PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Intermediate Filaments”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 55 records · Page 3Linked to original sources
PubMed1993

A cDNA from Drosophila melanogaster encodes a lamin C-like intermediate filament protein.

A novel intermediate filament cDNA, pG-IF, has been isolated from a Drosophila melanogaster embryonic expression library screened with a polyclonal antiserum produced against a 46 kDa cytoskeletal protein isolated from Kc cells. This 46 kDa protein is known to be immunologically related to vertebrate intermediate filament proteins. The screen resulted in the isolation of four different cDNA groups. Of these, one has been identified as the previously characterized Drosophila nuclear lamin cDNA, Dm0, and a second, pG-IF, demonstrates homology to Dm0 by cross hybridization on Southern blots. DNA sequence analysis reveals that pG-IF encodes a newly identified intermediate filament protein in Drosophila. Its nucleotide sequence is highly homologous to nuclear lamins with lower homology to cytoplasmic intermediate filament proteins. pG-IF predicts a protein of 621 amino acids with a predicted molecular mass of 69,855 daltons. In vitro transcription and translation of pG-IF yielded a protein with a SDS-PAGE estimated molecular weight of approximately 70 kDa. It contains sequence principles characteristic of class V intermediate filament proteins. Its near neutral pI (6.83) and the lack of a terminal CaaX motif suggests that it may represent a lamin C subtype in Drosophila. In situ hybridization to polytene chromosomes detects one band of hybridization on the right arm of chromosome 2 at or near 51A. This in conjunction with Southern blot analysis of various genomic digests suggests one or more closely placed genes while Northern blot analysis detects two messages in Kc cells.

Amino Acid Sequence↗
PubMed1985

Intermediate filaments with novel protein composition from certain goldfish cells.

Using the conditions for vimentin filament recycling, intermediate filaments (approximately 10 nm) were prepared from the cytoskeleton of a goldfish tumor cell line (erythrophoroma or xanthophoroma). 2-D analysis showed unusual protein composition, with four proteins of molecular weights of 60, 45, 56 and 51 kilodaltons in ratios of approximately 4:4:1:1. These correspond to four of the major cytoskeletal proteins of both the tumor cells and normal xanthophores.

Animals↗
PubMedDate not supplied

Prenatal low-dose gamma irradiation of the inner ear induces changes in the expression of intermediate filaments.

The expression of intermediate filaments (1F) was analysed in the inner ear in normally developed adult CBA/CBA mice and in mice of the same age which had been gamma irradiated in utero with a low dose 1-2 Gy single exposure. Well characterized monoclonal antibodies (mAbs) against all classes of intermediate filament proteins (cytokeratins-Cks, vimentin, neurofilaments, desmin and glial fibrillar acidic protein) were used. With the exception of neurofilament proteins, the expression of intermediate filament proteins was the same in adult normal and irradiated inner ears, irrespective of gestational age at exposure. A complex Ck pattern occurred in the various cell types comprising the membranous labyrinth. In spite of the differences in cell shape and internal organization of organelles, epithelia actively involved in inner ear fluid homeostasis (stria vascularis, dark cell epithelium, endolymphatic duct and sac) revealed, according to our mAbs, the same expression of Cks, except for the mouse counterpart of human Ck 7, which was found exclusively in the stria vascularis and the endolymphatic duct and sac. The pattern of intermediate filament composition in the labyrinth was the same in the mouse as in man. Irradiation on gestational days 12 or 13 (the otocyst stage)--but not at more advanced embryonic age--induced immunoreactivity for neurofilament proteins in vestibular hair cells (HC) and to a minor extent also in cochlear HC. No such positivity was found in the control material.

Abnormalities, Radiation-Induced↗
PubMed1996

[Intermediate filaments].

The antibodies for intermediate filaments, including keratin, vimentin, desmin, GFAP and neurofilaments, have been much useful in routinely-processed immunohistochemical study for identifying characteristics of tumor cells or making the definite diagnosis. In general, when neoplastic transformation has taken place, the affected cells would reveal to some extent alterated immunolocalization of intermediate filaments in the cytoplasm. Whether the tumor cells are of epithelial or non-epithelial origin is significant from diagnostic points of view when utilizing those intermediate filaments as tumor markers. But there are many "exceptional" cases of epithelial tumors with expression of vimentin, or those of non-epithelial tumors with expression of keratin, indicating some "variants". Immunohistochemical application of the intermediate filaments is indispensable not only as "a diagnostic tool for surgical pathologists", but also a method for analyzing relationship between morphological changes and functional aspects of the tumor cells.

Humans↗
PubMed1988

[Intermediate filament proteins as markers in tumor diagnosis].

Classification of tumors is based on histogenesis and on determination of malignancy. In well differentiated neoplasias the tumor tissue reveals a similar morphological pattern similar to that of the normal tissue from which they have originated. In contrast less differentiated neoplasias do not show such similarities to normal tissue in conventional stains and special procedures such as electron microscopy or immunohistology have to be performed in order to detect cell specific products. In many undifferentiated tumors this is not possible because loss of differentiation and organisation in tumor cells do not allow the production of cell specific substances. A new possibility for determining the histogenesis of tumors is the use of antibodies which are specific for one type of intermediate filaments. Intermediate filaments are structures, which together with microtubules and microfilaments form the cytoskeleton. Intermediate filaments are composed of different polypeptides, which show a cell type specificity. Keratins are the intermediate filaments characteristically found in keratinizing and nonkeratinizing epithelia. Desmin is the specific intermediate filament type of sarcomeric, visceral and some type of vascular smooth muscle tissue. Vimentin filaments are characteristic of endothelial cells, fibroblasts, macrophages, chondrocytes and most but not all lymphatic cells and the only intermediate filament type present in these cells. Neurofilaments are composed of three different polypeptides, which form the so called neurofilament triplet and are characteristically found in central and peripheral neurons. Glial fibrillary acidic protein (GFAP) forms the intermediate filament system of normal and reactive astrocytes and also some ependymal cells contain GFAP. Thus cells and tissues can be divided into five different types by the use of appropriate polyclonal or monoclonal antibodies. In the current study we were interested to determine with a large number of specimens, whether primary tumors or metastases continue to express the intermediate type characteristic of the normal tissue. The following results demonstrate, there is abundant evidence that intermediate filaments can be used as cell type specific markers both for normal tissue and for tumors. 1. To exclude wrong negative results by intermediate filament typing, a reliable detection of intermediate filaments should be performed on cryostat sections or on material, which has been recently ethanol fixed and paraffin embedded. With many antibodies fixation of the tissue in formalin results in a decrease of reactivity.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomarkers, Tumor↗
PubMed1989

Intermediate filaments in biology and disease.

Intermediate filaments comprise a large heterogenous family of proteins in animal cells. Distinct from microfilaments and microtubules, they are a major component of the cytoskeleton and nuclear envelope. The expression of intermediate filament protein types is developmentally regulated and relatively cell type specific. Although there are at least five distinct classes of intermediate filament types, all the subunit proteins have similar structural features and appear to have envolved from some common gene ancestor. The cytoplasmic intermediate filaments exhibit a complex organization, forming associations with components of the nucleus, plasma membrane, and potentially other cytoplasmic structures such as microtubules. The specific function of this prominent cytoplasmic structure is currently unknown. However, the organization or expression of intermediate filaments is known to be altered in association with a variety of human diseases. Currently, specific antibodies to individual intermediate filament proteins are being used as an immunohistochemical aid for tumor typing in diagnostic pathology.

Animals↗
PubMed1986

The teleost cone cytoskeleton. Localization of actin, microtubules, and intermediate filaments.

This laboratory has been using the teleost retinal cone as a model for studying the mechanisms and regulation of retinal cell motility. In previous inhibitor studies, the authors have shown that dark-induced cone elongation requires microtubules, whereas light-induced contraction requires actin filaments. This study examines the distributions of actin filaments, microtubules, and intermediate filaments in the cone cytoskeleton. Actin filaments have been localized in isolated cones by labeling with fluorescent derivatives of phalloidin; microtubules were localized by immunofluorescent labeling with anti-tubulin. Actin, microtubule, and intermediate filament distributions have also been examined in detergent-lysed motile cell models of cones fixed with a new method that enhances preservation of the cytoskeleton. Longitudinal bundles of actin filaments extend from the cone's calycal processes through the ellipsoid and into the myoid. No actin filaments are detectable in the perinuclear region and axon, but filaments are present in both pre- and post-synaptic components of the synapse. Intermediate filaments are numerous in the perinuclear region and cone axon but relatively sparse in the myoid. In contrast, microtubule distribution is more uniform: numerous longitudinally oriented microtubules are present throughout the length of the cell. Thus the cone cytoskeleton reflects the highly polarized shape and function of the cell, with actin filaments localized to the distal movable part of the cell and intermediate filaments localized to the proximal part of the cell, which is anchored in the retina.

Actins↗
PubMed1994

Mallory body filaments become insoluble after normal assembly into intermediate filaments.

The deposition of 8-to-10-nm filaments into inclusion bodies is a fundamental cellular change that occurs in several degenerative processes of many tissues. However, little is known about the pathological filaments including whether the filaments assemble by the same mechanisms that govern the assembly of normal intermediate filaments. We have addressed this issue by studying the in vitro reassembly of the cytokeratin filaments that are deposited into experimental murine Mallory bodies (MBs) but have not yet become covalently crosslinked components of the MB. The reassembly process of both normal hepatocellular and MB-derived cytokeratins (CKs) was similar and characterized by a hierarchy of protofilament and protofibrils with a prominent axial periodicity of approximately 21 nm (normal hepatocellular CK, 20.7 +/- 2 nm; MB-derived CK, 20.1 +/- 2 nm). Purified MB-derived CK and normal hepatocellular CK comigrated in polyacrylamide gel electrophoresis indicating composition by similar CK isoforms. These results indicate that intermediate filaments formed from MB-derived CK are indistinguishable from filaments assembled from normal CK. On this basis, we conclude that the intermediate filaments that form inclusion bodies are not aberrantly assembled but become aggregated and post-translationally modified after their initial formation.

Animals↗
PubMed1992

Intermediate filament dynamics.

The view of intermediate filaments as static cytoskeletal elements is changing. Studies of exogenous intermediate filament proteins, either microinjected or expressed from transfected genes, have demonstrated that a continuous incorporation of subunits into the polymerized filaments is taking place. This incorporation appears to be required for maintaining normal cytoplasmic networks of intermediate filaments. At the post-translational level, phosphorylation is an important factor in regulating dynamic aspects of intermediate filament organization and structure.

Animals↗
PubMedDate not supplied

Alterations of intermediate filaments in various histopathological conditions.

Intermediate filament proteins belong to a multigene family and constitute an important cytoskeletal component of most vertebrate cells. Their pattern of expression is tissue specific and is highly controlled during embryonic development. Numerous pathologies are known to be associated with modifications of intermediate filament organisation, although their precise role has not yet been elucidated. The present review focuses on the most recent data concerning the possible causes of intermediate filaments disorganization in specific pathologic conditions affecting the epidermis, the liver, and the nervous system. We discuss the formation of abnormal intermediate filament networks that arise as a consequence of mutations that directly affect intermediate filament structure or are induced by multifactorial causes such as modifications of post-translational processes and changes in the levels of expression.

Humans↗
PubMed1982

The conduction system in the human heart at midgestation--immunohistochemical demonstration of the intermediate filament protein skeletin.

The intermediate filaments have during recent years increasingly attracted attention and new information on the distribution of the subunits of the filaments has become available by the use of specific antibodies. In the present study human fetal hearts at midgestation were studied with immunofluorescence microscopy for a demonstration of the intermediate filament subunit skeletin. In the ordinary ventricular and atrial myocytes the fluorescence was moderate, mainly concentrated to the Z disk levels. The proximal parts of the conduction system also showed a moderate fluorescence, while the fluorescence was intense in the cells in the peripheral parts. The shift from moderate to intense fluorescence occurred in the very proximal part of the left bundle branch and in the distal part of the intramural right bundle branch. We conclude that the conduction cells attain Purkinje fibre-like characteristics at these levels, as evidenced by the content of skeletin. Furthermore, the human fetal Purkinje fibres are more easily distinguished with the technique used herein than with conventional histological techniques. The observed differences in content of skeletin are discussed in terms of the cytoskeletal function of intermediate filaments and the embryology of the conduction system.

Cholinesterases↗
PubMed1993

Assembly of intermediate filaments.

The assembly of intermediate filaments is a fundamental property of the central rod domain of the individual subunit proteins. This rod domain, with its high propensity for alpha-helix formation, is the common and identifying feature of this family of proteins. Assembly occurs in vitro in the absence of other proteins or exogenous sources of energy; in vivo, it appears as if other factors, as yet poorly understood, modulate the assembly of intermediate filaments. Parallel, in-register dimers form via coiled-coil interactions of the rod domain. Tetramers may form from staggered arrays of parallel or antiparallel arrangements of dimers. Higher-order polymerization, which occurs spontaneously if the ionic strength of a mixture of dimers and tetramers is raised, proceeds rapidly through poorly described intermediates to the final 10 nm filament. This process is dependent on and modulated by the non-alpha-helical end domains, as well as those amino acids present at the very beginning and end of the rod domain. The interactions governing tetramer formation are most probably the same ones that are responsible for the lateral and longitudinal associations within intermediate filaments.

Amino Acid Sequence↗
PubMed1993

Network incorporation of intermediate filament molecules differs between preexisting and newly assembling filaments.

When studying the way in which intermediate filaments assemble in vivo, it is important to distinguish between the incorporation of intermediate filament proteins into an existing intermediate filament network and the ability to form a new network within cells. To distinguish between these alternatives, we have made a hybrid construct consisting of the rod and tail domains of murine glial fibrillary acidic protein (GFAP) coupled to the head domain of bovine keratin 19, called K19GFAP. The assembly characteristics of K19GFAP were analyzed in vitro and in vivo. Replacement of the head domain with the bovine K19 sequence did not prevent the incorporation of K19GFAP into the existing network of vimentin intermediate filaments in NIH 3T3 cells but it was incompatible with de novo formation of filament networks in the epithelial cell line MCF-7, which lacks an endogenous vimentin network. By in vitro assembly studies, it was confirmed that K19GFAP was unable to assemble into typical intermediate filaments. We also investigated the ability of an appropriate type II keratin partner to rescue K19GFAP from incorporation into a vimentin network and initiate de novo filament assembly, using the fibroblast cell line KF-K8(3), an NIH 3T3 fibroblast cell line expressing a single human keratin, K8. The results confirm the importance of the coiled coil interactions in determining the fate of intermediate filament proteins. The results also emphasize that filament networks can not only tolerate but also incorporate assembly-deficient intermediate filament protein subunits.

3T3 Cells↗
PubMed1983

Involvement of the N-terminal polypeptide of vimentin in the formation of intermediate filaments.

The potential to form intermediate filaments of a 54 X 10(3) molecular weight (Mr) polypeptide derived from vimentin by cleavage by the intermediate filament-specific, Ca2+-activated proteinase was investigated. Under physiological conditions of assembly, the breakdown product did not form intermediate filaments. Electron microscopy revealed short, rod-like structures similar to those described by Geisler et al. for a 38 X 10(3) Mr alpha-helical core particle derived from desmin. Since the specific, Ca2+-activated proteinase degrades vimentin preferentially from its N terminus, this result suggests the involvement of the basic, N-terminal polypeptide of vimentin in the assembly of intermediate filaments. This was supported by the observation that arginine inhibits the formation of intermediate filaments from intact vimentin. Whereas lysine had very little effect on the assembly process, guanidinium hydrochloride was effective at the same concentration as arginine. On the basis of these findings, an affinity chromatography method for the identification and isolation of intermediate filament subunit proteins was developed. Beside vimentin, desmin, the 68 X 10(3) Mr neurofilament triplet protein, the glial fibrillary acidic protein and cytokeratins also bound to arginine methylester Sepharose 4B in a salt-stable manner and could be eluted with arginine. The 145 X 10(3) Mr neurofilament triplet protein exhibited reduced binding activity, whereas the 210 X 10(3) Mr subunit did not bind to the affinity matrix. Among the degradation products of vimentin produced by the specific, Ca2+-activated proteinase, only those with molecular weights higher than 40 X 10(3) bound to arginine methylester Sepharose 4B. The same applied to the high molecular weight degradation products of desmin with a protein-resistant 37 X 10(3) Mr polypeptide as the major component. The results suggest that arginine residues of the non-alpha-helical, N-terminal polypeptides of intermediate filament subunit proteins play an important role in filament assembly.

Animals↗
PubMed1982

Intermediate filaments of Schwann cells.

Intermediate filaments were prepared from distal stumps of rabbit sciatic nerve 5 weeks after nerve section, at which time Schwann cells account for 85--90% of the cell area. A polypeptide of molecular weight 58,000 was the main component of this fraction. An antiserum raised in guinea pig against this polypeptide stained all cells present in the distal stump, as well as Schwann cells and 3T3 cells in culture. The identity of the molecular weight 58,000 polypeptide obtained from distal stumps with vimentin was proved with one and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and with immunoautoradiography. It is concluded that the intermediate filament subunit of undifferentiated Schwann cells is vimentin. The possibility that Schwann cells in normal nerve may have another type of intermediate filament besides vimentin cannot be ruled out.

Animals↗
PubMed1994

Myofibers from Duchenne/Becker muscular dystrophy and myositis express the intermediate filament nestin.

The intermediate filament nestin is transiently expressed in developing skeletal muscle. In the present investigation, we analyzed by immunohistochemistry the presence of nestin, as well as vimentin and desmin, in skeletal muscle affected by two diseases characterized by various degrees of necrosis and muscle regeneration: Duchenne/Becker muscular dystrophy and myositis. Nestin-positive areas were found in all analyzed muscle biopsies of both diseases. The same areas were, in most cases, also positive for vimentin and stained more intensely for desmin than surrounding myofibers. Only nestin was found specifically in myopathic muscle fibers; vimentin was in addition present in muscle fibroblasts and desmin in all myofibers. The areas staining positive for nestin were typically basophilic, small-diameter myofibers, often with centrally located nuclei. With the interesting exception of a 73-year-old healthy control with abundant ring fibers, nestin was not detected in the muscle of healthy controls. The intracellular distribution of nestin in the myopathic muscle fibers, as well as in the ring fibers, was confined to the vicinity of Z-bands. The presence of nestin protein in myopathic regenerating areas and in ring fibers correlated more closely to the presence of desmin than to vimentin immunoreactivity. Our results suggest that nestin is specifically expressed in newly formed muscle fibers also during regeneration, and that nestin may serve as a useful marker of regenerating muscle fibers in pathological conditions.

Adolescent↗