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1.
Proc Natl Acad Sci U S A ; 121(16): e2315958121, 2024 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-38588427

RESUMO

The ability of neurons to rapidly remodel their synaptic structure and strength in response to neuronal activity is highly conserved across species and crucial for complex brain functions. However, mechanisms required to elicit and coordinate the acute, activity-dependent structural changes across synapses are not well understood, as neurodevelopment and structural plasticity are tightly linked. Here, using an RNAi screen in Drosophila against genes affecting nervous system functions in humans, we uncouple cellular processes important for synaptic plasticity and synapse development. We find mutations associated with neurodegenerative and mental health disorders are 2-times more likely to affect activity-induced synaptic remodeling than synapse development. We report that while both synapse development and activity-induced synaptic remodeling at the fly NMJ require macroautophagy (hereafter referred to as autophagy), bifurcation in the autophagy pathway differentially impacts development and synaptic plasticity. We demonstrate that neuronal activity enhances autophagy activation but diminishes degradative autophagy, thereby driving the pathway towards autophagy-based secretion. Presynaptic knockdown of Snap29, Sec22, or Rab8, proteins implicated in the secretory autophagy pathway, is sufficient to abolish activity-induced synaptic remodeling. This study uncovers secretory autophagy as a transsynaptic signaling mechanism modulating synaptic plasticity.


Assuntos
Proteínas de Drosophila , Junção Neuromuscular , Animais , Humanos , Junção Neuromuscular/metabolismo , Sinapses/metabolismo , Drosophila/fisiologia , Neurônios/metabolismo , Autofagia/genética , Plasticidade Neuronal/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Transmissão Sináptica/fisiologia , GTP Fosfo-Hidrolases/metabolismo
2.
Cell Commun Signal ; 22(1): 218, 2024 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-38581012

RESUMO

Signal transduction through G protein-coupled receptors (GPCRs) has been a major focus in cell biology for decades. Numerous disorders are associated with GPCRs that utilize Gi proteins to inhibit adenylyl cyclase (AC) as well as regulate other effectors. Several early studies have successfully defined the AC-interacting domains of several members of Gαi by measuring the loss of activity upon homologous replacements of putative regions of constitutive active Gαi mutants. However, whether such findings can indeed be translated into the context of a receptor-activated Gαi have not been rigorously verified. To address this issue, an array of known and new chimeric mutations was introduced into GTPase-deficient Q204L (QL) and R178C (RC) mutants of Gαi1, followed by examinations on their ability to inhibit AC. Surprisingly, most chimeras failed to abolish the constitutive activity brought on by the QL mutation, while some were able to eliminate the inhibitory activity of RC mutants. Receptor-mediated inhibition of AC was similarly observed in the same chimeric constructs harbouring the pertussis toxin (PTX)-resistant C351I mutation. Moreover, RC-bearing loss-of-function chimeras appeared to be hyper-deactivated by endogenous RGS protein. Molecular docking revealed a potential interaction between AC and the α3/ß5 loop of Gαi1. Subsequent cAMP assays support a cooperative action of the α3/ß5 loop, the α4 helix, and the α4/ß6 loop in mediating AC inhibition by Gαi1-i3. Our results unveiled a notable functional divergence between constitutively active mutants and receptor-activated Gαi1 to inhibit AC, and identified a previously unknown AC-interacting domain of Gαi subunits. These results collectively provide valuable insights on the mechanism of AC inhibition in the cellular environment.


Assuntos
Adenilil Ciclases , GTP Fosfo-Hidrolases , Adenilil Ciclases/genética , Adenilil Ciclases/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Simulação de Acoplamento Molecular , Proteínas de Ligação ao GTP/genética , Proteínas de Ligação ao GTP/metabolismo , Proteínas de Transporte , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/genética , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/metabolismo
3.
Cells ; 13(7)2024 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-38607086

RESUMO

Miro GTPases are key components in the machinery responsible for transporting mitochondria and peroxisomes along microtubules, and also play important roles in regulating calcium homeostasis and organizing contact sites between mitochondria and the endoplasmic reticulum. Moreover, Miro GTPases have been shown to interact with proteins that actively regulate cytoskeletal organization and dynamics, suggesting that these GTPases participate in organizing cytoskeletal functions and organelle transport. Derailed mitochondrial transport is associated with neuropathological conditions such as Parkinson's and Alzheimer's diseases. This review explores our recent understanding of the diverse roles of Miro GTPases under cytoskeletal control, both under normal conditions and during the course of human diseases such as neuropathological disorders.


Assuntos
GTP Fosfo-Hidrolases , Mitocôndrias , Humanos , GTP Fosfo-Hidrolases/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Transporte Biológico , Microtúbulos/metabolismo
4.
J Neuroinflammation ; 21(1): 81, 2024 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-38566081

RESUMO

BACKGROUND: Senescent astrocytes play crucial roles in age-associated neurodegenerative diseases, including Parkinson's disease (PD). Metformin, a drug widely used for treating diabetes, exerts longevity effects and neuroprotective activities. However, its effect on astrocyte senescence in PD remains to be defined. METHODS: Long culture-induced replicative senescence model and 1-methyl-4-phenylpyridinium/α-synuclein aggregate-induced premature senescence model, and a mouse model of PD were used to investigate the effect of metformin on astrocyte senescence in vivo and in vitro. Immunofluorescence staining and flow cytometric analyses were performed to evaluate the mitochondrial function. We stereotactically injected AAV carrying GFAP-promoter-cGAS-shRNA to mouse substantia nigra pars compacta regions to specifically reduce astrocytic cGAS expression to clarify the potential molecular mechanism by which metformin inhibited the astrocyte senescence in PD. RESULTS: We showed that metformin inhibited the astrocyte senescence in vitro and in PD mice. Mechanistically, metformin normalized mitochondrial function to reduce mitochondrial DNA release through mitofusin 2 (Mfn2), leading to inactivation of cGAS-STING, which delayed astrocyte senescence and prevented neurodegeneration. Mfn2 overexpression in astrocytes reversed the inhibitory role of metformin in cGAS-STING activation and astrocyte senescence. More importantly, metformin ameliorated dopamine neuron injury and behavioral deficits in mice by reducing the accumulation of senescent astrocytes via inhibition of astrocytic cGAS activation. Deletion of astrocytic cGAS abolished the suppressive effects of metformin on astrocyte senescence and neurodegeneration. CONCLUSIONS: This work reveals that metformin delays astrocyte senescence via inhibiting astrocytic Mfn2-cGAS activation and suggest that metformin is a promising therapeutic agent for age-associated neurodegenerative diseases.


Assuntos
Metformina , Doença de Parkinson , Camundongos , Animais , Doença de Parkinson/metabolismo , Metformina/farmacologia , Metformina/uso terapêutico , Astrócitos/metabolismo , Neurônios Dopaminérgicos , Nucleotidiltransferases/metabolismo , Mitocôndrias/metabolismo , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , GTP Fosfo-Hidrolases/farmacologia
5.
PLoS Genet ; 20(3): e1011169, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38437244

RESUMO

The basement membrane (BM) is an essential structural element of tissues, and its diversification participates in organ morphogenesis. However, the traffic routes associated with BM formation and the mechanistic modulations explaining its diversification are still poorly understood. Drosophila melanogaster follicular epithelium relies on a BM composed of oriented BM fibrils and a more homogenous matrix. Here, we determined the specific molecular identity and cell exit sites of BM protein secretory routes. First, we found that Rab10 and Rab8 define two parallel routes for BM protein secretion. When both routes were abolished, BM production was fully blocked; however, genetic interactions revealed that these two routes competed. Rab10 promoted lateral and planar-polarized secretion, whereas Rab8 promoted basal secretion, leading to the formation of BM fibrils and homogenous BM, respectively. We also found that the dystrophin-associated protein complex (DAPC) and Rab10 were both present in a planar-polarized tubular compartment containing BM proteins. DAPC was essential for fibril formation and sufficient to reorient secretion towards the Rab10 route. Moreover, we identified a dual function for the exocyst complex in this context. First, the Exo70 subunit directly interacted with dystrophin to limit its planar polarization. Second, the exocyst complex was also required for the Rab8 route. Altogether, these results highlight important mechanistic aspects of BM protein secretion and illustrate how BM diversity can emerge from the spatial control of distinct traffic routes.


Assuntos
Proteínas de Drosophila , Drosophila melanogaster , Animais , Membrana Basal/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Distrofina , Citoplasma/metabolismo , Epitélio/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo
6.
Neurobiol Dis ; 193: 106467, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38452947

RESUMO

Mutations in the gene encoding MFN2 have been identified as associated with Charcot-Marie-Tooth disease type 2A (CMT2A), a neurological disorder characterized by a broad clinical phenotype involving the entire nervous system. MFN2, a dynamin-like GTPase protein located on the outer mitochondrial membrane, is well-known for its involvement in mitochondrial fusion. Numerous studies have demonstrated its participation in a network crucial for various other mitochondrial functions, including mitophagy, axonal transport, and its controversial role in endoplasmic reticulum (ER)-mitochondria contacts. Considerable progress has been made in the last three decades in elucidating the disease pathogenesis, aided by the generation of animal and cellular models that have been instrumental in studying disease physiology. A review of the literature reveals that, up to now, no definitive pharmacological treatment for any CMT2A variant has been established; nonetheless, recent years have witnessed substantial progress. Many treatment approaches, especially concerning molecular therapy, such as histone deacetylase inhibitors, peptide therapy to increase mitochondrial fusion, the new therapeutic strategies based on MF1/MF2 balance, and SARM1 inhibitors, are currently in preclinical testing. The literature on gene silencing and gene replacement therapies is still limited, except for a recent study by Rizzo et al.(Rizzo et al., 2023), which recently first achieved encouraging results in in vitro and in vivo models of the disease. The near-future goal for these promising therapies is to progress to the stage of clinical translation.


Assuntos
Doença de Charcot-Marie-Tooth , Animais , Doença de Charcot-Marie-Tooth/genética , Doença de Charcot-Marie-Tooth/terapia , Doença de Charcot-Marie-Tooth/metabolismo , Mitocôndrias/metabolismo , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Fenótipo , Proteínas Mitocondriais/metabolismo , Mutação
7.
Nat Commun ; 15(1): 2488, 2024 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-38509071

RESUMO

Homotypic membrane fusion of the endoplasmic reticulum (ER) is mediated by dynamin-like GTPase atlastin (ATL). This fundamental process relies on GTP-dependent domain rearrangements in the N-terminal region of ATL (ATLcyto), including the GTPase domain and three-helix bundle (3HB). However, its conformational dynamics during the GTPase cycle remain elusive. Here, we combine single-molecule FRET imaging and molecular dynamics simulations to address this conundrum. Different from the prevailing model, ATLcyto can form a loose crossover dimer upon GTP binding, which is tightened by GTP hydrolysis for membrane fusion. Furthermore, the α-helical motif between the 3HB and transmembrane domain, which is embedded in the surface of the lipid bilayer and self-associates in the crossover dimer, is required for ATL function. To recycle the proteins, Pi release, which disassembles the dimer, activates frequent relative movements between the GTPase domain and 3HB, and subsequent GDP dissociation alters the conformational preference of the ATLcyto monomer for entering the next reaction cycle. Finally, we found that two disease-causing mutations affect human ATL1 activity by destabilizing GTP binding-induced loose crossover dimer formation and the membrane-embedded helix, respectively. These results provide insights into ATL-mediated homotypic membrane fusion and the pathological mechanisms of related disease.


Assuntos
Proteínas de Drosophila , Humanos , Proteínas de Drosophila/metabolismo , Fusão de Membrana/fisiologia , GTP Fosfo-Hidrolases/metabolismo , Hidrólise , Guanosina Trifosfato/metabolismo
8.
Int J Biol Macromol ; 264(Pt 1): 130504, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38442830

RESUMO

Long non-coding RNA FENDRR possesses both anti-fibrotic and anti-cancer properties, but its significance in the development of premalignant oral submucous fibrosis (OSF) remains unclear. Here, we showed that FENDRR was downregulated in OSF specimens and fibrotic buccal mucosal fibroblasts (fBMFs), and overexpression of FENDRR mitigated various myofibroblasts hallmarks, and vice versa. In the course of investigating the mechanism underlying the implication of FENDRR in myofibroblast transdifferentiation, we found that FENDRR can directly bind to miR-214 and exhibit its suppressive effect on myofibroblast activation via titrating miR-214. Moreover, we showed that mitofusin 2 (MFN2), a protein that is crucial to the fusion of mitochondria, was a direct target of miR-214. Our data suggested that FENDRR was positively correlated with MFN2 and MFN2 was required for the inhibitory property of FENDRR pertaining to myofibroblast phenotypes. Additionally, our results showed that the FENDRR/miR-214 axis participated in the arecoline-induced reactive oxygen species (ROS) accumulation and myofibroblast transdifferentiation. Building on these results, we concluded that the aberrant downregulation of FENDRR in OSF may be associated with chronic exposure to arecoline, leading to upregulation of ROS and myofibroblast activation via the miR-214-mediated suppression of MFN2.


Assuntos
MicroRNAs , Fibrose Oral Submucosa , Humanos , Miofibroblastos/metabolismo , Arecolina/efeitos adversos , Arecolina/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Fibrose Oral Submucosa/genética , Fibrose Oral Submucosa/metabolismo , Fibrose Oral Submucosa/patologia , Mucosa Bucal/metabolismo , Fibroblastos , MicroRNAs/genética , MicroRNAs/metabolismo , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , GTP Fosfo-Hidrolases/farmacologia , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo
9.
PLoS Pathog ; 20(3): e1011830, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38512975

RESUMO

Human myxovirus resistance 2 (MX2/MXB) is an interferon-induced GTPase that inhibits human immunodeficiency virus-1 (HIV-1) infection by preventing nuclear import of the viral preintegration complex. The HIV-1 capsid (CA) is the major viral determinant for sensitivity to MX2, and complex interactions between MX2, CA, nucleoporins (Nups), cyclophilin A (CypA), and other cellular proteins influence the outcome of viral infection. To explore the interactions between MX2, the viral CA, and CypA, we utilized a CRISPR-Cas9/AAV approach to generate CypA knock-out cell lines as well as cells that express CypA from its endogenous locus, but with specific point mutations that would abrogate CA binding but should not affect enzymatic activity or cellular function. We found that infection of CypA knock-out and point mutant cell lines with wild-type HIV-1 and CA mutants recapitulated the phenotypes observed upon cyclosporine A (CsA) addition, indicating that effects of CsA treatment are the direct result of blocking CA-CypA interactions and are therefore independent from potential interactions between CypA and MX2 or other cellular proteins. Notably, abrogation of GTP hydrolysis by MX2 conferred enhanced antiviral activity when CA-CypA interactions were abolished, and this effect was not mediated by the CA-binding residues in the GTPase domain, or by phosphorylation of MX2 at position T151. We additionally found that elimination of GTPase activity also altered the Nup requirements for MX2 activity. Our data demonstrate that the antiviral activity of MX2 is affected by CypA-CA interactions in a virus-specific and GTPase activity-dependent manner. These findings further highlight the importance of the GTPase domain of MX2 in regulation of substrate specificity and interaction with nucleocytoplasmic trafficking pathways.


Assuntos
Capsídeo , Complexo de Proteínas Formadoras de Poros Nucleares , Humanos , Capsídeo/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Ciclofilina A/genética , Ciclofilina A/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Proteínas do Capsídeo/genética , Proteínas do Capsídeo/metabolismo , Antivirais/metabolismo , Proteínas de Resistência a Myxovirus/genética , Proteínas de Resistência a Myxovirus/metabolismo
10.
BMC Pediatr ; 24(1): 104, 2024 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-38341530

RESUMO

BACKGROUND: Mitochondrial diseases are heterogeneous in terms of clinical manifestations and genetic characteristics. The dynamin 1-like gene (DNM1L) encodes dynamin-related protein 1 (DRP1), a member of the GTPases dynamin superfamily responsible for mitochondrial and peroxisomal fission. DNM1L variants can lead to mitochondrial fission dysfunction. CASE PRESENTATION: Herein, we report a distinctive clinical phenotype associated with a novel variant of DNM1L and review the relevant literature. A 5-year-old girl presented with paroxysmal hemiplegia, astigmatism, and strabismus. Levocarnitine and coenzyme Q10 supplement showed good efficacy. Based on the patient's clinical data, trio whole-exome sequencing (trio-WES) and mtDNA sequencing were performed to identify the potential causative genes, and Sanger sequencing was used to validate the specific variation in the proband and her family members. The results showed a novel de novo heterozygous nonsense variant in exon 20 of the DNM1L gene, c.2161C>T, p.Gln721Ter, which is predicted to be a pathogenic variant according to the ACMG guidelines. The proband has a previously undescribed clinical manifestation, namely hemiparesis, which may be an additional feature of the growing phenotypic spectrum of DNM1L-related diseases. CONCLUSION: Our findings elucidate a novel variant in DNM1L-related disease and reveal an expanding phenotypic spectrum associated with DNM1L variants. This report highlights the necessity of next generation sequencing for early diagnosis of patients, and that further clinical phenotypic and genotypic analysis may help to improve the understanding of DNM1L-related diseases.


Assuntos
Dinaminas , Proteínas Associadas aos Microtúbulos , Feminino , Humanos , Pré-Escolar , Proteínas Associadas aos Microtúbulos/genética , Dinaminas/genética , Dinaminas/metabolismo , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Fenótipo , Mitocôndrias
11.
Cancer Imaging ; 24(1): 26, 2024 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-38342905

RESUMO

BACKGROUND: To investigate the association between Kirsten rat sarcoma viral oncogene homolog (KRAS) / neuroblastoma rat sarcoma viral oncogene homolog (NRAS) /v-raf murine sarcoma viral oncogene homolog B (BRAF) mutations and the tumor habitat-derived radiomic features obtained during pretreatment 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in patients with colorectal cancer (CRC). METHODS: We retrospectively enrolled 62 patients with CRC who had undergone 18F-FDG PET/computed tomography from January 2017 to July 2022 before the initiation of therapy. The patients were randomly split into training and validation cohorts with a ratio of 6:4. The whole tumor region radiomic features, habitat-derived radiomic features, and metabolic parameters were extracted from 18F-FDG PET images. After reducing the feature dimension and selecting meaningful features, we constructed a hierarchical model of KRAS/NRAS/BRAF mutations by using the support vector machine. The convergence of the model was evaluated by using learning curve, and its performance was assessed based on the area under the receiver operating characteristic curve (AUC), calibration curve, and decision curve analysis. The SHapley Additive exPlanation was used to interpret the contributions of various features to predictions of the model. RESULTS: The model constructed by using habitat-derived radiomic features had adequate predictive power with respect to KRAS/NRAS/BRAF mutations, with an AUC of 0.759 (95% CI: 0.585-0.909) on the training cohort and that of 0.701 (95% CI: 0.468-0.916) on the validation cohort. The model exhibited good convergence, suitable calibration, and clinical application value. The results of the SHapley Additive explanation showed that the peritumoral habitat and a high_metabolism habitat had the greatest impact on predictions of the model. No meaningful whole tumor region radiomic features or metabolic parameters were retained during feature selection. CONCLUSION: The habitat-derived radiomic features were found to be helpful in stratifying the status of KRAS/NRAS/BRAF in CRC patients. The approach proposed here has significant implications for adjuvant treatment decisions in patients with CRC, and needs to be further validated on a larger prospective cohort.


Assuntos
Neoplasias Colorretais , Fluordesoxiglucose F18 , Animais , Camundongos , Humanos , Fluordesoxiglucose F18/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas B-raf/genética , Neoplasias Colorretais/diagnóstico por imagem , Neoplasias Colorretais/genética , Estudos Retrospectivos , Estudos Prospectivos , 60570 , Tomografia por Emissão de Pósitrons/métodos , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Mutação , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo
12.
J Phys Chem B ; 128(7): 1573-1585, 2024 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-38350435

RESUMO

The Rho GTPase binding domain of Plexin-B1 (RBD) prevails in solution as dimer. Under appropriate circumstances, it binds the small GTPase Rac1 to yield the complex RBD-Rac1. Here, we study RBD dimerization and complex formation from a symmetry-based perspective using data derived from 1 µs long MD simulations. The quantities investigated are the local potentials, u(MD), prevailing at the N-H sites of the protein. These potentials are statistical in character providing an empirical description of the local structure. To establish more methodical description, a method for approximating them by explicit functions, u(simulated), was developed in the preceding article in this journal issue. These functions are combinations of analytical Wigner functions, DL,K, belonging to the D2h point group. The D2h subgroups Ag and B2u are found to dominate u(simulated); the B1u subgroup contributes in some cases. The Ag (B2u) functions have axial or rhombic symmetry. For the first time, local potentials in proteins can be quantitatively characterized in terms of their strength (rhombicity) evaluated by axial Ag (rhombic Ag and B2u) contributions. Until now, the chain-segment [ß3-L3-ß4] and to some extent the α2-helix have been associated with GTPase binding. Here, we find that this process causes an increase (decrease) in the potential strength of ß3 and ß4 (the preceding L2 loop and the remote chain-segment [(α2-helix)-(α2/ß5-turn)-(ß5-strand)]), suggesting effects of counterbalancing and allostery. There is evidence for the L2 loop being associated with RBD-GTPase binding. Until now only the L4 loop has been associated with RBD dimerization. The latter process is found to cause an increase (decrease) in the potential strength and rhombicity of the L4 loop (the adjacent chain-segment [(α2-helix)-(α2/ß5-turn)-(ß5-strand)]), suggesting counterbalancing activity. On average, the RBD dimer features stronger local potentials than RBD-Rac1. The novel information inherent in these findings is mesoscopic in character. Prospects of interest include exploring relation to atomistic force-field parameters.


Assuntos
Simulação de Dinâmica Molecular , Receptores de Superfície Celular , Receptores de Superfície Celular/química , Ligação Proteica , Dimerização , GTP Fosfo-Hidrolases/metabolismo , Sítios de Ligação
13.
Sci Total Environ ; 918: 170668, 2024 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-38320701

RESUMO

BACKGROUND: Transient receptor potential (TRP) ankyrin 1 (TRPA1) could mediate ozone-induced lung injury. Optic Atrophy 1 (OPA1) is one of the significant mitochondrial fusion proteins. Impaired mitochondrial fusion, resulting in mitochondrial dysfunction and ferroptosis, may drive the onset and progression of lung injury. In this study, we examined whether TRPA1 mediated ozone-induced bronchial epithelial cell and lung injury by activating PI3K/Akt with the involvement of OPA1, leading to ferroptosis. METHODS: Wild-type, TRPA1-knockout (KO) mice (C57BL/6 J background) and ferrostatin-1 (Fer-1)-pretreated mice were exposed to 2.5 ppm ozone for 3 h. Human bronchial epithelial (BEAS-2B) cells were treated with 1 ppm ozone for 3 h in the presence of TRPA1 inhibitor A967079 or TRPA1-knockdown (KD) as well as pharmacological modulators of PI3K/Akt-OPA1-ferroptosis. Transcriptome was used to screen and decipher the differential gene expressions and pathways. Oxidative stress, inflammation and ferroptosis were measured together with mitochondrial morphology, function and dynamics. RESULTS: Acute ozone exposure induced airway inflammation and airway hyperresponsiveness (AHR), reduced mitochondrial fusion, and enhanced ferroptosis in mice. Similarly, acute ozone exposure induced inflammatory responses, altered redox responses, abnormal mitochondrial structure and function, reduced mitochondrial fusion and enhanced ferroptosis in BEAS-2B cells. There were increased mitochondrial fusion, reduced inflammatory responses, decreased redox responses and ferroptosis in ozone-exposed TRPA1-KO mice and Fer-1-pretreated ozone-exposed mice. A967079 and TRPA1-KD enhanced OPA1 and prevented ferroptosis through the PI3K/Akt pathway in BEAS-2B cells. These in vitro results were further confirmed in pharmacological modulator experiments. CONCLUSION: Exposure to ozone induces mitochondrial dysfunction in human bronchial epithelial cells and mouse lungs by activating TRPA1, which results in ferroptosis mediated via a PI3K/Akt/OPA1 axis. This supports a potential role of TRPA1 blockade in preventing the deleterious effects of ozone.


Assuntos
Ferroptose , Lesão Pulmonar , Doenças Mitocondriais , Oximas , Ozônio , Humanos , Camundongos , Animais , Lesão Pulmonar/induzido quimicamente , Proteínas Proto-Oncogênicas c-akt/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Ozônio/metabolismo , Camundongos Endogâmicos C57BL , Inflamação/induzido quimicamente , Células Epiteliais , Doenças Mitocondriais/metabolismo , Pulmão/metabolismo , GTP Fosfo-Hidrolases/metabolismo , GTP Fosfo-Hidrolases/farmacologia , Canal de Cátion TRPA1/metabolismo
14.
Nat Commun ; 15(1): 1328, 2024 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-38351080

RESUMO

Mitochondrial fission is a critical cellular event to maintain organelle function. This multistep process is initiated by the enhanced recruitment and oligomerization of dynamin-related protein 1 (Drp1) at the surface of mitochondria. As such, Drp1 is essential for inducing mitochondrial division in mammalian cells, and homologous proteins are found in all eukaryotes. As a member of the dynamin superfamily of proteins (DSPs), controlled Drp1 self-assembly into large helical polymers stimulates its GTPase activity to promote membrane constriction. Still, little is known about the mechanisms that regulate correct spatial and temporal assembly of the fission machinery. Here we present a cryo-EM structure of a full-length Drp1 dimer in an auto-inhibited state. This dimer reveals two key conformational rearrangements that must be unlocked through intramolecular rearrangements to achieve the assembly-competent state observed in previous structures. This structural insight provides understanding into the mechanism for regulated self-assembly of the mitochondrial fission machinery.


Assuntos
GTP Fosfo-Hidrolases , Dinâmica Mitocondrial , Animais , GTP Fosfo-Hidrolases/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Dinaminas/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Mamíferos/metabolismo
15.
Adv Sci (Weinh) ; 11(14): e2307749, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38311582

RESUMO

The heart primarily derives its energy through lipid oxidation. In cardiomyocytes, lipids are stored in lipid droplets (LDs) and are utilized in mitochondria, although the structural and functional connections between these two organelles remain largely unknown. In this study, visible evidence have presented indicating that a complex is formed at the mitochondria-LD membrane contact (MLC) site, involving mitochondrion-localized Mfn2 and LD-localized Hsc70. This complex serves to tether mitochondria to LDs, facilitating the transfer of fatty acids (FAs) from LDs to mitochondria for ß-oxidation. Reduction of Mfn2 induced by lipid overload inhibits MLC, hinders FA transfer, and results in lipid accumulation. Restoring Mfn2 reinstates MLC, alleviating myocardial lipotoxicity under lipid overload conditions both in-vivo and in-vitro. Additionally, prolonged lipid overload induces Mfn2 degradation through the ubiquitin-proteasome pathway, following Mfn2 acetylation at the K243 site. This leads to the transition from adaptive lipid utilization to maladaptive lipotoxicity. The experimental findings are supported by clinical data from patients with obesity and age-matched non-obese individuals. These translational results make a significant contribution to the molecular understanding of MLC in the heart, and offer new insights into its role in myocardial lipotoxicity.


Assuntos
GTP Fosfo-Hidrolases , Proteínas de Choque Térmico HSC70 , Gotículas Lipídicas , Metabolismo dos Lipídeos , Miócitos Cardíacos , Humanos , Ácidos Graxos/metabolismo , Hidrolases/metabolismo , Gotículas Lipídicas/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Animais , Camundongos , GTP Fosfo-Hidrolases/metabolismo , Proteínas de Choque Térmico HSC70/metabolismo , Coração , Miócitos Cardíacos/metabolismo
16.
Biochim Biophys Acta Mol Cell Res ; 1871(3): 119685, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38342311

RESUMO

The best-known function of the essential GPN-loop GTPase Gpn3 is to contribute to RNA polymerase II assembly, a prerequisite for its nuclear targeting. Although this process occurs in the cytoplasm, we have previously shown that Gpn3 enters the cell nucleus before being polyubiquitinated. Here, we show that inhibiting Crm1-mediated nuclear export with leptomycin B, or the proteasome with MG132, caused the nuclear accumulation of recombinant and endogenous Gpn3 in MCF-12A cells. When added simultaneously, leptomycin B and MG132 had an additive effect. Analysis of Gpn3 primary sequence revealed the presence of at least five nuclear export sequence (NES) motifs, with some having a higher exposure to the solvent in the GTP-bound than GDP-bound state in a Gpn3 structural model. Inactivation of any of these NESes led to some degree of Gpn3 nuclear accumulation, although mutating NES1 or NES3 had the more robust effect. MCF-12A cells expressing exclusively a NES-deficient version of Gpn3R-Flag proliferated slower than cells expressing Gpn3R-Flag wt, indicating that nuclear export is important for Gpn3 function. Next, we searched for physiological conditions regulating Gpn3 nucleocytoplasmic shuttling. Interestingly, whereas Gpn3R-Flag was both nuclear and cytoplasmic in low-density growing MCF-12A cells, it was exclusively cytoplasmic in high-density areas. Furthermore, Gpn3R-Flag was cytoplasmic, mostly perinuclear, in sparse but starved MCF-12A cells, and serum-stimulation caused a rapid, although transient, Gpn3R-Flag nuclear accumulation. We conclude that Gpn3 nucleocytoplasmic shuttling is regulated by cell density and growth factors, and propose that Gpn3 has an unknown nuclear function positively linked to cell growth and/or proliferation.


Assuntos
Núcleo Celular , GTP Fosfo-Hidrolases , GTP Fosfo-Hidrolases/metabolismo , Transporte Ativo do Núcleo Celular , Núcleo Celular/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Contagem de Células
17.
Mol Cancer ; 23(1): 40, 2024 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-38383439

RESUMO

Finding effective therapeutic targets to treat NRAS-mutated melanoma remains a challenge. Long non-coding RNAs (lncRNAs) recently emerged as essential regulators of tumorigenesis. Using a discovery approach combining experimental models and unbiased computational analysis complemented by validation in patient biospecimens, we identified a nuclear-enriched lncRNA (AC004540.4) that is upregulated in NRAS/MAPK-dependent melanoma, and that we named T-RECS. Considering potential innovative treatment strategies, we designed antisense oligonucleotides (ASOs) to target T-RECS. T-RECS ASOs reduced the growth of melanoma cells and induced apoptotic cell death, while having minimal impact on normal primary melanocytes. Mechanistically, treatment with T-RECS ASOs downregulated the activity of pro-survival kinases and reduced the protein stability of hnRNPA2/B1, a pro-oncogenic regulator of MAPK signaling. Using patient- and cell line- derived tumor xenograft mouse models, we demonstrated that systemic treatment with T-RECS ASOs significantly suppressed the growth of melanoma tumors, with no noticeable toxicity. ASO-mediated T-RECS inhibition represents a promising RNA-targeting approach to improve the outcome of MAPK pathway-activated melanoma.


Assuntos
Melanoma , RNA Longo não Codificante , Humanos , Camundongos , Animais , Melanoma/patologia , RNA Longo não Codificante/genética , Apoptose/genética , Oligonucleotídeos Antissenso/genética , Oligonucleotídeos Antissenso/uso terapêutico , Linhagem Celular Tumoral , Proteínas de Membrana/genética , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo
18.
Toxicon ; 240: 107636, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38316294

RESUMO

Ample evidence indicates that bufalin (BFN), a cardiotonic steroid in Bufo toad toxin, possesses a potent anticancer activity mainly by stimulating apoptosis in cancer cells. Human red blood cells (RBCs) undergo eryptosis which contributes to a plethora of pathological conditions. No reports, however, have examined the potential toxicity of BFN to RBCs. This study aims to characterize the biochemical mechanisms governing the influence of BFN on the physiology and lifespan of RBCs. Isolated RBCs from healthy volunteers were exposed to anticancer concentrations of commercially available BFN from the skin of Bufo gargarizans (10-200 µM) for 24 h at 37 °C. Photometric assays were used to estimate hemolysis and hemolytic markers, and flow cytometry was used to detect eryptotic markers. Phosphatidylserine externalization was captured by fluorescein isothiocyante-labeled annexin V, cellular dimensions by light scatter patterns, and intracellular Ca2+ and reactive oxygen species (ROS) by fluorogenic dyes Fluo4/AM and 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), respectively. BFN caused Ca2+-independent hemolysis and release of LDH, AST, CK, and K+, and increased annexin V-bound cells, cytosolic Ca2+, cell shrinkage, and ROS levels. BFN also disrupted Na+ and Mg2+ trafficking, and was sensitive to PEG 8000, sucrose, SB203580, and NSC 23766. In whole blood, BFN depleted hemoglobin stores, increased fragmented RBCs, and was selectively toxic to reticulocytes, lymphocytes, and platelets. In conclusion, BFN elicits premature RBC death, subject to regulation by p38 MAPK and Rac1 GTPase, and is detrimental to other peripheral blood cells. Altogether, these novel findings prompt cautious consideration of the toxin in anticancer therapy.


Assuntos
Bufanolídeos , GTP Fosfo-Hidrolases , Proteínas Quinases p38 Ativadas por Mitógeno , Humanos , Espécies Reativas de Oxigênio/metabolismo , GTP Fosfo-Hidrolases/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Hemólise , Anexina A5/metabolismo , Longevidade , Eritrócitos , Cálcio/metabolismo , Fosfatidilserinas/metabolismo , Estresse Oxidativo
19.
Mo Med ; 121(1): 87-92, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38404440

RESUMO

Optic atrophy 1(OPA1) is a GTPase protein that controls mitochondrial fusion, cristae integrity, and mtDNA maintenance. In neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), the mitochondrial network morphology is compromised. Studies on TAR-DNA binding protein 43 (TDP-43) has been the focus in our lab. OPA1 and TDP-43 interaction may shed a light on how aberrant TDP-43 interacts with OPA1, which will lead to mitochondrial dysfunction. The preliminary study tested the idea of whether OPA1 and TDP-43 are physically interacting in human platelet derived mitochondria obtained from healthy human subjects.


Assuntos
Esclerose Amiotrófica Lateral , Proteínas de Ligação a DNA , GTP Fosfo-Hidrolases , Doenças Neurodegenerativas , Humanos , Esclerose Amiotrófica Lateral/metabolismo , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Mitocôndrias/genética , Mitocôndrias/metabolismo , Doenças Neurodegenerativas/metabolismo , Isoformas de Proteínas/metabolismo , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo
20.
J Biol Chem ; 300(3): 105696, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38301888

RESUMO

Interferon-gamma-inducible large GTPases, hGBPs, possess antipathogenic and antitumor activities in human cells. Like hGBP1, its closest homolog, hGBP3 has two domains; an N-terminal catalytic domain and a C-terminal helical domain, connected by an intermediate region. The biochemical function of this protein and the role of its domains in substrate hydrolysis have not yet been investigated. Here, we report that while hGBP3 can produce both GDP and GMP, GMP is the minor product, 30% (unlike 85% in hGBP1), indicating that hGBP3 is unable to produce enhanced GMP. To understand which domain(s) are responsible for this deficiency, we created hGBP3 truncated variants. Surprisingly, GMP production was similar upon deletion of the helical domain, suggesting that in contrast to hGBP1, the helical domain of hGBP3 cannot stimulate the second phosphate cleavage of GTP. We conducted computational and solution studies to understand the underlying basis. We found that the regulatory residue W79, present in the catalytic domain, forms an H-bond with the backbone carbonyl of K76 (located in the catalytic loop) of the substrate-bound hGBP3. However, after gamma-phosphate cleavage of GTP, the W79-containing region does not undergo a conformational change, failing to redirect the catalytic loop toward the beta-phosphate. This is necessary for efficient GMP formation because hGBP homologs utilize the same catalytic residue for both phosphate cleavages. We suggest that the lack of specific interdomain contacts mediated by the helical domain prevents the catalytic loop movement, resulting in reduced GMP formation. These findings may provide insight into how hGBP3 contributes to immunity.


Assuntos
Domínio Catalítico , Proteínas de Ligação ao GTP , Guanosina Trifosfato , Fosfatos , Humanos , Domínio Catalítico/genética , GTP Fosfo-Hidrolases/metabolismo , Guanosina Trifosfato/metabolismo , Fosfatos/metabolismo , Proteínas de Ligação ao GTP/genética , Proteínas de Ligação ao GTP/metabolismo
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