RESUMEN
The intercalated disc is an important structure in cardiomyocytes, as it is essential to maintain correct contraction and proper functioning of the heart. Adhesion and communication between cardiomyocytes are mediated by three main types of intercellular junctions, all residing in the intercalated disc: gap junctions, desmosomes and the areae compositae. Mutations in genes that encode junctional proteins, including αT-catenin (encoded by CTNNA3), have been linked to arrhythmogenic cardiomyopathy and sudden cardiac death. In mice, the loss of αT-catenin in cardiomyocytes leads to impaired heart function, fibrosis, changed expression of desmosomal proteins and increased risk for arrhythmias following ischemia-reperfusion. Currently, it is unclear how the intercalated disc and the intercellular junctions are organised in 3D in the hearts of this αT-catenin knockout (KO) mouse model. In order to scrutinise this, ventricular cardiac tissue of αT-catenin KO mice was used for volume electron microscopy (VEM), making use of Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), allowing a careful 3D reconstruction of the intercalated disc, including gap junctions and desmosomes. Although αT-catenin KO and control mice display a comparable organisation of the sarcomere and the different intercalated disc regions, the folds of the plicae region of the intercalated disc are longer and more narrow in the KO heart, and the pale region between the sarcomere and the intercalated disc is larger. In addition, αT-catenin KO intercalated discs appear to have smaller gap junctions and desmosomes in the plicae region, while gap junctions are larger in the interplicae region of the intercalated disc. Although the reason for this remodelling of the ultrastructure after αT-catenin deletion remains unclear, the excellent resolution of the FIB-SEM technology allows us to reconstruct details that were not reported before. LAY DESCRIPTION: Cardiomyocytes are cells that make up the heart muscle. As the chief cell type of the heart, cardiomyocytes are primarily involved in the contractile function of the heart that enables the pumping of blood around the body. Cardiac muscle cells are connected to each other at their short end by numerous intercellular junctions forming together a structure called the intercalated disc. These intercellular junctions comprise specific protein complexes, which are crucial for both intercellular adhesion and correct contraction of the heart. Imaging by conventional electron microscopy (EM) revealed a heavily folded intercalated disc with apparently random organization of the intercellular junctions. However, this conclusion was based on analysis in two dimensions (2D). 3D information of these structures is needed to unravel their true organization and function. In the present study, we used a more contemporary technique, called volume EM, to image and reconstruct the intercalated discs in 3D. By this approach, EM images are made from a whole block of tissue what differs significantly from classical EM methods that uses only one very thin slice for imaging. Further, we analyzed in comparison to normal mice also a mouse model for cardiomyopathy in which a specific protein of the cardiac intercellular junctions, αT-catenin, is absent. Volume EM revealed that in the hearts of these mice with cardiomyopathy, the finger-like folds of the intercalated disc are longer and thinner compared to control hearts. Also the intercellular junctions on the folded parts of the intercalated disc are smaller and their connection to the striated cytoskeleton seems further away. In conclusion, our volume EM study has expanded our understanding of 3D structures at the intercalated discs and will pave the way for more detailed models of disturbed cell-cell contacts associated with heart failure.
Asunto(s)
Desmosomas/ultraestructura , Uniones Comunicantes/ultraestructura , Miocardio/ultraestructura , Miocitos Cardíacos/ultraestructura , alfa Catenina/genética , Animales , Imagenología Tridimensional , Uniones Intercelulares/ultraestructura , Ratones , Ratones Noqueados , Microscopía Electrónica , MutaciónRESUMEN
With the current environmental impact of large-scale animal production and societal concerns about the welfare of farm animals, researchers are questioning whether we can cultivate animal cells for the purpose of food production. This review focuses on a pivotal aspect of the cellular agriculture domain: cells. We summarised information on the various cell types from farm animals currently used for the development of cultured meat, including mesenchymal stromal cells, myoblasts, and pluripotent stem cells. The review delves into the advantages and limitations of each cell type and considers factors like the selection of the appropriate cell source, as well as cell culture conditions that influence cell performance. As current research in cultured meat seeks to create muscle fibers to mimic the texture and nutritional profile of meat, we focused on the myogenic differentiation capacity of the cells. The most commonly used cell type for this purpose are myoblasts or satellite cells, but given their limited proliferation capacity, efforts are underway to formulate myogenic differentiation protocols for mesenchymal stromal cells and pluripotent stem cells. The multipotent character of the latter cell types might enable the creation of other tissues found in meat, such as adipose and connective tissues. This review can help guiding the selection of a cell type or culture conditions in the context of cultured meat development.
RESUMEN
To analyze the implication of PTEN in the control of tumor cell invasiveness, the canine kidney epithelial cell lines MDCKras-f and MDCKts-src, expressing activated Ras and a temperature-sensitive v-Src tyrosine kinase, respectively, were transfected with PTEN expression vectors. Likewise, the human PTEN-defective glioblastoma cell lines U87MG and U373MG, the melanoma cell line FM-45, and the prostate carcinoma cell line PC-3 were transfected. We demonstrate that ectopic expression of wild-type PTEN in MDCKts-src cells, but not expression of PTEN mutants deficient in either the lipid or both the lipid and protein phosphatase activities, reverted the morphological transformation, induced cell-cell aggregation, and suppressed the invasive phenotype in an E-cadherin-dependent manner. In contrast, overexpression of wild-type PTEN did not counteract Ras-induced invasiveness of MDCKras-f cells expressing low levels of E-cadherin. PTEN effects were not associated with marked changes in accumulation or phosphorylation levels of E-cadherin and associated catenins. Wild-type, but not mutant, PTEN also reverted the invasive phenotype of U87MG, U373MG, PC-3, and FM-45 cells. Interestingly, PTEN effects were mimicked by N-cadherin-neutralizing antibody in the glioblastoma cell lines. Our data confirm the differential activities of E- and N-cadherin on invasiveness and suggest that the lipid phosphatase activity of PTEN exerts a critical role in stabilizing junctional complexes and restraining invasiveness.
Asunto(s)
Glioblastoma/fisiopatología , Uniones Intercelulares/fisiología , Melanoma/fisiopatología , Invasividad Neoplásica , Monoéster Fosfórico Hidrolasas/genética , Neoplasias de la Próstata/fisiopatología , Proteínas Supresoras de Tumor/genética , Animales , Línea Celular , Glioblastoma/patología , Humanos , Masculino , Melanoma/patología , Fosfohidrolasa PTEN , Monoéster Fosfórico Hidrolasas/fisiología , Neoplasias de la Próstata/patología , Proteínas Recombinantes/metabolismo , Transfección , Células Tumorales Cultivadas , Proteínas Supresoras de Tumor/fisiologíaRESUMEN
The alpha-catenin molecule links E-cadherin/ beta-catenin or E-cadherin/plakoglobin complexes to the actin cytoskeleton. We studied several invasive human colon carcinoma cell lines lacking alpha-catenin. They showed a solitary and rounded morphotype that correlated with increased invasiveness. These round cell variants acquired a more normal epithelial phenotype upon transfection with an alpha-catenin expression plasmid, but also upon treatment with the protein kinase C (PKC) activator 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Video registrations showed that the cells started to establish elaborated intercellular junctions within 30 min after addition of TPA. Interestingly, this normalizing TPA effect was not associated with alpha-catenin induction. Classical and confocal immunofluorescence showed only minor TPA-induced changes in E-cadherin staining. In contrast, desmosomal and tight junctional proteins were dramatically rearranged, with a conversion from cytoplasmic clusters to obvious concentration at cell-cell contacts and exposition at the exterior cell surface. Electron microscopical observations revealed the TPA-induced appearance of typical desmosomal plaques. TPA-restored cell-cell adhesion was E-cadherin dependent as demonstrated by a blocking antibody in a cell aggregation assay. Addition of an antibody against the extracellular part of desmoglein-2 blocked the TPA effect, too. Remarkably, the combination of anti-E-cadherin and anti-desmoglein antibodies synergistically inhibited the TPA effect. Our studies show that it is possible to bypass the need for normal alpha-catenin expression to establish tight intercellular adhesion by epithelial cells. Apparently, the underlying mechanism comprises upregulation of desmosomes and tight junctions by activation of the PKC signaling pathway, whereas E-cadherin remains essential for basic cell-cell adhesion, even in the absence of alpha-catenin.
Asunto(s)
Proteínas del Citoesqueleto/deficiencia , Desmosomas/química , Desmosomas/enzimología , Proteína Quinasa C/metabolismo , Transactivadores , Antígenos de Superficie/metabolismo , Cadherinas/metabolismo , Adhesión Celular/efectos de los fármacos , Adhesión Celular/fisiología , Tamaño de la Célula/fisiología , Neoplasias del Colon , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/metabolismo , ADN Complementario , Detergentes , Humanos , Microscopía Electrónica , Solubilidad , Acetato de Tetradecanoilforbol/farmacología , Uniones Estrechas/química , Uniones Estrechas/enzimología , Transfección , Células Tumorales Cultivadas/citología , Células Tumorales Cultivadas/enzimología , Células Tumorales Cultivadas/ultraestructura , alfa Catenina , beta CateninaRESUMEN
N-cadherin is a well-studied classic cadherin involved in multiple developmental processes and is also known to have a signaling function. Using the zebrafish (Danio rerio) as a model, we tested the hypothesis that tooth morphogenesis is accompanied by dynamic changes in N-cadherin distribution and that absence of N-cadherin disturbs tooth development. N-cadherin, encoded by the gene cdh2, is absent during the initiation and morphogenesis stages of both primary (first-generation) and replacement teeth, as demonstrated by immunohistochemistry. However, N-cadherin is up-regulated at the onset of differentiation of cells of the inner dental epithelium and the dental papilla, i.e., the ameloblasts and odontoblasts, respectively. In the inner dental epithelium, N-cadherin is co-expressed with E-cadherin, excluding the occurrence of cadherin switching such as observed during human tooth development. While early lethality of N-cadherin knockout mice prevents any functional study of N-cadherin in mouse odontogenesis, zebrafish parachute (pac) mutants, deficient for N-cadherin, survive beyond the age when primary teeth normally start to form. In these mutants, the first tooth forms, but its development stops at the early cytodifferentiation stage. N-cadherin deficiency also completely inhibits the development of the other first-generation teeth, possibly due to the absence of N-cadherin signaling once the first tooth has differentiated.
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Cadherinas/metabolismo , Diferenciación Celular/fisiología , Odontogénesis/fisiología , Germen Dentario/metabolismo , Proteínas de Pez Cebra/metabolismo , Animales , Cadherinas/genética , Diferenciación Celular/genética , Odontoblastos/metabolismo , Odontogénesis/genética , Distribución Tisular , Germen Dentario/crecimiento & desarrollo , Pez Cebra , Proteínas de Pez Cebra/genéticaRESUMEN
Transcriptional activation of CTNNA3, encoding αT-catenin, by the Y153H mutated form of the human STOX1 transcription factor was proposed to be responsible for altered fetal trophoblast invasion into the maternal endometrium during placentation in pre-eclampsia. Here we have generated a mouse model to investigate the in vivo effects of ectopic αT-catenin expression on trophoblast invasion. Histological analysis was used to determine the invasive capacities of trophoblasts from transgenic embryos, as well as proliferation rates of spongiotrophoblasts in the junctional zone. Augmented expression of αT-catenin reduced the number of invading trophoblasts but did not cause embryonic mortality. The, αT-catenin positive cells could still invade into the decidual layer and migrated as deeply as wild-type trophoblasts. Furthermore, the junctional zone is enlarged in placentas of mice overexpressing αT-catenin due to hyperproliferation of the residing spongiotrophoblasts, suggesting a pivotal role of αT-catenin levels in the control of the proliferative versus invasive state of trophoblasts during placentation. Our study provides, for the first time, in vivo data on the effects of increased levels of αT-catenin in the placenta.
Asunto(s)
Placentación/fisiología , Trofoblastos/fisiología , alfa Catenina/genética , Animales , Proliferación Celular , Embrión de Mamíferos/metabolismo , Femenino , Expresión Génica , Heterocigoto , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mutación , Placenta/química , Placenta/citología , Placenta/metabolismo , Embarazo , Proteínas/genética , ARN no Traducido , Trofoblastos/citología , alfa Catenina/análisis , alfa Catenina/fisiologíaRESUMEN
Rho GTPases regulate diverse cellular functions including adhesion, cytokinesis and motility, as well as the activity of the transcription factors NF-kappaB, serum response factor and C/EBP. alpha-Catulin, an alpha-catenin-related protein that shares structural similarities with cytoskeletal linker proteins, facilitates Rho signalling by serving as a scaffold for the Rho-specific guanine nucleotide exchange factor Lbc. We report here that alpha-catulin also interacts with a key component of the NF-kappaB signalling pathway, namely the IkappaB kinase (IKK)-beta. In co-immunoprecipitations, alpha-catulin can bind IKK-beta and Lbc. Ectopic expression of alpha-catulin augmented NF-kappaB activity, promoted cell migration and increased resistance to apoptosis, whereas knockdown experiments showed the opposite effects. Together, these features suggest that alpha-catulin has tumorigenic potential.
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Apoptosis/genética , Quinasa I-kappa B/metabolismo , FN-kappa B/metabolismo , alfa Catenina/metabolismo , alfa Catenina/fisiología , Apoptosis/efectos de los fármacos , Movimiento Celular/genética , Células Cultivadas , Medio de Cultivo Libre de Suero/farmacología , Citoprotección/genética , Células HeLa , Humanos , Mediadores de Inflamación/metabolismo , Unión Proteica , Factor Rho/metabolismo , Factor Rho/fisiología , Transducción de Señal/fisiología , Distribución Tisular , Transfección , Factor de Necrosis Tumoral alfa/farmacología , alfa Catenina/genéticaRESUMEN
Armadillo-like proteins are characterized by a series of armadillo repeats that are typically 42 to 45 amino acids in length. Three major subfamilies of Armadillo-like proteins can be distinguished on the basis of their number of repeats, their overall sequence similarity, and dispersion of the repeats throughout the protein. One of these is the p120(ctn)/plakophilin subfamily, which contains at least six members. We mapped the corresponding human genes by PCR on a monochromosomal cell hybrid mapping panel and by fluorescence in situ hybridization. The gene for plakophilin-1 (PKP1) was located at 1q32, the plakophilin-2 gene (PKP2) was located at 12p13, while the gene for p0071 was located at 2q23-q31. We confirmed the chromosomal localization of the p120(ctn) gene (CTNND1) at 11q11, the ARVCF gene at 22q11, and the delta-catenin/NPRAP gene (CTNND2) at 5p15. Although some of the Armadillo proteins are highly related to one another, the corresponding genes are dispersed throughout the human genome.
Asunto(s)
Moléculas de Adhesión Celular/genética , Adhesión Celular/fisiología , Mapeo Cromosómico , Proteínas de Drosophila , Fosfoproteínas/genética , Proteínas/genética , Transactivadores , Proteínas del Dominio Armadillo , Cateninas , Bandeo Cromosómico , Cromosomas/genética , Desmosomas/fisiología , Humanos , Hibridación Fluorescente in Situ , Proteínas de Insectos/genética , Linfocitos/metabolismo , Datos de Secuencia Molecular , Placofilinas , Reacción en Cadena de la Polimerasa , Catenina deltaRESUMEN
We report on a novel Armadillo-like protein, termed plakophilin-3. The human protein, which is encoded by a 2.8 kb messenger RNA, has a predicted molecular mass of 87 kDa. The protein comprises 10 Armadillo-like repeats, preceded by an amino-terminal region of 293 amino acid residues and followed by a short carboxy-terminal region of 27 amino acid residues. Plakophilin-3 is classified as a member of the p120(ctn)/plakophilin subfamily of Armadillo proteins based on the number and organization of the Armadillo repeats and its high sequence similarity to other members of this family. CLUSTAL W alignment of p120(ctn)/plakophilin subfamily members showed the plakophilin-3 protein to be most similar to plakophilin-1 and -2. Western blot analysis of plakophilin-3 revealed expression in all epithelial cell lines tested but not in foreskin fibroblasts and various sarcoma-derived cell lines. This is unlike most other members of the p120(ctn)/plakophilin subfamily, which are widely expressed. By immunofluorescence, the plakophilin-3 protein was colocalized with desmoglein in desmosomes of epithelial cells. In addition, an intriguing speckle-like nuclear staining was observed. Hence, like plakophilin-1 and -2, plakophilin-3 displays a dual intracellular location, i.e. in the desmosomal plaque and in the nucleus. These results suggest the involvement of plakophilin-3 in both desmosome-dependent adhesion and signaling pathways. Furthermore, the human plakophilin-3 gene was mapped on the chromosomal locus 11p15 by fluorescent in situ hybridization.
Asunto(s)
Moléculas de Adhesión Celular/genética , Moléculas de Adhesión Celular/metabolismo , Núcleo Celular/metabolismo , Desmosomas/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Moléculas de Adhesión Celular/química , Línea Celular , Mapeo Cromosómico , Cromosomas Humanos Par 11/genética , Clonación Molecular , Cartilla de ADN/genética , Células Epiteliales/metabolismo , Humanos , Inmunohistoquímica , Ratones , Datos de Secuencia Molecular , Peso Molecular , Placofilinas , Proteínas/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Secuencias Repetitivas de Ácidos Nucleicos , Homología de Secuencia de AminoácidoRESUMEN
The Armadillo protein p120(ctn) associates with the cytoplasmic domain of cadherins and accumulates at cell-cell junctions. Particular Armadillo proteins such as beta-catenin and plakophilins show a partly nuclear location, suggesting gene-regulatory activities. For different human E-cadherin-negative carcinoma cancer cell lines we found expression of endogenous p120(ctn) in the nucleus. Expression of E-cadherin directed p120(ctn) out of the nucleus. Previously, we reported that the human p120(ctn) gene might encode up to 32 protein isoforms as products of alternative splicing. Overexpression of p120(ctn) isoforms B in various cell lines resulted in cytoplasmic immunopositivity but never in nuclear staining. In contrast, upon expression of p120(ctn) cDNAs lacking exon B, the isoforms were detectable within both nuclei and cytoplasm. A putative nuclear export signal (NES) with a characteristic leucine-rich motif is encoded by exon B. This sequence element was shown to be required for nuclear export and to function autonomously when fused to a carrier protein and microinjected into cell nuclei. Moreover, the NES function of endogenously or exogenously expressed p120(ctn) isoforms B was sensitive to the nuclear export inhibitor leptomycin B. Expression of exogenous E-cadherin down-regulated nuclear p120(ctn) whereas activation of protein kinase C increased the level of nuclear p120(ctn). These results reveal molecular mechanisms controlling the subcellular distribution of p120(ctn).
Asunto(s)
Cadherinas/fisiología , Moléculas de Adhesión Celular/biosíntesis , Núcleo Celular/fisiología , Fosfoproteínas/biosíntesis , Adenocarcinoma , Secuencia de Aminoácidos , Neoplasias de la Mama , Cadherinas/genética , Cateninas , Moléculas de Adhesión Celular/análisis , Moléculas de Adhesión Celular/genética , Núcleo Celular/ultraestructura , Neoplasias del Colon , Exones , Femenino , Humanos , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Orgánulos/fisiología , Orgánulos/ultraestructura , Fosfoproteínas/análisis , Fosfoproteínas/genética , Isoformas de Proteínas/análisis , Isoformas de Proteínas/biosíntesis , Isoformas de Proteínas/genética , Proteínas Recombinantes/análisis , Proteínas Recombinantes/biosíntesis , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Transfección , Células Tumorales Cultivadas , Catenina deltaRESUMEN
A pseudogene (CTNNAP1) for the human alpha E-catenin gene was isolated from a human genomic phage library. The pseudogene sequence shows 90% similarity to the alpha E-catenin mRNA at the nucleotide level. Thirty-eight stop codons in all three reading frames and multiple other mutations were found, indicating that the pseudogene does not encode a functional protein. No introns were found in the region corresponding to the open reading frame of the alpha E-catenin cDNA, and two direct repeats flank this same region. Hence, the pseudogene can be classified as a processed pseudogene. Polymerase chain reaction with pseudogene-specific primers on genomic DNA and cDNA from human cell lines and healthy blood donors demonstrated the general occurrence of the pseudogene and the lack of its transcription. By fluorescence in situ hybridization the pseudogene was mapped to human chromosome 5q22 and the alpha E-catenin gene to the formerly disputed locus 5q31. This is the first report of a pseudogene for a member of the cadherin-catenin cell-cell adhesion complex.
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Cromosomas Humanos Par 5 , Proteínas del Citoesqueleto/genética , Genes , Seudogenes , Secuencia de Bases , Línea Celular , Mapeo Cromosómico , Proteínas del Citoesqueleto/clasificación , ADN Complementario/genética , Biblioteca de Genes , Humanos , Hibridación Fluorescente in Situ , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , Reacción en Cadena de la Polimerasa , Secuencias Repetitivas de Ácidos Nucleicos , Homología de Secuencia de Ácido Nucleico , alfa CateninaRESUMEN
The E-cadherin-catenin complex, by mediating intercellular adhesion, regulates the architectural integrity of epithelia. Down-regulation of its expression is thought to contribute to invasion of carcinoma cells. To investigate the involvement of the E-cadherin-catenin adhesion system in the progression of human bronchopulmonary carcinomas, we compared the immunohistochemical distribution of E-cadherin, alpha-catenin, and beta-catenin in four human bronchial cancer cell lines with different invasive abilities and in 44 primary bronchopulmonary tumors. Although invasive bronchial cell lines did not express E-cadherin and alpha-catenin, complete down-regulation of cadherin-catenin complex expression was a rare event in vivo in bronchopulmonary carcinomas. Nevertheless, a spotty and cytoplasmic pattern of E-cadherin and catenins was observed in 32 primary tumors, only in invasive tumor clusters. Immunoprecipitation experiments showed that this redistribution was not related to a disruption of cadherin-catenin interaction but to down-regulated tyrosine phosphorylation of E-cadherin. We conclude that loss of E-cadherin and/or catenins is not a prominent early event in the invasive progression of human bronchopulmonary carcinomas in vivo. The decreased tyrosine phosphorylation of E-cadherin may reflect a loss of functionality of the complex and implicates a major role in tumor invasion.
Asunto(s)
Cadherinas/metabolismo , Proteínas del Citoesqueleto/metabolismo , Neoplasias Pulmonares/metabolismo , Transactivadores , Tirosina/metabolismo , Adenocarcinoma/metabolismo , Adenocarcinoma/patología , Carcinoma Broncogénico/metabolismo , Carcinoma Broncogénico/patología , Carcinoma de Células Escamosas/metabolismo , Carcinoma de Células Escamosas/patología , Regulación hacia Abajo , Humanos , Sustancias Macromoleculares , Invasividad Neoplásica , Fosforilación , Células Tumorales Cultivadas , alfa Catenina , beta CateninaRESUMEN
The human beta-catenin gene (CTNNB1) has been localized to 3p22-->p21.3 by fluorescence in situ hybridization. Recent studies have suggested the presence of one or more tumor suppressor genes on the short arm of chromosome 3. This raises the possibility that CTNNB1, for which important features are already known, is involved in tumor progression.
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Cromosomas Humanos Par 3 , Proteínas del Citoesqueleto/genética , Transactivadores , Secuencia de Bases , Mapeo Cromosómico , Humanos , Hibridación Fluorescente in Situ , Microscopía Fluorescente , Datos de Secuencia Molecular , beta CateninaRESUMEN
Catenins were discovered as proteins that are linked to the cytoplasmic domain of transmembrane cadherins. Among these junctional plaque proteins are several members of the Armadillo gene family: beta-catenin, plakoglobin, and p120ctn. Recently it became clear that some catenins also mediate nuclear signaling. We performed a detailed analysis of the human p120ctn gene (HGMW-approved symbol CTNND1) and its transcripts. The human p120ctn gene comprises 21 exons, potentially encoding up to 32 protein isoforms as products of alternative splicing. Human isoforms, designated 1 to 4, differ from each other by the start codon used. Additional isoforms are derived from combinations with alternatively used exons A (exon 18) and B (20), near the end of the open reading frame, and also with exon C (11) in the middle of the open reading frame. Hence, the longest isoform is of type 1ABC and comprises 968 amino acid residues. The functional consequence of the observed multitude of p120ctn splice variants awaits further study, but tissue-specific expression was obvious. Further, we demonstrate that the exon organization, which is not simply related to the Armadillo repeat structure, is very well conserved between the p120ctn gene and the related ARVCF gene, but not at all between these two genes and the beta-catenin or plakoglobin genes. The present data favor the concept that p120ctn is the prototype of a subfamily of Armadillo proteins, comprising ARVCF, p0071, delta-catenin/NPRAP, and plakophilins 1 and 2, that are more related to each other than to other Armadillo proteins.
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Empalme Alternativo/genética , Moléculas de Adhesión Celular/genética , Clonación Molecular , Fosfoproteínas/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Cateninas , Moléculas de Adhesión Celular/química , Codón Iniciador/genética , Codón de Terminación/genética , ADN Complementario/genética , Biblioteca de Genes , Humanos , Intrones/genética , Ratones , Datos de Secuencia Molecular , Técnicas de Amplificación de Ácido Nucleico , Sistemas de Lectura Abierta/genética , Fosfoproteínas/química , Reacción en Cadena de la Polimerasa , ARN Mensajero/genética , Análisis de Secuencia de ADN , Células Tumorales Cultivadas , Catenina deltaRESUMEN
E-cadherin is a Ca(2+)-dependent epithelial cell-cell adhesion molecule. Downregulation of E-cadherin expression often correlates with strong invasive potential and poor prognosis of human carcinomas. By using recombinant lambda phage, cosmid, and P1 phage clones, we isolated the full-length human E-cadherin gene (CDH1). The gene spans a region of approximately 100 kb, and its location on chromosome 16q22.1 was confirmed by FISH analysis. Detailed restriction mapping and partial sequence analysis of the gene allowed us to identify 16 exons and a 65-kb-long intron 2. The intron-exon boundaries are highly conserved in comparison with other "classical cadherins." In intron 1 we identified a 5' high-density CpG island that may be implicated in transcription regulation during embryogenesis and malignancy.
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Cadherinas/genética , Cromosomas Humanos Par 16 , Genes , Secuencia de Aminoácidos , Secuencia de Bases , Adhesión Celular , Mapeo Cromosómico , Clonación Molecular , Elementos de Facilitación Genéticos , Exones , Regulación de la Expresión Génica , Humanos , Hibridación Fluorescente in Situ , Intrones , Datos de Secuencia Molecular , Invasividad Neoplásica , Alineación de Secuencia , Homología de Secuencia de AminoácidoRESUMEN
A prominent tyrosine-phosphorylated protein of approximately 100 kDa (designated pp100) in epidermal growth factor (EGF)-stimulated A431 cells was found to be a main interaction partner of the protein-tyrosine phosphatase SHP-1 in pull-down experiments with a glutathione S-transferase-SHP-1 fusion protein. Binding was largely mediated by the N-terminal SH2 domain of SHP-1 and apparently direct and independent from the previously described association of SHP-1 with the activated EGF receptor. pp100 was partially purified and identified by mass spectrometric analysis of tryptic fragments, partial amino acid sequencing, and use of authentic antibodies as the 3A isoform of the Armadillo repeat protein superfamily member p120 catenin (p120(ctn)). Different p120(ctn) isoforms expressed in human embryonal kidney 293 cells, exhibited differential binding to SHP-1 that correlated partly with the extent of EGF-dependent p120(ctn) tyrosine phosphorylation. Despite strong phosphorylation, p120(ctn) isoforms 3B and 3AB bound, however, less readily to SHP-1. SHP-1 associated transiently with p120(ctn) in EGF-stimulated A431 cells stably transfected with a tetracycline-responsive SHP-1 expression construct, and p120(ctn) exhibited elevated phosphorylation upon a tetracycline-mediated decrease in the SHP-1 level. Functions of p120(ctn), which are regulated by tyrosine phosphorylation, may be modulated by the described SHP-1-p120(ctn) interaction.
Asunto(s)
Moléculas de Adhesión Celular/metabolismo , Fosfoproteínas/metabolismo , Proteínas Tirosina Fosfatasas/metabolismo , Dominios Homologos src , Cateninas , Línea Celular , Electroforesis en Gel de Poliacrilamida , Factor de Crecimiento Epidérmico/metabolismo , Humanos , Péptidos y Proteínas de Señalización Intracelular , Peso Molecular , Fosforilación , Unión Proteica , Proteína Tirosina Fosfatasa no Receptora Tipo 11 , Proteína Tirosina Fosfatasa no Receptora Tipo 6 , Proteínas Tirosina Fosfatasas con Dominio SH2 , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Catenina deltaRESUMEN
Cadherins are major cell-cell adhesion proteins whose cytoplasmic domains bind to catenin proteins. Strong intercellular adhesion depends on linkage of the cadherin/catenin complex to the actin cytoskeleton via alpha-catenin. To date, it is not clear how different cell types achieve the variable strength of cell-cell adhesion clearly needed in a multicellular organism. Here, we report the cloning and molecular characterization of alphaT(testis)-catenin, a novel human cDNA encoding a protein with homology to both human alphaE(epithelial)-catenin and alphaN(neural)-catenin. Although originally discovered in testis, alphaT-catenin is expressed in other tissues, the highest levels being observed in heart. Immunohistochemical analysis showed human alphaT-catenin localization at intercalated discs of cardiomyocytes and in peritubular myoid cells of testis. In cells transfected with alphaT-catenin cDNA, interaction with beta-catenin was demonstrated by co-immunoprecipitation. Transfection of alpha-catenin-deficient colon carcinoma cells recruited E-cadherin and beta-catenin to cell-cell contacts and functional cadherin-mediated cell-cell adhesion was restored in this way. Moreover, compaction of these cells was at least as prominent as in the case of cells expressing endogenous alphaE-catenin. We propose that alphaT-catenin is necessary for the formation of stretch-resistant cell-cell adhesion complexes, in particular, muscle cells.
Asunto(s)
Cadherinas/metabolismo , Cadherinas/fisiología , Proteínas del Citoesqueleto/química , Proteínas del Citoesqueleto/metabolismo , Proteínas del Citoesqueleto/fisiología , Transactivadores , Secuencia de Aminoácidos , Animales , Western Blotting , Adhesión Celular , Comunicación Celular , Línea Celular , Células Cultivadas , Clonación Molecular , ADN Complementario/metabolismo , Electroforesis en Gel de Poliacrilamida , Proteínas Fluorescentes Verdes , Humanos , Inmunohistoquímica , Proteínas Luminiscentes/metabolismo , Masculino , Ratones , Microscopía Fluorescente , Datos de Secuencia Molecular , Músculos/citología , Miocardio/citología , Miocardio/metabolismo , Plásmidos/metabolismo , Pruebas de Precipitina , Unión Proteica , Estructura Terciaria de Proteína , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Aminoácido , Testículo/citología , Testículo/metabolismo , Distribución Tisular , Transfección , Células Tumorales Cultivadas , Vinculina/metabolismo , alfa Catenina , beta CateninaRESUMEN
Little is known about the the signalling pathways driving the adenoma-to-carcinoma sequence in human colonic epithelial cells. Accumulation and activation of the src tyrosine kinase in colon cancer suggest a potential role of this oncogene in this early progression. Therefore, we introduced either activated src (m-src), polyoma-MT alone or combined with normal c-src in the adenoma PC/AA/C1 cell line (PC) to define the function and phenotypic transformations induced by these oncogenes in familial adenomatous polyposis (FAP) colonic epithelial cells. Functional expression of these oncoproteins induced the adenoma-to-carcinoma conversion, overexpression of the hepatocyte growth factor (HGF) receptor Met, but failed to confer invasiveness in vivo and in vitro, or to produce alterations in cell proliferation and differentiation. In contrast, PC-msrc cells became susceptible to the HGF-induced invasion of collagen gels and exhibited sustained activation of the pp60src tyrosine kinase and Tyr phosphorylation of the 120-kDa E-cadherin, which was further increased by HGF Transcripts of HGF were clearly identified by reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot in the parental and transformed PC cells, suggesting an autocrine mechanism. Taken together, the data indicate that: (1) experimental activation of src and PyMT pathways directly induces tumorigenicity and Met upregulation in a colon adenoma cell line; (2) HGF-activated Met and src cooperate in inducing invasion; (3) in view of the molecular associations between catenins and cadherin or the tumour-suppressor gene product APC, the cell adhesion molecule E-cadherin may constitute a downstream effector of src and Met.