Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Intermediate Filaments”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1982

The amino acid sequence of chicken muscle desmin provides a common structural model for intermediate filament proteins.

The complete amino acid sequence of muscle desmin reported here is the first for an intermediate filament protein. Alignment with partial data available for vimentin, glial fibrillary acid protein, neurofilament 68 K, two wool alpha-keratins, and a recently described DNA clone covering 90% of an epidermal keratin shows that all seven proteins have extensive homologies and therefore form a complex multigene family, the intermediate filament proteins. The hard alpha-keratins of wool appear to be a special subset of epithelial keratins. The sequence information reveals, as the dominant structural principle, a rod-like middle domain arising from several alpha-helical segments able to form interchain coiled-coil elements. The proposed helices are separated by short spacers, which like the two terminal domains seem built from non-alpha-helical material. Attention is drawn to the sometimes very striking sequence homologies along the rod and the high sequence variability in the terminal domains. Finally, chemical cross-linking experiments performed on the isolated desmin rod show that intermediate filament structure seems not to be based on triple-stranded coiled-coils as currently thought, but rather reflects protofilament units built as a dimer of normal interchain double-stranded coiled-coils.

Amino Acid Sequence↗
PubMed2001

Anomalous apical plasma membrane phenotype in CK8-deficient mice indicates a novel role for intermediate filaments in the polarization of simple epithelia.

Previous results from our laboratory have indicated a requirement for CK intermediate filaments (IF) for the organization of the apical domain in polarized epithelial cells in culture. The results seemed to be challenged by the phenotype of cytokeratin (CK) 8-deficient mice, which comprises only colorectal hyperplasia, female sterility and a weaker hepatocyte integrity. In this work localization with anti-CK antibodies indicated that many Ck8-/- epithelia still form IF in CK8-deficient mice, perhaps because of the expression of the promiscuous CK7. In the small intestine, only villus enterocytes lacked IFs. These cells appeared to lose syntaxin 3, and three apical membrane proteins (alkaline phosphatase, sucrase isomaltase and cystic fibrosis transmembrane conductance regulator) as they progressed along the villus. At the distal third of the villi, gamma-tubulin was found scattered within the cytoplasm of enterocytes, in contrast to its normal sub-apical localization, and the microtubules were disorganized. These results could not be attributed to increased numbers of apoptotic or necrotic cells. The only other cell type we found without IFs in CK8 null mice, the hepatocyte, displayed increased basolateral levels of one apical marker (HA4), indicating a correlation between the lack of intermediate filaments and an apical domain phenotype. These data suggest a novel function for intermediate filaments organizing the apical pole of simple polarized epithelial cells.

Amino Acid Sequence↗
PubMed1998

Intermediate filament cytoskeletal proteins associated with bovine lens native membrane fractions.

PURPOSE: To examine the intermediate filament cytoskeletal proteins associated with native membrane fractions isolated from bovine lenses. METHODS: Decapsulated bovine lenses were divided into cortex and nucleus. The lens regions were homogenized and separated into water-soluble and water-insoluble fractions by centrifugation. Sedimenting membrane fractions were isolated from the water-insoluble fraction by discontinuous sucrose-density-gradient centrifugation and the non-sedimenting membrane fractions were isolated from the Kbr high-density water-soluble fractions by flotation, during overnight centrifugation. The intermediate filament peptides of the membrane fractions were examined by Western blot analysis, using monoclonal antibodies to filensin, cytoskeletal protein 49 (CP49) and vimentin. RESULTS: Filensin immunoreactive peptides were found in all membrane fractions of both cortex and nucleus. The parent 115 kDa filensin was found almost exclusively in the urea-soluble protein of cortical membrane fractions, and was the predominant filensin immunoreactive peptide only in the urea-soluble protein of the cortical sedimenting membrane fraction isolated from the 25%/45% sucrose density interface. The predominant filensin immunoreactive peptide of all other samples migrated with a M(r) of 53 kDa. CP49 immunoreactive peptides were found almost exclusively in the urea-soluble protein of all membrane fractions from both the cortex and nucleus. The cortical non-sedimenting membrane fraction and the nuclear membrane fraction of the 25%/45% sucrose density interface were notably deficient in CP49. Vimentin immunoreactive peptides were found in both urea-soluble and urea-insoluble proteins of membrane fractions from the cortex only. Vimentin was particularly enriched in the cortical non-sedimenting membrane fraction. The urea-insoluble filensin immunoreactive peptides were only partially removed by alkali extraction, indicating a very avid association with the membrane. Two dimensional electrophoresis revealed that the urea-soluble protein of the major cortical membrane fraction contained two different filensin-derived 53 kDa fragments. CONCLUSIONS: The non-sedimenting membrane fraction, which may reflect a distinct domain of the lens plasma membrane, possesses a membrane-associated cytoskeletal composition different from that of the major sedimenting membrane fractions.

Animals↗
PubMed1997

Experimental co-expression of vimentin and keratin intermediate filaments in human breast cancer cells results in phenotypic interconversion and increased invasive behavior.

The expression of intermediate filament proteins is remarkably tissue specific, which suggests that the intermediate filament type(s) present in cells is somehow related to their biological function. However, in some cancers, particularly malignant breast carcinoma, there is a strong indication that vimentin is co-expressed with keratins, thus presenting as a dedifferentiated or interconverted (between epithelial and mesenchymal) phenotype. In the present study, we recapitulated the interconverted phenotype by developing stable transfectants of MCF-7 human breast cancer cells, termed MoVi clones, to express both vimentin and keratins. Overexpression of vimentin in these cells led to augmentation of motility and invasiveness in vitra. These activities could be transiently down-regulated by vimentin antisense oligonucleotides in MoVi clones and MDA-MB-231 cells (which constitutively co-express keratins and vimentin). Furthermore, in the MoVi experimental transfectants expressing the highest percentage of vimentin-positive cells, their proliferative capacity, clonogenic potential, and tumorigenicity increased. However, the metastatic ability of the MoVi transfectants remained unchanged compared with MCF-7neo controls. The MDA-MB-231 cells metastasized to axillary lymph nodes in a SCID mouse model. Finally, we explored the possibility that potential changes could occur with respect to cell surface integrins. These studies revealed a decrease in the alpha 2- and alpha 3-containing promiscuous integrins, in addition to beta 1 containing integrins, concomitant with an increase in the alpha 6-containing laminin receptor integrin. Further functional analysis of the alpha 6 observation showed an increase in the baptotactic migration of MoVi transfectants toward a laminin substrate. From these data, it is postulated that the ability to co-express vimentin and keratins confers a selective advantage to breast cancer cells in their interpretation of signaling cues from the extracellular matrix; however the addition of vimentin intermediate filaments alone is not sufficient to confer the metastatic phenotype.

Animals↗
PubMed1985

Coexpression of intermediate filaments in human epithelial neoplasms.

A wide variety of human neoplasms were examined by immunocytochemical and ultrastructural techniques. In most, one intermediate filament (IF) type was expressed reflecting the tissue of origin. However, multiple classes of intermediate filaments were regularly found in a subgroup of these tumors. We chose to subdivide them into those with a complex or mixed growth pattern, and those which showed a more "monomorphic" histologic growth pattern. This latter group is the subject of this paper. Regular coexpression of cytokeratin and vimentin was observed in tumors of endometrial, thyroid, ovarian and renal origin, and coexpression of cytokeratin and neurofilament was observed in a subgroup of neuroendocrine tumors. Immunocytochemical/ultrastructural correlation demonstrated few, if any, observable intermediate filaments in tumors expressing only low molecular weight cytokeratin, whereas vimentin and neural filament characteristically were randomly dispersed or formed whorled bundles of cytoplasmic filaments. The potential diagnostic usefulness of these observations in surgical pathology is discussed.

Carcinoid Tumor↗
PubMed1989

Relationship between tektins and intermediate filament proteins: an immunological study.

Affinity-purified antibodies raised against three flagellar tektins (tektin A, B, and C) from each of two sea urchin species (Lytechinus pictus and Strongylocentrotus purpuratus) were used to study the immunological relationship between tektins and intermediate filament proteins. By immunofluorescence microscopy, several antitektins revealed a staining of intermediate filament-like arrays in three vertebrate cell lines tested. Immunoelectron microscopy substantiated the cross reaction of antitektins with intermediate filaments. When the cells were treated with cytochalasin B, the arrangement of the filaments recognized by anti-(Lp)-tektin B was altered; the alteration observed is typical for keratin filaments. By immunoblot, it was found that anti-(Lp)-tektin B cross reacted with two isoforms or different proteins of approximately 54 kD with pIs of 6.1 and 6.2 in human carcinoma epithelia (HeLa) cells and with two isoforms or different proteins of approximately 55 kD with pIs of 6.1 and 6.3 in pig kidney epithelia (LLC-PK1) cells. Furthermore, when antitektin antibodies were affinity purified with the 54 kD HeLa keratin, these keratin-specific antibodies again restained the original tektins on immunoblots. From these observations, it can be concluded that tektins and keratins are to a certain extent immunologically related. To determine the degree of the immunological relationship, tektin filaments and purified intermediate filaments from HeLa cells were cleaved with alpha-chymotrypsin and examined by quantitative immunoblot analysis. On immunoblots of digested tektins from L. pictus, anti-(Lp)-tektin B recognized several cleavage products in the range of 20 kD to 46 kD. However, when immunoblots of digested intermediate filaments from HeLa cells were probed, the cross reaction of anti-(Lp)-tektin B with HeLa keratins was eliminated by more than 98% within 2 min, suggesting that tektins have epitopes in common with the end domains of certain keratins.

Animals↗
PubMed1991

Complexity of expression of intermediate filament proteins, including glial filament protein, in endometrial and ovarian adenocarcinomas.

The expression patterns of intermediate filament proteins of primary and metastatic endometrial (n = 18) and ovarian (n = 24) adenocarcinomas were analyzed by immunocytochemistry using a panel of specific antibodies and by gel electrophoresis of cytoskeletal preparations, followed by immunoblotting. All cells of all endometrial adenocarcinomas studied contained the "simple epithelial"-type cytokeratins (CKs) 8, 18, and (mostly) 19, with variable numbers of cells also positive for CK 7 and vimentin. In addition, most of these tumors contained individual cells or groups of cells that were positive for the stratification-related CKs 4, 5, 6, 13, 14, and 17. The latter CKs were often associated with squamous cell foci, but were also found in some single (nonsquamous) tumor cells, indicative of early stages of squamous cell differentiation. Ovarian carcinomas of various histologic types and grades contained predominantly CKs 7, 8, 18, and 19. Serous, endometrioid, and anaplastic tumors, but not mucinous and clear cell tumors, also contained minor amounts of stratification-related CKs in variable combinations, mostly including CK 4. In all tumor types except mucinous tumors, vimentin was consistently detected in variable proportions of tumor cells which, however, were rather low in anaplastic carcinomas. Surprisingly, glial filament protein was detected in a minor proportion (< or = 20%) of tumor cells in seven of 14 serous and endometrioid ovarian carcinomas and in three of 18 endometrial carcinomas. These different intermediate filament expression patterns of müllerian duct-type carcinomas, only partly related to the morphologic appearance of the specific type of tumor, might reflect the multipotentiality of differentiation of müllerian duct-derived epithelia. Cytoskeletal features of potential diagnostic value, especially in metastatic carcinomas, are discussed.

Adenocarcinoma↗
PubMed1992

Identification and developmental expression of a novel low molecular weight neuronal intermediate filament protein expressed in Xenopus laevis.

Xenopus laevis is a valuable model system for the study of vertebrate neuroembryogenesis. However, very few well-characterized nervous system-specific molecular markers are available for studies in this organism. We screened a X. laevis adult brain cDNA library using a cDNA probe for mouse low molecular weight neurofilament protein (NF-L) in order to identify neuron-specific intermediate filament proteins. Clones for two distinct neuron-specific intermediate filament proteins were isolated and sequenced. One of these encoded for a Xenopus NF-L (XNF-L) and the other for a novel neuron-specific Xenopus intermediate filament protein (XNIF) that was present earlier and more abundantly than XNF-L during development. XNIF contained a central rod domain with multiple sequence features characteristic of IF proteins. The XNF-L was very similar to mouse NF-L, with a 77% sequence identity in the rod domain and the presence of a polyglutamic acid region in the tail domain, characteristic of type IV neurofilament proteins. In contrast, XNIF showed only 60% identity to mouse NF-L in the rod domain and lacked the glutamic acid-rich sequence in the tail domain. XNIF also had a very low (approximately 38%) sequence identity in the head and tail domains as compared to NF-L and other neurofilament proteins (45% identity to the head domain of alpha-internexin). In the adult frog, XNIF mRNA is detected by Northern blots only within the nervous system and by in situ hybridization histochemistry exclusively in neurons, particularly in the medullary reticular system and spinal cord. Antisera raised against the unique tail region of XNIF detected a single distinct 60 kDa band in Western blots of nervous system cytoskeletal preparations, and this XNIF immunoreactivity was concentrated in axons in the PNS and in small perikarya in the dorsal root ganglion. In contrast, NF-L immunoreactivity was principally in the large perikarya in the dorsal root ganglion. In development, XNIF mRNA appears more abundant than XNF-L mRNA in all premetamorphic stages examined. XNIF mRNA is first detectable at stage 24 (26 hr), whereas stable expression of XNF-L is at stage 35/36 (50 hr). XNIF immunoreactivity is detectable within the cement gland, within many neuronal cell bodies and axon tracts within the developing nervous system, and within all cellular layers of the developing retina. The availability of these two distinct neuron-specific intermediate filament proteins, with different temporal and spatial expression patterns, should provide new markers as well as targets for functional perturbation in the developing X. laevis nervous system.

Amino Acid Sequence↗
PubMed1986

Changes in the organization of non-epithelial intermediate filaments induced by triethyl lead chloride.

The in vivo effect of triethyl lead chloride (TriEL) (10(-6)-10(-8) M) on the organization of non-epithelial intermediate filaments (vimentin and desmin filaments) was studied by indirect immunofluorescence microscopy employing different mammalian cell lines. The in vitro effect of TriEL on filament formation as well as on the structure of preformed filaments was investigated by electron microscopy. TriEL induces perinuclear coil formation of intermediate filaments in SV40-transformed human fibroblasts and baby hamster kidney (BHK21) cells. The rearrangements observed are not correlated with significant changes in the microtubular system as tested by double labelling of both filament systems. The effect of TriEL is reversible. Assembly of intermediate filaments in vitro is disturbed in the presence of TriEL such that only short filaments and various kinds of fragments are formed. When preformed filaments are incubated in the presence of TriEL, unravelling of fibres into protofilamentous strands is observed. Possible mechanisms of TriEL-filament interaction are discussed.

Animals↗
PubMed1978

Heavy meromyosin labeling of intermediate filaments in cultured connective tissue cells.

Mild treatment with trypsin causes a radical change in the heavy meromyosin (HMM) binding properties of intermediate filaments in glycerinated, myosin-extracted cultured chick embryo connective tissue cells. In non-trypsin-treated cells, HMM labeling of filaments was often indistinct and variable in its distribution. By contrast, in cells treated with trypsin (under conditions which allowed most intermediate filaments to survive), virtually all filaments, including those of intermediate size, decorated with HMM to give distinct arrowhead patterns. We suggest that most intermediate filaments in such cells contain a core of F-actin masked by trypsin-labile accessory proteins.

Actins↗
PubMed1986

Distribution of intermediate filament proteins in normal and diseased human glomeruli.

The distribution of intermediate filament proteins (vimentin, desmin, and cytokeratin) was studied by means of immunofluorescence in the normal human and rat glomerulus and in pathologic human glomeruli. Antifibronectin antibodies were used as mesangial markers. In normal human glomeruli, vimentin antibodies stained endothelial cells, podocytes, and mesangial cells; desmin antibodies, surprisingly, stained podocytes. In normal rat glomeruli, the pattern of vimentin staining was the same as in humans, but desmin antibodies stained both mesangial cells and podocytes. In human and rat glomeruli cytokeratin staining was confined to segments of Bowman's capsule. In human pathologic glomeruli, vimentin and desmin antibodies stained the structures that were positive in normal glomeruli, giving a characteristic pattern for each pathologic condition examined. These results are compatible with the mesenchymal origin of podocytes and mesangial cells and suggest that both cells have smooth muscle-like phenotypic features. Mesangial cells may have slightly different differentiation paths in humans and rats, leading to a distinct expression of intermediate filament proteins.

Animals↗
PubMed1989

Visualization of intermediate filaments in living cells using fluorescently labeled desmin.

Fluorescently labeled desmin was incorporated into intermediate filaments when microinjected into living tissue culture cells. The desmin, purified from chicken gizzard smooth muscle and labeled with the fluorescent dye iodoacetamido rhodamine, was capable of forming a network of 10-nm filaments in solution. The labeled protein associated specifically with the native vimentin filaments in permeabilized, unfixed interphase and mitotic PtK2 cells. The labeled desmin was microinjected into living, cultured embryonic skeletal myotubes, where it became incorporated in straight fibers aligned along the long axis of the myotubes. Upon exposure to nocodazole, microinjected myotubes exhibited wavy, fluorescent filament bundles around the muscle nuclei. In PtK2 cells, an epithelial cell line, injected desmin formed a filamentous network, which colocalized with the native vimentin intermediate filaments but not with the cytokeratin networks and microtubular arrays. Exposure of the injected cells to nocadazole or acrylamide caused the desmin network to collapse and form a perinuclear cap that was indistinguishable from vimentin caps in the same cells. During mitosis, labeled desmin filaments were excluded from the spindle area, forming a cage around it. The filaments were partitioned into two groups either during anaphase or at the completion of cytokinesis. In the former case, the perispindle desmin filaments appeared to be stretched into two parts by the elongating spindle. In the latter case, a continuous bundle of filaments extended along the length of the spindle and appeared to be pinched in two by the contracting cleavage furrow. In these cells, desmin filaments were present in the midbody where they gradually were removed as the desmin filament network became redistributed throughout the cytoplasm of the spreading daughter cells.

Animals↗
PubMed1993

Binding of lipid droplets and mitochondria to intermediate filaments in rat Leydig cells.

We have examined the distribution of lipid droplets and mitochondria in relation to the cytoskeletons of Leydig cells in primary culture by using light and electron microscopy on living, intact and detergent-extracted cells. After mild extraction with Triton X-100 lipid droplets and mitochondria retained their original distribution within the cell. Double immunofluorescent microscopy showed that both structures co-localise with intermediate filaments. Transmission electron microscopy of intact (unextracted) and mildly extracted Leydig cells showed that intermediate filaments are closely associated with mitochondria and lipid droplets. By examination of stereo pairs, intermediate filaments were shown to establish direct contact with mitochondria and lipid droplets. The association of droplets and mitochondria with intermediate filaments suggests possible mechanisms by which the transport of cholesterol takes place from droplets to mitochondria where this substrate enters the steroidogenic pathway.

Animals↗
PubMed1992

Selective distribution of the 66-kDa neuronal intermediate filament protein in the sensory and autonomic nervous system of the guinea-pig.

The immunohistochemical distribution of a recently identified 66-kDa neurofilament protein (NF-66) was investigated in peripheral and autonomic ganglia of the guinea-pig where it has been previously established that other neuronal intermediate filament proteins have a selective distribution. NF-66 immunoreactivity was observed in distinct subpopulations of neurons and did not coexist completely with either the neurofilament triplet or a 57-kDa intermediate filament protein (peripherin). NF-66 labelling was identical to that observed with an antibody to a 150-kDa intermediate filament or associated protein (CH1). These results further demonstrate that different neuronal intermediate filament proteins are present in selective subpopulations of neurons and that these proteins are, therefore, likely to have cell type-specific roles.

Animals↗
PubMed1983

Intermediate filaments as histologic markers: an overview.

Determination of the type of intermediate filaments (IFs) present in a cell or tissue can yield information about its origin. Thus cells can be grouped into six different classes, i.e. epithelial cells characterized by cytokeratins, most but not all neurones characterized by neurofilaments (NFs), glial cells characterized by the presence of glial fibrillary acidic filaments, muscle cells characterized by the presence of desmin filaments, mesenchymal cells and certain other nonepithelial cell types characterized by the presence of vimentin, and other cells that appear not to contain IFs. The assignments made by immunologic techniques are supported by protein chemistry of the isolated proteins. Information derived from protein sequences as well as from DNA sequences establish that the major intermediate-filament proteins are different but related molecules and show also that the alpha-keratins of wool belong to this multigene family. Applications of IF typing to human pathologic material, and especially to the different major subgroups of human tumors, are reviewed. Thus, for instance, carcinomas continue to express cytokeratins, many tumors of neuronal origin express NFs, gliomas express glial fibrillary acidic protein (GFA), rhabdomyosarcomas express desmin, and nonmuscle sarcomas express vimentin. Further subclassification of epithelial cells and carcinomas is discussed. The subdivisions obtained by IF typing are striking because they follow well-known histologic principles; thus IF typing seems useful in certain instances where diagnosis is difficult by conventional techniques.

Animals↗
PubMed2002

Interaction of periplakin and envoplakin with intermediate filaments.

Periplakin is a component of desmosomes and the epidermal cornified envelope. Its N-terminal domain interacts with the plasma membrane; it heterodimerises with envoplakin via its rod domain; and its C-terminus interacts with intermediate filaments. Periplakin has the shortest C-terminus of the plakin family, comprising only the linker domain found in all conventional plakins. By transient transfection of COS7 cells and primary human epidermal keratinocytes with deletion mutants of the periplakin C-terminus we mapped sequences required for intermediate filament interaction to two regions of the linker motif that are most highly conserved amongst the plakins. The results were confirmed by overlay assays of the binding of in vitro translated periplakin constructs to keratins and vimentin. We found that envoplakin and periplakin could still associate with each other when parts of their rod domains were deleted and, surprisingly, that removal of the entire rod domain did not completely inhibit their interaction. Co-transfection of constructs containing the C-termini of envoplakin and periplakin suggested that the periplakin C-terminus may stabilise the interaction of the envoplakin C-terminus with intermediate filaments. We conclude that the periplakin C-terminus plays an important role in linking periplakin and envoplakin to intermediate filaments.

Amino Acid Sequence↗
PubMed1985

Identification of basement membrane components and intermediate filaments in calcifying epithelial odontogenic tumors.

An immunohistochemical technique was used on paraffin-embedded tissues of four cases of calcifying epithelial odontogenic tumors (CEOT). These studies were performed to gain an additional understanding of the nature of amyloid-like deposits in these tumors. For these studies antibodies to Type IV collagen, laminin, and the five classes of intermediate filament proteins were employed. In all of the tumors examined basement membrane components and intermediate filament proteins (cytokeratin) were demonstrated both in the epithelial tumor islands and within the extracellular amyloid-like deposits. Antibodies to vimentin intermediate filaments were localized only in the stromal fibroblasts. Limited proteolysis or the use of a chaotropic agent was required to express the antigenic determinants present. These studies substantiate the presence of basement membrane components in the amyloid-like deposits of CEOT. In addition, these extracellular deposits are shown to be heterogenous in composition by the immunohistochemical demonstration of cytokeratin intermediate filament proteins.

Adult↗
PubMed1979

Isolation and partial characterization of intermediate filament protein (skeletin) from cow heart Purkinje fibres.

The intermediate filament protein skeletin from cow heart Purkinje fibres was purified to homogeneity by a selective extraction procedure and gel chromatography in the presence of sodium dodecyl sulphate. Monospecific antibodies were obtained by immunisation of rabbits with the sodium dodecyl sulphate-skeletin complex, and rocket electrophoresis made it possible to quantify the concentration of protein. The skeletin monomer has a molecular weight of 55 000. Amino acid analysis revealed that skeletin has a high content of glutamic acid, aspartic acid, alanine and leucine, together constituting more than 50% of the molecule. The isoelectric point is determined as 6.35. Skeletin is insoluble at pH 4--6 in the absence of detergent and shows increasing solubility at higher and lower pH. The biochemical characteristics are discussed in relation to the cytoskeletal function of the filaments. Comparison with intermediate-sized filament protein of other tissues show certain important similarities suggesting that the filaments may share a common evolutionary ancestry.

Amino Acids↗