862021

RESUMO

Faithful transmission of genetic material is crucial for the survival of all organisms. In many eukaryotes, a feedback control mechanism called the spindle checkpoint ensures chromosome segregation fidelity by delaying cell cycle progression until all chromosomes achieve proper attachment to the mitotic spindle. Kinetochores are the macromolecular complexes that act as the interface between chromosomes and spindle microtubules. While most eukaryotes have canonical kinetochore proteins that are widely conserved, kinetoplastids such as Trypanosoma brucei have a seemingly unique set of kinetochore proteins including KKT1-25. It remains poorly understood how kinetoplastids regulate cell cycle progression or ensure chromosome segregation fidelity. Here, we report a crystal structure of the C-terminal domain of KKT14 from Apiculatamorpha spiralis and uncover that it is a pseudokinase. Its structure is most similar to the kinase domain of a spindle checkpoint protein Bub1. In addition, KKT14 has a putative ABBA motif that is present in Bub1 and its paralogue BubR1. We also find that the N-terminal part of KKT14 interacts with KKT15, whose WD40 repeat beta-propeller is phylogenetically closely related to a direct interactor of Bub1/BubR1 called Bub3. Our findings indicate that KKT14-KKT15 are divergent orthologues of Bub1/BubR1-Bub3, which promote accurate chromosome segregation in trypanosomes.


Assuntos
Cinetocoros , Proteínas de Protozoários , Cinetocoros/metabolismo , Cinetocoros/química , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/química , Proteínas Serina-Treonina Quinases/genética , Modelos Moleculares , Sequência de Aminoácidos , Filogenia , Ligação Proteica , Cristalografia por Raios X , Segregação de Cromossomos , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética
17.
PLoS Pathog ; 20(6): e1012333, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38935804

RESUMO

The bloodstream form of Trypanosoma brucei expresses large poly-N-acetyllactosamine (pNAL) chains on complex N-glycans of a subset of glycoproteins. It has been hypothesised that pNAL may be required for receptor-mediated endocytosis. African trypanosomes contain a unique family of glycosyltransferases, the GT67 family. Two of these, TbGT10 and TbGT8, have been shown to be involved in pNAL biosynthesis in bloodstream form Trypanosoma brucei, raising the possibility that deleting both enzymes simultaneously might abolish pNAL biosynthesis and provide clues to pNAL function and/or essentiality. In this paper, we describe the creation of a TbGT10 null mutant containing a single TbGT8 allele that can be excised upon the addition of rapamycin and, from that, a TbGT10 and TbGT8 double null mutant. These mutants were analysed by lectin blotting, glycopeptide methylation linkage analysis and flow cytometry. The data show that the mutants are defective, but not abrogated, in pNAL synthesis, suggesting that other GT67 family members can compensate to some degree for loss of TbGT10 and TbGT8. Despite there being residual pNAL synthesis in these mutants, certain glycoproteins appear to be particularly affected. These include the lysosomal CBP1B serine carboxypeptidase, cell surface ESAG2 and the ESAG6 subunit of the essential parasite transferrin receptor (TfR). The pNAL deficient TfR in the mutants continued to function normally with respect to protein stability, transferrin binding, receptor mediated endocytosis of transferrin and subcellular localisation. Further the pNAL deficient mutants were as viable as wild type parasites in vitro and in in vivo mouse infection experiments. Although we were able to reproduce the inhibition of transferrin uptake with high concentrations of pNAL structural analogues (N-acetylchito-oligosaccharides), this effect disappeared at lower concentrations that still inhibited tomato lectin uptake, i.e., at concentrations able to outcompete lectin-pNAL binding. Based on these findings, we recommend revision of the pNAL-dependent receptor mediated endocytosis hypothesis.


Assuntos
Endocitose , Glicosiltransferases , Transferrina , Trypanosoma brucei brucei , Trypanosoma brucei brucei/metabolismo , Trypanosoma brucei brucei/genética , Animais , Endocitose/fisiologia , Camundongos , Transferrina/metabolismo , Glicosiltransferases/metabolismo , Glicosiltransferases/genética , Tripanossomíase Africana/parasitologia , Tripanossomíase Africana/metabolismo , Mutação , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Receptores da Transferrina/metabolismo , Receptores da Transferrina/genética , Polissacarídeos
18.
Mol Biol Cell ; 35(8): ar106, 2024 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-38865178

RESUMO

Outer dynein arms (ODAs) are responsible for ciliary beating in eukaryotes. They are assembled in the cytoplasm and shipped by intraflagellar transport (IFT) before attachment to microtubule doublets via the docking complex. The LRRC56 protein has been proposed to contribute to ODAs maturation. Mutations or deletion of the LRRC56 gene lead to reduced ciliary motility in all species investigated so far, but with variable impact on dynein arm presence. Here, we investigated the role of LRRC56 in the protist Trypanosoma brucei, where its absence results in distal loss of ODAs, mostly in growing flagella. We show that LRRC56 is a transient cargo of IFT trains during flagellum construction and surprisingly, is required for efficient attachment of a subset of docking complex proteins present in the distal portion of the organelle. This relation is interdependent since the knockdown of the distal docking complex prevents LRRC56's association with the flagellum. Intriguingly, lrrc56-/- cells display shorter flagella whose maturation is delayed. Inhibition of cell division compensates for the distal ODAs absence thanks to the redistribution of the proximal docking complex, restoring ODAs attachment but not the flagellum length phenotype. This work reveals an unexpected connection between LRRC56 and the docking complex.


Assuntos
Dineínas , Flagelos , Proteínas de Protozoários , Trypanosoma brucei brucei , Trypanosoma brucei brucei/metabolismo , Flagelos/metabolismo , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/genética , Dineínas/metabolismo , Microtúbulos/metabolismo , Cílios/metabolismo , Transporte Biológico/fisiologia , Axonema/metabolismo
19.
Bioessays ; 46(7): e2400053, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38713161

RESUMO

Trypanosoma brucei is the causal agent of African Trypanosomiasis in humans and other animals. It maintains a long-term infection through an antigenic variation based population survival strategy. To proliferate in a mammal, T. brucei acquires iron and haem through the receptor mediated uptake of host transferrin and haptoglobin-hemoglobin respectively. The receptors are exposed to host antibodies but this does not lead to clearance of the infection. Here we discuss how the trypanosome avoids this fate in the context of recent findings on the structure and cell biology of the receptors.


Assuntos
Trypanosoma brucei brucei , Tripanossomíase Africana , Trypanosoma brucei brucei/imunologia , Trypanosoma brucei brucei/metabolismo , Humanos , Animais , Tripanossomíase Africana/imunologia , Tripanossomíase Africana/parasitologia , Haptoglobinas/metabolismo , Receptores de Superfície Celular/metabolismo , Receptores de Superfície Celular/imunologia , Transferrina/metabolismo , Hemoglobinas/metabolismo , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/imunologia , Interações Hospedeiro-Parasita/imunologia , Ferro/metabolismo , Anticorpos Antiprotozoários/imunologia
20.
J Integr Bioinform ; 21(2)2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38797876

RESUMO

Protein structure determination has made progress with the aid of deep learning models, enabling the prediction of protein folding from protein sequences. However, obtaining accurate predictions becomes essential in certain cases where the protein structure remains undescribed. This is particularly challenging when dealing with rare, diverse structures and complex sample preparation. Different metrics assess prediction reliability and offer insights into result strength, providing a comprehensive understanding of protein structure by combining different models. In a previous study, two proteins named ARM58 and ARM56 were investigated. These proteins contain four domains of unknown function and are present in Leishmania spp. ARM refers to an antimony resistance marker. The study's main objective is to assess the accuracy of the model's predictions, thereby providing insights into the complexities and supporting metrics underlying these findings. The analysis also extends to the comparison of predictions obtained from other species and organisms. Notably, one of these proteins shares an ortholog with Trypanosoma cruzi and Trypanosoma brucei, leading further significance to our analysis. This attempt underscored the importance of evaluating the diverse outputs from deep learning models, facilitating comparisons across different organisms and proteins. This becomes particularly pertinent in cases where no previous structural information is available.


Assuntos
Dobramento de Proteína , Proteínas de Protozoários , Proteínas de Protozoários/química , Proteínas de Protozoários/metabolismo , Trypanosoma cruzi , Leishmania , Aprendizado Profundo , Trypanosoma brucei brucei/metabolismo , Modelos Moleculares , Biologia Computacional/métodos
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