RESUMO
In Alzheimer's disease, chronic neuroinflammation is accompanied by amyloid and tau pathologies. Especially, aberrant microglial activation is known to precede the regional tau pathology development, but the mechanisms how microglia affect tau spread remain largely unknown. Here, we found that toll-like receptor 2 (TLR2) in microglia recognizes oligomeric tau as a pathogenic ligand and induces inflammatory responses. Knockout of TLR2 reduced tau pathology and microglial activation in rTg4510 tau transgenic mice. Treatment of oligomeric tau induced TLR2 activation and increased inflammatory responses in microglial cells. TLR2 further mediated the tau-induced microglial activation and promoted tau uptake into neurons in neuron-microglia co-culture system and in mouse hippocampus after intracranial tau injection. Importantly, treatment with anti-TLR2 monoclonal antibody Tomaralimab blocked TLR2 activation and inflammatory responses in a dose-dependent manner, and significantly reduced tau spread and memory loss in rTg4510 mice. These results suggest that TLR2 plays a crucial role in tau spread by causing aberrant microglial activation in response to pathological tau, and blocking TLR2 with immunotherapy may ameliorate tau pathogenesis in Alzheimer's disease.
Assuntos
Doença de Alzheimer , Imunoterapia , Transtornos da Memória , Camundongos Transgênicos , Microglia , Doenças Neuroinflamatórias , Neurônios , Receptor 2 Toll-Like , Proteínas tau , Animais , Receptor 2 Toll-Like/metabolismo , Camundongos , Proteínas tau/metabolismo , Microglia/metabolismo , Doença de Alzheimer/metabolismo , Imunoterapia/métodos , Doenças Neuroinflamatórias/metabolismo , Transtornos da Memória/metabolismo , Neurônios/metabolismo , Hipocampo/metabolismo , Modelos Animais de Doenças , Camundongos Knockout , Inflamação/metabolismo , Camundongos Endogâmicos C57BLRESUMO
Transmembrane protein 9 (TMEM9) is a transmembrane protein that regulates lysosomal acidification by interacting with the v-type ATPase complex. However, the role of TMEM9 in the lysosome-dependent autophagy machinery has yet to be identified. In this study, we demonstrate that the lysosomal protein TMEM9, which is involved in vesicle acidification, regulates Rab9-dependent alternative autophagy through its interaction with Beclin1. The cytosolic domain of TMEM9 interacts with Beclin1 via its Bcl-2-binding domain. This interaction between TMEM9 and Beclin1 dissociates Bcl-2, an autophagy-inhibiting partner, from Beclin1, thereby activating LC3-independent and Rab9-dependent alternative autophagy. Late endosomal and lysosomal TMEM9 apparently colocalizes with Rab9 but not with LC3. Furthermore, we show that multiple glycosylation of TMEM9, essential for lysosomal localization, is essential for its interaction with Beclin1 and the activation of Rab9-dependent alternative autophagy. These findings reveal that TMEM9 recruits and activates the Beclin1 complex at the site of Rab9-dependent autophagosome to induce alternative autophagy.
Assuntos
Autofagia , Proteína Beclina-1 , Lisossomos , Proteínas de Membrana , Proteínas rab de Ligação ao GTP , Proteína Beclina-1/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Proteínas rab de Ligação ao GTP/metabolismo , Lisossomos/metabolismo , Células HEK293 , Ligação Proteica , Células HeLa , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Animais , Autofagossomos/metabolismoRESUMO
BACKGROUND: In tauopathies, brain regions with tau accumulation strongly correlate with clinical symptoms, and spreading of misfolded tau along neural network leads to disease progression. However, the underlying mechanisms by which tau proteins enter neurons during pathological propagation remain unclear. METHODS: To identify membrane receptors responsible for neuronal propagation of tau oligomers, we established a cell-based tau uptake assay and screened complementary DNA expression library. Tau uptake and propagation were analyzed in vitro and in vivo using a microfluidic device and stereotactic injection. The cognitive function of mice was assessed using behavioral tests. RESULTS: From a genome-wide cell-based functional screening, RAGE (receptor for advanced glycation end products) was isolated to stimulate the cellular uptake of tau oligomers. Rage deficiency reduced neuronal uptake of pathological tau prepared from rTg4510 mouse brains or cerebrospinal fluid from patients with Alzheimer's disease and slowed tau propagation between neurons cultured in a 3-chamber microfluidic device. RAGE levels were increased in the brains of rTg4510 mice and tau oligomer-treated neurons. Rage knockout decreased tau transmission in the brains of nontransgenic mice after injection with Alzheimer's disease patient-derived tau and ameliorated memory loss after injection with GFP-P301L-tau-AAV. Treatment of RAGE antagonist FPS-ZM1 blocked transsynaptic tau propagation and inflammatory responses and alleviated cognitive impairment in rTg4510 mice. CONCLUSIONS: These results suggest that in neurons and microglia, RAGE binds to pathological tau and facilitates neuronal tau pathology progression and behavioral deficits in tauopathies.
Assuntos
Doença de Alzheimer , Receptor para Produtos Finais de Glicação Avançada , Tauopatias , Proteínas tau , Animais , Camundongos , Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Modelos Animais de Doenças , Transtornos da Memória/metabolismo , Camundongos Transgênicos , Receptor para Produtos Finais de Glicação Avançada/metabolismo , Proteínas tau/metabolismo , Tauopatias/metabolismoRESUMO
Impaired activities and abnormally enlarged structures of endolysosomes are frequently observed in Alzheimer disease (AD) brains. However, little is known about whether and how endolysosomal dysregulation is triggered and associated with AD. Here, we show that vacuolar ATPase (V-ATPase) is a hub that mediates proteopathy of oligomeric amyloid beta (Aß) and hyperphosphorylated MAPT/Tau (p-MAPT/Tau). Endolysosomal integrity was largely destroyed in Aß-overloaded or p-MAPT/Tau-positive neurons in culture and AD brains, which was a necessary step for triggering neurotoxicity, and treatments with acidic nanoparticles or endocytosis inhibitors rescued the endolysosomal impairment and neurotoxicity. Interestingly, we found that the lumenal ATP6V0C and cytosolic ATP6V1B2 subunits of the V-ATPase complex bound to the internalized Aß and cytosolic PHF-1-reactive MAPT/Tau, respectively. Their interactions disrupted V-ATPase activity and accompanying endolysosomal activity in vitro and induced neurodegeneration. Using a genome-wide functional screen, we isolated a suppressor, HYAL (hyaluronidase), which reversed the endolysosomal dysfunction and proteopathy and alleviated the memory impairment in 3xTg-AD mice. Further, we found that its metabolite hyaluronic acid (HA) and HA receptor CD44 attenuated neurotoxicity in affected neurons via V-ATPase. We propose that endolysosomal V-ATPase is a bona fide proteotoxic receptor that binds to pathogenic proteins and deteriorates endolysosomal function in AD, leading to neurodegeneration in proteopathy.Abbreviations: AAV, adeno-associated virus; Aß, amyloid beta; AD, Alzheimer disease; APP, amyloid beta precursor protein; ATP6V0C, ATPase H+ transporting V0 subunit c; ATP6V1A, ATPase H+ transporting V1 subunit A; ATP6V1B2, ATPase H+ transporting V1 subunit B2; CD44.Fc, CD44-mouse immunoglobulin Fc fusion construct; Co-IP, co-immunoprecipitation; CTSD, cathepsin D; HA, hyaluronic acid; HMWHA, high-molecular-weight hyaluronic acid; HYAL, hyaluronidase; i.c.v, intracerebroventricular; LMWHA, low-molecular-weight hyaluronic acid; NPs, nanoparticles; p-MAPT/Tau, hyperphosphorylated microtubule associated protein tau; PI3K, phosphoinositide 3-kinase; V-ATPase, vacuolar-type H+-translocating ATPase; WT, wild-type.
Assuntos
Doença de Alzheimer , ATPases Vacuolares Próton-Translocadoras , Camundongos , Animais , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , ATPases Vacuolares Próton-Translocadoras/metabolismo , Hialuronoglucosaminidase/metabolismo , Ácido Hialurônico , Fosfatidilinositol 3-Quinases/metabolismo , Autofagia , Proteínas tau/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Proteínas de Transporte , Camundongos Transgênicos , Modelos Animais de DoençasRESUMO
Primary cilia help to maintain cellular homeostasis by sensing conditions in the extracellular environment, including growth factors, nutrients, and hormones that are involved in various signaling pathways. Recently, we have shown that enhanced primary ciliogenesis in dopamine neurons promotes neuronal survival in a Parkinson's disease model. Moreover, we performed fecal metabolite screening in order to identify several candidates for improving primary ciliogenesis, including L-carnitine and acetyl-L-carnitine. However, the role of carnitine in primary ciliogenesis has remained unclear. In addition, the relationship between primary cilia and neurodegenerative diseases has remained unclear. In this study, we have evaluated the effects of carnitine on primary ciliogenesis in 1-methyl-4-phenylpyridinium ion (MPP+)-treated cells. We found that both L-carnitine and acetyl-L-carnitine promoted primary ciliogenesis in SH-SY5Y cells. In addition, the enhancement of ciliogenesis by carnitine suppressed MPP+-induced mitochondrial reactive oxygen species overproduction and mitochondrial fragmentation in SH-SY5Y cells. Moreover, carnitine inhibited the production of pro-inflammatory cytokines in MPP+-treated SH-SY5Y cells. Taken together, our findings suggest that enhanced ciliogenesis regulates MPP+-induced neurotoxicity and inflammation.
Assuntos
Neuroblastoma , Síndromes Neurotóxicas , 1-Metil-4-fenilpiridínio/toxicidade , Acetilcarnitina/farmacologia , Apoptose , Carnitina/farmacologia , Linhagem Celular Tumoral , Neurônios Dopaminérgicos , Humanos , InflamaçãoRESUMO
The RAS-BRAF signaling is a major pathway of cell proliferation and their mutations are frequently found in human cancers. Adenylate kinase 2 (AK2), which modulates balance of adenine nucleotide pool, has been implicated in cell death and cell proliferation independently of its enzyme activity. Recently, the role of AK2 in tumorigenesis was in part elucidated in some cancer types including lung adenocarcinoma and breast cancer, but the underlying mechanism is not clear. Here, we show that AK2 is a BRAF-suppressor. In in vitro assays and cell model, AK2 interacted with BRAF and inhibited BRAF activity and downstream ERK phosphorylation. Energy-deprived conditions in cell model and the addition of AMP to cell lysates strengthened the AK2-BRAF interaction, suggesting that AK2 is involved in the regulation of BRAF activity in response to cell metabolic state. AMP facilitated the AK2-BRAF complex formation through binding to AK2. In a panel of HCC cell lines, AK2 expression was inversely correlated with ERK/MAPK activation, and AK2-knockdown or -knockout increased BRAF activity and promoted cell proliferation. Tumors from HCC patients showed low-AK2 protein expression and increased ERK activation compared to non-tumor tissues and the downregulation of AK2 was also verified by two microarray datasets (TCGA-LIHC and GSE14520). Moreover, AK2/BRAF interaction was abrogated by RAS activation in in vitro assay and cell model and in a mouse model of HRASG12V-driven HCC, and AK2 ablation promoted tumor growth and BRAF activity. AK2 also bound to BRAF inhibitor-insensitive BRAF mutants and attenuated their activities. These findings indicate that AK2 monitoring cellular AMP levels is indeed a negative regulator of BRAF, linking the metabolic status to tumor growth.
Assuntos
Monofosfato de Adenosina , Adenilato Quinase , Carcinoma Hepatocelular , Neoplasias Hepáticas , Proteínas Proto-Oncogênicas B-raf , Monofosfato de Adenosina/metabolismo , Adenilato Quinase/metabolismo , Animais , Carcinogênese/genética , Carcinoma Hepatocelular/enzimologia , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Humanos , Neoplasias Hepáticas/enzimologia , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patologia , Camundongos , Mutação , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas B-raf/metabolismoRESUMO
AIMS: Well-controlled mitochondrial homeostasis, including a mitochondria-specific form of autophagy (hereafter referred to as mitophagy), is essential for maintaining cardiac function. The molecular mechanism mediating mitophagy during pressure overload (PO) is poorly understood. We have shown previously that mitophagy in the heart is mediated primarily by Atg5/Atg7-independent mechanisms, including Unc-51-like kinase 1 (Ulk1)-dependent alternative mitophagy, during myocardial ischaemia. Here, we investigated the role of alternative mitophagy in the heart during PO-induced hypertrophy. METHODS AND RESULTS: Mitophagy was observed in the heart in response to transverse aortic constriction (TAC), peaking at 3-5 days. Whereas mitophagy is transiently up-regulated by TAC through an Atg7-dependent mechanism in the heart, peaking at 1 day, it is also activated more strongly and with a delayed time course through an Ulk1-dependent mechanism. TAC induced more severe cardiac dysfunction, hypertrophy, and fibrosis in ulk1 cardiac-specific knock-out (cKO) mice than in wild-type mice. Delayed activation of mitophagy was characterized by the co-localization of Rab9 dots and mitochondria and phosphorylation of Rab9 at Ser179, major features of alternative mitophagy. Furthermore, TAC-induced decreases in the mitochondrial aspect ratio were abolished and the irregularity of mitochondrial cristae was exacerbated, suggesting that mitochondrial quality control mechanisms are impaired in ulk1 cKO mice in response to TAC. TAT-Beclin 1 activates mitophagy even in Ulk1-deficient conditions. TAT-Beclin 1 treatment rescued mitochondrial dysfunction and cardiac dysfunction in ulk1 cKO mice during PO. CONCLUSION: Ulk1-mediated alternative mitophagy is a major mechanism mediating mitophagy in response to PO and plays an important role in mediating mitochondrial quality control mechanisms and protecting the heart against cardiac dysfunction.
Assuntos
Proteína Homóloga à Proteína-1 Relacionada à Autofagia , Cardiomegalia , Mitofagia , Animais , Aorta/cirurgia , Proteína Homóloga à Proteína-1 Relacionada à Autofagia/genética , Proteína Homóloga à Proteína-1 Relacionada à Autofagia/metabolismo , Proteína Beclina-1/genética , Proteína Beclina-1/metabolismo , Cardiomegalia/etiologia , Cardiomegalia/genética , Cardiomegalia/metabolismo , Hipertensão/etiologia , Hipertensão/genética , Hipertensão/metabolismo , Hipertrofia , Camundongos , Mitofagia/genética , Mitofagia/fisiologia , Isquemia Miocárdica/etiologia , Isquemia Miocárdica/genética , Isquemia Miocárdica/metabolismo , Proteínas rab de Ligação ao GTP/genética , Proteínas rab de Ligação ao GTP/metabolismoRESUMO
Toxic amyloid beta (Aß) species cause synaptic dysfunction and neurotoxicity in Alzheimer's disease (AD). As of yet, however, there are no reported regulators for gamma-secretase, which links a risky environment to amyloid accumulation in AD. Here, we report that pyruvate kinase M2 (PKM2) is a positive regulator of gamma-secretase under hypoxia. From a genome-wide functional screen, we identify PKM2 as a gamma-secretase activator that is highly expressed in the brains of both patients and murine models with AD. PKM2 regulates Aß production and the amount of active gamma-secretase complex by changing the gene expression of aph-1 homolog. Hypoxia induces PKM2 expression, thereby promoting gamma-secretase activity. Moreover, transgenic expression of PKM2 in 3xTg AD model mice enhances hippocampal production of Aß and exacerbates the impairment of spatial and recognition memory. Taken together, these findings indicate that PKM2 is an important gamma-secretase regulator that promotes Aß production and memory impairment under hypoxia.
Assuntos
Doença de Alzheimer/enzimologia , Comportamento Animal , Encéfalo/enzimologia , Endopeptidases/metabolismo , Proteínas de Membrana/metabolismo , Memória , Piruvato Quinase/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/genética , Doença de Alzheimer/fisiopatologia , Doença de Alzheimer/psicologia , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/fisiopatologia , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Estudos de Casos e Controles , Bases de Dados Genéticas , Modelos Animais de Doenças , Endopeptidases/genética , Feminino , Regulação Enzimológica da Expressão Gênica , Humanos , Masculino , Proteínas de Membrana/genética , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pessoa de Meia-Idade , Piruvato Quinase/genética , Reconhecimento Psicológico , Transdução de Sinais , Memória Espacial , Hormônios Tireóideos/genética , Hormônios Tireóideos/metabolismo , Transcrição Gênica , Proteínas de Ligação a Hormônio da TireoideRESUMO
The maintenance of lysosomal integrity is essential for lysosome function and cell fate. Damaged lysosomes are degraded by lysosomal autophagy, lysophagy. The mechanism underlying lysophagy remains largely unknown; this study aimed to contribute to the understanding of this topic. A cell-based screening system was used to identify novel lysophagy modulators. Triamterene (6-phenylpteridine-2,4,7-triamine) was identified as one of the most potent lysophagy inducers from the screening process. We found that triamterene causes lysosomal rupture without affecting other cellular organelles and increases autophagy flux in HepG2 cells. Damaged lysosomes in triamterene-treated cells were removed by autophagy-mediated pathway, which was inhibited by depletion of the autophagy regulator, ATG5 or SQSTM1. In addition, treatment of triamterene decreased the integrity of lysosome and cell viability, which were rescued by removing the triamterene treatment in HepG2 cells. Hence, our data suggest that triamterene is a novel lysophagy inducer through the disruption of lysosomal integrity.
Assuntos
Autofagia/efeitos dos fármacos , Bloqueadores do Canal de Sódio Epitelial/farmacologia , Lisossomos/efeitos dos fármacos , Triantereno/farmacologia , Autofagia/fisiologia , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Células HeLa , Células Hep G2 , Humanos , Lisossomos/metabolismoRESUMO
As a dynamic organelle, mitochondria continuously fuse and divide with adjacent mitochondria. Imbalance in mitochondria dynamics leads to their dysfunction, which implicated in neurodegenerative diseases. However, how mitochondria alteration and glucose defect contribute to pathogenesis of Alzheimer's disease (AD) is still largely unknown. Dynamin-related protein 1 (Drp1) is an essential regulator for mitochondria fission. Among various posttranslational modifications, O-GlcNAcylation plays a role as a sensor for nutrient and oxidative stress. In this study, we identified that Drp1 is regulated by O-GlcNAcylation in AD models. Treatment of Aß as well as PugNAc resulted in mitochondrial fragmentation in neuronal cells. Moreover, we found that AD mice brain exhibits an upregulated Drp1 O-GlcNAcylation. However, depletion of OGT inhibited Drp1 O-GlcNAcylation in Aß-treated cells. In addition, overexpression of O-GlcNAc defective Drp1 mutant (T585A and T586A) decreased Drp1 O-GlcNAcylation and Aß-induced mitochondria fragmentation. Taken together, these finding suggest that Aß regulates mitochondrial fission by increasing O-GlcNAcylation of Drp1.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Dinaminas/metabolismo , Dinâmica Mitocondrial , Neurônios/metabolismo , Animais , Células Cultivadas , Glicosilação , Humanos , Camundongos TransgênicosRESUMO
Proteinopathy in neurodegenerative diseases is typically characterized by deteriorating activity of specific protein aggregates. In tauopathies, including Alzheimer's disease (AD), tau protein abnormally accumulates and induces dysfunction of the affected neurons. Despite active identification of tau modifications responsible for tau aggregation, a critical modulator inducing tau proteinopathy by affecting its protein degradation flux is not known. Here, we report that anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase, is crucial for the tau-mediated AD pathology. ALK caused abnormal accumulation of highly phosphorylated tau in the somatodendritic region of neurons through its tyrosine kinase activity. ALK-induced LC3-positive axon swelling and loss of spine density, leading to tau-dependent neuronal degeneration. Notably, ALK activation in neurons impaired Stx17-dependent autophagosome maturation and this defect was reversed by a dominant-negative Grb2. In a Drosophila melanogaster model, transgenic flies neuronally expressing active Drosophila Alk exhibited the aggravated tau rough eye phenotype with retinal degeneration and shortened lifespan. In contrast, expression of kinase-dead Alk blocked these phenotypes. Consistent with the previous RNAseq analysis showing upregulation of ALK expression in AD [1], ALK levels were significantly elevated in the brains of AD patients showing autophagosomal defects. Injection of an ALK.Fc-lentivirus exacerbated memory impairment in 3xTg-AD mice. Conversely, pharmacologic inhibition of ALK activity with inhibitors reversed the memory impairment and tau accumulation in both 3xTg-AD and tauC3 (caspase-cleaved tau) transgenic mice. Together, we propose that aberrantly activated ALK is a bona fide mediator of tau proteinopathy that disrupts autophagosome maturation and causes tau accumulation and aggregation, leading to neuronal dysfunction in AD.
Assuntos
Doença de Alzheimer , Tauopatias , Doença de Alzheimer/genética , Quinase do Linfoma Anaplásico/genética , Animais , Drosophila melanogaster , Humanos , Camundongos , Camundongos Transgênicos , Tauopatias/genética , Proteínas tau/genéticaRESUMO
The enzyme γ-secretase generates ß-amyloid (Aß) peptides by cleaving amyloid protein precursor (APP); the aggregation of these peptides is associated with Alzheimer's disease (AD). Despite the development of various γ-secretase regulators, their clinical use is limited by coincident disruption of other γ-secretase-regulated substrates, such as Notch. Using a genome-wide functional screen of γ-secretase activity in cells and a complementary DNA expression library, we found that SERP1 is a previously unknown γ-secretase activator that stimulates Aß generation in cells experiencing endoplasmic reticulum (ER) stress, such as is seen with diabetes. SERP1 interacted with a subcomplex of γ-secretase (APH1A/NCT) through its carboxyl terminus to enhance the assembly and, consequently, the activity of the γ-secretase holoenzyme complex. In response to ER stress, SERP1 preferentially recruited APP rather than Notch into the γ-secretase complex and enhanced the subcellular localization of the complex into lipid rafts, increasing Aß production. Moreover, SERP1 abundance, γ-secretase assembly, and Aß production were increased both in cells exposed to high amounts of glucose and in diabetic AD model mice. Conversely, Aß production was decreased by knocking down SERP1 in cells or in the hippocampi of mice. Compared to postmortem samples from control individuals, those from patients with AD showed increased SERP1 expression in the hippocampus and parietal lobe. Together, our findings suggest that SERP1 is an APP-biased regulator of γ-secretase function in the context of cell stress, providing a possible molecular explanation for the link between diabetes and sporadic AD.
Assuntos
Doença de Alzheimer/metabolismo , Secretases da Proteína Precursora do Amiloide/metabolismo , Proteínas de Membrana/metabolismo , Transdução de Sinais , Estresse Fisiológico , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/genética , Animais , Linhagem Celular Tumoral , Células Cultivadas , Células HEK293 , Células HeLa , Humanos , Proteínas de Membrana/genética , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Ligação ProteicaRESUMO
Quality control of peroxisomes is essential for cellular homeostasis. However, the mechanism underlying pexophagy is largely unknown. In this study, we identified HSPA9 as a novel pexophagy regulator. Downregulation of HSPA9 increased macroautophagy/autophagy but decreased the number of peroxisomes in vitro and in vivo. The loss of peroxisomes by HSPA9 depletion was attenuated in SQSTM1-deficient cells. In HSPA9-deficient cells, the level of peroxisomal reactive oxygen species (ROS) increased, while inhibition of ROS blocked pexophagy in HeLa and SH-SY5Y cells. Importantly, reconstitution of HSPA9 mutants found in Parkinson disease failed to rescue the loss of peroxisomes, whereas reconstitution with wild type inhibited pexophagy in HSPA9-depleted cells. Knockdown of Hsc70-5 decreased peroxisomes in Drosophila, and the HSPA9 mutants failed to rescue the loss of peroxisomes in Hsc70-5-depleted flies. Taken together, our findings suggest that the loss of HSPA9 enhances peroxisomal degradation by pexophagy.
Assuntos
Autofagia/fisiologia , Proteínas de Choque Térmico HSP70/metabolismo , Macroautofagia/fisiologia , Proteínas Mitocondriais/metabolismo , Peroxissomos/metabolismo , Humanos , Espécies Reativas de Oxigênio/metabolismoRESUMO
Mitochondrial quality control maintains mitochondrial function by regulating mitochondrial dynamics and mitophagy. Despite the identification of mitochondrial quality control factors, little is known about the crucial regulators coordinating both mitochondrial fission and mitophagy. Through a cell-based functional screening assay, FK506 binding protein 8 (FKBP8) was identified to target microtubule-associated protein 1 light chain 3 (LC3) to the mitochondria and to change mitochondrial morphology. Microscopy analysis revealed that the formation of tubular and enlarged mitochondria was observed in FKBP8 knockdown HeLa cells and the cortex of Fkbp8 heterozygote-knockout mouse embryos. Under iron depletion-induced stress, FKBP8 was recruited to the site of mitochondrial division through budding and colocalized with LC3. FKBP8 was also found to be required for mitochondrial fragmentation and mitophagy under hypoxic stress. Conversely, FKBP8 overexpression induced mitochondrial fragmentation in HeLa cells, human fibroblasts and mouse embryo fibroblasts (MEFs), and this fragmentation occurred in Drp1 knockout MEF cells, FIP200 knockout HeLa cells and BNIP3/NIX double knockout HeLa cells, but not in Opa1 knockout MEFs. Interestingly, we found an LIR motif-like sequence (LIRL), as well as an LIR motif, at the N-terminus of FKBP8 and LIRL was essential for both inducing mitochondrial fragmentation and binding of FKBP8 to OPA1. Together, we suggest that FKBP8 plays an essential role in mitochondrial fragmentation through LIRL during mitophagy and this activity of FKBP8 together with LIR is required for mitophagy under stress conditions.
Assuntos
Fibroblastos/metabolismo , Mitocôndrias/metabolismo , Dinâmica Mitocondrial , Estresse Fisiológico , Proteínas de Ligação a Tacrolimo/metabolismo , Animais , Células HEK293 , Células HeLa , Humanos , Camundongos , Camundongos Knockout , Proteínas Associadas aos Microtúbulos/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Mitocôndrias/genética , Proteínas de Ligação a Tacrolimo/genéticaRESUMO
The transient receptor potential vanilloid 1 (TRPV1) protein is a pain receptor that elicits a hot sensation when an organism eats the capsaicin of red chili peppers. This calcium (Ca2+)-permeable cation channel is mostly expressed in the peripheral nervous system sensory neurons but also in the central nervous system (e.g. hippocampus and cortex). Preclinical studies found that TRPV1 mediates behaviors associated with anxiety and depression. Loss of TRPV1 functionality increases expression of genes related to synaptic plasticity and neurogenesis. Thus, we hypothesized that TRPV1 deficiency may modulate Alzheimer's disease (AD). We generated a triple-transgenic AD mouse model (3xTg-AD+/+) with wild-type (TRPV1+/+), hetero (TRPV1+/-) and knockout (TRPV1-/-) TRPV1 to investigate the role of TRPV1 in AD pathogenesis. We analyzed the animals' memory function, hippocampal Ca2+ levels and amyloid-ß (Aß) and tau pathologies when they were 12 months old. We found that compared with 3xTg-AD-/-/TRPV1+/+ mice, 3xTg-AD+/+/TRPV1+/+ mice had memory impairment and increased levels of hippocampal Ca2+, Aß and total and phosphorylated tau. However, 3xTg-AD+/+/TRPV1-/- mice had better memory function and lower levels of hippocampal Ca2+, Aß, tau and p-tau, compared with 3xTg-AD+/+/TRPV1+/+ mice. Examination of 3xTg-AD-derived primary neuronal cultures revealed that the intracellular Ca2+ chelator BAPTA/AM and the TRPV1 antagonist capsazepine decreased the production of Aß, tau and p-tau. Taken together, these results suggested that TRPV1 deficiency had anti-AD effects and promoted resilience to memory loss. These findings suggest that drugs or food components that modulate TRPV1 could be exploited as therapeutics to prevent or treat AD.
Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Cálcio/metabolismo , Transtornos da Memória/metabolismo , Canais de Cátion TRPV/metabolismo , Proteínas tau/metabolismo , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/genética , Animais , Canais de Cálcio/metabolismo , Capsaicina/análogos & derivados , Capsaicina/farmacologia , Quelantes/farmacologia , Modelos Animais de Doenças , Ácido Egtázico/análogos & derivados , Ácido Egtázico/farmacologia , Hipocampo/metabolismo , Aprendizagem/efeitos dos fármacos , Transtornos da Memória/genética , Camundongos , Camundongos Knockout , Nociceptores/metabolismo , Nociceptores/patologia , Canais de Cátion TRPV/antagonistas & inibidores , Canais de Cátion TRPV/genética , Proteínas tau/genéticaRESUMO
Despite enduring diverse insults, mitochondria maintain normal functions through mitochondrial quality control. However, the failure of mitochondrial quality control resulting from excess damage and mechanical defects causes mitochondrial dysfunction, leading to various human diseases. Recent studies have reported that mitochondrial defects are found in Alzheimer's disease (AD) and worsen AD symptoms. In AD pathogenesis, mitochondrial dysfunction-driven generation of reactive oxygen species (ROS) and their contribution to neuronal damage has been widely studied. In contrast, studies on mitochondrial dysfunction-associated inflammatory responses have been relatively scarce. Moreover, ROS produced upon failure of mitochondrial quality control may be linked to the inflammatory response and influence the progression of AD. Thus, this review will focus on inflammatory pathways that are associated with and initiated through defective mitochondria and will summarize recent progress on the role of mitochondria-mediated inflammation in AD. We will also discuss how reducing mitochondrial dysfunction-mediated inflammation could affect AD. [BMB Reports 2020; 53(1): 35-46].
Assuntos
Doença de Alzheimer/imunologia , Inflamação/metabolismo , Mitocôndrias/imunologia , Mitocôndrias/metabolismo , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/etiologia , Doença de Alzheimer/patologia , Animais , Humanos , Inflamação/imunologia , Inflamação/terapia , Camundongos , Microglia/metabolismo , Mitocôndrias/patologia , Mitocôndrias/ultraestrutura , Neurônios/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/imunologiaRESUMO
Upon necroptosis activation, receptor interacting serine/threonine kinase (RIPK)1 and RIPK3 form a necrosome complex with pseudokinase mixed lineage kinase-like (MLKL). Although protein phosphorylation is a key event for RIPK1 and RIPK3 activation in response to a necroptosis signal, relatively little is known about other factors that might regulate the activity of these kinases or necrosome formation. Through a gain-of-function screen with 546 kinases and 127 phosphatases, we identified casein kinase 1 gamma (CK1γ) as a candidate necroptosis-promoting factor. Here, we show that the decreased activity or amounts of CK1γ1 and CK1γ3, either by treatment with a chemical inhibitor or knockdown in cells, reduced TNFα-induced necroptosis. Conversely, ectopic expression of CK1γ1 or CK1γ3 exacerbated necroptosis, but not apoptosis. Similar to RIPK1 and RIPK3, CK1γ1 was also cleaved at Asp343 by caspase-8 during apoptosis. CK1γ1 and CK1γ3 formed a protein complex and were recruited to the necrosome harboring RIPK1, RIPK3 and MLKL. In particular, an autophosphorylated form of CK1γ3 at Ser344/345 was detected in the necrosome and was required to mediate the necroptosis. In addition, in vitro assays with purified proteins showed that CK1γ phosphorylated RIPK3, affecting its activity, and in vivo assays showed that the CK1γ-specific inhibitor Gi prevented abrupt death in mice with hypothermia in a model of TNFα-induced systemic inflammatory response syndrome. Collectively, these data suggest that CK1γ1 and CK1γ3 are required for TNFα-induced necroptosis likely by regulating RIPK3.
Assuntos
Caseína Quinase I/genética , Inflamação/genética , Necroptose/genética , Necrose/genética , Proteína Serina-Treonina Quinases de Interação com Receptores/genética , Animais , Apoptose/genética , Caspase 8/genética , Morte Celular/genética , Humanos , Inflamação/patologia , Camundongos , Fosforilação , Proteínas Quinases/genéticaRESUMO
A primary cilium is an antenna-like structure on the cell surface that plays a crucial role in sensory perception and signal transduction. Mitochondria, the 'powerhouse' of the cell, control cell survival, and death. The cellular ability to remove dysfunctional mitochondria through mitophagy is important for cell survival. We show here that mitochondrial stress, caused by respiratory complex inhibitors and excessive fission, robustly stimulates ciliogenesis in different types of cells including neuronal cells. Mitochondrial stress-induced ciliogenesis is mediated by mitochondrial reactive oxygen species generation, subsequent activation of AMP-activated protein kinase and autophagy. Conversely, abrogation of ciliogenesis compromises mitochondrial stress-induced autophagy, leading to enhanced cell death. In mice, treatment with mitochondrial toxin, MPTP elicits ciliary elongation and autophagy in the substantia nigra dopamine neurons. Blockade of cilia formation in these neurons attenuates MPTP-induced autophagy but facilitates dopamine neuronal loss and motor disability. Our findings demonstrate the important role of primary cilia in cellular pro-survival responses during mitochondrial stress.
Assuntos
Autofagia/genética , Mitocôndrias/genética , Mitofagia/genética , Doença de Parkinson/genética , Proteínas Quinases Ativadas por AMP/genética , Animais , Apoptose/genética , Linhagem Celular Tumoral , Sobrevivência Celular , Cílios/genética , Cílios/patologia , Modelos Animais de Doenças , Dopamina/metabolismo , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Humanos , Camundongos , Camundongos Knockout , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Espécies Reativas de Oxigênio/metabolismo , Estresse Fisiológico/genética , Substância Negra/metabolismo , Substância Negra/patologiaAssuntos
Apoptose , Traumatismos da Medula Espinal , Araquidonato 12-Lipoxigenase , Humanos , Inflamação , NeurôniosRESUMO
In ischemic human hearts, the induction of adenosine receptor A2B (ADORA2B) is associated with cardioprotection against ischemic heart damage, but the mechanism underlying this association remains unclear. Apaf-1-interacting protein (APIP) and ADORA2B transcript levels in human hearts are substantially higher in patients with heart failure than in controls. Interestingly, the APIP and ADORA2B mRNA levels are highly correlated with each other (R = 0.912). APIP expression was significantly increased in primary neonatal cardiomyocytes under hypoxic conditions and this induction reduced myocardial cell death via the activation of the AKT-HIF1α pathway. Accordingly, infarct sizes of APIP transgenic mice after left anterior descending artery ligation were significantly reduced compared to those of wild-type mice. Strikingly, knockdown of APIP expression impaired the cytoprotective effects of ADORA2B during hypoxic damage. Immunoprecipitation and proximity ligation assays revealed that APIP interacts with ADORA2B, leading to the stabilization of both proteins by interfering with lysosomal degradation, and to the activation of the downstream PKA-CREB signaling pathways. ADORA2B levels in the hearts of APIPTg/Tg, APIPTg/+, and Apip+/- mice were proportionally downregulated. In addition, ADORA2B D296G derived from the rs200741295 polymorphism failed to bind to APIP and did not exert cardioprotective activity during hypoxia. Moreover, Adora2b D296G knock-in mice were more vulnerable than control mice to myocardial infarction and intentional increases in APIP levels overcame the defective protection of the ADORA2B SNP against ischemic injury. Collectively, APIP is crucial for cardioprotection against myocardial infarction by virtue of binding to and stabilizing ADORA2B, thereby dampening ischemic heart injury.