RESUMO
Tissue and organ development during embryogenesis relies on the collective and coordinated action of many cells. Recent studies have revealed that tissue material properties, including transitions between fluid and solid tissue states, are controlled in space and time to shape embryonic structures and regulate cell behaviours. Although the collective cellular flows that sculpt tissues are guided by tissue-level physical changes, these ultimately emerge from cellular-level and subcellular-level molecular mechanisms. Adherens junctions are key subcellular structures, built from clusters of classical cadherin receptors. They mediate physical interactions between cells and connect biochemical signalling to the physical characteristics of cell contacts, hence playing a fundamental role in tissue morphogenesis. In this Review, we take advantage of the results of recent, quantitative measurements of tissue mechanics to relate the molecular and cellular characteristics of adherens junctions, including adhesion strength, tension and dynamics, to the emergent physical state of embryonic tissues. We focus on systems in which cell-cell interactions are the primary contributor to morphogenesis, without significant contribution from cell-matrix interactions. We suggest that emergent tissue mechanics is an important direction for future research, bridging cell biology, developmental biology and mechanobiology to provide a holistic understanding of morphogenesis in health and disease.
Assuntos
Junções Aderentes , Caderinas , Junções Aderentes/metabolismo , Caderinas/metabolismo , Comunicação Celular , Morfogênese , Desenvolvimento Embrionário , Adesão Celular/fisiologiaRESUMO
Embryo morphogenesis is impacted by dynamic changes in tissue material properties, which have been proposed to occur via processes akin to phase transitions (PTs). Here, we show that rigidity percolation provides a simple and robust theoretical framework to predict material/structural PTs of embryonic tissues from local cell connectivity. By using percolation theory, combined with directly monitoring dynamic changes in tissue rheology and cell contact mechanics, we demonstrate that the zebrafish blastoderm undergoes a genuine rigidity PT, brought about by a small reduction in adhesion-dependent cell connectivity below a critical value. We quantitatively predict and experimentally verify hallmarks of PTs, including power-law exponents and associated discontinuities of macroscopic observables. Finally, we show that this uniform PT depends on blastoderm cells undergoing meta-synchronous divisions causing random and, consequently, uniform changes in cell connectivity. Collectively, our theoretical and experimental findings reveal the structural basis of material PTs in an organismal context.
Assuntos
Embrião não Mamífero/fisiologia , Desenvolvimento Embrionário , Animais , Blastoderma/citologia , Blastoderma/fisiologia , Caderinas/antagonistas & inibidores , Caderinas/genética , Caderinas/metabolismo , Adesão Celular , Embrião não Mamífero/citologia , Morfolinos/metabolismo , Reologia , Viscosidade , Peixe-Zebra/crescimento & desenvolvimentoRESUMO
The central pathogen-immune interface in tuberculosis is the granuloma, a complex host immune structure that dictates infection trajectory and physiology. Granuloma macrophages undergo a dramatic transition in which entire epithelial modules are induced and define granuloma architecture. In tuberculosis, relatively little is known about the host signals that trigger this transition. Using the zebrafish-Mycobacterium marinum model, we identify the basis of granuloma macrophage transformation. Single-cell RNA-sequencing analysis of zebrafish granulomas and analysis of Mycobacterium tuberculosis-infected macaques reveal that, even in the presence of robust type 1 immune responses, countervailing type 2 signals associate with macrophage epithelialization. We find that type 2 immune signaling, mediated via stat6, is absolutely required for epithelialization and granuloma formation. In mixed chimeras, stat6 acts cell autonomously within macrophages, where it is required for epithelioid transformation and incorporation into necrotic granulomas. These findings establish the signaling pathway that produces the hallmark structure of mycobacterial infection.
Assuntos
Granuloma/patologia , Imunidade/fisiologia , Infecções por Mycobacterium não Tuberculosas/patologia , Animais , Animais Geneticamente Modificados/genética , Animais Geneticamente Modificados/metabolismo , Caderinas/genética , Caderinas/metabolismo , Diferenciação Celular , Modelos Animais de Doenças , Células Epitelioides/citologia , Células Epitelioides/imunologia , Células Epitelioides/metabolismo , Granuloma/imunologia , Granuloma/metabolismo , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/metabolismo , Interferon gama/metabolismo , Interleucina-12/metabolismo , Macrófagos/citologia , Macrófagos/imunologia , Macrófagos/metabolismo , Infecções por Mycobacterium não Tuberculosas/imunologia , Mycobacterium marinum/isolamento & purificação , Mycobacterium marinum/fisiologia , Necrose , RNA Guia de Cinetoplastídeos/metabolismo , Receptores de Interleucina-4/antagonistas & inibidores , Receptores de Interleucina-4/genética , Receptores de Interleucina-4/metabolismo , Fator de Transcrição STAT6/antagonistas & inibidores , Fator de Transcrição STAT6/genética , Fator de Transcrição STAT6/metabolismo , Transdução de Sinais , Peixe-Zebra/crescimento & desenvolvimento , Peixe-Zebra/metabolismoRESUMO
This year's Canada Gairdner International Prize is shared by Rolf Kemler and Masatoshi Takeichi for the discovery of the cadherin family of Ca2+-dependent cell-cell adhesion proteins, which play essential roles in animal evolution, tissue development, and homeostasis, and are disrupted in human cancers.
Assuntos
Caderinas/metabolismo , Caderinas/fisiologia , Comunicação Celular/fisiologia , Animais , Distinções e Prêmios , Fenômenos Biofísicos , Canadá , Adesão Celular/fisiologia , História do Século XX , História do Século XXI , Homeostase/fisiologia , Humanos , MasculinoRESUMO
Human cerebral cortex size and complexity has increased greatly during evolution. While increased progenitor diversity and enhanced proliferative potential play important roles in human neurogenesis and gray matter expansion, the mechanisms of human oligodendrogenesis and white matter expansion remain largely unknown. Here, we identify EGFR-expressing "Pre-OPCs" that originate from outer radial glial cells (oRGs) and undergo mitotic somal translocation (MST) during division. oRG-derived Pre-OPCs provide an additional source of human cortical oligodendrocyte precursor cells (OPCs) and define a lineage trajectory. We further show that human OPCs undergo consecutive symmetric divisions to exponentially increase the progenitor pool size. Additionally, we find that the OPC-enriched gene, PCDH15, mediates daughter cell repulsion and facilitates proliferation. These findings indicate properties of OPC derivation, proliferation, and dispersion important for human white matter expansion and myelination.
Assuntos
Caderinas/metabolismo , Córtex Cerebral/citologia , Células Ependimogliais/metabolismo , Neurogênese/genética , Células Precursoras de Oligodendrócitos/metabolismo , Proteínas Relacionadas a Caderinas , Caderinas/genética , Proliferação de Células/genética , Células Cultivadas , Córtex Cerebral/embriologia , Córtex Cerebral/metabolismo , Células Ependimogliais/citologia , Receptores ErbB/genética , Receptores ErbB/metabolismo , Células HEK293 , Humanos , Imuno-Histoquímica , Células Precursoras de Oligodendrócitos/citologia , RNA Interferente Pequeno , RNA-Seq , Análise de Célula Única , Substância Branca/citologia , Substância Branca/embriologia , Substância Branca/metabolismoRESUMO
The assembly of organized colonies is the earliest manifestation in the derivation or induction of pluripotency in vitro. However, the necessity and origin of this assemblance is unknown. Here, we identify human pluripotent founder cells (hPFCs) that initiate, as well as preserve and establish, pluripotent stem cell (PSC) cultures. PFCs are marked by N-cadherin expression (NCAD+) and reside exclusively at the colony boundary of primate PSCs. As demonstrated by functional analysis, hPFCs harbor the clonogenic capacity of PSC cultures and emerge prior to commitment events or phenotypes associated with pluripotent reprogramming. Comparative single-cell analysis with pre- and post-implantation primate embryos revealed hPFCs share hallmark properties with primitive endoderm (PrE) and can be regulated by non-canonical Wnt signaling. Uniquely informed by primate embryo organization in vivo, our study defines a subset of founder cells critical to the establishment pluripotent state.
Assuntos
Antígenos CD/metabolismo , Caderinas/metabolismo , Células-Tronco Pluripotentes/citologia , Células-Tronco Pluripotentes/metabolismo , Diferenciação Celular , Linhagem da Célula , Desenvolvimento Embrionário , Células-Tronco Embrionárias/metabolismo , Endoderma/metabolismo , Expressão Gênica/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Humanos , Análise de Célula Única , Via de Sinalização WntRESUMO
Stochastic activation of clustered Protocadherin (Pcdh) α, ß, and γ genes generates a cell-surface identity code in individual neurons that functions in neural circuit assembly. Here, we show that Pcdhα gene choice involves the activation of an antisense promoter located in the first exon of each Pcdhα alternate gene. Transcription of an antisense long noncoding RNA (lncRNA) from this antisense promoter extends through the sense promoter, leading to DNA demethylation of the CTCF binding sites proximal to each promoter. Demethylation-dependent CTCF binding to both promoters facilitates cohesin-mediated DNA looping with a distal enhancer (HS5-1), locking in the transcriptional state of the chosen Pcdhα gene. Uncoupling DNA demethylation from antisense transcription by Tet3 overexpression in mouse olfactory neurons promotes CTCF binding to all Pcdhα promoters, resulting in proximity-biased DNA looping of the HS5-1 enhancer. Thus, antisense transcription-mediated promoter demethylation functions as a mechanism for distance-independent enhancer/promoter DNA looping to ensure stochastic Pcdhα promoter choice.
Assuntos
Caderinas/genética , Desmetilação do DNA , RNA Antissenso/metabolismo , RNA Longo não Codificante/genética , Animais , Sítios de Ligação , Fator de Ligação a CCCTC/química , Fator de Ligação a CCCTC/metabolismo , Caderinas/metabolismo , Linhagem Celular , Elementos Facilitadores Genéticos , Éxons , Feminino , Humanos , Camundongos , Camundongos Transgênicos , Família Multigênica , Neurônios/citologia , Neurônios/metabolismo , Regiões Promotoras Genéticas , RNA Polimerase II/metabolismo , RNA Antissenso/genética , Transcrição GênicaRESUMO
Tools capable of imaging and perturbing mechanical signaling pathways with fine spatiotemporal resolution have been elusive, despite their importance in diverse cellular processes. The challenge in developing a mechanogenetic toolkit (i.e., selective and quantitative activation of genetically encoded mechanoreceptors) stems from the fact that many mechanically activated processes are localized in space and time yet additionally require mechanical loading to become activated. To address this challenge, we synthesized magnetoplasmonic nanoparticles that can image, localize, and mechanically load targeted proteins with high spatiotemporal resolution. We demonstrate their utility by investigating the cell-surface activation of two mechanoreceptors: Notch and E-cadherin. By measuring cellular responses to a spectrum of spatial, chemical, temporal, and mechanical inputs at the single-molecule and single-cell levels, we reveal how spatial segregation and mechanical force cooperate to direct receptor activation dynamics. This generalizable technique can be used to control and understand diverse mechanosensitive processes in cell signaling. VIDEO ABSTRACT.
Assuntos
Técnicas Genéticas , Mecanotransdução Celular , Nanopartículas Metálicas , Receptores Notch/metabolismo , Actinas/metabolismo , Caderinas/metabolismo , Linhagem Celular , Células Cultivadas , Humanos , Mecanorreceptores/fisiologia , Nanopartículas Metálicas/química , Microesferas , Técnicas de Sonda Molecular , Proteínas Recombinantes de Fusão/metabolismo , Análise Espacial , TempoRESUMO
Spotted fever group (SFG) rickettsiae are human pathogens that infect cells in the vasculature. They disseminate through host tissues by a process of cell-to-cell spread that involves protrusion formation, engulfment, and vacuolar escape. Other bacterial pathogens rely on actin-based motility to provide a physical force for spread. Here, we show that SFG species Rickettsia parkeri typically lack actin tails during spread and instead manipulate host intercellular tension and mechanotransduction to promote spread. Using transposon mutagenesis, we identified surface cell antigen 4 (Sca4) as a secreted effector of spread that specifically promotes protrusion engulfment. Sca4 interacts with the cell-adhesion protein vinculin and blocks association with vinculin's binding partner, α-catenin. Using traction and monolayer stress microscopy, we show that Sca4 reduces vinculin-dependent mechanotransduction at cell-cell junctions. Our results suggest that Sca4 relieves intercellular tension to promote protrusion engulfment, which represents a distinctive strategy for manipulating cytoskeletal force generation to enable spread.
Assuntos
Antígenos de Bactérias/metabolismo , Proteínas de Bactérias/metabolismo , Interações Hospedeiro-Patógeno , Mecanotransdução Celular , Infecções por Rickettsia/metabolismo , Infecções por Rickettsia/microbiologia , Rickettsia/patogenicidade , Vinculina/metabolismo , Actinas/metabolismo , Sequência de Aminoácidos , Antígenos de Bactérias/genética , Proteínas de Bactérias/genética , Caderinas/metabolismo , Adesão Celular , Linhagem Celular Tumoral , Elementos de DNA Transponíveis/genética , Febre/metabolismo , Febre/microbiologia , Humanos , Mutagênese Insercional , Mutação , Rickettsia/metabolismo , alfa Catenina/metabolismoRESUMO
Self-avoidance, a process preventing interactions of axons and dendrites from the same neuron during development, is mediated in vertebrates through the stochastic single-neuron expression of clustered protocadherin protein isoforms. Extracellular cadherin (EC) domains mediate isoform-specific homophilic binding between cells, conferring cell recognition through a poorly understood mechanism. Here, we report crystal structures for the EC1-EC3 domain regions from four protocadherin isoforms representing the α, ß, and γ subfamilies. All are rod shaped and monomeric in solution. Biophysical measurements, cell aggregation assays, and computational docking reveal that trans binding between cells depends on the EC1-EC4 domains, which interact in an antiparallel orientation. We also show that the EC6 domains are required for the formation of cis-dimers. Overall, our results are consistent with a model in which protocadherin cis-dimers engage in a head-to-tail interaction between EC1-EC4 domains from apposed cell surfaces, possibly forming a zipper-like protein assembly, and thus providing a size-dependent self-recognition mechanism.
Assuntos
Caderinas/química , Caderinas/metabolismo , Neurônios/citologia , Neurônios/fisiologia , Sequência de Aminoácidos , Animais , Cristalografia por Raios X , Camundongos , Modelos Moleculares , Dados de Sequência Molecular , Fenômenos Fisiológicos do Sistema Nervoso , Estrutura Terciária de Proteína , Alinhamento de SequênciaRESUMO
Dendritic spines are postsynaptic compartments of excitatory synapses that undergo dynamic changes during development, including rapid spinogenesis in early postnatal life and significant pruning during adolescence. Spine pruning defects have been implicated in developmental neurological disorders such as autism, yet much remains to be uncovered regarding its molecular mechanism. Here, we show that spine pruning and maturation in the mouse somatosensory cortex are coordinated via the cadherin/catenin cell adhesion complex and bidrectionally regulated by sensory experience. We further demonstrate that locally enhancing cadherin/catenin-dependent adhesion or photo-stimulating a contacting channelrhodopsin-expressing axon stabilized the manipulated spine and eliminated its neighbors, an effect requiring cadherin/catenin-dependent adhesion. Importantly, we show that differential cadherin/catenin-dependent adhesion between neighboring spines biased spine fate in vivo. These results suggest that activity-induced inter-spine competition for ß-catenin provides specificity for concurrent spine maturation and elimination and thus is critical for the molecular control of spine pruning during neural circuit refinement.
Assuntos
Caderinas/metabolismo , Cateninas/metabolismo , Espinhas Dendríticas/metabolismo , Córtex Somatossensorial/citologia , Animais , Transtorno do Espectro Autista/metabolismo , Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Caderinas/genética , Cateninas/genética , Camundongos , Complexos Multiproteicos/metabolismo , Neurônios/metabolismo , Células Piramidais/metabolismo , Córtex Somatossensorial/metabolismo , Vibrissas/lesõesRESUMO
Invasive lobular carcinoma (ILC) is the second most prevalent histologic subtype of invasive breast cancer. Here, we comprehensively profiled 817 breast tumors, including 127 ILC, 490 ductal (IDC), and 88 mixed IDC/ILC. Besides E-cadherin loss, the best known ILC genetic hallmark, we identified mutations targeting PTEN, TBX3, and FOXA1 as ILC enriched features. PTEN loss associated with increased AKT phosphorylation, which was highest in ILC among all breast cancer subtypes. Spatially clustered FOXA1 mutations correlated with increased FOXA1 expression and activity. Conversely, GATA3 mutations and high expression characterized luminal A IDC, suggesting differential modulation of ER activity in ILC and IDC. Proliferation and immune-related signatures determined three ILC transcriptional subtypes associated with survival differences. Mixed IDC/ILC cases were molecularly classified as ILC-like and IDC-like revealing no true hybrid features. This multidimensional molecular atlas sheds new light on the genetic bases of ILC and provides potential clinical options.
Assuntos
Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Carcinoma Lobular/genética , Carcinoma Lobular/patologia , Antígenos CD , Neoplasias da Mama/metabolismo , Caderinas/química , Caderinas/genética , Caderinas/metabolismo , Carcinoma Ductal de Mama/genética , Carcinoma Ductal de Mama/patologia , Carcinoma Lobular/metabolismo , Feminino , Fator 3-alfa Nuclear de Hepatócito/química , Fator 3-alfa Nuclear de Hepatócito/genética , Fator 3-alfa Nuclear de Hepatócito/metabolismo , Humanos , Modelos Moleculares , Mutação , Análise de Sequência com Séries de Oligonucleotídeos , Proteína Oncogênica v-akt/metabolismo , TranscriptomaRESUMO
Western equine encephalitis virus (WEEV) is an arthropod-borne virus (arbovirus) that frequently caused major outbreaks of encephalitis in humans and horses in the early twentieth century, but the frequency of outbreaks has since decreased markedly, and strains of this alphavirus isolated in the past two decades are less virulent in mammals than strains isolated in the 1930s and 1940s1-3. The basis for this phenotypic change in WEEV strains and coincident decrease in epizootic activity (known as viral submergence3) is unclear, as is the possibility of re-emergence of highly virulent strains. Here we identify protocadherin 10 (PCDH10) as a cellular receptor for WEEV. We show that multiple highly virulent ancestral WEEV strains isolated in the 1930s and 1940s, in addition to binding human PCDH10, could also bind very low-density lipoprotein receptor (VLDLR) and apolipoprotein E receptor 2 (ApoER2), which are recognized by another encephalitic alphavirus as receptors4. However, whereas most of the WEEV strains that we examined bind to PCDH10, a contemporary strain has lost the ability to recognize mammalian PCDH10 while retaining the ability to bind avian receptors, suggesting WEEV adaptation to a main reservoir host during enzootic circulation. PCDH10 supports WEEV E2-E1 glycoprotein-mediated infection of primary mouse cortical neurons, and administration of a soluble form of PCDH10 protects mice from lethal WEEV challenge. Our results have implications for the development of medical countermeasures and for risk assessment for re-emerging WEEV strains.
Assuntos
Caderinas , Vírus da Encefalite Equina do Oeste , Receptores Virais , Animais , Camundongos , Humanos , Receptores Virais/metabolismo , Caderinas/metabolismo , Feminino , Receptores de LDL/metabolismo , Receptores de LDL/genética , Masculino , Encefalomielite Equina/virologia , Encefalomielite Equina/transmissão , Encefalomielite Equina/veterináriaRESUMO
Neurodevelopmental cognitive disorders provide insights into mechanisms of human brain development. Here, we report an intellectual disability syndrome caused by the loss of APC7, a core component of the E3 ubiquitin ligase anaphase promoting complex (APC). In mechanistic studies, we uncover a critical role for APC7 during the recruitment and ubiquitination of APC substrates. In proteomics analyses of the brain from mice harboring the patient-specific APC7 mutation, we identify the chromatin-associated protein Ki-67 as an APC7-dependent substrate of the APC in neurons. Conditional knockout of the APC coactivator protein Cdh1, but not Cdc20, leads to the accumulation of Ki-67 protein in neurons in vivo, suggesting that APC7 is required for the function of Cdh1-APC in the brain. Deregulated neuronal Ki-67 upon APC7 loss localizes predominantly to constitutive heterochromatin. Our findings define an essential function for APC7 and Cdh1-APC in neuronal heterochromatin regulation, with implications for understanding human brain development and disease.
Assuntos
Subunidade Apc7 do Ciclossomo-Complexo Promotor de Anáfase/metabolismo , Encéfalo/enzimologia , Heterocromatina/metabolismo , Deficiência Intelectual/enzimologia , Células-Tronco Neurais/enzimologia , Neurogênese , Adolescente , Animais , Antígenos CD , Subunidade Apc7 do Ciclossomo-Complexo Promotor de Anáfase/genética , Comportamento Animal , Encéfalo/crescimento & desenvolvimento , Caderinas/genética , Caderinas/metabolismo , Linhagem Celular , Criança , Pré-Escolar , Modelos Animais de Doenças , Feminino , Heterocromatina/genética , Humanos , Lactente , Deficiência Intelectual/patologia , Deficiência Intelectual/fisiopatologia , Deficiência Intelectual/psicologia , Inteligência , Antígeno Ki-67/genética , Antígeno Ki-67/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitose , Mutação , Células-Tronco Neurais/patologia , Proteólise , Transdução de Sinais , Síndrome , Ubiquitinação , Adulto JovemRESUMO
The protocadherin Fat is known as a tumor suppressor regulating growth in Drosophila and for its conserved function during planar cell polarity establishment. McNeill and colleagues now identify an unsuspected role for a C-terminal proteolytic product of Fat in mitochondria: regulating the electron transport machinery and metabolism.
Assuntos
Caderinas/metabolismo , Moléculas de Adesão Celular/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Mitocôndrias/metabolismo , Animais , HumanosRESUMO
E-cadherin is a major homophilic cell-cell adhesion molecule that inhibits motility of individual cells on matrix. However, its contribution to migration of cells through cell-rich tissues is less clear. We developed an in vivo sensor of mechanical tension across E-cadherin molecules, which we combined with cell-type-specific RNAi, photoactivatable Rac, and morphodynamic profiling, to interrogate how E-cadherin contributes to collective migration of cells between other cells. Using the Drosophila ovary as a model, we found that adhesion between border cells and their substrate, the nurse cells, functions in a positive feedback loop with Rac and actin assembly to stabilize forward-directed protrusion and directionally persistent movement. Adhesion between individual border cells communicates direction from the lead cell to the followers. Adhesion between motile cells and polar cells holds the cluster together and polarizes each individual cell. Thus, E-cadherin is an integral component of the guidance mechanisms that orchestrate collective chemotaxis in vivo.
Assuntos
Caderinas/metabolismo , Movimento Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citologia , Animais , Fenômenos Biomecânicos , Adesão Celular , Quimiotaxia , Técnicas Citológicas , Drosophila melanogaster/metabolismo , Feminino , Dados de Sequência Molecular , Ovário/citologia , Proteínas rac de Ligação ao GTP/metabolismoRESUMO
Complex retinal circuits process visual information and deliver it to the brain. Few molecular determinants of synaptic specificity in this system are known. Using genetic and optogenetic methods, we identified two types of bipolar interneurons that convey visual input from photoreceptors to a circuit that computes the direction in which objects are moving. We then sought recognition molecules that promote selective connections of these cells with previously characterized components of the circuit. We found that the type II cadherins, cdh8 and cdh9, are each expressed selectively by one of the two bipolar cell types. Using loss- and gain-of-function methods, we showed that they are critical determinants of connectivity in this circuit and that perturbation of their expression leads to distinct defects in visually evoked responses. Our results reveal cellular components of a retinal circuit and demonstrate roles of type II cadherins in synaptic choice and circuit function.
Assuntos
Caderinas/metabolismo , Retina/fisiologia , Células Bipolares da Retina/metabolismo , Vias Visuais , Animais , Axônios/metabolismo , Caderinas/genética , Técnicas de Introdução de Genes , Camundongos , Retina/citologia , SinapsesRESUMO
Individual mammalian neurons stochastically express distinct repertoires of α, ß, and γ protocadherin (Pcdh) proteins, which function in neural circuit assembly. We report that all three subfamilies of clustered Pcdhs can engage in specific homophilic interactions, that cell surface delivery of Pcdhα isoforms requires cis interactions with other Pcdhs, and that the extracellular cadherin domain EC6 plays a critical role in this process. Examination of homophilic interactions between specific combinations of multiple Pcdh isoforms revealed that Pcdh combinatorial recognition specificities depend on the identity of all of the expressed isoforms. A single mismatched Pcdh isoform can interfere with these combinatorial homophilic interactions. A theoretical analysis reveals that assembly of Pcdh isoforms into multimeric recognition units and the observed tolerance for mismatched isoforms can generate cell surface diversity sufficient for single-cell identity. However, the competing demands of nonself discrimination and self-recognition place limitations on the mechanisms by which homophilic recognition units can function.
Assuntos
Caderinas/metabolismo , Neurônios/química , Isoformas de Proteínas/metabolismo , Sequência de Aminoácidos , Animais , Proteínas Relacionadas a Caderinas , Caderinas/química , Caderinas/genética , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Neurônios/metabolismo , Domínios e Motivos de Interação entre Proteínas , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Alinhamento de SequênciaRESUMO
Fat (Ft) cadherins are enormous cell adhesion molecules that function at the cell surface to regulate the tumor-suppressive Hippo signaling pathway and planar cell polarity (PCP) tissue organization. Mutations in Ft cadherins are found in a variety of tumors, and it is presumed that this is due to defects in either Hippo signaling or PCP. Here, we show Drosophila Ft functions in mitochondria to directly regulate mitochondrial electron transport chain integrity and promote oxidative phosphorylation. Proteolytic cleavage releases a soluble 68 kDa fragment (Ft(mito)) that is imported into mitochondria. Ft(mito) binds directly to NADH dehydrogenase ubiquinone flavoprotein 2 (Ndufv2), a core component of complex I, stabilizing the holoenzyme. Loss of Ft leads to loss of complex I activity, increases in reactive oxygen species, and a switch to aerobic glycolysis. Defects in mitochondrial activity in ft mutants are independent of Hippo and PCP signaling and are reminiscent of the Warburg effect.
Assuntos
Caderinas/metabolismo , Moléculas de Adesão Celular/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Mitocôndrias/metabolismo , Sequência de Aminoácidos , Animais , Moléculas de Adesão Celular/química , Polaridade Celular , Proteínas de Drosophila/química , Complexo de Proteínas da Cadeia de Transporte de Elétrons/metabolismo , Complexo I de Transporte de Elétrons/metabolismo , Olho/crescimento & desenvolvimento , Genes Supressores de Tumor , Humanos , MAP Quinase Quinase 4/metabolismo , Dados de Sequência Molecular , Transporte Proteico , Espécies Reativas de Oxigênio/metabolismo , Asas de Animais/crescimento & desenvolvimentoRESUMO
Transporting epithelial cells build apical microvilli to increase membrane surface area and enhance absorptive capacity. The intestinal brush border provides an elaborate example with tightly packed microvilli that function in nutrient absorption and host defense. Although the brush border is essential for physiological homeostasis, its assembly is poorly understood. We found that brush border assembly is driven by the formation of Ca(2+)-dependent adhesion links between adjacent microvilli. Intermicrovillar links are composed of protocadherin-24 and mucin-like protocadherin, which target to microvillar tips and interact to form a trans-heterophilic complex. The cytoplasmic domains of microvillar protocadherins interact with the scaffolding protein, harmonin, and myosin-7b, which promote localization to microvillar tips. Finally, a mouse model of Usher syndrome lacking harmonin exhibits microvillar protocadherin mislocalization and severe defects in brush border morphology. These data reveal an adhesion-based mechanism for brush border assembly and illuminate the basis of intestinal pathology in patients with Usher syndrome. PAPERFLICK: