RESUMO
The mechanistic target of rapamycin complex 1 (mTORC1) is a key metabolic hub that controls the cellular response to environmental cues by exerting its kinase activity on multiple substrates1-3. However, whether mTORC1 responds to diverse stimuli by differentially phosphorylating specific substrates is poorly understood. Here we show that transcription factor EB (TFEB), a master regulator of lysosomal biogenesis and autophagy4,5, is phosphorylated by mTORC1 via a substrate-specific mechanism that is mediated by Rag GTPases. Owing to this mechanism, the phosphorylation of TFEB-unlike other substrates of mTORC1, such as S6K and 4E-BP1- is strictly dependent on the amino-acid-mediated activation of RagC and RagD GTPases, but is insensitive to RHEB activity induced by growth factors. This mechanism has a crucial role in Birt-Hogg-Dubé syndrome, a disorder that is caused by mutations in the RagC and RagD activator folliculin (FLCN) and is characterized by benign skin tumours, lung and kidney cysts and renal cell carcinoma6,7. We found that constitutive activation of TFEB is the main driver of the kidney abnormalities and mTORC1 hyperactivity in a mouse model of Birt-Hogg-Dubé syndrome. Accordingly, depletion of TFEB in kidneys of these mice fully rescued the disease phenotype and associated lethality, and normalized mTORC1 activity. Our findings identify a mechanism that enables differential phosphorylation of mTORC1 substrates, the dysregulation of which leads to kidney cysts and cancer.
Assuntos
Síndrome de Birt-Hogg-Dubé/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Animais , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/química , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/deficiência , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Síndrome de Birt-Hogg-Dubé/genética , Síndrome de Birt-Hogg-Dubé/patologia , Linhagem Celular , Modelos Animais de Doenças , Ativação Enzimática , Células HeLa , Humanos , Neoplasias Renais/metabolismo , Neoplasias Renais/patologia , Camundongos , Camundongos Knockout , Proteínas Monoméricas de Ligação ao GTP/metabolismo , Fosforilação , Ligação Proteica , Proteínas Proto-Oncogênicas/deficiência , Proteínas Proto-Oncogênicas/genética , Proteína Enriquecida em Homólogo de Ras do Encéfalo/metabolismo , Especificidade por Substrato , Proteína 2 do Complexo Esclerose Tuberosa/metabolismo , Proteínas Supressoras de Tumor/deficiência , Proteínas Supressoras de Tumor/genéticaRESUMO
Since the discovery of lysosomes more than 70 years ago, much has been learned about the functions of these organelles. Lysosomes were regarded as exclusively degradative organelles, but more recent research has shown that they play essential roles in several other cellular functions, such as nutrient sensing, intracellular signalling and metabolism. Methodological advances played a key part in generating our current knowledge about the biology of this multifaceted organelle. In this review, we cover current methods used to analyze lysosome morphology, positioning, motility and function. We highlight the principles behind these methods, the methodological strategies and their advantages and limitations. To extract accurate information and avoid misinterpretations, we discuss the best strategies to identify lysosomes and assess their characteristics and functions. With this review, we aim to stimulate an increase in the quantity and quality of research on lysosomes and further ground-breaking discoveries on an organelle that continues to surprise and excite cell biologists.
Assuntos
Lisossomos , Redes e Vias Metabólicas , Lisossomos/metabolismo , Transdução de SinaisRESUMO
Vertebrate vision relies on the daily phagocytosis and lysosomal degradation of photoreceptor outer segments (POS) within the retinal pigment epithelium (RPE). However, how these events are controlled by light is largely unknown. Here, we show that the light-responsive miR-211 controls lysosomal biogenesis at the beginning of light-dark transitions in the RPE by targeting Ezrin, a cytoskeleton-associated protein essential for the regulation of calcium homeostasis. miR-211-mediated down-regulation of Ezrin leads to Ca2+ influx resulting in the activation of calcineurin, which in turn activates TFEB, the master regulator of lysosomal biogenesis. Light-mediated induction of lysosomal biogenesis and function is impaired in the RPE from miR-211-/- mice that show severely compromised vision. Pharmacological restoration of lysosomal biogenesis through Ezrin inhibition rescued the miR-211-/- phenotype, pointing to a new therapeutic target to counteract retinal degeneration associated with lysosomal dysfunction.
Assuntos
Cálcio/metabolismo , Proteínas do Citoesqueleto/metabolismo , Regulação da Expressão Gênica , Lisossomos/metabolismo , MicroRNAs/metabolismo , Animais , Autofagia , Proteínas do Citoesqueleto/antagonistas & inibidores , Proteínas do Citoesqueleto/genética , Regulação para Baixo , Luz , Lisossomos/ultraestrutura , Camundongos , Camundongos Knockout , MicroRNAs/genética , Fagocitose , Fagossomos/metabolismo , Fagossomos/ultraestrutura , Epitélio Pigmentado da Retina/metabolismoRESUMO
Lysosomal degradation of the endoplasmic reticulum (ER) via autophagy (ER-phagy) is emerging as a critical regulator of cell homeostasis and function. The recent identification of ER-phagy receptors has shed light on the molecular mechanisms underlining this process. However, the signaling pathways regulating ER-phagy in response to cellular needs are still largely unknown. We found that the nutrient responsive transcription factors TFEB and TFE3-master regulators of lysosomal biogenesis and autophagy-control ER-phagy by inducing the expression of the ER-phagy receptor FAM134B. The TFEB/TFE3-FAM134B axis promotes ER-phagy activation upon prolonged starvation. In addition, this pathway is activated in chondrocytes by FGF signaling, a critical regulator of skeletal growth. FGF signaling induces JNK-dependent proteasomal degradation of the insulin receptor substrate 1 (IRS1), which in turn inhibits the PI3K-PKB/Akt-mTORC1 pathway and promotes TFEB/TFE3 nuclear translocation and enhances FAM134B transcription. Notably, FAM134B is required for protein secretion in chondrocytes, and cartilage growth and bone mineralization in medaka fish. This study identifies a new signaling pathway that allows ER-phagy to respond to both metabolic and developmental cues.
Assuntos
Autofagia , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Núcleo Celular/metabolismo , Retículo Endoplasmático/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/metabolismo , Transdução de Sinais , Transporte Ativo do Núcleo Celular , Animais , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Núcleo Celular/genética , Retículo Endoplasmático/genética , Células HeLa , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Alvo Mecanístico do Complexo 1 de Rapamicina/genética , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Proteínas de Membrana/genética , Camundongos , OryziasRESUMO
The role of astrocytes in neurodegenerative processes is increasingly appreciated. Here we investigated the contribution of astrocytes to neurodegeneration in multiple sulfatase deficiency (MSD), a severe lysosomal storage disorder caused by mutations in the sulfatase modifying factor 1 (SUMF1) gene. Using Cre/Lox mouse models, we found that astrocyte-specific deletion of Sumf1 in vivo induced severe lysosomal storage and autophagy dysfunction with consequential cytoplasmic accumulation of autophagic substrates. Lysosomal storage in astrocytes was sufficient to induce degeneration of cortical neurons in vivo. Furthermore, in an ex vivo coculture assay, we observed that Sumf1(-/-) astrocytes failed to support the survival and function of wild-type cortical neurons, suggesting a non-cell autonomous mechanism for neurodegeneration. Compared with the astrocyte-specific deletion of Sumf1, the concomitant removal of Sumf1 in both neurons and glia in vivo induced a widespread neuronal loss and robust neuroinflammation. Finally, behavioral analysis of mice with astrocyte-specific deletion of Sumf1 compared with mice with Sumf1 deletion in both astrocytes and neurons allowed us to link a subset of neurological manifestations of MSD to astrocyte dysfunction. This study indicates that astrocytes are integral components of the neuropathology in MSD and that modulation of astrocyte function may impact disease course.
Assuntos
Astrócitos/patologia , Doença da Deficiência de Múltiplas Sulfatases/patologia , Degeneração Neural/patologia , Neurônios/patologia , Sulfatases/genética , Animais , Comunicação Celular/fisiologia , Sobrevivência Celular/fisiologia , Células Cultivadas , Cerebelo/patologia , Córtex Cerebral/patologia , Doenças por Armazenamento dos Lisossomos do Sistema Nervoso/genética , Doenças por Armazenamento dos Lisossomos do Sistema Nervoso/patologia , Lisossomos/patologia , Lisossomos/ultraestrutura , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Microscopia Eletrônica , Doença da Deficiência de Múltiplas Sulfatases/genética , Neurônios/ultraestrutura , Oxirredutases atuantes sobre Doadores de Grupo Enxofre , Células de Purkinje/patologia , Células de Purkinje/ultraestruturaRESUMO
Tuberous Sclerosis Complex (TSC) is caused by TSC1 or TSC2 mutations, leading to hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1) and lesions in multiple organs including lung (lymphangioleiomyomatosis) and kidney (angiomyolipoma and renal cell carcinoma). Previously, we found that TFEB is constitutively active in TSC. Here, we generated two mouse models of TSC in which kidney pathology is the primary phenotype. Knockout of TFEB rescues kidney pathology and overall survival, indicating that TFEB is the primary driver of renal disease in TSC. Importantly, increased mTORC1 activity in the TSC2 knockout kidneys is normalized by TFEB knockout. In TSC2-deficient cells, Rheb knockdown or Rapamycin treatment paradoxically increases TFEB phosphorylation at the mTORC1-sites and relocalizes TFEB from nucleus to cytoplasm. In mice, Rapamycin treatment normalizes lysosomal gene expression, similar to TFEB knockout, suggesting that Rapamycin's benefit in TSC is TFEB-dependent. These results change the view of the mechanisms of mTORC1 hyperactivation in TSC and may lead to therapeutic avenues.
Assuntos
Neoplasias Renais , Esclerose Tuberosa , Animais , Camundongos , Alvo Mecanístico do Complexo 1 de Rapamicina , Camundongos Knockout , Sirolimo/farmacologia , Esclerose Tuberosa/genéticaRESUMO
Synapses represent an important target of Alzheimer disease (AD), and alterations of their excitability are among the earliest changes associated with AD development. Synaptic activation has been shown to be protective in models of AD, and deep brain stimulation (DBS), a surgical strategy that modulates neuronal activity to treat neurological and psychiatric disorders, produced positive effects in AD patients. However, the molecular mechanisms underlying the protective role(s) of brain stimulation are still elusive. We have previously demonstrated that induction of synaptic activity exerts protection in mouse models of AD and frontotemporal dementia (FTD) by enhancing the macroautophagy/autophagy flux and lysosomal degradation of pathological MAPT/Tau. We now provide evidence that TFEB (transcription factor EB), a master regulator of lysosomal biogenesis and autophagy, is a key mediator of this cellular response. In cultured primary neurons from FTD-transgenic mice, synaptic stimulation inhibits MTORC1 signaling, thus promoting nuclear translocation of TFEB, which, in turn, induces clearance of MAPT/Tau oligomers. Conversely, synaptic activation fails to promote clearance of toxic MAPT/Tau in neurons expressing constitutively active RRAG GTPases, which sequester TFEB in the cytosol, or upon TFEB depletion. Activation of TFEB is also confirmed in vivo in DBS-stimulated AD mice. We also demonstrate that DBS reduces pathological MAPT/Tau and promotes neuroprotection in Parkinson disease patients with tauopathy. Altogether our findings indicate that stimulation of synaptic activity promotes TFEB-mediated clearance of pathological MAPT/Tau. This mechanism, underlying the protective effect of DBS, provides encouraging support for the use of synaptic stimulation as a therapeutic treatment against tauopathies.Abbreviations: 3xTg-AD: triple transgenic AD mice; AD: Alzheimer disease; CSA: cyclosporine A; DBS: deep brain stimulation; DIV: days in vitro; EC: entorhinal cortex; FTD: frontotemporal dementia; gLTP: glycine-induced long-term potentiation; GPi: internal segment of the globus pallidus; PD: Parkinson disease; STN: subthalamic nucleus; TFEB: transcription factor EB.
Assuntos
Doença de Alzheimer , Demência Frontotemporal , Doença de Parkinson , Tauopatias , Camundongos , Animais , Doença de Alzheimer/metabolismo , Demência Frontotemporal/metabolismo , Doença de Parkinson/metabolismo , Autofagia , Tauopatias/metabolismo , Camundongos Transgênicos , Lisossomos/metabolismo , Fatores de Transcrição/metabolismo , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Proteínas tau/metabolismoRESUMO
Birt-Hogg-Dubé (BHD) syndrome is an inherited familial cancer syndrome characterized by the development of cutaneous lesions, pulmonary cysts, renal tumors and cysts and caused by loss-of-function pathogenic variants in the gene encoding the tumor-suppressor protein folliculin (FLCN). FLCN acts as a negative regulator of TFEB and TFE3 transcription factors, master controllers of lysosomal biogenesis and autophagy, by enabling their phosphorylation by the mechanistic Target Of Rapamycin Complex 1 (mTORC1). We have previously shown that deletion of Tfeb rescued the renal cystic phenotype of kidney-specific Flcn KO mice. Using Flcn/Tfeb/Tfe3 double and triple KO mice, we now show that both Tfeb and Tfe3 contribute, in a differential and cooperative manner, to kidney cystogenesis. Remarkably, the analysis of BHD patient-derived tumor samples revealed increased activation of TFEB/TFE3-mediated transcriptional program and silencing either of the two genes rescued tumorigenesis in human BHD renal tumor cell line-derived xenografts (CDXs). Our findings demonstrate in disease-relevant models that both TFEB and TFE3 are key drivers of renal tumorigenesis and suggest novel therapeutic strategies based on the inhibition of these transcription factors.
Assuntos
Síndrome de Birt-Hogg-Dubé , Cistos , Neoplasias Renais , Humanos , Camundongos , Animais , Rim/patologia , Neoplasias Renais/genética , Neoplasias Renais/patologia , Síndrome de Birt-Hogg-Dubé/genética , Síndrome de Birt-Hogg-Dubé/patologia , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Fatores de Transcrição , Carcinogênese/genéticaRESUMO
The mechanistic target of rapamycin complex 1 (mTORC1) signaling hub integrates multiple environmental cues to modulate cell growth and metabolism. Over the past decade considerable knowledge has been gained on the mechanisms modulating mTORC1 lysosomal recruitment and activation. However, whether and how mTORC1 is able to elicit selective responses to diverse signals has remained elusive until recently. We discuss emerging evidence for a 'non-canonical' mTORC1 signaling pathway that controls the function of microphthalmia/transcription factor E (MiT-TFE) transcription factors, key regulators of cell metabolism. This signaling pathway is mediated by a specific mechanism of substrate recruitment, and responds to stimuli that appear to converge on the lysosomal surface. We discuss the relevance of this pathway in physiological and disease conditions.
Assuntos
Lisossomos , Transdução de Sinais , Humanos , Lisossomos/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis and insulin resistance and there are currently no approved drugs for its treatment. Hyperactivation of mTOR complex 1 (mTORC1) and subsequent impairment of the transcription factor EB (TFEB)-mediated autophagy-lysosomal pathway (ALP) are implicated in the development of NAFLD. Accordingly, agents that augment hepatic TFEB transcriptional activity may have therapeutic potential against NAFLD. The objective of this study was to investigate the effects of nuciferine, a major active component from lotus leaf, on NAFLD and its underlying mechanism of action. Here we show that nuciferine activated ALP and alleviated steatosis, insulin resistance in the livers of NAFLD mice and palmitic acid-challenged hepatocytes in a TFEB-dependent manner. Mechanistic investigation revealed that nuciferine interacts with the Ragulator subunit hepatitis B X-interacting protein and impairs the interaction of the Ragulator complex with Rag GTPases, thereby suppressing lysosomal localization and activity of mTORC1, which activates TFEB-mediated ALP and further ameliorates hepatic steatosis and insulin resistance. Our present results indicate that nuciferine may be a potential agent for treating NAFLD and that regulation of the mTORC1-TFEB-ALP axis could represent a novel pharmacological strategy to combat NAFLD.
RESUMO
The 7th Birt-Hogg-Dubé (BHD) International Symposium convened virtually in October 2021. The meeting attracted more than 200 participants internationally and highlighted recent findings in a variety of areas, including genetic insight and molecular understanding of BHD syndrome, structure and function of the tumor suppressor Folliculin (FLCN), therapeutic and clinical advances as well as patients' experiences living with this malady.
Assuntos
Síndrome de Birt-Hogg-Dubé , Síndrome de Birt-Hogg-Dubé/genética , HumanosRESUMO
Macro (Autophagy) is a catabolic process that relies on the cooperative function of two organelles: the lysosome and the autophagosome. The recent discovery of a transcriptional gene network that co-regulates the biogenesis and function of these two organelles, and the identification of transcription factors, miRNAs and epigenetic regulators of autophagy, demonstrated that this catabolic process is controlled by both transcriptional and post-transcriptional mechanisms. In this review article, we discuss the nuclear events that control autophagy, focusing particularly on the role of the MiT/TFE transcription factor family. In addition, we will discuss evidence suggesting that the transcriptional regulation of autophagy could be targeted for the treatment of human genetic diseases, such as lysosomal storage disorders (LSDs) and neurodegeneration.
RESUMO
Cancer cells have an increased demand for energy sources to support accelerated rates of growth. When nutrients become limiting, cancer cells may switch to nonconventional energy sources that are mobilized through nutrient scavenging pathways involving autophagy and the lysosome. Thus, several cancers are highly reliant on constitutive activation of these pathways to degrade and recycle cellular materials. Here, we focus on the MiT/TFE family of transcription factors, which control transcriptional programs for autophagy and lysosome biogenesis and have emerged as regulators of energy metabolism in cancer. These new findings complement earlier reports that chromosomal translocations and amplifications involving the MiT/TFE genes contribute to the etiology and pathophysiology of renal cell carcinoma, melanoma, and sarcoma, suggesting pleiotropic roles for these factors in a wider array of cancers. Understanding the interplay between the oncogenic and stress-adaptive roles of MiT/TFE factors could shed light on fundamental mechanisms of cellular homeostasis and point to new strategies for cancer treatment.
RESUMO
The lysosome is a catabolic organelle devoted to the degradation of cellular components, such as protein complexes and whole or portion of organelles that reach the lysosomes through (macro)autophagy. The lysosomes also function as signaling organelles by controlling the activity of key metabolic kinases, such as the mechanistic target of Rapamycin complex 1 (mTORC1). Lysosome dysfunction has dramatic consequences on cellular homeostasis and causes lysosomal storage disorders (LSDs). Here we review the recently proposed mechanisms by which impairment of lysosome/autophagy pathway affects extracellular matrix formation and skeletal development and growth. In particular, we will highlight the role of autophagy as a collagen quality control pathway in collagen-producing cells. An impairment of autophagy, such as the one observed in LSDs, leads to a collagen proteostatic defects and can explain, at least in part, the skeletal phenotypes characterizing patients with lysosomal storage disorders.
Assuntos
Colágeno/metabolismo , Matriz Extracelular/metabolismo , Doenças por Armazenamento dos Lisossomos/metabolismo , Animais , Autofagia , Humanos , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Fenótipo , ProteostaseRESUMO
During starvation the transcriptional activation of catabolic processes is induced by the nuclear translocation and consequent activation of transcription factor EB (TFEB), a master modulator of autophagy and lysosomal biogenesis. However, how TFEB is inactivated upon nutrient refeeding is currently unknown. Here we show that TFEB subcellular localization is dynamically controlled by its continuous shuttling between the cytosol and the nucleus, with the nuclear export representing a limiting step. TFEB nuclear export is mediated by CRM1 and is modulated by nutrient availability via mTOR-dependent hierarchical multisite phosphorylation of serines S142 and S138, which are localized in proximity of a nuclear export signal (NES). Our data on TFEB nucleo-cytoplasmic shuttling suggest an unpredicted role of mTOR in nuclear export.
Assuntos
Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Núcleo Celular/metabolismo , Serina-Treonina Quinases TOR/metabolismo , Sequência de Aminoácidos , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/química , Citosol/metabolismo , Células HEK293 , Células HeLa , Humanos , Carioferinas , Cinética , Fosforilação , Transporte Proteico , Receptores Citoplasmáticos e Nucleares , Proteína Exportina 1RESUMO
Human anti-ErbB2 immunoRNase with Erbicin fused to HP-RNase (ERB-hRNase) is a fully human immunoRNase made up of human pancreatic RNase fused to a human anti-ErbB2 scFv. It binds selectively with high affinity to ErbB2-positive cells, and specifically inhibits their proliferation, in vitro and in vivo. An investigation of its mechanism of action and its intracellular destination has revealed that ERB-hRNase depends on its RNase activity for cytotoxic action; it reaches the cytosol directly from the endosomal compartment; it is inhibited by the cytosolic RNase inhibitor (cRI), but the levels that ERB-hRNase reaches in the cytosol neutralize cRI, thus inducing cell death by apoptosis.
Assuntos
Antineoplásicos/farmacologia , Imunotoxinas/farmacologia , Receptor ErbB-2/antagonistas & inibidores , Proteínas Recombinantes de Fusão/farmacologia , Ribonucleases/farmacologia , Antineoplásicos/análise , Antineoplásicos/antagonistas & inibidores , Apoptose , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Citosol/enzimologia , Inibidores Enzimáticos , Humanos , Imunotoxinas/análise , RNA/efeitos dos fármacos , RNA/metabolismo , Proteínas Recombinantes de Fusão/análise , Proteínas Recombinantes de Fusão/antagonistas & inibidores , Ribonucleases/análise , Ribonucleases/antagonistas & inibidoresRESUMO
The mechanistic target of rapamycin complex 1 (mTORC1) is recruited to the lysosome by Rag guanosine triphosphatases (GTPases) and regulates anabolic pathways in response to nutrients. We found that MiT/TFE transcription factors-master regulators of lysosomal and melanosomal biogenesis and autophagy-control mTORC1 lysosomal recruitment and activity by directly regulating the expression of RagD. In mice, this mechanism mediated adaptation to food availability after starvation and physical exercise and played an important role in cancer growth. Up-regulation of MiT/TFE genes in cells and tissues from patients and murine models of renal cell carcinoma, pancreatic ductal adenocarcinoma, and melanoma triggered RagD-mediated mTORC1 induction, resulting in cell hyperproliferation and cancer growth. Thus, this transcriptional regulatory mechanism enables cellular adaptation to nutrient availability and supports the energy-demanding metabolism of cancer cells.
Assuntos
Retroalimentação Fisiológica/fisiologia , Regulação Neoplásica da Expressão Gênica , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Neoplasias/fisiopatologia , Animais , Restrição Calórica , Linhagem Celular Tumoral , Proliferação de Células/genética , Células Cultivadas , Células HEK293 , Células HeLa , Células Hep G2 , Humanos , Fígado/enzimologia , Fígado/fisiopatologia , Masculino , Alvo Mecanístico do Complexo 1 de Rapamicina/genética , Camundongos , Camundongos Endogâmicos C57BL , Neoplasias/enzimologia , Transdução de SinaisRESUMO
Sulfatases are key enzymatic regulators of sulfate homeostasis with several biological functions including degradation of glycosaminoglycans (GAGs) and other macromolecules in lysosomes. In a severe lysosomal storage disorder, multiple sulfatase deficiency (MSD), global sulfatase activity is deficient due to mutations in the sulfatase-modifying factor 1 (SUMF1) gene, encoding the essential activator of all sulfatases. We identify a novel regulatory layer of sulfate metabolism mediated by a microRNA. miR-95 depletes SUMF1 protein levels and suppresses sulfatase activity, causing the disruption of proteoglycan catabolism and lysosomal function. This blocks autophagy-mediated degradation, causing cytoplasmic accumulation of autophagosomes and autophagic substrates. By targeting miR-95 in cells from MSD patients, we can effectively increase residual SUMF1 expression, allowing for reactivation of sulfatase activity and increased clearance of sulfated GAGs. The identification of this regulatory mechanism opens the opportunity for a unique therapeutic approach in MSD patients where the need for exogenous enzyme replacement is circumvented.