RESUMEN
Schwann cells respond to acute axon damage by transiently transdifferentiating into specialized repair cells that restore sensorimotor function. However, the molecular systems controlling repair cell formation and function are not well defined, and consequently, it is unclear whether this form of cellular plasticity has a role in peripheral neuropathies. Here, we identify Mitf as a transcriptional sensor of axon damage under the control of Nrg-ErbB-PI3K-PI5K-mTorc2 signaling. Mitf regulates a core transcriptional program for generating functional repair Schwann cells following injury and during peripheral neuropathies caused by CMT4J and CMT4D. In the absence of Mitf, core genes for epithelial-to-mesenchymal transition, metabolism, and dedifferentiation are misexpressed, and nerve repair is disrupted. Our findings demonstrate that Schwann cells monitor axonal health using a phosphoinositide signaling system that controls Mitf nuclear localization, which is critical for activating cellular plasticity and counteracting neural disease.
Asunto(s)
Traumatismos de los Nervios Periféricos , Enfermedades del Sistema Nervioso Periférico , Humanos , Enfermedades del Sistema Nervioso Periférico/metabolismo , Células de Schwann/metabolismo , Axones/metabolismo , Transducción de Señal/fisiología , Plasticidad de la Célula , Regeneración Nerviosa/fisiología , Traumatismos de los Nervios Periféricos/genética , Traumatismos de los Nervios Periféricos/metabolismo , Nervio Ciático/metabolismoRESUMEN
Growing evidence suggests that many essential intracellular signaling events are compartmentalized within kinetically distinct microdomains in cells. Genetically encoded fluorescent biosensors are powerful tools to dissect compartmentalized signaling, but current approaches to probe these microdomains typically rely on biosensor fusion and overexpression of critical regulatory elements. Here, we present a novel class of biosensors named FluoSTEPs (fluorescent sensors targeted to endogenous proteins) that combine self-complementing split green fluorescent protein, CRISPR-mediated knock-in, and fluorescence resonance energy transfer biosensor technology to probe compartmentalized signaling dynamics in situ. We designed FluoSTEPs for simultaneously highlighting endogenous microdomains and reporting domain-specific, real-time signaling events including kinase activities, guanosine triphosphatase activation, and second messenger dynamics in live cells. A FluoSTEP for 3',5'-cyclic adenosine monophosphate (cAMP) revealed distinct cAMP dynamics within clathrin microdomains in response to stimulation of G protein-coupled receptors, showcasing the utility of FluoSTEPs in probing spatiotemporal regulation within endogenous signaling architectures.
Asunto(s)
Técnicas Biosensibles , AMP Cíclico , Colorantes , AMP Cíclico/metabolismo , Transferencia Resonante de Energía de Fluorescencia , Proteínas Fluorescentes Verdes/genética , Transducción de SeñalRESUMEN
G-protein-coupled receptor-regulated cAMP production from endosomes can specify signaling to the nucleus by moving the source of cAMP without changing its overall amount. How this is possible remains unknown because cAMP gradients dissipate over the nanoscale, whereas endosomes typically localize micrometers from the nucleus. We show that the key location-dependent step for endosome-encoded transcriptional control is nuclear entry of cAMP-dependent protein kinase (PKA) catalytic subunits. These are sourced from punctate accumulations of PKA holoenzyme that are densely distributed in the cytoplasm and titrated by global cAMP into a discrete metastable state, in which catalytic subunits are bound but dynamically exchange. Mobile endosomes containing activated receptors collide with the metastable PKA puncta and pause in close contact. We propose that these properties enable cytoplasmic PKA to act collectively like a semiconductor, converting nanoscale cAMP gradients generated from endosomes into microscale elevations of free catalytic subunits to direct downstream signaling.
Asunto(s)
Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Citoplasma/metabolismo , Endosomas/metabolismo , Receptores Adrenérgicos beta 2/metabolismo , Transducción de Señal/genética , Animales , Dominio Catalítico , Núcleo Celular/metabolismo , Núcleo Celular/ultraestructura , Cadenas Pesadas de Clatrina/antagonistas & inhibidores , Cadenas Pesadas de Clatrina/genética , Cadenas Pesadas de Clatrina/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/genética , Citoplasma/ultraestructura , Dinamina I/genética , Dinamina I/metabolismo , Endosomas/ultraestructura , Regulación de la Expresión Génica , Genes Reporteros , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Células HEK293 , Holoenzimas/genética , Holoenzimas/metabolismo , Humanos , Luciferasas/genética , Luciferasas/metabolismo , Unión Proteica , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Ratas , Receptores Adrenérgicos beta 2/genéticaRESUMEN
We designed an epi-illumination SPIM system that uses a single objective and has a sample interface identical to that of an inverted fluorescence microscope with no additional reflection elements. It achieves subcellular resolution and single-molecule sensitivity, and is compatible with common biological sample holders, including multi-well plates. We demonstrated multicolor fast volumetric imaging, single-molecule localization microscopy, parallel imaging of 16 cell lines and parallel recording of cellular responses to perturbations.
Asunto(s)
Drosophila/metabolismo , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional/métodos , Iluminación/instrumentación , Microscopía Fluorescente/métodos , Imagen Molecular/métodos , Análisis de la Célula Individual/métodos , Animales , Células HEK293 , Humanos , Análisis Espacio-TemporalRESUMEN
Self-complementing split fluorescent proteins (FPs) have been widely used for protein labeling, visualization of subcellular protein localization, and detection of cell-cell contact. To expand this toolset, we have developed a screening strategy for the direct engineering of self-complementing split FPs. Via this strategy, we have generated a yellow-green split-mNeonGreen21-10/11 that improves the ratio of complemented signal to the background of FP1-10-expressing cells compared to the commonly used split GFP1-10/11; as well as a 10-fold brighter red-colored split-sfCherry21-10/11. Based on split sfCherry2, we have engineered a photoactivatable variant that enables single-molecule localization-based super-resolution microscopy. We have demonstrated dual-color endogenous protein tagging with sfCherry211 and GFP11, revealing that endoplasmic reticulum translocon complex Sec61B has reduced abundance in certain peripheral tubules. These new split FPs not only offer multiple colors for imaging interaction networks of endogenous proteins, but also hold the potential to provide orthogonal handles for biochemical isolation of native protein complexes.Split fluorescent proteins (FPs) have been widely used to visualise proteins in cells. Here the authors develop a screen for engineering new split FPs, and report a yellow-green split-mNeonGreen2 with reduced background, a red split-sfCherry2 for multicolour labeling, and its photoactivatable variant for super-resolution use.
Asunto(s)
Proteínas Luminiscentes/química , Microscopía Fluorescente/métodos , Ingeniería de Proteínas , Canales de Translocación SEC/análisis , Retículo Endoplásmico/metabolismo , Células HEK293 , Humanos , Transporte de Proteínas , Canales de Translocación SEC/química , Canales de Translocación SEC/genéticaRESUMEN
Labeling proteins with high specificity and efficiency is a fundamental prerequisite for microscopic visualization of subcellular protein structures and interactions. Although the comparatively small size of epitope tags makes them less perturbative to fusion proteins, they require the use of large antibodies that often limit probe accessibility and effective resolution. Here we use the covalent SpyTag-SpyCatcher system as an epitope-like tag for fluorescent labeling of intracellular proteins in fixed cells for both conventional and super-resolution microscopy. We also applied this method to endogenous proteins by gene editing, demonstrating its high labeling efficiency and capability for isoform-specific labeling.
Asunto(s)
Adhesinas Bacterianas/química , Proteínas Portadoras/química , Fragmentos de Péptidos/química , Péptidos/química , Actinas/química , Adhesinas Bacterianas/metabolismo , Carbocianinas/química , Proteínas Portadoras/metabolismo , Cadenas Ligeras de Clatrina/química , Cadenas Ligeras de Clatrina/metabolismo , Invaginaciones Cubiertas de la Membrana Celular/metabolismo , Colorantes Fluorescentes , Edición Génica , Células HeLa , Humanos , Queratinas/química , Microscopía Fluorescente , Fragmentos de Péptidos/metabolismo , Canales de Translocación SEC/química , Canales de Translocación SEC/metabolismo , Proteínas de Unión al GTP rab/química , Proteínas de Unión al GTP rab/metabolismoRESUMEN
G-protein-coupled receptors (GPCRs) are increasingly recognized to operate from intracellular membranes as well as the plasma membrane. The ß2-adrenergic GPCR can activate Gs-linked cyclic AMP (Gs-cAMP) signaling from endosomes. We show here that the homologous human ß1-adrenergic receptor initiates an internal Gs-cAMP signal from the Golgi apparatus. By developing a chemical method to acutely squelch G-protein coupling at defined membrane locations, we demonstrate that Golgi activation contributes significantly to the overall cellular cAMP response. Golgi signaling utilizes a preexisting receptor pool rather than receptors delivered from the cell surface, requiring separate access of extracellular ligands. Epinephrine, a hydrophilic endogenous ligand, accesses the Golgi-localized receptor pool by facilitated transport requiring the organic cation transporter 3 (OCT3), whereas drugs can access the Golgi pool by passive diffusion according to hydrophobicity. We demonstrate marked differences, among both agonist and antagonist drugs, in Golgi-localized receptor access and show that ß-blocker drugs currently used in the clinic differ markedly in ability to antagonize the Golgi signal. We propose 'location bias' as a new principle for achieving functional selectivity of GPCR-directed drug action.
Asunto(s)
Antagonistas Adrenérgicos beta/farmacología , Dobutamina/farmacología , Epinefrina/farmacología , Receptores Adrenérgicos beta 1/metabolismo , Antagonistas Adrenérgicos beta/química , Dobutamina/química , Epinefrina/química , Aparato de Golgi/efectos de los fármacos , Aparato de Golgi/metabolismo , Células HeLa , Humanos , Ligandos , Relación Estructura-ActividadRESUMEN
Quorum sensing (QS) is a bacterial communication mechanism in which secreted signaling molecules impact population function and gene expression. QS-like phenomena have been reported in eukaryotes with largely unknown contributing molecules, functions, and mechanisms. We identify Qsp1, a secreted peptide, as a central signaling molecule that regulates virulence in the fungal pathogen Cryptococcus neoformans. QSP1 is a direct target of three transcription factors required for virulence, and qsp1Δ mutants exhibit attenuated infection, slowed tissue accumulation, and greater control by primary macrophages. Qsp1 mediates autoregulatory signaling that modulates secreted protease activity and promotes cell wall function at high cell densities. Peptide production requires release from a secreted precursor, proQsp1, by a cell-associated protease, Pqp1. Qsp1 sensing requires an oligopeptide transporter, Opt1, and remarkably, cytoplasmic expression of mature Qsp1 complements multiple phenotypes of qsp1Δ. Thus, C. neoformans produces an autoregulatory peptide that matures extracellularly but functions intracellularly to regulate virulence.
Asunto(s)
Criptococosis/microbiología , Cryptococcus neoformans/metabolismo , Cryptococcus neoformans/patogenicidad , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Factores de Virulencia/metabolismo , Animales , Pared Celular/fisiología , Criptococosis/metabolismo , Cryptococcus neoformans/genética , Modelos Animales de Enfermedad , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Péptidos y Proteínas de Señalización Intercelular/genética , Macrófagos/metabolismo , Melaninas/metabolismo , Proteínas de Transporte de Membrana/genética , Meningitis/microbiología , Ratones , Ratones Endogámicos C57BL , Mutación , Péptido Hidrolasas/metabolismo , Percepción de Quorum , Conejos , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Factores de Virulencia/genéticaRESUMEN
We tested the hypothesis that mutant tau proteins that cause neurodegeneration and dementia differentially alter kinesin translocation along microtubules (MTs) relative to normal tau in vitro. We employed complementary in vitro motility assays using purified recombinant kinesin, purified recombinant tau, and purified bovine brain α:ß tubulin to isolate interactions among these components without any contribution by cellular regulatory mechanisms. We found that kinesin translocates slower along MTs assembled by any of three independent tau mutants (4-repeat P301L tau, 4-repeat ΔN296 tau, and 4-repeat R406W tau) relative to its translocation rate along MTs assembled by normal, 4-repeat wild type (WT) tau. Moreover, the R406W mutation exhibited isoform specific effects; while kinesin translocation along 4-repeat R406W tau assembled MTs is slower than along MTs assembled by 4-repeat WT tau, the R406W mutation had no effect in the 3-repeat tau context. These data provide strong support for the notion that aberrant modulation of kinesin translocation is a component of tau-mediated neuronal cell death and dementia. Finally, we showed that assembling MTs with taxol before coating them with mutant tau obscured effects of the mutant tau that were readily apparent using more physiologically relevant MTs assembled with tau alone, raising important issues regarding the use of taxol as an experimental reagent and novel insights into therapeutic mechanisms of taxol action.
Asunto(s)
Encéfalo/metabolismo , Cinesinas/metabolismo , Microtúbulos/metabolismo , Mutación , Proteínas tau/genética , Proteínas tau/metabolismo , Animales , Encéfalo/efectos de los fármacos , Bovinos , Humanos , Microtúbulos/efectos de los fármacos , Enfermedades Neurodegenerativas/genética , Paclitaxel/farmacología , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Puntos Cuánticos , Tubulina (Proteína)/metabolismo , Moduladores de Tubulina/farmacologíaRESUMEN
Using a suite of biophysical tools, we assess the mechanical, structural, and functional properties of microtubules (MTs) stabilized by the chemotherapeutic compounds epothilone-A, epothilone-B, and taxol in vitro. We demonstrate that MTs stabilized by epothilone-A or epothilone-B are competent to bind tau proteins and support kinesin translocation. Kinesin speed is sensitive not only to the type of small molecule stabilizer used but also to the presence of the essential MT-associated protein tau. Epothilone-stabilized MTs are substantially less stiff than taxol-stabilized MTs. The addition of tau proteins to MTs stabilized by either epothilone compound or taxol further reduces stiffness. Taken together, these results suggest that small molecule stabilizers do not simply stabilize a "native" MT structure, but rather they modulate the structure, function, and mechanics of the MTs they bind. This may have important consequences to the therapeutic use of these agents in cancer chemotherapies.