RESUMEN
Cytoplasmic accumulation of TDP-43 is a disease hallmark for many cases of amyotrophic lateral sclerosis (ALS), associated with a neuroinflammatory cytokine profile related to upregulation of nuclear factor κB (NF-κB) and type I interferon (IFN) pathways. Here we show that this inflammation is driven by the cytoplasmic DNA sensor cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS) when TDP-43 invades mitochondria and releases DNA via the permeability transition pore. Pharmacologic inhibition or genetic deletion of cGAS and its downstream signaling partner STING prevents upregulation of NF-κB and type I IFN induced by TDP-43 in induced pluripotent stem cell (iPSC)-derived motor neurons and in TDP-43 mutant mice. Finally, we document elevated levels of the specific cGAS signaling metabolite cGAMP in spinal cord samples from patients, which may be a biomarker of mtDNA release and cGAS/STING activation in ALS. Our results identify mtDNA release and cGAS/STING activation as critical determinants of TDP-43-associated pathology and demonstrate the potential for targeting this pathway in ALS.
Asunto(s)
Esclerosis Amiotrófica Lateral/metabolismo , ADN Mitocondrial/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas de la Membrana/metabolismo , Poro de Transición de la Permeabilidad Mitocondrial/metabolismo , Nucleotidiltransferasas/metabolismo , Alarminas/metabolismo , Esclerosis Amiotrófica Lateral/patología , Animales , Citoplasma/metabolismo , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Células HEK293 , Humanos , Células Madre Pluripotentes Inducidas/metabolismo , Inflamación/metabolismo , Interferón Tipo I/metabolismo , Ratones , Ratones Endogámicos C57BL , Mitocondrias/metabolismo , FN-kappa B/metabolismo , Degeneración Nerviosa/patología , Fosfotransferasas (Aceptor de Grupo Alcohol) , Subunidades de Proteína/metabolismo , Transducción de SeñalRESUMEN
Mutations in the protein kinase PINK1 lead to defects in mitophagy and cause autosomal recessive early onset Parkinson's disease1,2. PINK1 has many unique features that enable it to phosphorylate ubiquitin and the ubiquitin-like domain of Parkin3-9. Structural analysis of PINK1 from diverse insect species10-12 with and without ubiquitin provided snapshots of distinct structural states yet did not explain how PINK1 is activated. Here we elucidate the activation mechanism of PINK1 using crystallography and cryo-electron microscopy (cryo-EM). A crystal structure of unphosphorylated Pediculus humanus corporis (Ph; human body louse) PINK1 resolves an N-terminal helix, revealing the orientation of unphosphorylated yet active PINK1 on the mitochondria. We further provide a cryo-EM structure of a symmetric PhPINK1 dimer trapped during the process of trans-autophosphorylation, as well as a cryo-EM structure of phosphorylated PhPINK1 undergoing a conformational change to an active ubiquitin kinase state. Structures and phosphorylation studies further identify a role for regulatory PINK1 oxidation. Together, our research delineates the complete activation mechanism of PINK1, illuminates how PINK1 interacts with the mitochondrial outer membrane and reveals how PINK1 activity may be modulated by mitochondrial reactive oxygen species.
Asunto(s)
Proteínas de Insectos , Pediculus , Proteínas Quinasas , Animales , Microscopía por Crioelectrón , Proteínas de Insectos/metabolismo , Mitocondrias , Mitofagia , Fosforilación , Conformación Proteica , Proteínas Quinasas/metabolismo , Ubiquitina/metabolismoRESUMEN
A fluorescent emitter simultaneously transmits its identity, location, and cellular context through its emission pattern. We developed smNet, a deep neural network for multiplexed single-molecule analysis to retrieve such information with high accuracy. We demonstrate that smNet can extract three-dimensional molecule location, orientation, and wavefront distortion with precision approaching the theoretical limit, and therefore will allow multiplexed measurements through the emission pattern of a single molecule.
Asunto(s)
Aprendizaje Profundo , Microscopía Fluorescente/métodos , Mitocondrias/metabolismo , Proteínas Mitocondriales/análisis , Redes Neurales de la Computación , Análisis de la Célula Individual/métodos , Animales , Células COS , Chlorocebus aethiops , Proteínas Mitocondriales/metabolismoRESUMEN
Application of single-molecule switching nanoscopy (SMSN) beyond the coverslip surface poses substantial challenges due to sample-induced aberrations that distort and blur single-molecule emission patterns. We combined active shaping of point spread functions and efficient adaptive optics to enable robust 3D-SMSN imaging within tissues. This development allowed us to image through 30-µm-thick brain sections to visualize and reconstruct the morphology and the nanoscale details of amyloid-ß filaments in a mouse model of Alzheimer's disease.
Asunto(s)
Encéfalo/anatomía & histología , Encéfalo/metabolismo , Imagen Individual de Molécula/métodos , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/genética , Animales , Modelos Animales de Enfermedad , Femenino , Imagenología Tridimensional/métodos , Masculino , Glicoproteínas de Membrana/deficiencia , Glicoproteínas de Membrana/genética , Ratones , Ratones Noqueados , Ratones Mutantes , Fenómenos Ópticos , Placa Amiloide/metabolismo , Placa Amiloide/patología , Presenilina-1/genética , Receptores Inmunológicos/deficiencia , Receptores Inmunológicos/genéticaRESUMEN
The lipid phosphatidylinositol 4,5-bisphosphate (PIP2) forms nanoscopic clusters in cell plasma membranes; however, the processes determining PIP2 mobility and thus its spatial patterns are not fully understood. Using super-resolution imaging of living cells, we find that PIP2 is tightly colocalized with and modulated by overexpression of the influenza viral protein hemagglutinin (HA). Within and near clusters, HA and PIP2 follow a similar spatial dependence, which can be described by an HA-dependent potential gradient; PIP2 molecules move as if they are attracted to the center of clusters by a radial force of 0.079 ± 0.002 pN in HAb2 cells. The measured clustering and dynamics of PIP2 are inconsistent with the unmodified forms of the raft, tether, and fence models. Rather, we found that the spatial PIP2 distributions and how they change in time are explained via a novel, to our knowledge, dynamic mechanism: a radial gradient of PIP2 binding sites that are themselves mobile. This model may be useful for understanding other biological membrane domains whose distributions display gradients in density while maintaining their mobility.
Asunto(s)
Membrana Celular/química , Membrana Celular/metabolismo , Colorantes Fluorescentes/metabolismo , Hemaglutininas Virales/metabolismo , Orthomyxoviridae , Fosfatidilinositol 4,5-Difosfato/metabolismo , Animales , Supervivencia Celular , Ratones , Modelos Biológicos , Células 3T3 NIHRESUMEN
Methods based on single-molecule localization and photophysics have brought nanoscale imaging with visible light into reach. This has enabled single-particle tracking applications for studying the dynamics of molecules and nanoparticles and contributed to the recent revolution in super-resolution localization microscopy techniques. Crucial to the optimization of such methods are the precision and accuracy with which single fluorophores and nanoparticles can be localized. We present a lucid synthesis of the developments on this localization precision and accuracy and their practical implications in order to guide the increasing number of researchers using single-particle tracking and super-resolution localization microscopy.
Asunto(s)
Colorantes Fluorescentes/química , Microscopía Fluorescente/métodos , Microscopía Fluorescente/normas , Reproducibilidad de los ResultadosRESUMEN
Biological membrane organization mediates numerous cellular functions and has also been connected with an immense number of human diseases. However, until recently, experimental methodologies have been unable to directly visualize the nanoscale details of biological membranes, particularly in intact living cells. Numerous models explaining membrane organization have been proposed, but testing those models has required indirect methods; the desire to directly image proteins and lipids in living cell membranes is a strong motivation for the advancement of technology. The development of super-resolution microscopy has provided powerful tools for quantification of membrane organization at the level of individual proteins and lipids, and many of these tools are compatible with living cells. Previously inaccessible questions are now being addressed, and the field of membrane biology is developing rapidly. This chapter discusses how the development of super-resolution microscopy has led to fundamental advances in the field of biological membrane organization. We summarize the history and some models explaining how proteins are organized in cell membranes, and give an overview of various super-resolution techniques and methods of quantifying super-resolution data. We discuss the application of super-resolution techniques to membrane biology in general, and also with specific reference to the fields of actin and actin-binding proteins, virus infection, mitochondria, immune cell biology, and phosphoinositide signaling. Finally, we present our hopes and expectations for the future of super-resolution microscopy in the field of membrane biology.
Asunto(s)
Membrana Celular/metabolismo , Proteínas de Microfilamentos/metabolismo , Microscopía/métodos , Mitocondrias/ultraestructura , Virus/ultraestructura , Animales , Humanos , Modelos BiológicosRESUMEN
EphB6 is an understudied ephrin receptor tyrosine pseudokinase that is downregulated in multiple types of metastatic cancers. Unlike its kinase-active counterparts which autophosphorylate and transmit signals upon intercellular interaction, little is known about how EphB6 functions in the absence of intrinsic kinase activity. Here, we unveil a molecular mechanism of cell-cell interaction driven by EphB6. We identify ephrinB1 as a cognate ligand of EphB6 and show that in trans interaction of EphB6 with ephrinB1 on neighboring cells leads to the formation of large co-clusters at the plasma membrane. These co-clusters exhibit a decreased propensity towards endocytosis, suggesting a unique characteristic for this type of cell-cell interaction. Using lattice light-sheet microscopy, 3D structured illumination microscopy and cryo-electron tomography techniques, we show that co-clustering of EphB6 and ephrinB1 promotes the formation of double-membrane tubular structures between cells. Importantly, we also demonstrate that these intercellular structures stabilize cell-cell adhesion, leading to a reduction in the invasive behavior of cancer cells. Our findings rationalize a role for EphB6 pseudokinase as a tumor suppressor when interacting with its ligands in trans.
Asunto(s)
Fosforilación , Invasividad NeoplásicaRESUMEN
With resistance to most antimalarials increasing, it is imperative that new drugs are developed. We previously identified an aryl acetamide compound, MMV006833 (M-833), that inhibited the ring-stage development of newly invaded merozoites. Here, we select parasites resistant to M-833 and identify mutations in the START lipid transfer protein (PF3D7_0104200, PfSTART1). Introducing PfSTART1 mutations into wildtype parasites reproduces resistance to M-833 as well as to more potent analogues. PfSTART1 binding to the analogues is validated using organic solvent-based Proteome Integral Solubility Alteration (Solvent PISA) assays. Imaging of invading merozoites shows the inhibitors prevent the development of ring-stage parasites potentially by inhibiting the expansion of the encasing parasitophorous vacuole membrane. The PfSTART1-targeting compounds also block transmission to mosquitoes and with multiple stages of the parasite's lifecycle being affected, PfSTART1 represents a drug target with a new mechanism of action.
Asunto(s)
Acetamidas , Antimaláricos , Plasmodium falciparum , Proteínas Protozoarias , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/genética , Plasmodium falciparum/metabolismo , Plasmodium falciparum/crecimiento & desarrollo , Acetamidas/farmacología , Acetamidas/química , Proteínas Protozoarias/metabolismo , Proteínas Protozoarias/genética , Antimaláricos/farmacología , Antimaláricos/química , Animales , Proteínas Portadoras/metabolismo , Proteínas Portadoras/genética , Mutación , Malaria Falciparum/parasitología , Malaria Falciparum/prevención & control , Malaria Falciparum/tratamiento farmacológico , Humanos , Resistencia a Medicamentos/genética , Resistencia a Medicamentos/efectos de los fármacos , Estadios del Ciclo de Vida/efectos de los fármacosRESUMEN
ZRANB1 (human Trabid) missense mutations have been identified in children diagnosed with a range of congenital disorders including reduced brain size, but how Trabid regulates neurodevelopment is not understood. We have characterized these patient mutations in cells and mice to identify a key role for Trabid in the regulation of neurite growth. One of the patient mutations flanked the catalytic cysteine of Trabid and its deubiquitylating (DUB) activity was abrogated. The second variant retained DUB activity, but failed to bind STRIPAK, a large multiprotein assembly implicated in cytoskeleton organization and neural development. Zranb1 knock-in mice harboring either of these patient mutations exhibited reduced neuronal and glial cell densities in the brain and a motor deficit consistent with fewer dopaminergic neurons and projections. Mechanistically, both DUB-impaired and STRIPAK-binding-deficient Trabid variants impeded the trafficking of adenomatous polyposis coli (APC) to microtubule plus-ends. Consequently, the formation of neuronal growth cones and the trajectory of neurite outgrowth from mutant midbrain progenitors were severely compromised. We propose that STRIPAK recruits Trabid to deubiquitylate APC, and that in cells with mutant Trabid, APC becomes hyperubiquitylated and mislocalized causing impaired organization of the cytoskeleton that underlie the neuronal and developmental phenotypes.
Asunto(s)
Poliposis Adenomatosa del Colon , Neuritas , Animales , Niño , Humanos , Ratones , Poliposis Adenomatosa del Colon/metabolismo , Proteína de la Poliposis Adenomatosa del Colon/genética , Proteína de la Poliposis Adenomatosa del Colon/metabolismo , Axones/metabolismo , Mutación , Neuritas/metabolismoRESUMEN
A complete understanding of synaptic-vesicle recycling requires the use of multiple microscopy methods to obtain complementary information. However, many currently available probes are limited to a specific microscopy modality, which necessitates the use of multiple probes and labeling paradigms. Given the complexity of vesicle populations and recycling pathways, having new single-vesicle probes that could be used for multiple microscopy techniques would complement existing sets of tools for studying vesicle function. Here, we present a probe based on the membrane-binding C2 domain of cytosolic phospholipase A2 (cPLA2) that fulfills this need. By conjugating the C2 domain with different detectable tags, we demonstrate that a single, modular probe can allow synaptic vesicles to be imaged at multiple levels of spatial and temporal resolution. Moreover, as a general endocytic marker, the C2 domain may also be used to study membrane recycling in many cell types.
Asunto(s)
Imagen Multimodal , Vesículas Sinápticas , Vesículas Sinápticas/químicaRESUMEN
RhopH complexes consists of Clag3, RhopH2 and RhopH3 and are essential for growth of Plasmodium falciparum inside infected erythrocytes. Proteins are released from rhoptry organelles during merozoite invasion and trafficked to the surface of infected erythrocytes and enable uptake of nutrients. RhopH3, unlike other RhopH proteins, is required for parasite invasion, suggesting some cellular processes RhopH proteins function as single players rather than a complex. We show the RhopH complex has not formed during merozoite invasion. Clag3 is directly released into the host cell cytoplasm, whilst RhopH2 and RhopH3 are released into the nascent parasitophorous vacuole. Export of RhopH2 and RhopH3 from the parasitophorous vacuole into the infected erythrocyte cytoplasm enables assembly of Clag3/RhopH2/RhopH3 complexes and incorporation into the host cell membrane concomitant with activation of nutrient uptake. This suggests compartmentalisation prevents premature channel assembly before intact complex is assembled at the host cell membrane.
Asunto(s)
Membrana Eritrocítica , Malaria Falciparum , Membrana Eritrocítica/metabolismo , Eritrocitos/parasitología , Humanos , Malaria Falciparum/metabolismo , Plasmodium falciparum/metabolismo , Proteínas Protozoarias/metabolismoRESUMEN
Coatomer complex I (COPI) mediates retrograde vesicular trafficking from Golgi to the endoplasmic reticulum (ER) and within Golgi compartments. Deficiency in subunit alpha causes COPA syndrome and is associated with type I IFN signalling, although the upstream innate immune sensor involved was unknown. Using in vitro models we find aberrant activation of the STING pathway due to deficient retrograde but probably not intra-Golgi transport. Further we find the upstream cytosolic DNA sensor cGAS as essentially required to drive type I IFN signalling. Genetic deletion of COPI subunits COPG1 or COPD similarly induces type I IFN activation in vitro, which suggests that inflammatory diseases associated with mutations in other COPI subunit genes may exist. Finally, we demonstrate that inflammation in COPA syndrome patient peripheral blood mononuclear cells and COPI-deficient cell lines is ameliorated by treatment with the small molecule STING inhibitor H-151, suggesting targeted inhibition of the cGAS/STING pathway as a promising therapeutic approach.
Asunto(s)
Leucocitos Mononucleares , Nucleotidiltransferasas , Vesículas Cubiertas por Proteínas de Revestimiento/metabolismo , Proteína Coat de Complejo I/metabolismo , Complejo I de Transporte de Electrón/metabolismo , Humanos , Leucocitos Mononucleares/metabolismo , Nucleotidiltransferasas/genética , Nucleotidiltransferasas/metabolismo , Transducción de SeñalRESUMEN
Imaging volumes as thick as whole cells at three-dimensional (3D) super-resolution is required to reveal unknown features of cellular organization. We report a light microscope that generates images with translationally invariant 30 x 30 x 75 nm resolution over a depth of several micrometers. This method, named biplane (BP) FPALM, combines a double-plane detection scheme with fluorescence photoactivation localization microscopy (FPALM) enabling 3D sub-diffraction resolution without compromising speed or sensitivity.
Asunto(s)
Biofisica/métodos , Imagenología Tridimensional/métodos , Microscopía Fluorescente/métodos , Biofisica/economía , Biofisica/instrumentación , Fluoresceína/farmacología , Colorantes Fluorescentes/farmacología , Aumento de la Imagen , Interpretación de Imagen Asistida por Computador/métodos , Imagenología Tridimensional/instrumentación , Rayos Láser , Luz , Microscopía/métodos , Microscopía Fluorescente/instrumentación , Programas InformáticosRESUMEN
The recent development of diffraction-unlimited far-field fluorescence microscopy has overcome the classical resolution limit of ~250 nm of conventional light microscopy by about a factor of ten. The improved resolution, however, reveals not only biological structures at an unprecedented resolution, but is also susceptible to sample drift on a much finer scale than previously relevant. Without correction, sample drift leads to smeared images with decreased resolution, and in the worst case to misinterpretation of the imaged structures. This poses a problem especially for techniques such as Fluorescence Photoactivation Localization Microscopy (FPALM/PALM) or Stochastic Optical Reconstruction Microscopy (STORM), which often require minutes recording time. Here we discuss an approach that corrects for three-dimensional (3D) drift in images of fixed samples without the requirement for fiduciary markers or instrument modifications. Drift is determined by calculating the spatial cross-correlation function between subsets of localized particles imaged at different times. Correction down to ~5 nm precision is achieved despite the fact that different molecules are imaged in each frame. We demonstrate the performance of our drift correction algorithm with different simulated structures and analyze its dependence on particle density and localization precision. By imaging mitochondria with Biplane FPALM we show our algorithm's feasibility in a practical application.
Asunto(s)
Imagenología Tridimensional/métodos , Microscopía Fluorescente/métodos , Algoritmos , Simulación por Computador , Células Hep G2 , Humanos , Procesamiento de Imagen Asistido por Computador , Luz , Microscopía/métodos , Mitocondrias/metabolismo , Óptica y Fotónica , Reproducibilidad de los Resultados , Procesos EstocásticosRESUMEN
Host membrane remodeling is indispensable for viruses, bacteria, and parasites, to subvert the membrane barrier and obtain entry into cells. The malaria parasite Plasmodium spp. induces biophysical and molecular changes to the erythrocyte membrane through the ordered secretion of its apical organelles. To understand this process and address the debate regarding how the parasitophorous vacuole membrane (PVM) is formed, we developed an approach using lattice light-sheet microscopy, which enables the parasite interaction with the host cell membrane to be tracked and characterized during invasion. Our results show that the PVM is predominantly formed from the erythrocyte membrane, which undergoes biophysical changes as it is remodeled across all stages of invasion, from pre-invasion through to PVM sealing. This approach enables a functional interrogation of parasite-derived lipids and proteins in PVM biogenesis and echinocytosis during Plasmodium falciparum invasion and promises to yield mechanistic insights regarding how this is more generally orchestrated by other intracellular pathogens.
Asunto(s)
Membrana Eritrocítica/parasitología , Eritrocitos/parasitología , Tomografía Computarizada Cuatridimensional/métodos , Interacciones Huésped-Parásitos/fisiología , Malaria/parasitología , Vacuolas/metabolismo , Animales , Membrana Eritrocítica/metabolismo , Humanos , Merozoítos , Parásitos , Plasmodium/metabolismo , Plasmodium falciparum/metabolismo , Proteínas Protozoarias/metabolismoRESUMEN
The proximity pattern and radial distribution of chromosome territories within spherical nuclei are random and non-random, respectively. Whether this distribution pattern is conserved in the partitioned or lobed nuclei of polymorphonuclear cells is unclear. Here we use chromosome paint technology to examine the chromosome territories of all 46 chromosomes in hundreds of single human neutrophils - an abundant and famously polymorphonuclear immune cell. By comparing the distribution of chromosomes to randomly shuffled controls and validating with orthogonal chromosome conformation capture technology, we show for the first time that human chromosomes randomly distribute to neutrophil nuclear lobes, while maintaining a non-random radial distribution within these lobes. Furthermore, we demonstrate that chromosome length correlates with three-dimensional volume not only in neutrophils but other human immune cells. This work demonstrates that chromosomes are largely passive passengers during the neutrophil lobing process but are able to subsequently maintain their macro-level organization within lobes.
RESUMEN
Mixed lineage kinase domain-like (MLKL) is the terminal protein in the pro-inflammatory necroptotic cell death program. RIPK3-mediated phosphorylation is thought to initiate MLKL oligomerization, membrane translocation and membrane disruption, although the precise choreography of events is incompletely understood. Here, we use single-cell imaging approaches to map the chronology of endogenous human MLKL activation during necroptosis. During the effector phase of necroptosis, we observe that phosphorylated MLKL assembles into higher order species on presumed cytoplasmic necrosomes. Subsequently, MLKL co-traffics with tight junction proteins to the cell periphery via Golgi-microtubule-actin-dependent mechanisms. MLKL and tight junction proteins then steadily co-accumulate at the plasma membrane as heterogeneous micron-sized hotspots. Our studies identify MLKL trafficking and plasma membrane accumulation as crucial necroptosis checkpoints. Furthermore, the accumulation of phosphorylated MLKL at intercellular junctions accelerates necroptosis between neighbouring cells, which may be relevant to inflammatory bowel disease and other necroptosis-mediated enteropathies.