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1.
Immunity ; 56(9): 2086-2104.e8, 2023 09 12.
Artículo en Inglés | MEDLINE | ID: mdl-37572655

RESUMEN

The limited efficacy of immunotherapies against glioblastoma underscores the urgency of better understanding immunity in the central nervous system. We found that treatment with αCTLA-4, but not αPD-1, prolonged survival in a mouse model of mesenchymal-like glioblastoma. This effect was lost upon the depletion of CD4+ T cells but not CD8+ T cells. αCTLA-4 treatment increased frequencies of intratumoral IFNγ-producing CD4+ T cells, and IFNγ blockade negated the therapeutic impact of αCTLA-4. The anti-tumor activity of CD4+ T cells did not require tumor-intrinsic MHC-II expression but rather required conventional dendritic cells as well as MHC-II expression on microglia. CD4+ T cells interacted directly with microglia, promoting IFNγ-dependent microglia activation and phagocytosis via the AXL/MER tyrosine kinase receptors, which were necessary for tumor suppression. Thus, αCTLA-4 blockade in mesenchymal-like glioblastoma promotes a CD4+ T cell-microglia circuit wherein IFNγ triggers microglia activation and phagocytosis and microglia in turn act as antigen-presenting cells fueling the CD4+ T cell response.


Asunto(s)
Glioblastoma , Ratones , Animales , Glioblastoma/tratamiento farmacológico , Glioblastoma/metabolismo , Antígeno CTLA-4 , Células TH1 , Microglía , Linfocitos T CD8-positivos , Fagocitosis , Células Dendríticas , Linfocitos T CD4-Positivos
2.
Immunity ; 54(7): 1561-1577.e7, 2021 07 13.
Artículo en Inglés | MEDLINE | ID: mdl-34102100

RESUMEN

A common metabolic alteration in the tumor microenvironment (TME) is lipid accumulation, a feature associated with immune dysfunction. Here, we examined how CD8+ tumor infiltrating lymphocytes (TILs) respond to lipids within the TME. We found elevated concentrations of several classes of lipids in the TME and accumulation of these in CD8+ TILs. Lipid accumulation was associated with increased expression of CD36, a scavenger receptor for oxidized lipids, on CD8+ TILs, which also correlated with progressive T cell dysfunction. Cd36-/- T cells retained effector functions in the TME, as compared to WT counterparts. Mechanistically, CD36 promoted uptake of oxidized low-density lipoproteins (OxLDL) into T cells, and this induced lipid peroxidation and downstream activation of p38 kinase. Inhibition of p38 restored effector T cell functions in vitro, and resolution of lipid peroxidation by overexpression of glutathione peroxidase 4 restored functionalities in CD8+ TILs in vivo. Thus, an oxidized lipid-CD36 axis promotes intratumoral CD8+ T cell dysfunction and serves as a therapeutic avenue for immunotherapies.


Asunto(s)
Antígenos CD36/metabolismo , Linfocitos T CD8-positivos/metabolismo , Peroxidación de Lípido/fisiología , Lipoproteínas LDL/metabolismo , Neoplasias/metabolismo , Receptores Depuradores/metabolismo , Animales , Transporte Biológico/fisiología , Línea Celular Tumoral , Células HEK293 , Humanos , Leucocitos Mononucleares/metabolismo , Linfocitos Infiltrantes de Tumor/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Microambiente Tumoral/fisiología
3.
J Biol Chem ; 299(3): 102918, 2023 03.
Artículo en Inglés | MEDLINE | ID: mdl-36657642

RESUMEN

Multiple proteins bind to telomeric DNA and are important for the role of telomeres in genome stability. A recent study established a broad-complex, tramtrack and bric-à-brac - zinc finger (BTB-ZF) protein, ZBTB10 (zinc finger and BTB domain-containing protein 10), as a telomeric variant repeat-binding protein at telomeres that use an alternative method for lengthening telomeres). ZBTB10 specifically interacts with the double-stranded telomeric variant repeat sequence TTGGGG by employing its tandem C2H2 zinc fingers (ZF1-2). Here, we solved the crystal structure of human ZBTB10 ZF1-2 in complex with a double-stranded DNA duplex containing the sequence TTGGGG to assess the molecular details of this interaction. Combined with calorimetric analysis, we identified the vital residues in TTGGGG recognition and determined the specific recognition mechanisms that are different from those of TZAP (telomere zinc finger-associated protein), a recently defined telomeric DNA-binding protein. Following these studies, we further identified a single amino-acid mutant (Arg767Gln) of ZBTB10 ZF1-2 that shows a preference for the telomeric DNA repeat TTAGGG sequence. We solved the cocrystal structure, providing a structural basis for telomeric DNA recognition by C2H2 ZF proteins.


Asunto(s)
Proteínas de Unión al ADN , Proteínas Represoras , Humanos , ADN/metabolismo , Proteínas de Unión al ADN/metabolismo , Unión Proteica , Proteínas Represoras/metabolismo , Telómero/metabolismo , Dedos de Zinc/genética
4.
J Am Chem Soc ; 146(19): 13527-13535, 2024 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-38691638

RESUMEN

Closing the carbon and nitrogen cycles by electrochemical methods using renewable energy to convert abundant or harmful feedstocks into high-value C- or N-containing chemicals has the potential to transform the global energy landscape. However, efficient conversion avenues have to date been mostly realized for the independent reduction of CO2 or NO3-. The synthesis of more complex C-N compounds still suffers from low conversion efficiency due to the inability to find effective catalysts. To this end, here we present amorphous bismuth-tin oxide nanosheets, which effectively reduce the energy barrier of the catalytic reaction, facilitating efficient and highly selective urea production. With enhanced CO2 adsorption and activation on the catalyst, a C-N coupling pathway based on *CO2 rather than traditional *CO is realized. The optimized orbital symmetry of the C- (*CO2) and N-containing (*NO2) intermediates promotes a significant increase in the Faraday efficiency of urea production to an outstanding value of 78.36% at -0.4 V vs RHE. In parallel, the nitrogen and carbon selectivity for urea formation is also enhanced to 90.41% and 95.39%, respectively. The present results and insights provide a valuable reference for the further development of new catalysts for efficient synthesis of high-value C-N compounds from CO2.

5.
J Am Chem Soc ; 146(28): 19295-19302, 2024 Jul 17.
Artículo en Inglés | MEDLINE | ID: mdl-38943666

RESUMEN

Oxygen vacancies are generally considered to play a crucial role in the oxygen evolution reaction (OER). However, the generation of active sites created by oxygen vacancies is inevitably restricted by their condensation and elimination reactions. To overcome this limitation, here, we demonstrate a novel photoelectric reconstruction strategy to incorporate atomically dispersed Cu into ultrathin (about 2-3 molecular) amorphous oxyhydroxide (a-CuM, M = Co, Ni, Fe, or Zn), facilitating deprotonation of the reconstructed oxyhydroxide to generate high-valence Cu. The in situ XAFS results and first-principles calculations reveal that Cu atoms are stabilized at high valence during the OER process due to Jahn-Teller distortion, resulting in para-type double oxygen vacancies as dynamically stable catalytic sites. The optimal a-CuCo catalyst exhibits a record-high mass activity of 3404.7 A g-1 at an overpotential of 300 mV, superior to the benchmarking hydroxide and oxide catalysts. The developed photoelectric reconstruction strategy opens up a new pathway to construct in situ stable oxygen vacancies by high-valence Cu single sites, which extends the design rules for creating dynamically stable active sites.

6.
J Phys Chem A ; 128(17): 3273-3284, 2024 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-38635947

RESUMEN

Herein, we report a computation study based on the density functional theory calculations to understand the mechanism and ligand effect of the base-stabilized dialumenes toward dihydrogen activation. Among all of the examined modes of dihydrogen activation using the base-stabilized dialumene, we found that the concerted 1,2-hydrogenation of the Al═Al double bond is kinetically more preferable. The concerted 1,2-hydrogenation of the Al═Al double bond adopts an electron-transfer model with certain asynchrony. That is, the initial electron donation from the H-H σ bonding orbital to the empty 3p orbital of the Al1 center is followed by the backdonation from the lone pair electron of the Al2 center to the H-H σ antibonding orbital. Combined with the energy decomposition analysis on the transition states of the concerted 1,2-hydrogenation of the Al═Al double bond and the topographic steric mapping analysis on the free dialumenes, we ascribe the higher reactivity of the aryl-substituted dialumene over the silyl-substituted analogue in dihydrogen activation to the stronger electron-withdrawing effect of the aryl group, which not only increases the flexibility of the Al═Al double bond but also enhances the Lewis acidity of the Al═Al core. Consequently, the aryl-substituted dialumene fragment suffers less geometric deformation, and the orbital interactions between the dialumene and dihydrogen moieties are more attractive during the 1,2-hydrogenation process. Moreover, our calculations also predict that the Al═Al double bond has a good tolerance with the stronger electron-withdrawing group (-CF3) and the weaker σ-donating N-heterocyclic carbene (NHC) analogue (e.g., triazol carbene and NHSi). The reactivity of the dialumene in dihydrogen activation can be further improved by introducing these groups as the supporting ligand and the stabilizing base on the Al═Al core, respectively.

7.
Neuroimage ; 281: 120374, 2023 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-37729795

RESUMEN

The study of neural circuits, which underlies perception, cognition, emotion, and behavior, is essential for understanding the mammalian brain, a complex organ consisting of billions of neurons. To study the structure and function of the brain, in vivo neuronal labeling and imaging techniques are crucial as they provide true physiological information that ex vivo methods cannot offer. In this paper, we present a new strategy for in vivo neuronal labeling and quantification using MRI. We demonstrate the efficacy of this method by delivering the oatp1a1 gene to the target neurons using rAAV2-retro virus. OATP1A1 protein expression on the neuronal membrane increased the uptake of a specific MRI contrast agent (Gd-EOB-DTPA), leading to hyperintense signals on T1W images of labeled neuronal populations. We also used dynamic contrast enhancement-based methods to obtain quantitative information on labeled neuronal populations in vivo.

8.
Fish Shellfish Immunol ; 127: 766-777, 2022 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-35810966

RESUMEN

Red seaweeds have several biofunctional properties, including immunomodulatory, antitumor, antioxidant, and antibacterial activities. In this study, we examined the effects of diets containing Sarcodia suae on the immune response, immune-related gene expressions, and disease resistance against Vibrio alginolyticus in white shrimp Litopenaeus vannamei. In addition, 1H NMR metabolomics was applied to analyze the metabolites extracted from shrimp fed with S. suae and their functions in regulating immunity. A diet containing only fish meal was used as the control diet (S0), and three diets containing different concentrations of S. suae powder, 2.5% (S2.5), 5% (S5), and 7.5% (S7.5) were used as experimental diets. Shrimp were fed diets for 20 days. Compared to the control group (S0), results showed that (1) shrimp fed diets supplemented with 5-7.5% of S. suae powder significantly increased anti-V. alginolyticus activity; (2) phagocytic activity (PA) increased in all shrimp fed with S. suae, but total haemocyte count (THC) only increased in S7.5 group; and (3) the expression of glutathione peroxidase (GPx) in haemocyte were significantly higher in S7.5 groups. Results from the 1H NMR analysis revealed that 19 heapatopancreatic metabolites were matched and identified among groups. Based on the KEGG enrichment analysis, the up-regulated metabolites in the shrimp fed S5 and S7.5 diets were primarily due to the metabolism of purine and phenylalanine and their respective pathways. Results from these trials reveal that diets containing S. suae can increase immune response, thereby increasing shrimp resistance to V. alginolyticus. The purine and phenylalanine metabolic pathways may be considered as the relevant pathways for optimizing immunomodulatory responses.


Asunto(s)
Penaeidae , Rhodophyta , Animales , Resistencia a la Enfermedad , Inmunidad Innata , Redes y Vías Metabólicas , Fenilalanina , Polvos/farmacología , Purinas/farmacología , Vibrio alginolyticus/fisiología
9.
J Integr Plant Biol ; 63(9): 1606-1610, 2021 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-34427973

RESUMEN

Streptococcus canis Cas9 (ScCas9) is an RNA-guided endonuclease with NNG protospacer adjacent motif (PAM) specificity whose genome-editing activity in rice is locus-dependent. Here we investigated the performance of a ScCas9 variant named Sc++ at different NNG PAM sites in the rice genome; Sc++ harbors a T1227K mutation and the substitution of a positively charged loop (residues 367-376). Sc++ nuclease achieved broader genome editing compared to the original ScCas9, and its nickase improved targeted base editing in transgenic rice plants. Using the high-efficiency adenine base editor rBE73b, we generated many new OsGS1 alleles suitable for screening of rice germplasm for potential herbicide resistance in the future. The CRISPR/Sc++ system expands the genome-editing toolkit for rice.


Asunto(s)
Proteína 9 Asociada a CRISPR/genética , Sistemas CRISPR-Cas , Edición Génica/métodos , Oryza/genética , Genoma de Planta , Streptococcus/genética
10.
Psychol Med ; 48(16): 2658-2667, 2018 12.
Artículo en Inglés | MEDLINE | ID: mdl-29852885

RESUMEN

Help-seeking is important to access appropriate care and improve mental health. However, individuals often delay or avoid seeking help for mental health problems. Interventions to improve help-seeking have been developed, but their effectiveness is unclear. A systematic review and meta-analysis were therefore conducted to examine the effectiveness of mental health related help-seeking interventions. Nine databases in English, German and Chinese were searched for randomised and non-randomised controlled trials. Effect sizes were calculated for attitudes, intentions and behaviours to seek formal, informal and self-help. Ninety-eight studies with 69 208 participants were included. Interventions yielded significant short-term benefits in terms of formal help-seeking, self-help, as well as mental health literacy and personal stigma. There were also positive long-term effects on formal help-seeking behaviours. The most common intervention types were strategies to increase mental health literacy, destigmatisation (both had positive short-term effects on formal help-seeking behaviours) as well as motivational enhancement (with positive long-term effects on formal help-seeking behaviours). Interventions improved formal help-seeking behaviours if delivered to people with or at risk of mental health problems, but not among children, adolescents or the general public. There was no evidence that interventions increased the use of informal help. Few studies were conducted in low- and middle-income countries (LMICs). This study provides evidence for the effectiveness of help-seeking interventions in terms of improving attitudes, intentions and behaviours to seek formal help for mental health problems among adults. Future research should develop effective interventions to improve informal help-seeking, for specific target groups and in LMICs settings.


Asunto(s)
Conocimientos, Actitudes y Práctica en Salud , Promoción de la Salud/métodos , Trastornos Mentales/terapia , Evaluación de Resultado en la Atención de Salud , Aceptación de la Atención de Salud , Humanos
11.
Eur Arch Psychiatry Clin Neurosci ; 268(2): 209-212, 2018 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-28188369

RESUMEN

Stigma limits life opportunities of persons with mental illness. Self-stigma, the internalization of negative stereotypes, undermines empowerment and could hinder recovery. Here we examined self-stigma's effect on recovery among 222 disability pensioners with mental illness over 2 years, controlling for age, gender, symptoms and recovery at baseline measured by the Recovery Assessment Scale. More self-stigma at baseline was associated with a significant decrease in recovery after 1 year (not significant after 2 years). An increase of self-stigma from baseline to follow-up predicted less recovery 1 and 2 years later. Interventions that reduce self-stigma could therefore improve recovery.


Asunto(s)
Trastornos Mentales/psicología , Trastornos Mentales/rehabilitación , Recuperación de la Función/fisiología , Autoimagen , Estigma Social , Adulto , Factores de Edad , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Factores Sexuales , Estadísticas no Paramétricas , Suiza , Adulto Joven
12.
Soc Psychiatry Psychiatr Epidemiol ; 53(3): 309-312, 2018 03.
Artículo en Inglés | MEDLINE | ID: mdl-29380026

RESUMEN

People with severe mental illness and a history of involuntary hospitalization may experience stigma-related stress and suffer negative consequences as a result. However, the long-term impact of stigma stress on suicidality in this population remains unknown. This longitudinal study therefore examined stigma stress, self-stigma, self-esteem and suicidal ideation among 186 individuals with mental illness and recent involuntary hospitalization. After adjusting for age, gender, diagnoses and symptoms, more stigma stress at baseline predicted suicidal ideation after 2 years, mediated by increased self-stigma and decreased self-esteem after 1 year. Anti-stigma interventions that reduce stigma stress and self-stigma could therefore support suicide prevention.


Asunto(s)
Tratamiento Involuntario , Trastornos Mentales/psicología , Estigma Social , Estrés Psicológico/psicología , Suicidio/psicología , Adulto , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Ensayos Clínicos Controlados Aleatorios como Asunto , Autoimagen , Ideación Suicida
13.
Biochem Biophys Res Commun ; 489(2): 270-274, 2017 07 22.
Artículo en Inglés | MEDLINE | ID: mdl-28571742

RESUMEN

Serine/threonine-protein kinase-like protein ARABIDOPSIS CRINKLY4 (ACR4), a transmembrane protein of Arabidopsis thaliana, plays important roles in cell division and differentiation. Although accumulating studies shed light on the function of ACR4, the structure and catalytic mechanism of ACR4 remain to be elucidated. Here, we report the purification and enzymatic properties of the intracellular kinase domain (residues 464-799) of ACR4 (ACR4IKD). Through Ni-affinity chromatography and gel filter chromatography methods, we successfully obtain high-purity ACR4IKD protein from Escherichia coli. Dynamic light scattering and gel-filtration methods reveal that ACR4IKD distributes with high homogeneity and exists as a monomer in solution. In addition, the ACR4IKD protein has typical kinase activity with myelin basic protein (MBP) as the substrate. Our study may lay the foundation for structure determination of ACR4IKD and further functional research, for example, screening significant substrates of ACR4 in Arabidopsis thaliana.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimología , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores de Superficie Celular/metabolismo , Secuencia de Aminoácidos , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/aislamiento & purificación , Activación Enzimática , Proteínas Serina-Treonina Quinasas/química , Proteínas Serina-Treonina Quinasas/aislamiento & purificación , Receptores de Superficie Celular/química , Receptores de Superficie Celular/aislamiento & purificación
14.
Eur Arch Psychiatry Clin Neurosci ; 267(4): 359-361, 2017 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-27169427

RESUMEN

Mental illness stigma is a source of distress for persons with mental illness. Self-stigma occurs when negative stereotypes are internalized, leading to low self-esteem, shame and hopelessness. Due to its consequences self-stigma may contribute to suicidality and be a modifiable target for suicide prevention. Based on 222 disability pensioners with mental illness we examined whether self-stigma at baseline is associated with suicidal ideation over a 2-year period, controlling for baseline suicidal ideation, symptoms, age and gender. More self-stigma predicted suicidal ideation at baseline and longitudinally. Interventions on different levels to reduce self-stigma could improve suicide prevention.


Asunto(s)
Trastornos Mentales/psicología , Estigma Social , Ideación Suicida , Adulto , Femenino , Humanos , Estudios Longitudinales , Masculino , Trastornos Mentales/epidemiología , Persona de Mediana Edad , Suiza , Adulto Joven
15.
J Org Chem ; 81(6): 2488-93, 2016 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-26898573

RESUMEN

Seventeen examples of aza-Morita-Baylis-Hillman (aza-MBH) adducts have been synthesized by reacting chiral N-phosphonyl imines with acrylonitrile in good to excellent yields (up to 96%) and high diastereoselectivity (up to 99:1 dr). The synthesis of these adducts followed the method of group-assisted purification (GAP) chemistry, in which the pure aza-MBH products were readily obtained by washing the crude products with cosolvents of hexane and ethyl acetate.


Asunto(s)
Acetatos/química , Acrilonitrilo/química , Hexanos/química , Iminas/química , Catálisis , Estructura Molecular , Estereoisomerismo
16.
Eur Arch Psychiatry Clin Neurosci ; 266(1): 79-82, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-25631617

RESUMEN

Mental health service use is helpful but rare among young people at risk of psychosis. The label and stigma associated with mental illness may affect attitudes towards help-seeking. We examined 67 individuals at risk of psychosis over the course of 1 year. An increase of self-labelling as "mentally ill" predicted more positive attitudes towards psychiatric medication, while increased perceived stigma and the cognitive appraisal of stigma as a stressor predicted poorer attitudes towards psychotherapy after 1 year. Early intervention could improve non-stigmatizing awareness of at-risk mental state and reduce the public stigma associated with at-risk status to facilitate help-seeking.


Asunto(s)
Actitud , Conducta de Búsqueda de Ayuda , Trastornos Psicóticos/psicología , Autoimagen , Estigma Social , Adolescente , Adulto , Distribución de Chi-Cuadrado , Femenino , Estudios de Seguimiento , Humanos , Modelos Lineales , Masculino , Valor Predictivo de las Pruebas , Escalas de Valoración Psiquiátrica , Trastornos Psicóticos/fisiopatología , Adulto Joven
18.
bioRxiv ; 2024 Oct 16.
Artículo en Inglés | MEDLINE | ID: mdl-39463932

RESUMEN

Epimutations modify gene expression and lead to phenotypic variation while the encoding DNA sequence remains unchanged. Epimutations mediated by RNA interference (RNAi) and/or chromatin modifications can confer antifungal drug resistance and may impact virulence traits in fungi (1-5). However, whether these epigenetic modifications can be transmitted across generations following sexual reproduction was unclear. This study demonstrates that RNAi epimutations conferring antifungal drug resistance are transgenerationally inherited in the human fungal pathogen Mucor circinelloides . Our research revealed that RNAi-based antifungal resistance follows a DNA sequence-independent, non-Mendelian inheritance pattern. Small RNAs (sRNAs) are the exclusive determinants of inheritance, transmitting drug resistance independently of other known repressive epigenetic modifications. Unique sRNA signature patterns can be traced through inheritance from parent to progeny, further supporting RNA as an alternative molecule for transmitting information across generations. This study marks a significant advance in understanding epigenetic inheritance, highlighting RNAi-exclusive epimutations as a widespread phenomenon in the pathogenic M. circinelloides species complex. Understanding how epimutations occur, propagate, and confer resistance may enable their detection in other eukaryotic pathogens, provide solutions for challenges posed by rising antimicrobial drug resistance (AMR), and also advance research on phenotypic adaptability and its evolutionary implications.

19.
ACS Chem Biol ; 19(3): 592-598, 2024 03 15.
Artículo en Inglés | MEDLINE | ID: mdl-38380973

RESUMEN

As ligand-gated ion channels, nicotinic acetylcholine receptors (nAChRs) are widely distributed in the central and peripheral nervous systems and are associated with the pathogenesis of various degenerative neurological diseases. Here, we report the results of phage display-based de novo screening of an 11-residue linear peptide (named LKP1794) that targets the α7 nAChR, which is among the most abundant nAChR subtypes in the brain. Moreover, two d-peptides were generated through mirror image and/or primary sequence inverso isomerization (termed DRKP1794 and DKP1794) and displayed improved inhibitory effects (IC50 = 0.86 and 0.35 µM, respectively) on α7 nAChR compared with the parent l-peptide LKP1794 (IC50 = 2.48 µM), which markedly enhanced serum stability. A peptide-based fluorescence probe was developed using proteolytically resistant DKP1794 to specifically image the α7 nAChR in living cells. This work provides a new peptide tool to achieve inhibitory modulation and specifically image the α7 nAChR.


Asunto(s)
Receptores Nicotínicos , Receptor Nicotínico de Acetilcolina alfa 7 , Receptor Nicotínico de Acetilcolina alfa 7/química , Receptor Nicotínico de Acetilcolina alfa 7/metabolismo , Isomerismo , Receptores Nicotínicos/metabolismo , Péptidos/farmacología , Péptidos/química , Encéfalo/metabolismo
20.
mBio ; 15(8): e0166124, 2024 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-38980037

RESUMEN

Mucormycoses are emerging fungal infections caused by a variety of heterogeneous species within the Mucorales order. Among the Mucor species complex, Mucor circinelloides is the most frequently isolated pathogen in mucormycosis patients and despite its clinical significance, there is an absence of established genome manipulation techniques to conduct molecular pathogenesis studies. In this study, we generated a spontaneous uracil auxotrophic strain and developed a genetic transformation procedure to analyze molecular mechanisms conferring antifungal drug resistance. With this new model, phenotypic analyses of gene deletion mutants were conducted to define Erg3 and Erg6a as key biosynthetic enzymes in the M. circinelloides ergosterol pathway. Erg3 is a C-5 sterol desaturase involved in growth, sporulation, virulence, and azole susceptibility. In other fungal pathogens, erg3 mutations confer azole resistance because Erg3 catalyzes the production of a toxic diol upon azole exposure. Surprisingly, M. circinelloides produces only trace amounts of this toxic diol and yet, it is still susceptible to posaconazole and isavuconazole due to alterations in membrane sterol composition. These alterations are severely aggravated by erg3Δ mutations, resulting in ergosterol depletion and, consequently, hypersusceptibility to azoles. We also identified Erg6a as the main C-24 sterol methyltransferase, whose activity may be partially rescued by the paralogs Erg6b and Erg6c. Loss of Erg6a function diverts ergosterol synthesis to the production of cholesta-type sterols, resulting in resistance to amphotericin B. Our findings suggest that mutations or epimutations causing loss of Erg6 function may arise during human infections, resulting in antifungal drug resistance to first-line treatments against mucormycosis. IMPORTANCE: The Mucor species complex comprises a variety of opportunistic pathogens known to cause mucormycosis, a potentially lethal fungal infection with limited therapeutic options. The only effective first-line treatments against mucormycosis consist of liposomal formulations of amphotericin B and the triazoles posaconazole and isavuconazole, all of which target components within the ergosterol biosynthetic pathway. This study uncovered M. circinelloides Erg3 and Erg6a as key enzymes to produce ergosterol, a vital constituent of fungal membranes. Absence of any of those enzymes leads to decreased ergosterol and consequently, resistance to ergosterol-binding polyenes such as amphotericin B. Particularly, losing Erg6a function poses a higher threat as the ergosterol pathway is channeled into alternative sterols similar to cholesterol, which maintain membrane permeability. As a result, erg6a mutants survive within the host and disseminate the infection, indicating that Erg6a deficiency may arise during human infections and confer resistance to the most effective treatment against mucormycoses.


Asunto(s)
Antifúngicos , Vías Biosintéticas , Farmacorresistencia Fúngica , Ergosterol , Mucor , Ergosterol/biosíntesis , Ergosterol/metabolismo , Antifúngicos/farmacología , Farmacorresistencia Fúngica/genética , Vías Biosintéticas/genética , Humanos , Mucor/genética , Mucor/efectos de los fármacos , Mucor/metabolismo , Mucormicosis/microbiología , Mucormicosis/tratamiento farmacológico , Pruebas de Sensibilidad Microbiana , Triazoles/farmacología , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Eliminación de Gen , Nitrilos/farmacología , Piridinas/farmacología , Oxidorreductasas
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