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 253 records · Page 14Linked to original sources
PubMed1996

Integration of intermediate filaments into cellular organelles.

The intermediate filaments represent core components of the cytoskeleton and are known to interact with several membranous organelles. Classic examples of this are the attachment of keratin filaments to the desmosomes and the association of the lamin filament meshwork with the inner nuclear membrane. At this point, the molecular mechanisms by which the filaments link to membranes are not clearly understood. However, since a substantial body of information has been amassed, the time is now ripe for comparing notes and formulating working hypotheses. With this objective in mind, we review here pioneering studies on this subject, together with work that has appeared more recently in the literature.

Animals↗
PubMed2006

Exploring the mechanical properties of single vimentin intermediate filaments by atomic force microscopy.

Intermediate filaments (IFs), together with actin filaments and microtubules, compose the cytoskeleton. Among other functions, IFs impart mechanical stability to cells when exposed to mechanical stress and act as a support when the other cytoskeletal filaments cannot keep the structural integrity of the cells. Here we present a study on the bending properties of single vimentin IFs in which we used an atomic force microscopy (AFM) tip to elastically deform single filaments hanging over a porous membrane. We obtained a value for the bending modulus of non-stabilized IFs between 300 MPa and 400 MPa. Our results together with previous ones suggest that IFs present axial sliding between their constitutive building blocks and therefore have a bending modulus that depends on the filament length. Measurements of glutaraldehyde-stabilized filaments were also performed to reduce the axial sliding between subunits and therefore provide a lower limit estimate of the Young's modulus of the filaments. The results show an increment of two to three times in the bending modulus for the stabilized IFs with respect to the non-stabilized ones, suggesting that the Young's modulus of vimentin IFs should be around 900 MPa or higher.

Aluminum Oxide↗
PubMed1988

Intermediate filament typing in tumour diagnostics--an aid in histogenetic classification?

It is commonly accepted, that a histogenetic correlation can be established between tumour and mother tissue by means of intermediate filament typing. Recent results concerning the co-expression of different intermediate filaments within one cell, the occurrence of epithelial-specific intermediate filaments in soft tissue tumours, and the modulation of intermediate filament type expression caused by some bioactive substances and viral infections cast doubts on the general acceptance of the histogenetic classification of human tumours by intermediate filament typing. Its characterization determines only the actual morphological differentiation of the neoplastic cells and represents a valuable tool for the diagnostic assessment of the tumour under the viewpoint of the functional differentiation of its cells. A doubtless conclusion concerning the mother tissue of the neoplasia (histogenetic origin) is therefore not possible.

Animals↗
PubMed1985

The intermediate filaments in human hepatocytes.

The intermediate filaments (IFs) in human hepatocytes were studied in biopsy specimens from patients with minimal histological changes. They were clearly visualized three-dimensionally by using polyethylene-glycol-embedding method after washing out cellular organelles and other components of cytoskeletons with a solution containing 0.15% Triton X-100 and saponin 0.5 mg/ml. We demonstrated that IFs were distributed throughout the cytoplasm in a meshwork fashion, attached to the junctional complex, encircled the bile canalicular lumen, and were directly attached to nucleus. Even after extensive washout of cytoplasmic structures, hepatocytes did not collapse, with the nuclei situated at due places in the cells. These findings may support the view that IFs play a role in nuclear positioning and in keeping the cytoplasmic space in human hepatocytes.

Adolescent↗
PubMed2003

The dynamic and motile properties of intermediate filaments.

For many years, cytoplasmic intermediate filaments (IFs) were considered to be stable cytoskeletal elements contributing primarily to the maintenance of the structural and mechanical integrity of cells. However, recent studies of living cells have revealed that IFs and their precursors possess a remarkably wide array of dynamic and motile properties. These properties are in large part due to interactions with molecular motors such as conventional kinesin, cytoplasmic dynein, and myosin. The association between IFs and motors appears to account for much of the well-documented molecular cross talk between IFs and the other major cytoskeletal elements, microtubules, and actin-containing microfilaments. Furthermore, the associations with molecular motors are also responsible for the high-speed, targeted delivery of nonfilamentous IF protein cargo to specific regions of the cytoplasm where they polymerize into IFs. This review considers the functional implications of the motile properties of IFs and discusses the potential relationships between malfunctions in these motile activities and human diseases.

Animals↗
PubMed1995

The predicted structure of chick lens CP49 and a variant thereof, CP49ins, the first vertebrate cytoplasmic intermediate filament protein with a lamin-like insertion in helix 1B.

The full length cDNA sequence for the lens-specific intermediate filament protein, CP49, from chicken is presented. The sequence contains features typical of the other intermediate filament proteins, including two major alpha-helical regions, helix I and II and appropriate linker regions. CP49 lacks a C-terminal non-alpha-helical domain and is only the second intermediate filament protein to be described missing this feature. Comparison to the bovine CP49 shows significant homology in all domains except the N-terminal non-alpha-helical domain. Besides bovine CP49, the other protein most homologous to chicken CP49 in the database was keratin 18, a type I keratin. A variant of CP49 is also described, called CP49ins. Of the 61 positive clones identified in the library, two encoded CP49ins, one of these being a full-length clone. The sequence differed to CP49 by the insertion of 49 amino acids in helix IB. This is the first chordate cytoplasmic intermediate filament protein sequence to be identified with an archetypal lamin-like insertion in this helical subdomain and represents a key discovery in tracing the evolutionary pathway of intermediate filament protein family.

Amino Acid Sequence↗
PubMed2006

Expression of nestin--a stem cell associated intermediate filament in human CNS tumours.

BACKGROUND & OBJECTIVES: Nestin is an intermediate filament protein expressed in undifferentiated cells during the development of brain and is considered as a marker for neuroepithelial stem cells. Expression of this protein in various CNS tumour cells suggests the possibility of existence of tumour stem cell modulating the evolution. We carried out an immunohistochemical study to demonstrate the expression of nestin and its co-expression with neuronal and glial intermediate filament and correlate with the grade of malignancy. METHODS: Formalin fixed, paraffin processed sections from two human foetuses, 16 brain tumours of both neuronal and glial lineage and two metastatic tumours were immunostained with polyclonal antibody to nestin. Serial sections from primary brain tumours were also stained with monoclonal antibody to neurofilament (NF) and glial fibrillary acidic protein (GFAP). Fluorescent double labeling was carried out on four cases using laser confocal microscopy, to document co-localization of nestin with other intermediate filaments in the tumour cells. RESULTS: Nestin expression was observed along the paraventricular zone of human foetuses and in brain tumours of both glial and neuronal lineage, of both high and low grades of malignancy. In addition, mature dysplastic spinal motor neurons adjacent to tumour and cerebellar Purkinje cells also expressed nestin along with neurofilament. INTERPRETATION & CONCLUSION: Nestin expression was noted in both low and high grade brain tumours and dysplastic neurons and did not parallel the malignant grade of the tumour. The expression of nestin in tumour cells and dysplastic neurons suggests aberrant expression of antigenically primitive proteins in cells to facilitate remodelling of the cell and migration. More studies are needed to elucidate the concept.

Adolescent↗
PubMed1996

Cerebrospinal fluid of newborn infants contains a deglycosylated form of the intermediate filament nestin.

Nestin is an intermediate filament protein found in CNS progenitor cells. Nestin reappears in CNS tumor cells and reactive astrocytes after CNS injury. In this study we investigated whether nestin could be detected in the cerebrospinal fluid (CSF) of newborn infants and whether expression levels change with gestational age (GA) and/or brain injury. Using Western blot analysis, we examined the expression of nestin in the CSF of newborn infants (GA 25-42 wk) with asphyxia (n = 14), periventricular leukomalacia and peri(intra)ventricular hemorrhage (n = 7), and in a control group (n = 11). Protein extract from the periventricular brain tissue of a 1-wk-old infant was also analyzed. Nestin was detected in all the CSF samples and in the protein extract from the periventricular brain tissue. Although the CSF levels of nestin expression did not change with increasing GA, the asphyxia group had significantly lower levels of nestin in the CSF. An unexpected finding was that brain-derived nestin had an apparent molecular mass of approximately 240 kD, whereas all analyzed CSF samples contained two nestin-immunoreactive proteins at 200 and 220 kD. Experimental deglycosylation of the 240-kD form reduced the molecular mass to 220 kD, indicating that nestin undergoes a specific deglycosylation upon release into the CSF.

Apgar Score↗
PubMed2004

Spatial correlations between the neuronal inclusions, swollen achromatic neurons, and glial cells in neuronal intermediate filament inclusion disease (NIFID).

Neuronal intermediate filament (IF) inclusion disease (NIFID) is characterized by neuronal loss, neuronal cytoplasmic IF-positive inclusions (NI), swollen neurons (SN), and a glial cell reaction. We studied the spatial correlations between the clusters of NI, SN, and glial cells in four gyri of the temporal lobe (superior temporal gyrus, inferior temporal gyrus, lateral occipitotemporal gyrus, and parahippocampal gyrus) in four cases of NIFID. The densities of histological features (per 50 x 250 microm sample field) were as follows: NI (mean = 0.41, range 0.28-0.68), SN (mean = 1.41, range 0.47-2.65), glial cell nuclei (mean = 5.21, range 3.63-8.17). The NI and the SN were positively correlated in half of the brain regions examined, the correlations being present at the smallest field size (50 x 250 microm). The NI were also positively or negatively correlated with the glial cell nuclei in different areas, the negative correlations being present at the smallest field size. Glial cell nuclei were positively or negatively correlated with the SN in different brain areas, mainly at the larger field sizes (400 x 250 and 800 x 250 microm). The spatial correlation between the clusters of NI and SN in the cortex suggests their development within the same columns of cells. At first, the glial cell reaction is also confined to these columns but later becomes more generally distributed across the cortex.

Adult↗
PubMed1995

Hagfish biopolymer: a type I/type II homologue of epidermal keratin intermediate filaments.

In contrast to most intermediate filaments (IF) which function intracellularly or constitute epidermal appendages, the single massive (approximately 60 cm length, approximately 3 microns width) IF-rich 'thread' biopolymer synthesized by the specialized hagfish gland thread cell is released extracellularly via holocrine secretion to interact with mucins and seawater, thereby modifying the viscoelastic properties of the copious mucous exudate. Recently, using the Pacific hagfish (Eptatretus stouti, class Agnatha), a jawless scaleless marine vertebrate of ancient lineage, we determined that the deduced amino acid sequence of one thread IF chain (alpha, 66.6 kDa, native pI 7.5) contained an atypical, threonine-rich central rod domain of low identity (< 30%) with other vertebrate IF types, but that the N- and C-terminal domains exhibited several keratin-like features. From these and other unexpected characteristics, it was concluded that hagfish alpha is best categorized as a type II homologue of an epidermal keratin. We now report the deduced sequence of a second thread IF subunit (gamma, 62.7 kDa, native pI 5.3) which is co-expressed and co-assembles in vitro with alpha in a 1:1 ratio. As was found for alpha, the N- and C-terminal domains of gamma have keratin-like parameters, but the central rod has low identity to IFs of types I-V (< 31%), a cephalochordate IF (< 29%) and invertebrate IFs (< 20%) and no particular homology to type I or type II keratins. Central rod identity between gamma and alpha is also low (approximately 23%), as is typical of comparisons between different rod types but atypical of similar rod types (> 50%). The central rods of both gamma and alpha lack the 42-residue insert of helix 1B present in lamins and invertebrate IFs, have unusually high threonine contents (gamma, 10%; alpha, 13%) compared to other IF types (2-5%), contain a number of unexpected residues in consensus conserved sites, and employ a L12 segment of 21 residues rather than the 16 or 17 residues found in keratins. Theoretical analyses indicate that the hagfish molecules exist as coiled coil heterodimers (alpha/gamma) in which the chains are parallel, in axial register, and stabilized by significant numbers of ionic interactions. Fast Fourier-transform analyses revealed that the linear distribution period of approximately 9.55 for basic and acidic residues in other IF chains is not completely maintained, partly due to the high threonine content. The threonine residues occupy mainly outer sites b, c, f in the heptad substructure, possibly abetting parallel alignment of thousands of IFs within the thread, interactions with mucins at the thread periphery, and hierarchical IF chain assembly. It is suggested that the gamma and alpha chains from this most primitive extant vertebrate are type I and type II homologues of epidermal keratin chains, possibly related to early specialized keratins.

Amino Acid Sequence↗
PubMed1989

Vimentin cDNA clones covering the complete intermediate-filament protein are found in an EHS tumor cDNA library.

Intermediate filaments are part of the cytoskeleton of most cells. To analyze changes in intermediate filament synthesis, we have isolated two cDNA clones (pV-C25, pV-C877) that cover the complete coding sequence of the murine intermediate filament protein vimentin. The cDNA clones were isolated from a murine Engelbreth-Holm-Swan (EHS) tumor cDNA library by screening under (i) non-stringent conditions with a synthetic oligodeoxynucleotide (oligo), LW-36, which is specific for type-IV collagen, and (ii) stringent conditions with oligo LW75, which was derived from the vimentin clone pV-C25. The cDNA clones contain 38 nucleotides (nt) of the 5'-untranslated region, 1398 nt of the coding region and 7 nt of the 3'-untranslated region. Comparing the mouse sequence with the published sequence for vimentin from hamster, human and chicken, we find shared identities of 99, 97 and 87%, respectively. Since the cDNA clones have been isolated from a basement membrane tumor (EHS) cDNA library, we measured the vimentin mRNA production in EHS tumor cells in culture, and found that this mRNA is half as abundant as mRNA for type-IV mRNA.

Amino Acid Sequence↗
PubMed1984

The intermediate filament cytoskeleton of myofibroblasts: an immunofluorescence and ultrastructural study.

The intermediate filament cytoskeleton of stromal myofibroblasts from a series of twenty-eight infiltrating ductal breast carcinomas was examined by transmission electron microscopy (TEM) and indirect immunofluorescence (IF), the latter using antibodies to desmin, vimentin and prekeratin. Three cases of fibromatoses, selected as an additional source of myofibroblasts, were processed in the same manner. Stromal myofibroblasts from invasive ductal breast carcinomas rich in actin and readily identified by IF, were most numerous in the "young" edematous mesenchyme, areas corresponding to early stromal invasion or the peripheral invasive cellular front. Within the central sclerotic zone wherein clusters of neoplastic epithelial cells were surrounded by abundant collagen, most stromal cells corresponded by TEM to fibroblasts. In like fashion, myofibroblasts were most numerous in cellular, poorly collagenized portions of fibromatoses. By IF the only detectable intermediate filament protein of myofibroblasts in these two settings was vimentin. Since the appearance of stromal myofibroblasts appears to be associated with stromal invasion by malignant epithelium, their development by modulation of pre-existent periductal fibroblasts is postulated. With the exception of vascular smooth muscle cells and endothelial cells, the only periductal mesenchymal cells shown to contain vimentin were fibroblasts. The lack of desmin in myofibroblasts constitutes evidence against an origin from vascular smooth muscle cells. Because the molecular markers (intermediate filament proteins) of stromal cell differentiation presented quantitative but not qualitative modifications, the transformation of fibroblasts into myofibroblasts is quite likely, suggesting that myofibroblasts may be more closely related to fibroblasts than to smooth muscle cells.

Breast↗
PubMed1988

Cordycepin rapidly collapses the intermediate filament networks into juxtanuclear caps in fibroblasts and epidermal cells.

The nucleoside analog 3'-deoxyadenosine (cordycepin) rapidly collapses the intermediate filaments into juxtanuclear caps in interphase fibroblasts and keratinocytes. A minimum of 80 micrograms/ml cordycepin or 20 micrograms/ml cordycepin in combination with 2 micrograms/ml of the deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl)adenosine (EHNA) to inhibit its degradation is required to see these effects. This is the same concentration required for cordycepin to arrest cells at the onset of mitosis and depolymerize the microtubules to small asters. Cordycepin enters the cells rapidly and is phosphorylated to 3'-dATP with a concomitant drop in ATP levels. However, the direct reduction of ATP levels does not mimic the same rapid effects of cordycepin on either the intermediate filaments or microtubules. In addition, similar effects are not produced by a variety of other adenosine analogs with alterations in the 2'- and 3'-ribose positions. Although other pharmacological reagents result in alterations of the fibroblastic intermediate filaments, cordycepin is unusual because of the rapidity with which the fibroblastic intermediate filaments collapse into the juxtanuclear caps. The juxtanuclear caps have a morphology different from that of the perinuclear bundles of intermediate filaments that arise after long-term depolymerization of the microtubules. The keratin fibers in the epidermal cells retract to a perinuclear ring when treated with cordycepin.

Adenine↗
PubMed2005

Timing of neuronal intermediate filament proteins expression in the mouse vomeronasal organ during pre- and postnatal development. An immunohistochemical study.

Several types of intermediate filament proteins are expressed in developing and mature neurons; they cooperate with other cytoskeletal components to sustain neuronal function from early neurogenesis onward. In this work the timing of expression of nestin, peripherin, internexin, and the neuronal intermediate filament triplet [polypeptide subunits of low (NF-L), medium (NF-M), and high (NF-H) molecular weight] was investigated in the developing fetal and postnatal mouse vomeronasal organ (VNO) by means of immunohistochemistry. The results show that the sequence of expression of intermediate filament proteins is internexin, nestin, and NF-M in the developing vomeronasal sensory epithelium; internexin, peripherin, and NF-M in the developing vomeronasal nerve; and nestin, internexin and peripherin, NF-L, and NF-M in the nerve supply to accessory structures of the VNO. At sexual maturity (2 months) NF-M is only expressed in vomeronasal neurons and NF-M, NF-L and peripherin are expressed in extrinsic nerves supplying VNO structures. The differential distribution of intermediate filament proteins in the vomeronasal sensory epithelium and nerve is discussed in terms of the cell types present therein. It is concluded that several intermediate filament proteins are sequentially expressed during intrauterine development of the VNO neural structures in a different pattern according to the different components of the VNO.

Animals↗
PubMed1990

Heat shock causes the collapse of the intermediate filament cytoskeleton in Drosophila embryos.

Heat shock has a dramatic effect on the organization of the cytoplasm, causing the intermediate filament cytoskeleton to aggregate at the nucleus. This has previously been shown in cultured Drosophila and mammalian cells. In this paper we analyze the heat lability of the intermediate filament cytoskeleton in early Drosophila embryos by indirect immunofluorescence. At all stages of embryogenesis tested, the intermediate filament cytoskeleton, which is maternally provided, is severely disturbed by 30 min heat shock at 37 degrees C. After the nuclei have migrated to the subcortical cytoplasm, it collapses around them. Nuclei in all heat-shocked embryos are considerably enlarged and become displaced. Embryos before cellular blastoderm stage, in which heat shock protein synthesis is not inducible, are irreversibly arrested in development by heat shock. Embryos at or after cellular blastoderm, which do synthesize heat shock proteins in response to stress, are also immediately arrested in development but continue development when returned to 25 degrees C. We discuss the possibility that cytoplasmic events such as the intermediate filament cytoskeleton rearrangement may be involved in heat shock-mediated phenocopy induction.

Animals↗
PubMed1988

Expression of intermediate filaments and stromal proteins in granular cell tumor of the tongue.

Intermediate filament subunits as well as components of the extracellular matrix, were localized in three cases of granular cell tumor of the tongue. Of the five intermediate filament families, only vimentin was present within the tumor cells. No labeling was obtained with antibodies to cytokeratin, desmin, neurofilaments, and glial filaments; this suggests that this tumor is not derived from epithelium, muscle, neural, or astrocytic origins, respectively. Immunofluorescent staining of the tissue with antibodies to fibronectin and to collagen indicated that the tumor contained low levels of these extracellular matrix proteins. The results suggest the possible use of antibodies to intermediate filaments as histogenetic markers for the clarification of the origin of tumors whose nature cannot be unequivocally determined by conventional histopathologic methods.

Aged↗
PubMed1985

A structural comparison of tryptic fragments of three types of intermediate filaments.

We have compared tryptic fragments of three types of intermediate filaments, emphasizing structural characteristics as seen in the electron microscope. Variable, long alpha-helical rod fragments were found to be similar for keratin, neurofilaments and desmin filaments. Short rod fragments from keratin and neurofilaments appeared similar when observed by electron microscopy. Short rod fragments were not seen in desmin filament digests. In addition to these elongated particles, globular fragments, which have not been described previously, were obtained from all three types of intermediate filaments. These globular fragments were characterized by gel filtration and electron microscopy, and compared to globular proteins of known size using both methods. The diameter was about 6 nm and the molecular weight was estimated to be 50 000-60 000. These globular particles may comprise the short, nonhelical regions from several IF protein subunits, which are clustered into an interface in the intact filament or protofilaments.

Animals↗
PubMed1995

Filarin, a novel invertebrate intermediate filament protein present in axons and perikarya of developing and mature leech neurons.

The lan 3-8 monoclonal antibody recognizes a 63 kD antigen that is associated with the cytoskeleton in leech neurons. We have used this antibody to clone a novel invertebrate neuronal intermediate filament protein, filarin, by screening an expression vector library. A full-length clone of 2.2 kb identified by the antibody was isolated and sequenced. The protein contains a coiled-coil rod domain typical of the superfamily of intermediate filament proteins flanked by unique N- and C-terminal domains. The highest homology of filarin is to the alternatively spliced squid brain intermediate filament protein (Szaro et al., 1991, J. Biol. Chem. 266:15035-15041), the only other invertebrate neuronal intermediate filament in the data bank. However, apart from extensive homology in the two end regions of the rod domain, the similarity of the two proteins is limited to the general coiled-coil structure of intermediate filaments. Thus, filarin may represent a novel type of invertebrate neuronal intermediate filament protein. Filarin contains the extra 6 heptads characteristic of lamins and of all cytoplasmic invertebrate intermediate filaments analyzed so far. By Northern analysis, it appears that filarin is not alternatively spliced, since only a single transcript of 2.2 kb is recognized by the clone. Using the lan 3-8 antibody to follow its developmental expression, we found that filarin is present in all known neurons in the central and peripheral nervous system.

Amino Acid Sequence↗