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 415 records · Page 23Linked to original sources
PubMed1996

Intermediate filament aggregates in mitoses of primary cutaneous neuroendocrine (Merkel cell) carcinoma.

Primary cutaneous neuroendocrine carcinomas express different kinds of intermediate filaments and frequently in a 'paranuclear globular' pattern. We have observed the same pattern not only in interphase but also in mitotic cells, which are very frequent in these tumours. We report a quantitative and morphological study of eight primary cutaneous neuroendocrine carcinomas stained with different antibodies against cytokeratins (CAM 5.2 and anticytokeratin 20), neurofilaments (70 kDa and 200 kDa) and peripherin. We have found a predominance of CAM 5.2 expression in interphase cells and of neurofilament proteins in mitotic cells; 87.02% of the interphase cells were positive with CAM 5.2 whereas only 6.08% were positive for neurofilaments (P < 0.01); 35.41% of the mitotic cells were positive with CAM 5.2, whereas 50% were positive for neurofilaments (P < 0.01). A correlation between a globular pattern of intermediate filament proteins and prognosis has not been found. We describe for the first time the division of neoplastic cells with a globular pattern; the presence of intermediate filament proteins with a globular pattern in all mitotic stages; and the uneven distribution of this formation between the two daughter cells.

Aged↗
PubMed1999

Insoluble gamma-tubulin-containing structures are anchored to the apical network of intermediate filaments in polarized CACO-2 epithelial cells.

We have previously shown that a thin ( approximately 1 microm) layer of intermediate filaments located beneath the apical membrane of a variety of simple epithelial cells participates in the organization of apical microfilaments and microtubules. Here, I confirmed the apical distribution of gamma-tubulin-containing structures (potential microtubule-organizing centers) in CACO-2 cells and demonstrated perfect colocalization of centrosomes and nearly 50% of noncentrosomal gamma-tubulin with apical intermediate filaments, but not with apical F-actin. Furthermore, the antisense-oligonucleotide-mediated downregulation of cytokeratin 19, using two different antisense sequences, was more efficient than anticytoskeletal agents to delocalize centrosomes. Electron microscopy colocalization suggests that binding occurs at the outer boundary of the pericentriolar material. Type I cytokeratins 18 and 19 present in these cells specifically coimmunoprecipitated in multi-protein fragments of the cytoskeleton with gamma-tubulin. The size and shape of the fragments, visualized at the EM level, indicate that physical trapping is an unlikely explanation for this result. Drastic changes in the extraction protocol did not affect coimmunoprecipitation. These results from three independent techniques, indicate that insoluble gamma-tubulin-containing structures are attached to apical intermediate filaments.

Acrylamide↗
PubMed1982

Differentiation of the myofibrils and the intermediate filament system during postnatal development of the rat heart.

The differentiation of the myofibrils and the intermediate filament system during postnatal development of the rat heart has been investigated. Several aspects of some of the structural proteins, that means the intermediate filament subunit skeletin, myosin, and the myofibrillar M-line proteins MM-creatine kinase and myomesin have been studied by using gel electrophoresis as well as enzyme and immunohistochemical techniques in combination with electron microscopy of both plastic and cryosectional material. We show that marked changes take place in the organization of the intermediate filament system and in the contractile apparatus, both in atria and in ventricles of the rat heart during postnatal development. In the newborn rats no dense myofibrillar M-bands were present in the M-region and the sarcomeric bands were irregular while in the four-week-old rats dense M-bands composed of a set of five crossbridges interconnecting the thick filaments were present. The sarcomeric bands were now regular. These observations are related to the presence of different isomyosins in the atria and in the ventricles of the newborn and the four-week-old rats, to the observation that MM-creatine kinase was only present in the M-region in the four-week old rats and to the physiological maturation of the heart.

Animals↗
PubMed1999

Molecular parameters of type IV alpha-internexin and type IV-type III alpha-internexin-vimentin copolymer intermediate filaments.

During neuronal development, a dynamic replacement mechanism occurs in which the type VI nestin and type III vimentin intermediate filament proteins are replaced by a series of type IV proteins beginning with alpha-internexin. We have explored molecular details of how the type III to type IV replacement process may occur. First, we have demonstrated by cross-linking experiments that bacterially expressed forms of alpha-internexin and vimentin form heterodimer molecules in vitro that assemble into copolymer intermediate filaments. We show using a urea disassembly assay that alpha-internexin molecules are likely to be more stable than those of vimentin. Second, by analyses of the induced cross-links, we have determined the axial lengths of alpha-internexin homodimer and alpha-internexin-vimentin heterodimer molecules and their modes of alignments in filaments. We report that these dimensions are the same as those reported earlier for vimentin homopolymer molecules and, by implication, are also the same for the other neuronal type IV proteins. These data suggest that during neuronal development, alpha-internexin molecules are readily assimilated onto the pre-existing vimentin cytoskeletal intermediate filament network because the axial lengths and axial alignments of their molecules are the same. Furthermore, the dynamic replacement process may be driven by a positive equilibrium due to the increased stability of the alpha-internexin network.

Amino Acid Sequence↗
PubMed2002

Patterns of nestin and other intermediate filament expression distinguish between gastrointestinal stromal tumors, leiomyomas and schwannomas.

The KIT-positive specific gastrointestinal stromal tumors (GISTs), leiomyomas, and schwannomas are the three most common types of primary mesenchymal tumors of the gastrointestinal (GI) tract. The intermediate filaments are abundant cytoskeletal proteins commonly used as cell differentiation markers in diagnostic immunohistochemistry. Their patterns have not been fully characterized in GI mesenchymal tumors, and could offer differential diagnostically useful parameters. Very recently, nestin, a class VI intermediate filament expressed in neuroectodermal stem cells and skeletal muscle progenitor cells, has been shown in GISTs and suggested as a marker for these tumors. In this study we immunohistochemically examined the expression of nestin and other intermediate filament proteins, including desmin, keratins (Ks), glial fibrillary acidic protein (GFAP), neurofilament, and vimentin in GISTs of different sites, esophageal leiomyomas and GI schwannomas. Nestin was nearly consistently present in GISTs of different locations whether spindle cell or epithelioid, and benign or malignant. It was also detected in 23 of 24 (96%) GI schwannomas, whereas leiomyomas were uniformly negative. Vimentin was present in both GISTs and schwannomas, whereas it was typically absent in leiomyomas (25% positive, usually focally). Desmin was present in all leiomyomas, whereas only 3% of GISTs (4 of 140) were positive, and all schwannomas were negative. K18 was detected in a minority of GISTs, leiomyomas, and schwannomas. Malignant GISTs were more commonly keratin positive than the benign ones; there was 18% K18 positivity in malignant gastric and small intestinal GISTs, but 9% K18 positivity in benign gastric and small intestinal GISTs. Moreover, K8, albeit to a lesser degree, was detected in a minority of GISTs, but K7, K14, K19 and K20 were not detected. GFAP was present in the majority of schwannomas, whereas all GISTs were negative; some leiomyomas had weak cytoplasmic positivity. These results document distinctive patterns of intermediate filament proteins in GI mesenchymal tumors. Nestin is confirmed to be consistently expressed in GISTs but it is also present in most GI schwannomas; GFAP is helpful when separating GISTs and schwannomas, since only the latter are positive. The potential presence of K8 and K18 in GISTs should not lead to the misdiagnosis of carcinoma on biopsy.

Biomarkers, Tumor↗
PubMed1986

Antibodies to intermediate filaments in surgical pathology.

Most mammalian nucleated cells contain a cytoplasmic fibril system called intermediate filaments. Unlike other cytoskeletal proteins, the subunit proteins of intermediate filaments show a remarkable cell-type-specificity in their expression: mesenchymal, muscle, epithelial, glial and neuronal cells containing each their cell type specific filaments. In this review we discuss the possibilities to use antibodies to these filaments in the diagnosis and histogenetic analysis of human tumors. This approach is based on findings which indicate that these filaments retain their cell-type specific expression also in tumors.

Antibodies↗
PubMed1988

Effect of the intermediate filament inhibitor IDPN on steroid secretion by frog adrenal glands.

In order to determine the role of intermediate filaments in adrenal steroidogenesis, we have studied the effect of IDPN (beta-beta'iminodipropionitrile), an intermediate filaments perturbing agent, on corticosteroid secretion by frog interrenal glands in vitro. A 6-h administration of IDPN (10(-3) M) did not affect the spontaneous release of corticosterone and aldosterone. While IDPN did not alter the response of adrenal fragments to ACTH, the drug caused a marked decrease in angiotensin II-induced stimulation of corticosterone and aldosterone production. These results indicate that, in contrast to microfilaments, which play an important role in spontaneous steroidogenesis, intermediate filaments are not required for basal corticosteroid secretion but are involved in the mechanism of action of angiotensin in frog adrenocortical cells.

Actin Cytoskeleton↗
PubMedDate not supplied

Expression of the intermediate filament peripherin in skin tumors.

Peripherin is a neuronal intermediate filament reportedly expressed in neuroendocrine skin carcinomas and some melanocytic tumors. In order to assess the diagnostic usefulness of antibodies to peripherin in dermatopathology, we studied its expression in 68 skin tumors mostly of neural origin, and compared this expression with that of neurofilaments, a well-established neuronal marker. Antibodies to peripherin and neurofilaments both labeled dermal neurons present in normal skin and within the tumors. Specific labeling of tumor cells for peripherin was seen in only 2/5 neuroendocrine skin carcinomas, 3/18 benign nevi and 7/19 melanomas; even in these cases the percentage of tumor cells did not exceed 20%. We conclude that antibodies to peripherin may be used for the demonstration of cutaneous neurons in normal and diseased skin; however their diagnostic usefulness appears limited, less than that of antibodies to neurofilaments.

Humans↗
PubMed2004

Vmac: a novel protein associated with vimentin-type intermediate filament in podocytes of rat kidney.

Vimentin-type intermediate filaments (IFs) play an important role in cytoskeletal organization and cell morphology. We identified here a novel protein associated with vimentin-type IFs and named it vimentin-type IF-associated coiled-coil protein (Vmac). Vmac consists of 171 amino acids with a calculated Mr of 18,844 and has a coiled-coil domain in its N-terminal region and the PDZ-binding tetrapeptide consensus motif in its C-terminal region. Northern blotting showed that the Vmac mRNA was expressed in many rat tissues examined but most abundantly expressed in the kidney. Immunofluorescence microscopy revealed that Vmac was highly concentrated at podocytes of renal glomeruli. Podocytes are highly specialized epithelial cells characterized by a large cell body and numerous foot processes, and express vimentin-type IFs that are distributed in the cell body and the major processes. Immunoelectron microscopy revealed that Vmac was associated with vimentin-type IFs of podocytes. These results indicate that Vmac is a novel protein associated with vimentin-type IF in podocytes of rat kidney.

Amino Acid Sequence↗
PubMed1990

The role of intermediate filaments in adrenal steroidogenesis.

Cholesterol is stored in adrenal cells as ester in lipid droplets, which are transported to mitochondria to provide a substrate for steroid hormone synthesis. Using mouse adrenal tumour cells (Y-1), we show here that approximately 33% of the adrenal cell cholesterol ester is bound tightly to intermediate filaments while the rest is either loosely attached or free in the cytosol. Specific binding of droplets to intermediate filaments was demonstrated by immunofluorescence and electron microscopy. Immunofluorescence was based upon Nile Red to stain lipid and antibodies to vimentin, actin and tubulin. Electron microscopy, including immunoelectron microscopy with protein A conjugated to gold particles (5 nm), was used to examine whole mounts of cytoskeletons and intermediate filaments. Immunofluorescence reveals that bound droplets are surrounded by a capsule containing vimentin and can be removed from the filaments by extraction with ethanol or 6 M urea. Negative staining of the urea extracts revealed isolated droplets. To the extent that cholesterol ester is the storage form of steroidogenic cholesterol, the knowledge that lipid droplets containing such esters are attached to intermediate filaments may prove important in unravelling the complex process of the transport of cholesterol to mitochondria.

Adrenal Gland Neoplasms↗
PubMed1986

Intermediate filaments in the newborn inner ear of the mouse.

The presence of intermediate filaments in the inner ear of the newborn mouse was analyzed with immunofluorescence techniques using antibodies against the five classes of intermediate filaments: cytokeratins, vimentin, desmin, neurofilaments and glial fibrillary acid protein (GFA). Neurofilaments were found in all nerve fibers from the ganglion cell to the hair cell. In the vestibular ganglion two subpopulations of ganglion cells were identified: a minor part staining intensively with neurofilament and the major part of cells lacking this immunofluorescence. Vimentin occurred in a number of supporting structures in the membranous labyrinth, but not in vestibular or cochlear ganglion cells. Cytokeratins, desmin or GFA were not identified in the inner ear.

Animals↗
PubMedDate not supplied

Differential diagnosis of lymph node aspirates by intermediate filament typing of tumor cells.

Twenty-one lymph node aspirates for which a differential diagnosis was difficult or not possible by light microscopy alone were selected for further study by intermediate filament typing. The use of four monoclonal antibodies specific for different keratin subsets or for vimentin resulted in a definitive diagnosis in all instances. The results show that use of these antibodies can improve the accuracy of cytologic diagnosis and provide further evidence that intermediate filament typing can help differentiate (1) malignant melanoma from adenocarcinoma, (2) malignant lymphoma from small-cell anaplastic carcinoma and (3) squamous-cell carcinoma from adenocarcinoma. Intermediate filament typing can also be used to identify very small numbers of carcinoma cells in specimens that are apparently negative for tumor cells by light microscopy. The method is quick, relatively simple, reliable and unambiguous, provided that appropriate questions are asked and antibodies with well-defined specificities are used.

Antibodies, Monoclonal↗
PubMed1986

An electron microscopic study of the interaction in vitro of vimentin intermediate filaments with vesicles prepared from Ehrlich ascites tumor cell lipids.

The interaction of intermediate filaments prepared from pure, delipidated vimentin with vesicles obtained from Ehrlich ascites tumor (EAT) cell lipids was studied employing sucrose density gradient centrifugation in combination with electron microscopy. In negative stain electron microscopy, preformed vimentin filaments were seen in lateral association with lipid vesicles; end-on contacts of filaments with liposomes were rarely detected. When the reaction of filaments with vesicles was carried out at 0 degree C, sucrose density gradient equilibrium centrifugation of the reaction products led to the banding of relatively light filament-vesicle meshworks in clear separation from free filaments and free vesicles. With certain vimentin and lipid preparations, occasionally partial breakdown of the filaments during centrifugation and banding of vesicle-free fragments in denser regions of the sucrose gradients was observed. However, when the reaction mixtures were incubated at 37 degrees C prior to sucrose gradient analysis, all filaments were released from vesicles and totally fragmented during centrifugation. Electron microscopy showed unraveling of the filament fragments into subfilament strands. Employing lipid vesicles labeled with [3H]cholesterol, a low but significant amount of radioactivity was found to be associated with the fragments in a non-vesicular form. Filament reconstitution experiments performed in the presence of EAT cell lipids revealed an inhibitory effect of vesicles on filament assembly, particularly at lower temperatures. The mechanical labilization of the filament structure by lipid vesicles might play a role in the redistribution of intermediate filaments in the course of certain cellular processes involving turnover and fragmentation of intracellular membrane systems.

Animals↗
PubMed1998

Effects of follicle-stimulating hormone on intermediate filaments and cell division of Sertoli cells of fetal rat testis in culture.

The present study was aimed to examine the effects of follicle-stimulating hormone (FSH) on cell division of Sertoli cells from rat fetal testes and on the kinetics of 2 kinds of intermediate filaments, cytokeratin and vimentin, which comprise the cytoskeleton of Sertoli cells. Testes from rat fetuses of different ages (from day 15 to day 17 of gestation ) were cultured for 48 hr, with or without added FSH. In 15-day testes, FSH influenced neither cell division of Sertoli cells nor kinetics of intermediate filaments. In 16-day testes, FSH promoted cell division of Sertoli cells and kinetic differentiation of intermediate filaments distributed toward the lumen of the seminiferous tubules. These findings suggest that 16-day testes in culture can respond to FSH in a fashion that cell division of Sertoli cells is promoted and that intermediate filaments increase in number and change in intracellular distribution. It is concluded that FSH influences both proliferation and morphological differentiation of Sertoli cells.

Animals↗
PubMed1993

cDNA analysis of the 49 kDa lens fiber cell cytoskeletal protein: a new, lens-specific member of the intermediate filament family?

Two proteins, with molecular weights of 49 (CP49) and 115 kDa (CP115) as judged by SDS PAGE, have been shown by immunocytochemistry to be components of the beaded filament, a cytoskeletal structure thus far demonstrated only in the lens fiber cell. We have used antibodies reactive with CP49 to screen a mouse lens cDNA expression library. An immunoreactive clone with an approximately 1.0 kb insert was identified and purified. DNA sequence analysis shows the presence of an open reading frame that extends from the upstream cloning site for 660 bases. Contained within this reading frame are 2 peptide sequences nearly identical to 2 peptide sequences obtained from purified bovine CP49. Northern analysis revealed that the mRNA for the CP49 is not detectable in mouse brain, muscle, lung, liver, or heart. A search of the Genbank database showed that the partial cDNA sequence for the murine CP49 is unique, but that this partial sequence shows a strong similarity to multiple members of the intermediate filament family, with greatest similarity to type I acidic cytokeratins. The data presented here suggests that the CP49 is related to, and possibly represents a new member of the intermediate filament family. These data, in concert with previously published work, suggests 1) the CP49 and CP115, which have been localized to the beaded filament, are related to the family of IF proteins, and 2) these two proteins comprise a cytoskeletal structure which is structurally distinct from classical 8-11 nm intermediate filaments, thus possibly comprising a structurally novel form of intermediate filament.

Amino Acid Sequence↗
PubMed1988

The complete sequence of the human intermediate filament chain keratin 10. Subdomainal divisions and model for folding of end domain sequences.

We present the complete amino acid sequence of the human keratin 10 (type I) intermediate filament chain expressed in terminally differentiated epidermal cells. Comparisons of this sequence with its mouse and bovine counterparts allow us to describe structural features of the functional end domains. First, sections of their respective end domains are highly conserved and permit a redefinition of earlier models for their subdomainal organization. The amino-terminal end domain consists of El, the first 57-58 residues that are basic, glycine-rich, and have been highly conserved among the three species; V1, a region of well-defined quasi repeats of the motif aliphatic-serine/glycinen; and H1, a newly recognized short acidic sequence that has been conserved among the type I keratin family. The carboxyl-terminal end consists of V2 and E2 whose properties but not sequence resemble V1 and E1, respectively. Second, since the E1, H1, and E2 sequences have been highly conserved between the three species, we suggest they are critical elements in defining intermediate filament function. Third, we note that the E and V sequences of the keratin 10 (and other keratin) chains share many properties in common with protein chain turns found in globular proteins. We therefore propose a model in which these sequences form omega loop-like structures (Leszczynski, J. N. & Rose, G. D. (1986) Science 234, 849-855) on the surface of keratin intermediate filaments. This represents the first specific proposal for the end domain structure of any intermediate filament chain.

Amino Acid Sequence↗
PubMed1983

Immunocytochemical studies of intermediate filament aggregates and their relationship to microtubules in cultured skin fibroblasts from patients with giant axonal neuropathy.

Giant axonal neuropathy (GAN) is a severe autosomal recessive disease affecting both the peripheral and central nervous systems. It is characterized by segmental axonal ballooning due to large neurofilamentous masses and abnormal aggregation of filaments in other cell types including glial cells. Coomassie blue staining of the detergent-resistant cytoskeleton of cultured skin fibroblasts from three patients with GAN revealed the presence of large cytoplasmic filamentous aggregates in the great majority of cells. The aggregates were birefringent when viewed under polarization microscopy and electron microscopy showed that they were composed of aggregates of 8 to 10 nm intermediate filaments. The aggregates stained with antisera specific for vimentin but did not stain with antibodies to actin, tubulin, or the high molecular weight (HMW) microtubule associated protein. Examination of the fibroblasts containing the vimentin aggregates with antibodies to tubulin and the HMW protein showed that they had a normal distribution of microtubules and that the microtubules present were normally associated with the HMW protein. The results suggest that giant axonal neuropathy is a generalized inborn error of organization of intermediate filaments and that a defect in microtubules or their association with HMW protein is not responsible for the observed aggregation of intermediate filaments in this disease. Further study of GAN may be useful in understanding the function of intermediate filaments.

Child↗
PubMed1983

Polyacrylamide gel electrophoretic screening of mammalian cells cultured in vitro for the presence of the intermediate filament protein vimentin.

A total of 53 different cell lines originating from a variety of mammalian species were cultured in vitro and analysed for the presence of vimentin, employing polyacrylamide gradient slab gel electrophoresis in urea/acetic acid as buffer system. Irrespective of the cell culture conditions, and the growth potential and morphology of the cells, vimentin was expressed in all cell lines examined, with two exceptions: MPC-11 mouse myeloma and MOPC-31C mouse plasmacytoma cells. Immunoblotting with the monoclonal antibody alpha-IFA, which is directed against an antigenic determinant shared by all classes of intermediate filaments, did not detect any other of the known intermediate filament proteins in MPC-11 and MOPC-31C cells. Vimentin synthesized by various cell lines was characterized by four different criteria: (1) its extractability with Triton X-100 under various ionic conditions; (2) its behaviour in (NH4)2SO4 fractionation of cellular extracts; (3) its electrophoretic mobility in polyacrylamide gel electrophoresis in urea/acetic acid; and (4) the co-isolation of polypeptides of higher electrophoretic mobility, which, by comparison with degradation products of vimentin obtained with the Ca2+-activated proteinase specific for intermediate filament proteins in vitro, were identified as products of Ca2+-dependent proteolysis of vimentin. Although the degradation products occurred in different ratios in extracts of different cell lines, they constituted the same characteristic set of proteins whenever degradation of vimentin was observed. The formation of proteolytic breakdown products could be partially to totally suppressed when the cells were harvested, washed and processed in the presence of EGTA and proteinase inhibitors. The experimental data show that: (1) vimentin, as well as the Ca2+-activated proteinase specific for intermediate filament proteins, is highly conserved during the evolution of mammalian species; (2) the proteolytic breakdown products of vimentin, which give rise to a characteristic 'staircase' in two-dimensional gel electrophoresis, are probably artefacts of isolation; (3) the expression of vimentin is neither a prerequisite for nor necessarily indicative of rapid cell proliferation in vitro; and (4) the techniques described can be used for the routine identification of vimentin in cells and tissues in case vimentin-specific antibodies are not available.

Animals↗