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PubMed1990

Localization of intermediate filament proteins in various structures of the human placenta as revealed by immunoperoxidase technique.

Formalin-fixed, paraffin embedded fragments of normal human placenta were subjected to immunoperoxidase technique with the use of Dako Kits appropriate for detection of vimentin, desmin, and cytokeratins (K 660, 530, and 518 respectively). Distribution of the intermediate filament proteins in syncytiotrophoblast, connective tissue of villous stroma, walls of blood vessels as well as in cells of basal plate and placental islets was compared. General pattern of staining and its localization was characteristic for each of the 3 types of antibodies. In spite of that, most structures observed revealed the presence of more than one type of intermediate filament proteins, with the exception of syncytiotrophoblast containing cytokeratins only. Staining of blood serum and of connective tissue matrix with anti-desmin and anti-cytokeratin antibodies was also observed, whereas fibrinoid remained always negative.

Adult↗
PubMed1997

Intermediate filament structure: hard alpha-keratin.

Structurally there are four classes of intermediate filaments (IF) with distinct but closely related axial organisations. One of these, hard alpha-keratin IF, has been studied to clarify several apparently exceptional features which include the number of molecules in the IF cross-section and the mode by which the axial organisation of its constituent molecules is stabilised. Using the dark-field mode of the STEM at the Brookhaven National Laboratory (USA) mass measurements were obtained from unstained IF isolated from hair keratin. The data thus obtained show that the number of chains in cross-section is about 30 (+/-3: standard deviation) and is very similar to the numbers determined in previous STEM experiments for the dominant filament type in other classes of IF (about 32). Furthermore, re-analysis of the low-angle equatorial X-ray diffraction pattern reveals, in contrast to earlier work, solutions that are compatible with the number of chains in cross-section indicated by the STEM data. The absence of the head-to-tail overlap between parallel molecules characteristic of most of IF may be compensated in hard alpha-keratin by a network of intermolecular disulfide bonds. It is concluded that native IF of hard alpha-keratin and desmin/vimentin--and probably many other kinds of IF as well--contain about 32 chains in cross-section, and that the axial structures of these various kinds of IF differ in small but significant ways, while generally observing the same basic modes of aggregation.

Animals↗
PubMed1988

Ubiquitin is present on the cytokeratin intermediate filaments and Mallory bodies of hepatocytes.

To investigate the relationship of cytokeratin intermediate filaments (IFs) and Mallory bodies (MBs) to the regulatory protein ubiquitin, the griseofulvin-fed mouse was examined by double-label immunocytochemistry. In controls, immunofluorescence of hepatocytes showed that an antiserum specific to ubiquitin stained the cell border and the cytoplasm as well as the nuclear rim. In griseofulvin-fed liver cells, the MBs induced by this treatment were stained in an identical pattern by the antiserum to ubiquitin and a monoclonal antibody specific to cytokeratin (TROMA 1). Upon examination of the immunoreaction at the ultrastructural level, the ubiquitin antiserum decorated the cytokeratin filaments as well as MB filaments. Particularly striking was the coincidence of localization of TROMA 1 and ubiquitin epitopes, many IF surrounding MBs being either intensely decorated or alternatively nonimmunoreactive. These results suggest that normal cytokeratin IFs are lightly ubiquitinated, whereas MBs are heavily ubiquitinated. Immunoblot analysis of extracted cytoskeletal proteins separated by gel electrophoresis showed that extensive ubiquitination of peptides was present in the livers of the griseofulvin-fed mice. Further, the lack of ubiquitin and TROMA 1 epitopes in some liver IF suggest that loss of the TROMA 1 epitope may lead to concomitant loss of the ability to bind ubiquitin. Although the role ubiquitin plays in Mallory body formation remains to be elucidated, we suggest that its significance here may be related to its normal association with cytokeratin.

Animals↗
PubMed1986

Sclerosing hemangioma of the lung. Immunohistochemical demonstration of mesenchymal origin using antibodies to tissue-specific intermediate filaments.

A case of pulmonary sclerosing hemangioma of the lung was studied by light microscopy and indirect immunofluorescence using tissue-specific antibodies against intermediate filament subunits. All the tumor cells stained positively and exclusively with antivimentin antibodies thus indicating their mesenchymal origin. In addition, positive staining with cytokeratin antibodies was observed in cells lining cystic spaces and elongated slit-like spaces were occasionally encountered throughout the tumor, disclosing residual epithelial elements. Using brightfield microscopy, the keratin-positive areas were identified as distorted alveolar spaces lined by hyperplastic respiratory epithelium entrapped within the tumor. It is proposed that these entrapped epithelial elements may account for the conflicting results obtained by different investigators in previous attempts to determine the histogenesis of this tumor.

Antibodies↗
PubMed1979

Phosphorylation of subunit proteins of intermediate filaments from chicken muscle and nonmuscle cells.

The phosphorylation of the subunit proteins of intermediate (10-nm) filaments has been investigated in chicken muscle and nonmuscle cells by using a two-dimensional gel electrophoresis system. Desmin, the 50,000-dalton subunit protein of the intermediate filaments of muscle, had previously been shown to exist as two major isoelectric variants-alpha and beta-in smooth, skeletal, and cardiac chicken muscle. Incubation of skeletal and smooth muscle tissue with (32)PO(4) (3-) reveals that the acidic variant, alpha-desmin, and three other desmin variants are phosphorylated in vivo and in vitro. Under the same conditions, minor components of alpha- and beta-tropomyosin from skeletal muscle, but not smooth muscle, are also phosphorylated. Both the phosphorylated desmin variants and the nonphosphorylated beta-desmin variant remain insoluble under conditions that solubilize actin and myosin filaments, but leave Z-discs and intermediate filaments insoluble. Primary cultures of embryonic chicken muscle labeled with (32)PO(4) (3-) possess, in addition to the desmin variants described above, a major nonphosphorylated and multiple phosphorylated variants of the 52,000-dalton, fibroblast-type intermediate filament protein (IFP). Filamentous cytoskeletons, prepared from primary myogenic cultures by Triton X-100 extraction, contain actin and all of the phosphorylated and nonphosphorylated variants of both desmin and the IFP. Similarly, these proteins are the major components of the caps of aggregated 10-nm filaments isolated from the same cell cultures previously exposed to Colcemid. These results demonstrate that a nonphosphorylated and several phosphorylated variants of desmin and IFP are present in assembled structures in muscle and nonmuscle cells.

Animals↗
PubMed2001

Perinuclear mRNA localisation by vimentin 3'-untranslated region requires a 100 nucleotide sequence and intermediate filaments.

The role of the vimentin 3'-untranslated region (3'-UTR) in mRNA localisation was studied in cells transfected with a reporter sequence linked to subregions of the 3'-UTR. In situ hybridisation showed that nucleotides 37-137, including a previously identified protein-binding domain, were sufficient to localise transcripts to perinuclear cytoplasm. Transfection of two SW13 cell lines that do and do not express vimentin showed that perinuclear localisation due to either the vimentin or c-myc 3'-UTR requires intermediate filaments. The data suggest that both a specific protein-binding region of the vimentin 3'-UTR and intermediate filaments themselves are required to determine the site of vimentin synthesis.

3' Untranslated Regions↗
PubMed1995

Immunological studies on an Onchocerca volvulus intermediate-filament protein.

We report the complete sequence of the cDNA encoding an intermediate filament (IF) protein from Onchocerca volvulus. The OVIF cDNA encodes a protein of 613 amino acid residues, which has a predicted molecular weight of approximately 70 kD. The size of the protein encoded by the OVIF cDNA corresponds well with estimates obtained in Western blotting experiments, but these same experiments suggest that Onchocerca sp. may contain at least two IF proteins. To identify the domain(s) of the OVIF protein responsible for immunogenicity in human filariasis patients, fragments of the OVIF cDNA were subcloned into the appropriate pGEX vector and Western blots of the corresponding fusion proteins probed with human sera. Pooled sera from general onchocerciasis or Bancroftian filariasis patients reacted only with the C-terminal region of the OVIF protein, whereas sowda onchocerciasis sera reacted 1-2 orders of magnitude more strongly and with a number of other epitopes. Immunolocalization experiments implied that the OVIF protein is associated with both muscle and a number of specific membrane layers. These studies provide the basis for evaluation of the protective potential of the OVIF protein.

Amino Acid Sequence↗
PubMed2002

Distribution of the intermediate filament nestin in the muscularis propria of the human gastrointestinal tract.

The intermediate filament nestin is expressed in neural stem cells, neuroectodermal tumors and various adult tissues. In the gastrointestinal (GI) tract, nestin has been reported in glial cells. Recently, nestin has been reported in interstitial cells of Cajal (ICC) and in gastrointestinal stromal tumors, thought to derive from ICC. Here we investigated nestin immunoreactivity (-ir) in the normal human GI tract, with emphasis on Kit-ir ICC. Two different antibodies specific for human nestin and multicolor high-resolution confocal microscopy were used on material from our human GI tissue collection. The staining pattern of both nestin antibodies was similar. In labeled cells, nestin-ir appeared filamentous. Most intramuscular ICC in antrum and all myenteric ICC (ICC-MP) in small intestine were nestin-ir, while nestin-ir was not detected in deep muscular plexus ICC. In the colon, some - but not all - ICC-MP and most ICC in the circular musculature were nestin-ir while nestin-ir was not detected in ICC in the longitudinal musculature and in the submuscular plexus. In addition, many Kit-negative cells were nestin-ir in all regions. Neurons and smooth muscle cells were consistently nestin negative, while most S100-ir glial cells were nestin-ir. In addition, nestin-ir was also present in some CD34-ir fibroblast-like cells, in endothelium and in other cell types in the mucosa and serosa. In conclusion, nestin-ir is abundantly present in the normal human GI tract. Among a number of cell types, several, but not all, subpopulations of Kit-ir ICC were nestin-ir. The functional significance of nestin in the GI tract remains obscure.

Adolescent↗
PubMed1998

Effects of growth factors and basement membrane proteins on the phenotype of U-373 MG glioblastoma cells as determined by the expression of intermediate filament proteins.

Various growth factors and basement membrane proteins have been implicated in the pathobiology of astrocytomas. The goal of this study was to determine the relative contribution of these two factors in modulating the phenotype of U-373 MG glioblastoma cells as determined by the expression of the intermediate filament proteins glial fibrillary acidic protein, vimentin, and nestin. For these determinations, cells plated in serum-free medium were treated either with growth factors binding to tyrosine kinase receptors including transforming growth factor-alpha, epidermal growth factor, platelet-derived growth factor-AA, basic fibroblast growth factor, and insulin-like growth factor-1 or with basement membrane proteins including collagen IV, laminin, and fibronectin. The changes in the expression levels of intermediate filament proteins in response to these treatments were analyzed by quantitation of immunoblots. The results demonstrate that collagen IV and growth factors binding to tyrosine kinase receptors decrease the glial fibrillary acidic protein content of U-373 MG cells. Growth factors binding to tyrosine kinase receptors also decrease the vimentin content of these cells but do not affect their nestin content. On the other hand, basement membrane proteins decrease the nestin content of U-373 MG cells but do not affect their vimentin content. The significance of these results with respect to the role played by different factors in modulating the phenotype of neoplastic astrocytes during tumor progression is discussed.

Basement Membrane↗
PubMed1999

Specific and innervation-regulated expression of the intermediate filament protein nestin at neuromuscular and myotendinous junctions in skeletal muscle.

The intermediate filament proteins nestin, vimentin, and desmin show a specific temporal expression pattern during the development of myofibers from myogenic precursor cells. Nestin and vimentin are actively expressed during early developmental stages to be later down-regulated, vimentin completely and nestin to minimal levels, whereas desmin expression begins later and is maintained in mature myofibers, in which desmin participates in maintaining structural integrity. In this study we have analyzed the expression levels and distribution pattern of nestin in intact and denervated muscle in rat and in human. Nestin immunoreactivity was specifically and focally localized in the sarcoplasm underneath neuromuscular junctions (NMJs) and in the vicinity of the myotendinous junctions (MTJs), ie, in regions associated with acetylcholine receptors (AChRs). This association prompted us to analyze nestin in neurogenically and myogenically denervated muscle. Immunoblot analysis disclosed a marked overall increase of accumulated nestin protein. Similar to the extrajunctional redistribution of AChRs in denervated myofibers, nestin immunoreactivity extended widely beyond the NMJ region. Re-innervation caused complete reversion of these changes. Our study demonstrates that the expression levels and distribution pattern of nestin are regulated by innervation, ie, signal transduction into myofibers.

Adult↗
PubMed1992

Expression of intermediate filament proteins in the adult human vestibular labyrinth.

The immunohistochemical detection of intermediate filament proteins, cytoskeletal constituents that allow the characterization of tissues, was investigated in frozen sections of the chemically fixed, nondecalcified, adult human vestibular labyrinth. Cytokeratins (CKs) were detected in all epithelia (including the sensory epithelia), although substantial differences in the degree of staining between individual cells occurred. The expression of CKs 7, 8, 18, and 19 as detected with our subunit-specific monoclonal antibodies in the vestibular epithelia is typical of "simple" epithelia and is identical to the CK subtypes found in the human cochlea. Although immunostaining for CK 7 was very weak and was limited to certain vestibular wall cells, the other CKs demonstrated a pronounced and rather uniform distribution throughout the different epithelia. All epithelia (including the sensory epithelia) displayed expression of vimentin, thus demonstrating co-expression with CKs. Vimentin was also present in the subepithelial connective tissue fibroblasts and mesothelial lining of the vestibular labyrinth. Neurofilament proteins were detected in all neuronal structures. The intense staining for CKs in the maculae and cristae implies that these sensory organs are rigid structures, a finding that may possibly be of importance in the mechanoelectrical transduction process for the sense of equilibrium.

Aged↗
PubMed2001

Essential roles for four cytoplasmic intermediate filament proteins in Caenorhabditis elegans development.

The structural proteins of the cytoplasmic intermediate filaments (IFs) arise in the nematode Caenorhabditis elegans from eight reported genes and an additional three genes now identified in the complete genome. With the use of double-stranded RNA interference (RNAi) for all 11 C. elegans genes encoding cytoplasmic IF proteins, we observe phenotypes for the five genes A1, A2, A3, B1, and C2. These range from embryonic lethality (B1) and embryonic/larval lethality (A3) to larval lethality (A1 and A2) and a mild dumpy phenotype of adults (C2). Phenotypes A2 and A3 involve displaced body muscles and paralysis. They probably arise by reduction of hypodermal IFs that participate in the transmission of force from the muscle cells to the cuticle. The B1 phenotype has multiple morphogenetic defects, and the A1 phenotype is arrested at the L1 stage. Thus, at least four IF genes are essential for C. elegans development. Their RNAi phenotypes are lethal defects due to silencing of single IF genes. In contrast to C. elegans, no IF genes have been identified in the complete Drosophila genome, posing the question of how Drosophila can compensate for the lack of these proteins, which are essential in mammals and C. elegans. We speculate that the lack of IF proteins in Drosophila can be viewed as cytoskeletal alteration in which, for instance, stable microtubules, often arranged as bundles, substitute for cytoplasmic IFs.

Animals↗
PubMed1992

Intermediate filaments as differentiation markers of normal pancreas and pancreas cancer.

Expression of intermediate filaments (IF) is regulated during development and differentiation. The authors have studied the expression of vimentin and cytokeratins (CK) 4, 7, 8, 13, 18, 19 in normal pancreas, chronic pancreatitis, and pancreas cancer using monoclonal antibodies. Immunohistochemical assays were performed on fresh frozen tissue sections and on cultured pancreas cancer cells using the streptavidin-peroxidase method. In normal pancreas, acinar cells expressed CK 8 and 18, whereas ductal cells expressed CK 7, 8, 18, and 19. CK 4 was expressed by 5-10% of pancreas duct cells in all specimens of normal pancreas. CK 13 was not detected in any epithelial cells of normal pancreas or pancreatitis. CK 7, 8, 18, and 19 were homogeneously expressed in all pancreas cancers, whereas CK 4 was expressed only in 5-50% of cells in 10/16 tumors. Foci of squamous metaplasia expressed CK 13 but showed partial loss of expression of CK 7, 8, 18, and 19. Thirteen pancreas cancer cell lines examined showed homogeneous expression of CK 7, 8, 18, and 19; 2/11 lines expressed CK 4 weakly, and 6/11 expressed vimentin. CK 13 was not detected in any of the lines. These results indicate that pancreas cancer cells consistently express cytokeratin polypeptides characteristic of ductal epithelial cells and that this phenotype is retained in pancreas cancer cell lines. In addition, squamous metaplasia is associated with a coordinate change in the expression of CK polypeptides.

Biomarkers↗
PubMed1998

Distribution of neuronal intermediate filament proteins in the developing mouse olfactory system.

The distribution of neuronal intermediate filament proteins in the developing mouse olfactory bulb and olfactory epithelium was characterized by immunocytochemical approach. Antibodies against alpha-internexin, neurofilament triplet proteins (NFTPs; NF-L, NF-M, and NF-H) and peripherin were used to determine their expression at different developmental stages. Alpha-internexin and peripherin were first found to be co-localized in the olfactory neuroepithelium during early development. At the perinatal stage, expression patterns of alpha-internexin and peripherin are distinguishable by spatial and temporal manner: peripherin is predominantly expressed in the olfactory nerves; whereas alpha-internexin is expressed in both olfactory nerves and olfactory bulb. Our observation suggests that peripherin as well as alpha-internexin may play some roles in the process formation of olfactory nerves during development. In the developing olfactory periglomerulus, alpha-internexin was found around postnatal Day 3, whereas NFTPs were not observed until postnatal Day 7. Our data showed that the expression of alpha-internexin preceded those of the NFTPs in most neurons of the developing olfactory bulb. Some small neurons in the adult olfactory bulb were uniquely labeled with antibody to alpha-internexin. Our results suggest that alpha-internexin may play a functional role in the neuronal cytoarchitecture of developing olfactory system, and can be a neuronal marker for detecting postmitotic migrating neurons in the adult olfactory bulb.

Animals↗
PubMed1999

Altering the state of phosphorylation of rat liver keratin intermediate filaments by ethanol treatment in vivo changes their structure.

Dephosphorylation of keratin intermediate filaments (IF) in livers from ethanol-fed rats relative to controls occurs concurrently with a reorganization of the distribution of IF in the cells. One possible molecular mechanism for this reorganization is a phosphorylation-induced conformational change in the keratin that propagates as a change in the polymerization of the keratin subunits. To test this hypothesis, the structure of liver keratin IF, from both control and alcohol-fed rats, was explored by circular dichroism (CD), tryptophan fluorescence quenching, and 13C nuclear magnetic resonance (NMR). Keratin IF were isolated from livers of control rats and from livers of rats that had ethanol included in their feed for 6-40 weeks. A significant decrease in the intensity of the CD spectrum of keratin IF from livers of ethanol-treated animals, relative to controls, was observed. These data suggested either that a change in conformation or an increase in conformational motility in the keratin IF from ethanol-treated animals occurred as a result of the ethanol-induced dephosphorylation. 13C NMR data were obtained to distinguish between these two possibilities. An increase in resonance intensity of some 13C NMR resonances was observed in the keratin IF from livers of ethanol-treated animals, relative to controls. The CD and NMR data were therefore consistent with an increase in conformational motility of the rod domain in these keratin IF. No significant change was observed in the quenching of tryptophan fluorescence by KI. The change in protein dynamics detected in these experiments could be the molecular basis for the alteration of keratin IF organization in alcoholic hepatitis.

Animals↗
PubMed1996

Estrogen regulation of nuclear matrix-intermediate filament proteins in human breast cancer cells.

The tissue matrix consists of linkages and interactions of the nuclear matrix, cytoskeleton, and extracellular matrix. This system is a dynamic structural component of the cell that organizes and processes structural and functional information to maintain and coordinate cell function and gene expression. We have studied estrogen regulation of nuclear matrix associated proteins, including the intimately connected cytoskeletal intermediate filaments, in T-47D5 human breast cancer cells. Three proteins (identified as cytokeratins 8, 18, and 19) present in the nuclear matrix-intermediate filament fraction (NM-IF) of cells grown in estrogen-replete conditions were dramatically reduced when the cells were grown in acute (1 week) estrogen-depleted conditions. Replacing estrogen in the medium of acute estrogen-depleted cells restored expression of these proteins. T-47D5 cells that are chronically depleted of estrogen (T5-PRF) are estrogen-nonresponsive in culture. These cells overexpressed these three proteins, compared to parent cells grown in the presence of estrogen. Treatment of the T5-PRF cells with estrogen did not lead to further up-regulation of these proteins. Treating T-47D5 cells in estrogen-replete conditions with the antiestrogens 4-hydroxytamoxifen and ICI 164 384 (100 nM, 3 days) resulted in a significant reduction in these proteins, while no effect was seen in long-term chronic estrogen-depleted T-47D5 cells. In conclusion, we have identified NM-IF proteins (cytokeratins 8, 18, and 19) in human breast cancer cells that are estrogen regulated and may play a role in estrogen action in human breast cancer cells.

Antigens, Nuclear↗
PubMed1990

Intermediate filaments in the human pituitary gland: an immunohistochemical study.

Normal pituitaries, pituitaries showing CHC and selected adenomas were assessed for their possible content of intermediate filaments (IF), using immunohistochemical techniques. Normal pituitaries were stained for each of the five known IF (Cytokeratins (CK), glial fibrillary acidic protein (GFAP), desmin, vimentin, and neurofilaments (NF]. Desmin could not be demonstrated, and NF staining was limited to processes in the posterior gland. In serial sections, CK was demonstrated in some corticotrophs, somatotrophs, and lactotrophs. Vimentin was limited to processes in the posterior gland. Folliculo-stellate cells (FSC), demonstrated by staining for S100 protein, exhibited a small subpopulation staining for CK, and another subpopulation staining for GFAP. GFAP was also demonstrated in glial processes in the posterior gland. Cells showing Crooke's hyaline change stained intensely for CK. Null cell adenomas did not stain for CK. Corticotroph adenomas, somatotroph adenomas, with or without fibrous bodies, and lactotroph adenomas contain CK-immunoreactive cells. We conclude that CK is the major IF present in the anterior pituitary gland, within some normal corticotrophs, somatotrophs and lactotrophs, and also in adenomas derived from these cells.

Adenoma↗
PubMed1987

A comparative analysis of intermediate filament proteins in bovine heart Purkinje fibres and gastric smooth muscle.

The intermediate filament (IF) composition of muscle cells of various sources is still a controversial issue. In the present study, the IF composition of bovine Purkinje fibres (PFs), atrial and ventricular myocardium, and gastric smooth muscle (SM) has been compared using biochemical and immunocytochemical methods. The Mr of the major IF subunit protein in all four tissues was 55,000. In two-dimensional (2-D) electrophoresis gels of Triton-treated ordinary atrial and ventricular myocardium and the gastric muscular wall, two or three isoelectric isoforms were seen, whereas in PFs up to seven isoforms caused by phosphorylation were observed. In immunofluorescence studies antibodies against the Mr 55,000 subunit of PFs and gastric SM, respectively, both showed identical reactivity with PFs, atrial and ventricular myocytes, gastric SM cells and some SM cells in intramyocardial and gastric muscular wall blood vessels. A small amount of vimentin (Mr 57,000) was also detected in 2-D gel electrophoresis in all four tissues as well as in immunoblotting of PFs with antibodies to vimentin. Immunofluorescence studies using both polyclonal and monoclonal antibodies to vimentin showed that vimentin was present in the endothelium and SM cells of both intramyocardial and gastric muscular wall vessels, sometimes together with desmin in the vascular SM cells, but was never seen in PF, atrial, ventricular or gastric SM cells proper. As expected, vimentin was present in interstitial tissue, i.e., fibroblasts and capillaries. However, interestingly, the monoclonal antibodies, which recognized different antigenic determinants of vimentin, did not give identical staining patterns. Especially the staining of the vascular SM cells differed. Since this staining pattern did not change upon denaturation and unmasking experiments, it seems that the organization of vimentin in different mesenchymal cell types varies. Vimentin was also detected in isolated PFs but here it was located solely in the contaminating interstitial tissue. Thus, desmin is the sole IF protein expressed in PFs, in atrial and ventricular myocytes and in gastric SM cells proper; vimentin alone being present in the interstitial tissue cells, whilst in vascular SM cells desmin and vimentin are coexpressed in various proportions. The variation in number of isoforms of desmin and the heterogeneity in staining of mesenchymal tissues with monoclonal vimentin antibodies probably indicates that the IF cytoskeletons are differently organized in various cell types, even though they contain IFs of the same class.

Animals↗