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1.
Nature ; 585(7824): 251-255, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32848248

RESUMO

Mutation of C9orf72 is the most prevalent defect associated with amyotrophic lateral sclerosis and frontotemporal degeneration1. Together with hexanucleotide-repeat expansion2,3, haploinsufficiency of C9orf72 contributes to neuronal dysfunction4-6. Here we determine the structure of the C9orf72-SMCR8-WDR41 complex by cryo-electron microscopy. C9orf72 and SMCR8 both contain longin and DENN (differentially expressed in normal and neoplastic cells) domains7, and WDR41 is a ß-propeller protein that binds to SMCR8 such that the whole structure resembles an eye slip hook. Contacts between WDR41 and the DENN domain of SMCR8 drive the lysosomal localization of the complex in conditions of amino acid starvation. The structure suggested that C9orf72-SMCR8 is a GTPase-activating protein (GAP), and we found that C9orf72-SMCR8-WDR41 acts as a GAP for the ARF family of small GTPases. These data shed light on the function of C9orf72 in normal physiology, and in amyotrophic lateral sclerosis and frontotemporal degeneration.


Assuntos
Esclerose Amiotrófica Lateral/genética , Proteínas Relacionadas à Autofagia/química , Proteína C9orf72/química , Proteína C9orf72/genética , Proteínas de Transporte/química , Microscopia Crioeletrônica , Demência Frontotemporal/genética , Haploinsuficiência , Complexos Multiproteicos/química , Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Esclerose Amiotrófica Lateral/metabolismo , Proteínas Relacionadas à Autofagia/deficiência , Proteínas Relacionadas à Autofagia/metabolismo , Proteínas Relacionadas à Autofagia/ultraestrutura , Proteína C9orf72/metabolismo , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Transporte/ultraestrutura , Demência Frontotemporal/metabolismo , Humanos , Lisossomos/metabolismo , Modelos Moleculares , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Complexos Multiproteicos/ultraestrutura , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Mutação , Domínios Proteicos
2.
Nat Commun ; 11(1): 3922, 2020 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-32764664

RESUMO

The Plasmodium falciparum chloroquine resistance transporter (PfCRT) is a key contributor to multidrug resistance and is also essential for the survival of the malaria parasite, yet its natural function remains unresolved. We identify host-derived peptides of 4-11 residues, varying in both charge and composition, as the substrates of PfCRT in vitro and in situ, and show that PfCRT does not mediate the non-specific transport of other metabolites and/or ions. We find that drug-resistance-conferring mutations reduce both the peptide transport capacity and substrate range of PfCRT, explaining the impaired fitness of drug-resistant parasites. Our results indicate that PfCRT transports peptides from the lumen of the parasite's digestive vacuole to the cytosol, thereby providing a source of amino acids for parasite metabolism and preventing osmotic stress of this organelle. The resolution of PfCRT's native substrates will aid the development of drugs that target PfCRT and/or restore the efficacy of existing antimalarials.


Assuntos
Antimaláricos/farmacologia , Cloroquina/farmacologia , Proteínas de Membrana Transportadoras/metabolismo , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/metabolismo , Animais , Transporte Biológico Ativo , Resistência a Medicamentos/genética , Feminino , Interações Hospedeiro-Parasita/genética , Interações Hospedeiro-Parasita/fisiologia , Humanos , Malária Falciparum/tratamento farmacológico , Malária Falciparum/metabolismo , Malária Falciparum/parasitologia , Proteínas de Membrana Transportadoras/genética , Modelos Biológicos , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Oligopeptídeos/metabolismo , Oócitos/metabolismo , Plasmodium falciparum/genética , Transporte Proteico , Proteínas de Protozoários/genética , Xenopus laevis
3.
Nat Commun ; 11(1): 4258, 2020 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-32848127

RESUMO

Protein misfolding causes a wide spectrum of human disease, and therapies that target misfolding are transforming the clinical care of cystic fibrosis. Despite this success, however, very little is known about how disease-causing mutations affect the de novo folding landscape. Here we show that inherited, disease-causing mutations located within the first nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) have distinct effects on nascent polypeptides. Two of these mutations (A455E and L558S) delay compaction of the nascent NBD1 during a critical window of synthesis. The observed folding defect is highly dependent on nascent chain length as well as its attachment to the ribosome. Moreover, restoration of the NBD1 cotranslational folding defect by second site suppressor mutations also partially restores folding of full-length CFTR. These findings demonstrate that nascent folding intermediates can play an important role in disease pathogenesis and thus provide potential targets for pharmacological correction.


Assuntos
Regulador de Condutância Transmembrana em Fibrose Cística/genética , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Mutação , Substituição de Aminoácidos , Sítios de Ligação/genética , Fibrose Cística/genética , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/química , Células HEK293 , Humanos , Técnicas In Vitro , Modelos Moleculares , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Domínios Proteicos , Dobramento de Proteína , Modificação Traducional de Proteínas/genética , Estabilidade Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Ribossomos/metabolismo , Supressão Genética , Temperatura
4.
Nat Commun ; 11(1): 3690, 2020 07 23.
Artigo em Inglês | MEDLINE | ID: mdl-32704140

RESUMO

Mechanosensitive ion channels transduce physical force into electrochemical signaling that underlies an array of fundamental physiological processes, including hearing, touch, proprioception, osmoregulation, and morphogenesis. The mechanosensitive channels of small conductance (MscS) constitute a remarkably diverse superfamily of channels critical for management of osmotic pressure. Here, we present cryo-electron microscopy structures of a MscS homolog from Arabidopsis thaliana, MSL1, presumably in both the closed and open states. The heptameric MSL1 channel contains an unusual bowl-shaped transmembrane region, which is reminiscent of the evolutionarily and architecturally unrelated mechanosensitive Piezo channels. Upon channel opening, the curved transmembrane domain of MSL1 flattens and expands. Our structures, in combination with functional analyses, delineate a structural mechanism by which mechanosensitive channels open under increased membrane tension. Further, the shared structural feature between unrelated channels suggests the possibility of a unified mechanical gating mechanism stemming from membrane deformation induced by a non-planar transmembrane domain.


Assuntos
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Eucariotos/metabolismo , Ativação do Canal Iônico , Mecanotransdução Celular , Proteínas de Arabidopsis/ultraestrutura , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Canais Iônicos/química , Canais Iônicos/metabolismo , Modelos Moleculares , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Domínios Proteicos , Estrutura Secundária de Proteína
5.
Nat Commun ; 11(1): 2820, 2020 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-32499486

RESUMO

As an intrinsically disordered protein, monomeric alpha-synuclein (aSyn) occupies a large conformational space. Certain conformations lead to aggregation prone and non-aggregation prone intermediates, but identifying these within the dynamic ensemble of monomeric conformations is difficult. Herein, we used the biologically relevant calcium ion to investigate the conformation of monomeric aSyn in relation to its aggregation propensity. We observe that the more exposed the N-terminus and the beginning of the NAC region of aSyn are, the more aggregation prone monomeric aSyn conformations become. Solvent exposure of the N-terminus of aSyn occurs upon release of C-terminus interactions when calcium binds, but the level of exposure and aSyn's aggregation propensity is sequence and post translational modification dependent. Identifying aggregation prone conformations of monomeric aSyn and the environmental conditions they form under will allow us to design new therapeutics targeted to the monomeric protein.


Assuntos
Agregados Proteicos , alfa-Sinucleína/química , alfa-Sinucleína/metabolismo , Benzotiazóis/metabolismo , Cálcio/metabolismo , Humanos , Cinética , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Mutação/genética , Fosforilação , Conformação Proteica , Espectroscopia de Prótons por Ressonância Magnética , Relação Estrutura-Atividade
6.
PLoS One ; 15(6): e0233578, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32497097

RESUMO

The B7 family represents one of the best-studied subgroups within the Ig superfamily, yet new interactions continue to be discovered. However, this binding promiscuity represents a major challenge for defining the biological contribution of each specific interaction. We developed a strategy for addressing these challenges by combining cell microarray and high-throughput FACS methods to screen for promiscuous binding events, map binding interfaces, and generate functionally selective reagents. Applying this approach to the interactions of mPD-L1 with its receptor mPD-1 and its ligand mB7-1, we identified the binding interface of mB7-1 on mPD-L1 and as a result generated mPD-L1 mutants with binding selectivity for mB7-1 or mPD-1. Next, using a panel of mB7-1 mutants, we mapped the binding sites of mCTLA-4, mCD28 and mPD-L1. Surprisingly, the mPD-L1 binding site mapped to the dimer interface surface of mB7-1, placing it distal from the CTLA-4/CD28 recognition surface. Using two independent approaches, we demonstrated that mPD-L1 and mB7-1 bind in cis, consistent with recent reports from Chaudhri A et al. and Sugiura D et al. We further provide evidence that while CTLA-4 and CD28 do not directly compete with PD-L1 for binding to B7-1, they can disrupt the cis PD-L1:B7-1 complex by reorganizing B7-1 on the cell surface. These observations offer new functional insights into the regulatory mechanisms associated with this group of B7 family proteins and provide new tools to elucidate their function in vitro and in vivo.


Assuntos
Complexo Antígeno-Anticorpo/metabolismo , Antígeno B7-1/metabolismo , Antígeno B7-H1/metabolismo , Proteínas Mutantes/metabolismo , Animais , Antígenos de Superfície/metabolismo , Antígeno B7-1/genética , Antígeno B7-H1/genética , Sítios de Ligação , Antígenos CD28/metabolismo , Linfócitos T CD4-Positivos/metabolismo , Antígeno CTLA-4/metabolismo , Células HEK293 , Humanos , Ativação Linfocitária/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Ligação Proteica , Transfecção
7.
PLoS One ; 15(6): e0234375, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32555682

RESUMO

Renal dysplasia, the major cause of childhood renal failure, is characterized by defective branching morphogenesis and nephrogenesis. Beta-catenin, a transcription factor and cell adhesion molecule, is markedly increased in the nucleus of kidney cells in human renal dysplasia and contributes to its pathogenesis by altering target genes that are essential for kidney development. Quercetin, a naturally occurring flavonoid, reduces nuclear beta-catenin levels and reduces beta-catenin transcriptional activity. In this study, we utilized wild type and dysplastic mouse kidney organ explants to determine if quercetin reduces beta-catenin activity during kidney development and whether it improves the severity of renal dysplasia. In wild type kidney explants, quercetin treatment resulted in abnormal branching morphogenesis and nephrogenesis in a dose dependent manner. In wild type embryonic kidneys, quercetin reduced nuclear beta-catenin expression and decreased expression of beta-catenin target genes Pax2, Six2, and Gdnf, which are essential for kidney development. Our RDB mouse model of renal dysplasia recapitulates the overexpression of beta-catenin and histopathological changes observed in human renal dysplasia. RDB kidneys treated with quercetin resulted in improvements in the overall histopathology, tissue organization, ureteric branching morphogenesis, and nephrogenesis. Quercetin treatment also resulted in reduced nuclear beta-catenin and reduced Pax2 expression. These improvements were associated with the proper organization of vimentin, NCAM, and E-cadherin, and a 45% increase in the number of developing and maturing nephrons. Further, our results show that in human renal dysplasia, beta-catenin, vimentin, and e-cadherin also have abnormal expression patterns. Taken together, these data demonstrate that quercetin treatment reduces nuclear beta-catenin and this is associated with improved epithelial organization of developing nephrons, resulting in increased developing nephrons and a partial rescue of renal dysplasia.


Assuntos
Rim/anormalidades , Rim/efeitos dos fármacos , Quercetina/farmacologia , beta Catenina/metabolismo , Animais , Antígenos CD/metabolismo , Caderinas/metabolismo , Núcleo Celular/metabolismo , Modelos Animais de Doenças , Feminino , Humanos , Rim/metabolismo , Masculino , Camundongos , Camundongos Mutantes , Morfogênese/efeitos dos fármacos , Morfogênese/genética , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Técnicas de Cultura de Órgãos , Gravidez , Vimentina/metabolismo , beta Catenina/química , beta Catenina/genética
8.
Nat Commun ; 11(1): 3233, 2020 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-32591521

RESUMO

Tumour-associated KRAS mutations are the most prevalent in the three RAS-family isoforms and involve many different amino-acids. Therefore, molecules able to interfere with mutant KRAS protein are potentially important for wide-ranging tumour therapy. We describe the engineering of two RAS degraders based on protein macromolecules (macrodrugs) fused to specific E3 ligases. A KRAS-specific DARPin fused to the VHL E3 ligase is compared to a pan-RAS intracellular single domain antibody (iDAb) fused to the UBOX domain of the CHIP E3 ligase. We demonstrate that while the KRAS-specific DARPin degrader induces specific proteolysis of both mutant and wild type KRAS, it only inhibits proliferation of cancer cells expressing mutant KRAS in vitro and in vivo. Pan-RAS protein degradation, however, affects proliferation irrespective of the RAS mutation. These data show that specific KRAS degradation is an important therapeutic strategy to affect tumours expressing any of the range of KRAS mutations.


Assuntos
Substâncias Macromoleculares/metabolismo , Proteínas Mutantes/metabolismo , Mutação/genética , Neoplasias/metabolismo , Proteólise , Proteínas ras/metabolismo , Animais , Apoptose , Linhagem Celular Tumoral , Proliferação de Células , Humanos , Camundongos Nus , Domínios Proteicos , Engenharia de Proteínas , Transdução de Sinais
9.
PLoS One ; 15(5): e0233017, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32407401

RESUMO

Myotonia congenita and hypokalemic periodic paralysis type 2 are both rare genetic channelopathies caused by mutations in the CLCN1 gene encoding voltage-gated chloride channel CLC-1 and the SCN4A gene encoding voltage-gated sodium channel Nav1.4. The patients with concomitant mutations in both genes manifested different unique symptoms from mutations in these genes separately. Here, we describe a patient with myotonia and periodic paralysis in a consanguineous marriage pedigree. By using whole-exome sequencing, a novel F306S variant in the CLCN1 gene and a known R222W mutation in the SCN4A gene were identified in the pedigree. Patch clamp analysis revealed that the F306S mutant reduced the opening probability of CLC-1 and chloride conductance. Our study expanded the CLCN1 mutation database. We emphasized the value of whole-exome sequencing for differential diagnosis in atypical myotonic patients.


Assuntos
Canais de Cloreto/genética , Paralisia Periódica Hipopotassêmica/complicações , Paralisia Periódica Hipopotassêmica/genética , Miotonia Congênita/complicações , Miotonia Congênita/genética , Canal de Sódio Disparado por Voltagem NAV1.4/genética , Adolescente , Adulto , Idoso , Sequência de Aminoácidos , China , Canais de Cloreto/química , Canais de Cloreto/metabolismo , Consanguinidade , Sequência Conservada , Diagnóstico Diferencial , Feminino , Células HEK293 , Humanos , Paralisia Periódica Hipopotassêmica/metabolismo , Masculino , Pessoa de Meia-Idade , Modelos Moleculares , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Mutação , Miotonia Congênita/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.4/metabolismo , Linhagem , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Sequenciamento Completo do Exoma , Adulto Jovem
10.
Nat Commun ; 11(1): 2086, 2020 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-32350249

RESUMO

Gain of function (GOF) DNA binding domain (DBD) mutations of TP53 upregulate chromatin regulatory genes that promote genome-wide histone methylation and acetylation. Here, we therapeutically exploit the oncogenic GOF mechanisms of p53 codon 158 (Arg158) mutation, a DBD mutant found to be prevalent in lung carcinomas. Using high throughput compound screening and combination analyses, we uncover that acetylating mutp53R158G could render cancers susceptible to cisplatin-induced DNA stress. Acetylation of mutp53R158G alters DNA binding motifs and upregulates TRAIP, a RING domain-containing E3 ubiquitin ligase which dephosphorylates IĸB and impedes nuclear translocation of RelA (p65), thus repressing oncogenic nuclear factor kappa-B (NF-ĸB) signaling and inducing apoptosis. Given that this mechanism of cytotoxic vulnerability appears inapt in p53 wild-type (WT) or other hotspot GOF mutp53 cells, our work provides a therapeutic opportunity specific to Arg158-mutp53 tumors utilizing a regimen consisting of DNA-damaging agents and mutp53 acetylators, which is currently being pursued clinically.


Assuntos
Códon/genética , Mutação/genética , Neoplasias/genética , Proteína Supressora de Tumor p53/genética , Acetilação/efeitos dos fármacos , Animais , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacos , Apoptose/genética , Caspase 3/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Cisplatino/farmacologia , Epigênese Genética/efeitos dos fármacos , Mutação com Ganho de Função/genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Ácidos Hidroxâmicos/farmacologia , Camundongos SCID , Modelos Biológicos , Proteínas Mutantes/metabolismo , NF-kappa B/metabolismo , Neoplasias/tratamento farmacológico , Motivos de Nucleotídeos/genética , Poli(ADP-Ribose) Polimerases/metabolismo , Ligação Proteica/efeitos dos fármacos , Isoformas de Proteínas/genética , Sulfonamidas/farmacologia , Topotecan/farmacologia , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto
11.
PLoS One ; 15(5): e0233439, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32469934

RESUMO

In epithelial cells, the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated Cl- channel, plays a key role in water and electrolytes secretion. A dysfunctional CFTR leads to the dehydration of the external environment of the cells and to the production of viscous mucus in the airways of cystic fibrosis patients. Here, we applied the quadriwave lateral shearing interferometry (QWLSI), a quantitative phase imaging technique based on the measurement of the light wave shift when passing through a living sample, to study water transport regulation in human airway epithelial CFBE and CHO cells expressing wild-type, G551D- and F508del-CFTR. We were able to detect phase variations during osmotic challenges and confirmed that cellular volume changes reflecting water fluxes can be detected with QWLSI. Forskolin stimulation activated a phase increase in all CFBE and CHO cell types. This phase variation was due to cellular volume decrease and intracellular refractive index increase and was completely blocked by mercury, suggesting an activation of a cAMP-dependent water efflux mediated by an endogenous aquaporin (AQP). AQP3 mRNAs, not AQP1, AQP4 and AQP5 mRNAs, were detected by RT-PCR in CFBE cells. Readdressing the F508del-CFTR protein to the cell surface with VX-809 increased the detected water efflux in CHO but not in CFBE cells. However, VX-770, a potentiator of CFTR function, failed to further increase the water flux in either G551D-CFTR or VX-809-corrected F508del-CFTR expressing cells. Our results show that QWLSI could be a suitable technique to study water transport in living cells. We identified a CFTR and cAMP-dependent, mercury-sensitive water transport in airway epithelial and CHO cells that might be due to AQP3. This water transport appears to be affected when CFTR is mutated and independent of the chloride channel function of CFTR.


Assuntos
Aquaporina 3/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/metabolismo , Mucosa Respiratória/metabolismo , Água/metabolismo , Aminofenóis/farmacologia , Animais , Aquaporina 3/genética , Transporte Biológico Ativo/efeitos dos fármacos , Fenômenos Biofísicos , Brônquios/citologia , Brônquios/metabolismo , Células CHO , Linhagem Celular , Agonistas dos Canais de Cloreto/farmacologia , Colforsina/farmacologia , Cricetulus , Fibrose Cística/tratamento farmacológico , Fibrose Cística/genética , Fibrose Cística/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Células Epiteliais/metabolismo , Humanos , Microscopia de Interferência , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Osmose , Quinolonas/farmacologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Mucosa Respiratória/citologia
12.
Nucleic Acids Res ; 48(11): 6068-6080, 2020 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-32374842

RESUMO

We have previously found that UV-induced DNA damage causes hyperphosphorylation of the carboxy terminal domain (CTD) of RNA polymerase II (RNAPII), inhibition of transcriptional elongation and changes in alternative splicing (AS) due to kinetic coupling between transcription and splicing. In an unbiased search for protein kinases involved in the AS response to DNA damage, we have identified glycogen synthase kinase 3 (GSK-3) as an unforeseen participant. Unlike Cdk9 inhibition, GSK-3 inhibition only prevents CTD hyperphosphorylation triggered by UV but not basal phosphorylation. This effect is not due to differential degradation of the phospho-CTD isoforms and can be reproduced, at the AS level, by overexpression of a kinase-dead GSK-3 dominant negative mutant. GSK-3 inhibition abrogates both the reduction in RNAPII elongation and changes in AS elicited by UV. We show that GSK-3 phosphorylates the CTD in vitro, but preferentially when the substrate is previously phosphorylated, consistently with the requirement of a priming phosphorylation reported for GSK-3 efficacy. In line with a role for GSK-3 in the response to DNA damage, GSK-3 inhibition prevents UV-induced apoptosis. In summary, we uncover a novel role for a widely studied kinase in key steps of eukaryotic transcription and pre-mRNA processing.


Assuntos
Quinase 3 da Glicogênio Sintase/metabolismo , Proteínas Quinases/metabolismo , RNA Polimerase II/química , RNA Polimerase II/metabolismo , Processamento Alternativo/genética , Processamento Alternativo/efeitos da radiação , Apoptose/efeitos da radiação , Dano ao DNA/efeitos da radiação , Fluorescência , Genes Dominantes , Genes Reporter , Quinase 3 da Glicogênio Sintase/antagonistas & inibidores , Quinase 3 da Glicogênio Sintase/genética , Células HEK293 , Células HeLa , Histonas/metabolismo , Humanos , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Fosforilação/efeitos da radiação , Proteínas Quinases/genética , Transcrição Genética/efeitos da radiação , Raios Ultravioleta
14.
PLoS One ; 15(4): e0231812, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32302365

RESUMO

TMEM16A, a Ca2+-sensitive Cl- channel, plays key roles in many physiological functions related to Cl- transport across lipid membranes. Activation of this channel is mediated via binding intracellular Ca2+ to the channel with a relatively high apparent affinity, roughly in the sub-µM to low µM concentration range. Recently available high-resolution structures of TMEM16 molecules reveal that the high-affinity Ca2+ activation sites are formed by several acidic amino acids, using their negatively charged sidechain carboxylates to coordinate the bound Ca2+. In this study, we examine the interaction of TMEM16A with a divalent cation, Co2+, which by itself cannot activate current in TMEM16A. This divalent cation, however, has two effects when applied intracellularly. It inhibits the Ca2+-induced TMEM16A current by competing with Ca2+ for the aforementioned high-affinity activation sites. In addition, Co2+ also potentiates the Ca2+-induced current with a low affinity. This potentiation effect requires high concentration (mM) of Co2+, similar to our previous findings that high concentrations (mM) of intracellular Ca2+ ([Ca2+]i) can induce more TMEM16A current after the Ca2+-activation sites are saturated by tens of µM [Ca2+]i. The degrees of potentiation by Co2+ and Ca2+ also roughly correlate with each other. Interestingly, mutating a pore residue of TMEM16A, Y589, alters the degree of potentiation in that the smaller the sidechain of the replaced residue, the larger the potentiation induced by divalent cations. We suggest that the Co2+ potentiation and the Ca2+ potentiation share a similar mechanism by increasing Cl- flux through the channel pore, perhaps due to an increase of positive pore potential after the binding of divalent cations to phospholipids in the pore. A smaller sidechain of a pore residue may allow the pore to accommodate more phospholipids, thus enhancing the current potentiation caused by high concentrations of divalent cations.


Assuntos
Anoctaminas/agonistas , Anoctaminas/antagonistas & inibidores , Cobalto/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Anoctaminas/metabolismo , Cálcio , Agonistas dos Canais de Cloreto/farmacologia , Células HEK293 , Humanos , Interações Hidrofóbicas e Hidrofílicas , Íons , Cinética , Proteínas Mutantes/metabolismo
15.
PLoS One ; 15(4): e0231114, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32243476

RESUMO

Meiosis and oocyte maturation are tightly regulated processes. The meiosis arrest female 1 (MARF1) gene is essential for meiotic progression in animals; however, its detailed function remains unclear. In this study, we examined the molecular mechanism of dMarf1, a Drosophila homolog of MARF1 encoding an OST and RNA Recognition Motif (RRM) -containing protein for meiotic progression and oocyte maturation. Although oogenesis progressed in females carrying a dMarf1 loss-of-function allele, the dMarf1 mutant oocytes were found to contain arrested meiotic spindles or disrupted microtubule structures, indicating that the transition from meiosis I to II was compromised in these oocytes. The expression of the full-length dMarf1 transgene, but none of the variants lacking the OST and RRM motifs or the 47 conserved C-terminal residues among insect groups, rescued the meiotic defect in dMarf1 mutant oocytes. Our results indicate that these conserved residues are important for dMarf1 function. Immunoprecipitation of Myc-dMarf1 revealed that several mRNAs are bound to dMarf1. Of those, the protein expression of nanos (nos), but not its mRNA, was affected in the absence of dMarf1. In the control, the expression of Nos protein became downregulated during the late stages of oogenesis, while it remained high in dMarf1 mutant oocytes. We propose that dMarf1 translationally represses nos by binding to its mRNA. Furthermore, the downregulation of Nos induces cycB expression, which in turn activates the CycB/Cdk1 complex at the onset of oocyte maturation.


Assuntos
Proteínas de Ciclo Celular/metabolismo , Diferenciação Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citologia , Drosophila melanogaster/metabolismo , Oócitos/citologia , Oócitos/metabolismo , Proteínas de Ligação a RNA/metabolismo , Motivos de Aminoácidos , Animais , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética , Fusão Celular , Sequência Conservada , Ciclina B , Regulação para Baixo , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Feminino , Regulação da Expressão Gênica , Meiose , Proteínas Mutantes/metabolismo , Mutação/genética , Oogênese , Ovário/metabolismo , Ligação Proteica , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/genética , Tiorredoxinas/metabolismo
16.
Hum Genet ; 139(5): 657-673, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32219518

RESUMO

GM1-gangliosidosis, a lysosomal storage disorder, is associated with ~ 161 missense variants in the GLB1 gene. Affected patients present with ß-galactosidase (ß-Gal) deficiency in lysosomes. Loss of function in ER-retained misfolded enzymes with missense variants is often due to subcellular mislocalization. Deoxygalactonojirimycin (DGJ) and its derivatives are pharmaceutical chaperones that directly bind to mutated ß-Gal in the ER promoting its folding and trafficking to lysosomes and thus enhancing its activity. An Emirati child has been diagnosed with infantile GM1-gangliosidosis carrying the reported p.D151Y variant. We show that p.D151Y ß-Gal in patient's fibroblasts retained < 1% residual activity due to impaired processing and trafficking. The amino acid substitution significantly affected the enzyme conformation; however, p.D151Y ß-Gal was amenable for partial rescue in the presence of glycerol or at reduced temperature where activity was enhanced with ~ 2.3 and 7 folds, respectively. The butyl (NB-DGJ) and nonyl (NN-DGJ) derivatives of DGJ chaperoning function were evaluated by measuring their IC50s and ability to stabilize the wild-type ß-Gal against thermal degradation. Although NN-DGJ showed higher affinity to ß-Gal, it did not show a significant enhancement in p.D151Y ß-Gal activity. However, NB-DGJ promoted p.D151Y ß-Gal maturation and enhanced its activity up to ~ 4.5% of control activity within 24 h which was significantly increased to ~ 10% within 6 days. NB-DGJ enhancement effect was sustained over 3 days after washing it out from culture media. We therefore conclude that NB-DGJ might be a promising therapeutic chemical chaperone in infantile GM1 amenable variants and therefore warrants further analysis for its clinical applications.


Assuntos
1-Desoxinojirimicina/farmacologia , Fibroblastos/metabolismo , Gangliosidose GM1/metabolismo , Proteínas Mutantes/metabolismo , Mutação , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , beta-Galactosidase/metabolismo , 1-Desoxinojirimicina/química , Pré-Escolar , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/patologia , Gangliosidose GM1/tratamento farmacológico , Gangliosidose GM1/patologia , Humanos , Lisossomos/efeitos dos fármacos , Lisossomos/metabolismo , Lisossomos/patologia , Masculino , Chaperonas Moleculares/farmacologia , Proteínas Mutantes/química , Proteínas Mutantes/genética , Conformação Proteica , Transporte Proteico , beta-Galactosidase/química , beta-Galactosidase/genética
17.
PLoS One ; 15(3): e0230052, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32214327

RESUMO

Biallelic mutations in ACP5, encoding tartrate-resistant acid phosphatase (TRACP), have recently been identified to cause the inherited immuno-osseous disorder, spondyloenchondrodysplasia (SPENCD). This study was undertaken to characterize the eight reported missense mutations in ACP5 associated with SPENCD on TRACP expression. ACP5 mutant genes were synthesized, transfected into human embryonic kidney (HEK-293) cells and stably expressing cell lines were established. TRACP expression was assessed by cytochemical and immuno-cytochemical staining with a panel of monoclonal antibodies. Analysis of wild (WT) type and eight mutant stable cell lines indicated that all mutants lacked stainable enzyme activity. All ACP5 mutant constructs were translated into intact proteins by HEK-293 cells. The mutant TRACP proteins displayed variable immune reactivity patterns, and all drastically reduced enzymatic activity, revealing that there is no gross inhibition of TRACP biosynthesis by the mutations. But they likely interfere with folding thereby impairing enzyme function. TRACP exists as two isoforms. TRACP 5a is a less active monomeric enzyme (35kD), with the intact loop peptide and TRACP 5b is proteolytically cleaved highly active enzyme encompassing two subunits (23 kD and 16 kD) held together by disulfide bonds. None of the mutant proteins were proteolytically processed into isoform 5b intracellularly, and only three mutants were secreted in significant amounts into the culture medium as intact isoform 5a-like proteins. Analysis of antibody reactivity patterns revealed that T89I and M264K mutant proteins retained some native conformation, whereas all others were in "denatured" or "unfolded" forms. Western blot analysis with intracellular and secreted TRACP proteins also revealed similar observations indicating that mutant T89I is amply secreted as inactive protein. All mutant proteins were attacked by Endo-H sensitive glycans and none could be activated by proteolytic cleavage in vitro. In conclusion, determining the structure-function relationship of the SPENCD mutations in TRACP will expand our understanding of basic mechanisms underlying immune responsiveness and its involvement in dysregulated bone metabolism.


Assuntos
Doenças Autoimunes/patologia , Proteínas Mutantes/metabolismo , Mutação de Sentido Incorreto , Osteocondrodisplasias/patologia , Fosfatase Ácida Resistente a Tartarato/metabolismo , Substituição de Aminoácidos , Doenças Autoimunes/enzimologia , Doenças Autoimunes/genética , Glicosilação , Humanos , Proteínas Mutantes/química , Proteínas Mutantes/genética , Osteocondrodisplasias/enzimologia , Osteocondrodisplasias/genética , Proteólise , Fosfatase Ácida Resistente a Tartarato/química , Fosfatase Ácida Resistente a Tartarato/genética
18.
Nat Commun ; 11(1): 1475, 2020 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-32193462

RESUMO

Inter-individual differences in T helper (Th) cell responses affect susceptibility to infectious, allergic and autoimmune diseases. To identify factors contributing to these response differences, here we analyze in vitro differentiated Th1 cells from 16 inbred mouse strains. Haplotype-based computational genetic analysis indicates that the p53 family protein, p73, affects Th1 differentiation. In cells differentiated under Th1 conditions in vitro, p73 negatively regulates IFNγ production. p73 binds within, or upstream of, and modulates the expression of Th1 differentiation-related genes such as Ifng and Il12rb2. Furthermore, in mouse experimental autoimmune encephalitis, p73-deficient mice have increased IFNγ production and less disease severity, whereas in an adoptive transfer model of inflammatory bowel disease, transfer of p73-deficient naïve CD4+ T cells increases Th1 responses and augments disease severity. Our results thus identify p73 as a negative regulator of the Th1 immune response, suggesting that p73 dysregulation may contribute to susceptibility to autoimmune disease.


Assuntos
Diferenciação Celular , Células Th1/citologia , Células Th1/metabolismo , Proteína Tumoral p73/metabolismo , Alelos , Animais , Sequência de Bases , Sítios de Ligação , Colite/patologia , DNA/metabolismo , Modelos Animais de Doenças , Encefalomielite Autoimune Experimental/patologia , Deleção de Genes , Regulação da Expressão Gênica , Interferon gama/metabolismo , Camundongos , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Ligação Proteica , Domínios Proteicos , Índice de Gravidade de Doença , Proteína Tumoral p73/química , Proteína Tumoral p73/deficiência , Proteína Tumoral p73/genética , Proteína Supressora de Tumor p53/metabolismo
19.
Biochim Biophys Acta Bioenerg ; 1861(7): 148190, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32194062

RESUMO

Krokinobacter rhodopsin 2 (KR2) was discovered as the first light-driven sodium pumping rhodopsin (NaR) in 2013, which contains unique amino acid residues on C-helix (N112, D116, and Q123), referred to as an NDQ motif. Based on the recent X-ray crystal structures of KR2, the sodium transport pathway has been investigated by various methods. However, due to complicated structural information around the protonated Schiff base (PRSB) region in the dark state and lack of structural information in the intermediates with sodium bound in KR2, detailed sodium pump mechanism is still unclear. Here we applied comprehensive low-temperature light-induced difference FTIR spectroscopy on isotopically labeled KR2 WT and site-directed mutant proteins (N112A, D116E, R109A, and R109K). We assigned the N-D stretching vibration of the PRSB at 2095 cm-1 and elucidate the hydrogen bonding interaction with D116 (a counter ion for the PRSB). We also assigned strongly hydrogen-bonded water (2333 cm-1) near R109 and D251, and found that presence of a positive charge at the position of R109 is prerequisite for the pumping function of KR2.


Assuntos
Luz , Retinaldeído/química , Rodopsina/química , Bases de Schiff/química , ATPase Trocadora de Sódio-Potássio/metabolismo , Cristalografia por Raios X , Flavobacteriaceae/metabolismo , Ligação de Hidrogênio , Isomerismo , Modelos Moleculares , Mutagênese Sítio-Dirigida , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Isótopos de Nitrogênio , Espectroscopia de Infravermelho com Transformada de Fourier , Vibração , Água/química
20.
Proc Natl Acad Sci U S A ; 117(15): 8563-8572, 2020 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-32220963

RESUMO

The small GTPase RABL3 is an oncogene of unknown physiological function. Homozygous knockout alleles of mouse Rabl3 were embryonic lethal, but a viable hypomorphic allele (xiamen [xm]) causing in-frame deletion of four amino acids from the interswitch region resulted in profound defects in lymphopoiesis. Impaired lymphoid progenitor development led to deficiencies of B cells, T cells, and natural killer (NK) cells in Rabl3 xm/xm mice. T cells and NK cells exhibited impaired cytolytic activity, and mice infected with mouse cytomegalovirus (MCMV) displayed elevated titers in the spleen. Myeloid cells were normal in number and function. Biophysical and crystallographic studies demonstrated that RABL3 formed a homodimer in solution via interactions between the effector binding surfaces on each subunit; monomers adopted a typical small G protein fold. RABL3xm displayed a large compensatory alteration in switch I, which adopted a ß-strand configuration normally provided by the deleted interswitch residues, thereby permitting homodimer formation. Dysregulated effector binding due to conformational changes in the switch I-interswitch-switch II module likely underlies the xm phenotype. One such effector may be GPR89, putatively an ion channel or G protein-coupled receptor (GPCR). RABL3, but not RABL3xm, strongly associated with and stabilized GPR89, and an N-ethyl-N-nitrosourea (ENU)-induced mutation (explorer) in Gpr89 phenocopied Rabl3 xm.


Assuntos
Linfócitos B/imunologia , Linfopoese , Proteínas Mutantes/metabolismo , Receptores Acoplados a Proteínas-G/metabolismo , Linfócitos T/imunologia , Proteínas rab de Ligação ao GTP/química , Proteínas rab de Ligação ao GTP/fisiologia , Animais , Linfócitos B/metabolismo , Linfócitos B/patologia , Cristalografia por Raios X , Feminino , Infecções por Herpesviridae/imunologia , Infecções por Herpesviridae/virologia , Células Matadoras Naturais/imunologia , Células Matadoras Naturais/metabolismo , Células Matadoras Naturais/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Muromegalovirus/imunologia , Proteínas Mutantes/química , Proteínas Mutantes/genética , Mutação , Conformação Proteica , Linfócitos T/metabolismo , Linfócitos T/patologia
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