RESUMEN
Mechanosensation is the ability to detect dynamic mechanical stimuli (e.g., pressure, stretch, and shear stress) and is essential for a wide variety of processes, including our sense of touch on the skin. How touch is detected and transduced at the molecular level has proved to be one of the great mysteries of sensory biology. A major breakthrough occurred in 2010 with the discovery of a family of mechanically gated ion channels that were coined PIEZOs. The last 10 years of investigation have provided a wealth of information about the functional roles and mechanisms of these molecules. Here we focus on PIEZO2, one of the two PIEZO proteins found in humans and other mammals. We review how work at the molecular, cellular, and systems levels over the past decade has transformed our understanding of touch and led to unexpected insights into other types of mechanosensation beyond the skin.
Asunto(s)
Descubrimiento de Drogas/métodos , Canales Iónicos/química , Canales Iónicos/fisiología , Mecanotransducción Celular/fisiología , Animales , Barorreflejo/fisiología , Humanos , Canales Iónicos/genética , Canales Iónicos/metabolismo , Ratones , Propiocepción/fisiología , Células Madre/fisiología , TactoRESUMEN
Piezo1 is a stretch-gated ion channel required for mechanosensation in many organ systems. Recent findings point to a new role for Piezo1 in the gut, suggesting that it is a sensor of microbial single-stranded RNA (ssRNA) rather than mechanical force. If true, this would redefine the scope of Piezo biology. Here, we sought to replicate the central finding that fecal ssRNA is a natural agonist of Piezo1. While we observe that fecal extracts and ssRNA can stimulate calcium influx in certain cell lines, this response is independent of Piezo1. Additionally, sterilized dietary extracts devoid of gut biome RNA show similar cell line-specific stimulatory activity to fecal extracts. Together, our data highlight potential confounds inherent to gut-derived extracts, exclude Piezo1 as a receptor for ssRNA in the gut, and support a dedicated role for Piezo channels in mechanosensing.
Asunto(s)
Canales Iónicos , ARN , Canales Iónicos/metabolismo , Calcio/metabolismo , Línea Celular , Fenómenos Mecánicos , Mecanotransducción Celular/fisiologíaRESUMEN
Amyotrophic lateral sclerosis (ALS) is a progressive, neurodegenerative disease of the lower and upper motor neurons with sporadic or hereditary occurrence. Age of onset, pattern of motor neuron degeneration and disease progression vary widely among individuals with ALS. Various cellular processes may drive ALS pathomechanisms, but a monogenic direct metabolic disturbance has not been causally linked to ALS. Here we show SPTLC1 variants that result in unrestrained sphingoid base synthesis cause a monogenic form of ALS. We identified four specific, dominantly acting SPTLC1 variants in seven families manifesting as childhood-onset ALS. These variants disrupt the normal homeostatic regulation of serine palmitoyltransferase (SPT) by ORMDL proteins, resulting in unregulated SPT activity and elevated levels of canonical SPT products. Notably, this is in contrast with SPTLC1 variants that shift SPT amino acid usage from serine to alanine, result in elevated levels of deoxysphingolipids and manifest with the alternate phenotype of hereditary sensory and autonomic neuropathy. We custom designed small interfering RNAs that selectively target the SPTLC1 ALS allele for degradation, leave the normal allele intact and normalize sphingolipid levels in vitro. The role of primary metabolic disturbances in ALS has been elusive; this study defines excess sphingolipid biosynthesis as a fundamental metabolic mechanism for motor neuron disease.
Asunto(s)
Esclerosis Amiotrófica Lateral/metabolismo , Esfingolípidos/biosíntesis , Adolescente , Adulto , Alelos , Secuencia de Aminoácidos , Esclerosis Amiotrófica Lateral/enzimología , Esclerosis Amiotrófica Lateral/genética , Sistemas CRISPR-Cas , Niño , Femenino , Genes Dominantes , Células HEK293 , Humanos , Masculino , Persona de Mediana Edad , Mutación , Serina C-Palmitoiltransferasa/genética , Serina C-Palmitoiltransferasa/metabolismo , Adulto JovenRESUMEN
The basal lamina is a specialized sheet of dense extracellular matrix (ECM) linked to the plasma membrane of specific cell types in their tissue context, which serves as a structural scaffold for organ genesis and maintenance. Disruption of the basal lamina and its functions is central to many disease processes, including cancer metastasis, kidney disease, eye disease, muscular dystrophies and specific types of brain malformation. The latter three pathologies occur in the α-dystroglycanopathies, which are caused by dysfunction of the ECM receptor α-dystroglycan. However, opportunities to study the basal lamina in various human disease tissues are restricted owing to its limited accessibility. Here, we report the generation of embryoid bodies from human induced pluripotent stem cells that model the basal lamina. Embryoid bodies cultured via this protocol mimic pre-gastrulation embryonic development, consisting of an epithelial core surrounded by a basal lamina and a peripheral layer of ECM-secreting endoderm. In α-dystroglycanopathy patient embryoid bodies, electron and fluorescence microscopy reveal ultrastructural basal lamina defects and reduced ECM accumulation. By starting from patient-derived cells, these results establish a method for the in vitro synthesis of patient-specific basal lamina and recapitulate disease-relevant ECM defects seen in the α-dystroglycanopathies. Finally, we apply this system to evaluate an experimental ribitol supplement therapy on genetically diverse α-dystroglycanopathy patient samples.This article has an associated First Person interview with the first author of the paper.
Asunto(s)
Membrana Basal/metabolismo , Cuerpos Embrioides/metabolismo , Matriz Extracelular/metabolismo , Células Madre Embrionarias Humanas/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Síndrome de Walker-Warburg/metabolismo , Membrana Basal/efectos de los fármacos , Membrana Basal/ultraestructura , Estudios de Casos y Controles , Técnicas de Cultivo de Célula , Células Cultivadas , Niño , Preescolar , Distroglicanos/genética , Distroglicanos/metabolismo , Cuerpos Embrioides/efectos de los fármacos , Cuerpos Embrioides/ultraestructura , Matriz Extracelular/efectos de los fármacos , Matriz Extracelular/ultraestructura , Femenino , Regulación del Desarrollo de la Expresión Génica , Células Madre Embrionarias Humanas/efectos de los fármacos , Células Madre Embrionarias Humanas/ultraestructura , Humanos , Células Madre Pluripotentes Inducidas/efectos de los fármacos , Células Madre Pluripotentes Inducidas/ultraestructura , Recién Nacido , Masculino , Persona de Mediana Edad , Ribitol/farmacología , Síndrome de Walker-Warburg/tratamiento farmacológico , Síndrome de Walker-Warburg/genética , Síndrome de Walker-Warburg/patologíaRESUMEN
PIEZO2 is the essential transduction channel for touch discrimination, vibration, and proprioception. Mice and humans lacking Piezo2 experience severe mechanosensory and proprioceptive deficits and fail to develop tactile allodynia. Bradykinin, a proalgesic agent released during inflammation, potentiates PIEZO2 activity. Molecules that decrease PIEZO2 function could reduce heightened touch responses during inflammation. Here, we find that the dietary fatty acid margaric acid (MA) decreases PIEZO2 function in a dose-dependent manner. Chimera analyses demonstrate that the PIEZO2 beam is a key region tuning MA-mediated channel inhibition. MA reduces neuronal action potential firing elicited by mechanical stimuli in mice and rat neurons and counteracts PIEZO2 sensitization by bradykinin. Finally, we demonstrate that this saturated fatty acid decreases PIEZO2 currents in touch neurons derived from human induced pluripotent stem cells. Our findings report on a natural product that inhibits PIEZO2 function and counteracts neuronal mechanical sensitization and reveal a key region for channel inhibition.
Asunto(s)
Ácidos Grasos/administración & dosificación , Canales Iónicos/antagonistas & inhibidores , Mecanotransducción Celular/efectos de los fármacos , Neuronas/efectos de los fármacos , Propiocepción/efectos de los fármacos , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Algoritmos , Animales , Células Cultivadas , Humanos , Células Madre Pluripotentes Inducidas/efectos de los fármacos , Células Madre Pluripotentes Inducidas/metabolismo , Células Madre Pluripotentes Inducidas/fisiología , Canales Iónicos/genética , Canales Iónicos/metabolismo , Mecanotransducción Celular/genética , Mecanotransducción Celular/fisiología , Ratones Endogámicos C57BL , Ratones Noqueados , Neuronas/metabolismo , Neuronas/fisiología , Propiocepción/genética , Propiocepción/fisiología , Ratas , Tacto/efectos de los fármacos , Tacto/fisiologíaRESUMEN
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
RESUMEN
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disorder caused by a polyglutamine expansion in the androgen receptor (AR). Using gene expression analysis and ChIP sequencing, we mapped transcriptional changes in genetically engineered patient stem cell-derived motor neurons. We found that transcriptional dysregulation in SBMA can occur through AR-mediated histone modification. We detected reduced histone acetylation, along with decreased expression of genes encoding compensatory metabolic proteins and reduced substrate availability for mitochondrial function. Furthermore, we found that pyruvate supplementation corrected this deficiency and improved mitochondrial function and SBMA motor neuron viability. We propose that epigenetic dysregulation of metabolic genes contributes to reduced mitochondrial ATP production. Our results show a molecular link between altered epigenetic regulation and mitochondrial metabolism that contributes to neurodegeneration.
Asunto(s)
Epigénesis Genética/fisiología , Mitocondrias/metabolismo , Neuronas Motoras/metabolismo , Atrofia Muscular Espinal/fisiopatología , Humanos , Atrofia Muscular Espinal/metabolismo , Péptidos/metabolismo , Receptores Androgénicos/metabolismoRESUMEN
Efficient and homogeneous in vitro generation of peripheral sensory neurons may provide a framework for novel drug screening platforms and disease models of touch and pain. We discover that, by overexpressing NGN2 and BRN3A, human pluripotent stem cells can be transcriptionally programmed to differentiate into a surprisingly uniform culture of cold- and mechano-sensing neurons. Although such a neuronal subtype is not found in mice, we identify molecular evidence for its existence in human sensory ganglia. Combining NGN2 and BRN3A programming with neural crest patterning, we produce two additional populations of sensory neurons, including a specialized touch receptor neuron subtype. Finally, we apply this system to model a rare inherited sensory disorder of touch and proprioception caused by inactivating mutations in PIEZO2. Together, these findings establish an approach to specify distinct sensory neuron subtypes in vitro, underscoring the utility of stem cell technology to capture human-specific features of physiology and disease.
Asunto(s)
Células Madre Pluripotentes Inducidas/citología , Mecanotransducción Celular , Células Receptoras Sensoriales/citología , Transcripción Genética , Animales , Calcio/metabolismo , Línea Celular , Reprogramación Celular , Frío , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Humanos , Activación del Canal Iónico , Canales Iónicos/metabolismo , Ratones , Proteínas del Tejido Nervioso/metabolismo , Cresta Neural/citología , Cresta Neural/metabolismo , Fenotipo , Propiocepción/fisiología , Células Receptoras Sensoriales/metabolismo , Canales Catiónicos TRPM/metabolismo , Tacto/fisiología , Factor de Transcripción Brn-3A/metabolismoRESUMEN
Dystroglycan is a cell membrane protein that binds to the extracellular matrix in a variety of mammalian tissues. The α-subunit of dystroglycan (αDG) is heavily glycosylated, including a special O-mannosyl glycoepitope, relying upon this unique glycosylation to bind its matrix ligands. A distinct group of muscular dystrophies results from specific hypoglycosylation of αDG, and they are frequently associated with central nervous system involvement, ranging from profound brain malformation to intellectual disability without evident morphological defects. There is an expanding literature addressing the function of αDG in the nervous system, with recent reports demonstrating important roles in brain development and in the maintenance of neuronal synapses. Much of these data are derived from an increasingly rich array of experimental animal models. This Review aims to synthesize the information from such diverse models, formulating an up-to-date understanding about the various functions of αDG in neurons and glia of the central and peripheral nervous systems. Where possible, we integrate these data with our knowledge of the human disorders to promote translation from basic mechanistic findings to clinical therapies that take the neural phenotypes into account.