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 1,027 records · Page 57Linked to original sources
PubMed1986

A monoclonal antibody recognizes a form of intermediate filament protein in rat Sertoli cells that is not present in seminiferous peritubular cells.

We extracted intermediate filament proteins (IFP) that were insoluble in in detergent from cultured rat Sertoli and peritubular cells after labeling with [35S] methionine and resolved them by two-dimensional polyacrylamide gel electrophoresis, autoradiography and Western blotting. We found that vimentin was the predominant IFP in both Sertoli and peritubular cells. However, while two isoelectric variants of vimentin were observed in Sertoli cells, only one was detected in peritubular cells. In addition, vimentin in Sertoli cells generated a large number of breakdown products, many differing in molecular weight and isoelectric point when compared to peritubular cells. These findings suggested that a Ca2+-activated protease, usually found in cells containing vimentin, was capable of generating proteolytic fragment patterns that were specific to cell type. Monoclonal antibodies were generated against IFP extracted from cultured Sertoli cells and their reactivity monitored by indirect immunofluorescence using Sertoli cells, peritubular cells and intact testis. One monoclonal antibody, designated IFP-SC, was an immunoglobulin (IgM) that produced a vimentin-like immunofluorescent pattern in cultured Sertoli cells. This pattern consisted of an extensive filamentous network that extended throughout the cell and surrounded the nucleus. In cultured peritubular cells, IFP-SC generated a diffuse, nonfilamentous immunoreactivity. IFP-SC reacted with components of seminiferous tubules and displayed immunoreactivity associated with Sertoli cells but not with elements of the seminiferous peritubular cell wall. Because immunofluorescent patterns were distinctly specific to cell type in cultured cells and in the intact tissue, monoclonal antibody IFP-SC is useful for the quantitative evaluation of cell cross-contamination of Sertoli and peritubular cells and, therefore, allows a precise characterization of functional events specific to cell type and monitoring of the differentiation state of cells with time in culture.

Animals↗
PubMed1990

Intermediate filament reorganization during mitosis is mediated by p34cdc2 phosphorylation of vimentin.

As cells enter mitosis, the intermediate filament (IF) networks of interphase BHK-21 cells are depolymerized to form cytoplasmic aggregates of disassembled IFs, and the constituent IF proteins, vimentin and desmin are hyperphosphorylated at several specific sites. We have characterized one of two endogenous vimentin kinases from a particulate fraction of mitotic cell lysates. Through several purification steps, vimentin kinase activity copurifies with histone H1 kinase and both activities bind to p13suc1-Sepharose. The final enriched kinase preparation consists primarily of p34cdc2 and polypeptides of 65 and 110 kd. The purified kinase complex phosphorylates vimentin in vitro at a subset of sites phosphorylated in vivo during mitosis. Furthermore, phosphorylation of in vitro polymerized vimentin IFs by the purified kinase causes their disassembly. Therefore, vimentin is a substrate of p34cdc2 and phosphorylation of vimentin contributes to M phase reorganization of the IF network.

Animals↗
PubMed1982

Identification of a complex between alpha-actinin and the intermediate filament subunit skeletin in bovine heart Purkinje fibres.

A three-dimensional cytoskeleton, morphologically composed of intermediate filaments, desmosomes, and Z-disks, remains in bovine heart Purkinje fibres after extraction with Triton X-100 and low and high ionic strength solutions. Biochemically this cytoskeleton mainly consists of skeletin (Mr approximately 55 000) and of alpha-actinin (Mr approximately 95 000). Minor high molecular weight components are also present. By gel electrophoresis-derived enzyme-linked immunosorbent assay (GEDELISA) we show here that a 150 000-dalton component is a complex of alpha-actinin and skeletin. Furthermore, this 150 000-dalton component has now been purified and can be converted into 95 000- and 55 000-dalton subunits by reduction with a high concentration of beta-mercaptoethanol and heating. We also show that solubilized pure skeletin and pure alpha-ctinin from Purkinje fibres, after mixing, partly form a stable complex with a molecular weight of about 150 000 daltons.

Actinin↗
PubMed1992

Expression of intermediate filaments and other special markers by testicular germ cell tumors. With reference to embryogenesis.

Distribution of intermediate filament proteins (IFs) and several special markers was studied in 39 testicular germ cell tumors and 8 embryos and foetuses. The similarity and difference between development of germ cell tumor and embryogenesis were immunohistochemically investigated. Seminoma and embryonal carcinoma, as tumoral counterparts of undifferentiated germ cells, were characterized by little IF expression. This study revealed that the maturing and differentiating process in germ cell tumor is different from normal embryonal development and the tumor cells showed leaping maturing steps in tumorigenesis. Immunostaining for IFs helped to discover the further differentiation occurring in embryonal carcinoma and to demonstrate heterogeneous elements in non-seminoma germ cell tumors, which sometimes might not be apparent by light microscopical observation of H&E staining section. According to the findings, two patterns in mixed germ cell tumors are suggested; i.e., combined and diffuse types. The mechanism of tumorigenesis of the two types is supposed to be different. Clinically, the prognosis of most patients with testicular germ cell tumor is fairly good because of the improved chemotherapies that are dependent on histological diagnosis.

Adolescent↗
PubMed1998

Restricted expression of the neuronal intermediate filament protein plasticin during zebrafish development.

In the adult goldfish visual pathway, expression of the neuronal intermediate filament (nIF) protein plasticin is restricted to differentiating retinal ganglion cells (RGCs) at the margin of the retina. Following optic nerve injury, plasticin expression is elevated transiently in all RGCs coincident with the early stages of axon regeneration. These results suggest that plasticin may be expressed throughout the nervous system during the early stages of axonogenesis. To test this hypothesis, we analyzed plasticin expression during zebrafish (Danio rerio) neuronal development. By using immunocytochemistry and in situ hybridization, we found that plasticin is expressed in restricted subsets of early zebrafish neurons. Expression coincides with axon outgrowth in projection neurons that pioneer distinct axon tracts in the embryo. Plasticin is expressed first in trigeminal, Rohon-Beard, and posterior lateral line ganglia neurons, which are among the earliest neurons to initiate axonogenesis in zebrafish. Plasticin is expressed also in reticulospinal neurons and in caudal primary motoneurons. Together, these neurons establish the first behavioral responses in the embryo. Plasticin expression also coincides with initial RGC axonogenesis and progressively decreases after RGC axons reach the tectum. At later developmental stages, plasticin is expressed in a subset of the cranial nerves. The majority of plasticin-positive neurons are within or project axons to the peripheral nervous system. Our results suggest that plasticin subserves the changing requirements for plasticity and stability during axonal outgrowth in neurons that project long axons.

Animals↗
PubMed2000

In vivo expression of the intermediate filament peripherin in rat motoneurons: modulation by inhibitory and stimulatory signals.

Peripherin is a type III intermediate filament which, in contrast to the neurofilaments, is strongly up-regulated after nerve injury. Although peripherin expression is stimulated in vitro by neurotrophins and cytokines, little is known about its in vivo regulation. In this report, we show that the in vivo down-regulation of peripherin expression to normal levels during regeneration closely correlates with target reconnection in rat facial motoneurons. Prevention of reconnection, by transection and suture, results in the persistence of strong peripherin expression for prolonged periods of up to 11months. This contrasts with the modulation of the p75 low-affinity neurotrophin receptor, whose expression returns to normal even in the absence of reconnection. We further demonstrate that blockade of the axonal transport in non-injured motoneurons increases the expression of peripherin. Blockade of the axonal transport simultaneously to, or after injury of, facial motoneurons does not abolish the axotomy-induced peripherin up-regulation. These data demonstrate that the in vivo expression of peripherin is normally restrained by a distal retrogradely transported inhibitory signal. Thus, peripherin up-regulation results primarily from a lack of supply in this factor. Our results show that stimulatory factors released at the injury site are not required for the initial up-regulation and maintenance of high peripherin expression. However, they appear to enhance this increase during the acute post-lesion phase. Peripherin expression is thus finely tuned by both glial cell-derived stimulatory and distal inhibitory signals that reflect neuron-target interactions.

Animals↗
PubMed1991

Evidence that intermediate filament reorganization is induced by ATP-dependent contraction of the actomyosin cortex in permeabilized fibroblasts.

Intermediate filaments (IFs) undergo specific rearrangements in cells, some aspects of which can be induced experimentally. Centripetal aggregation of the IF network, for example, can be produced by a variety of perturbations. However, the source of motive force is clear for neither in vivo nor experimentally generated IF movements, since, unlike microtubules and actin filaments, IFs have no known force-generating system directly associated with them. We recently obtained evidence that the drug-induced aggregation of vimentin IFs in fibroblasts is an active event, which requires ATP and involves the actin cytoskeleton. In the present study, we sought to test the hypothesis that IF aggregation is driven by a centripetally directed contraction of the actomyosin cortex. To that end, we have permeabilized fibroblasts with Triton X-100 in a stabilizing buffer and reactivated cytoskeletal movements in vitro, under defined solution conditions. Upon nucleotide treatment, these permeabilized cells undergo a nucleotide-dependent centripetal aggregation of vimentin IFs similar in appearance and time course to that induced in intact cells by drug treatment. During in vitro IF aggregation, the permeabilized cells remain fully spread and adherent to the substratum, and the distal ends of the microtubules and actin microfilaments retain their positions in the cell periphery, IF aggregation is accompanied by a contraction of F-actin and myosin into focal aggregates in the same perinuclear region in which the IFs accumulate. If permeabilized cells are treated with the actin-severing protein gelsolin prior to the reactivation of IF movement, the actin cytoskeleton is eliminated and IF aggregation fails to occur when ATP is added. These results strongly support a model in which the motive force for IF movement is supplied indirectly by association with a contracting actomyosin network.

Actins↗
PubMed1986

Immunocytochemical demonstration of intermediate filament cytoskeleton proteins in human endocrine tissues and (neuro-) endocrine tumours.

The presence and distribution of intermediate filament proteins, such as cytokeratins, vimentin, neurofilament proteins and glial fibrillary acidic protein were assessed immunohistochemically in pituitary adenomas, medullary thyroid carcinomas, endocrine pancreatic tumours, gastric, intestinal and bronchial carcinoids, parathyroid adenomas, pheochromocytomas, paragangliomas and related non-neoplastic tissues. In some cases, immunohistochemical results were correlated with cytoskeletal proteins as analysed by SDS-polyacrylamide gel electrophoresis. Cytokeratin antibodies with broad range of immunoreactivity (i.e. to murine liver cytokeratin component D) reacted with epithelial cells in all non-neoplastic endocrine tissues and related neuroendocrine tumours studied, except for adrenal medulla, pheochromocytoma and paraganglioma, independently of hormone production and biological behaviour. In contrast, antibodies to epidermis-derived cytokeratins failed to stain endocrine tissues and tumours. Paranuclear cytokeratin accumulations were seen in bronchial, gastric, and intestinal carcinoids and seem to be a common feature of neuroendocrine tumours. One- and two-dimensional SDS-polyacrylamide gel electrophoresis of non-neoplastic endocrine tissues and related tumours revealed two major keratin polypeptides corresponding to cytokeratins No. 8 and 18 of the cytokeratin catalog of human cells (Moll et al. 1982). According to this cytokeratin polypeptide composition, endocrine tissues and related tumours conform to the "simple type" of epithelia. Vimentin-related immunoreactivity was restricted to stromal cells and to folliculo-stellate cells in normal pituitary gland, Schwann cells in carcinoids and satellite cells in normal adrenal medulla and in pheochromocytomas. Neurofilament protein- (70 kD)-antibodies only stained nerve fibers in normal tissues and at the periphery of carcinoid tumour cell complexes, and to a variable degree, cells in nontumorous adrenal medulla, pheochromocytomas and paragangliomas. Furthermore, neurofilament reactivity was observed along with cytokeratin expression in two bronchial carcinoids.

Electrophoresis, Polyacrylamide Gel↗
PubMed1996

Intermediate filament expression in prostate cancer.

The human prostate is composed of a series of tubular-alveolar glands and their ducts surrounded by a fibro-muscular stroma. The parenchymal glands secrete the seminal fluid and are anatomically arranged into the central, peripheral, and transitional zones. In this chapter the pattern of intermediate filament expression by the various epithelial components of the ducts, tubuloalveolar glands, and stroma are described. The changes which occur during malignant transformation from normal glands to prostatic intraepithelial neoplasia and subsequent invasive carcinoma are presented. The usefulness of cytokeratin markers in the diagnosis of prostate carcinoma is also discussed.

Humans↗
PubMed1981

Coiling of intermediate filaments induced by microinjection of a vimentin-specific antibody does not interfere with locomotion and mitosis.

Microinjection of polyclonal sheep anti-vimentin IgGs purified by affinity chromatography into a rat fibroblastoid line leads to a specific reorganization of the cytoskeleton. Immunofluorescence microscopy shows that cytoplasmic microtubules and microfilaments are unaffected by intermediate filaments collapse and are collected into a tight perinuclear cap containing antibody-crosslinked vimentin filaments. The crosslinking was further documented by electron microscopy after treatment with Triton X-100 and ferritin-labelled anti-sheep IgGs. Inspite of the presence of the caps, which are retained for about 30 h, cells show a normal morphology and are locomotive. The collapsed intermediate filaments do not interfere with subsequent mitosis or with cytokinesis. After mitosis the capped filaments can be distributed either to both daughter cells or to only one of the two daughter cells.

Animals↗
PubMed1994

Intermediate filaments and lipoprotein cholesterol.

The ability of cells to utilize cholesterol derived from lipoprotein is important in plasma membrane biosynthesis, steroidogenesis and the regulation of sterol synthesis. While the endocytosis of lipoprotein-derived cholesterol has been well characterized, the subsequent events that mediate its post-lysosomal intracellular transport are not understood. Recent studies have suggested that vimentin-type intermediate filaments may have a role in cholesterol transport. The mechanism by which vimentin filaments affect this process is not known, but future studies promise to provide new insights into both the post-lysosomal transport of cholesterol and the intracellular functions of intermediate filaments.

Journal Article↗
PubMed1985

Isolation of intermediate filament assemblies from human hair follicles.

We used developing human hair follicle cells for the isolation of hard alpha-keratin structural components. Intracellular dispersions examined by electron microscopy contained both individual alpha-keratin filaments and the tactoid-like filament assemblies observed in situ organized along subfibrillar arms of macrofibrils. The assemblies of average width 47 nm were composed of closely packed alpha-keratin filaments and originated from the initial filament arrays observed in sections of developing mammalian hair follicles. We have distinguished two types of assemblies: the para-like or hexagonally packed and the ortho-like spiral or whorl type. Axial banding extended across the width of filament assemblies, which suggested that hard alpha-keratin filaments pack in lateral register and form a lattice that contains interfilamentous bridges. We observed axial banding patterns with periods ranging from 20 to 22 nm, consistent with the 22-nm periodic structure deduced from x-ray diffraction studies and present in models proposed for hard alpha-keratin and other intermediate filaments. Preliminary biochemical studies of filaments and filament assemblies indicate that they consist of the closely related group of proteins (low-sulfur proteins) ubiquitous among extracts of hard mammalian keratins. Isolated hard alpha-keratin filament assemblies provide a new and valuable structural entity for investigating the assembly mechanisms involved in the formation of the filament-matrix framework found in hard mammalian keratin appendages.

Cytoskeleton↗
PubMed1983

Complete amino acid sequence of a mouse epidermal keratin subunit and implications for the structure of intermediate filaments.

We have determined the complete primary structure of an intermediate filament subunit, the 59,000 molecular weight subunit of mouse epidermal keratin, from the nucleotide sequence of cDNA clones. The central portion of the sequence forms extended tracts of a coiled-coil alpha-helical conformation. This is flanked at both termini by similar non-alpha-helical sequences that are extremely rich in glycine residues, frequently configured in tandem peptide repeats. Limited chymotryptic digestion of keratin filaments containing this protein suggests a structural organization whereby the terminal glycine-rich sequences protrude from a conserved core structure into which the coiled-coil alpha-helical segments are packed.

Amino Acid Sequence↗
PubMed2000

Characterisation and tissue-specific expression of the two keratin subfamilies of intermediate filament proteins in the cephalochordate Branchiostoma.

The cloning of three intermediate filament proteins expressed at the gastrula stage (kl, Y1, X1) extends the size of the IF multigene family of Branchiostoma to at least 13 members. This is one of the largest protein families established for the lancelet. Sequence comparisons indicate five keratin orthologs, three of type I (E1, k1, Y1) and two of type II (E2, D1). This assignment is confirmed by the obligatory heteropolymeric polymerisation behaviour of the recombinant proteins. In line with the hetero-coiled-coil principle IF are formed by any stoichiometric mixture of type I and II keratin orthologs. In spite of the strong sequence drift chimeric IF are formed between K8, a human keratin II, and two of the lancelet type I keratins. We discuss whether the remaining 8 IF proteins reflect three additional and potentially cephalochordate-specific subfamilies. The tissue-specific expression patterns of the 5 keratins and some other IF proteins were analysed by immunofluorescence in the adult. Keratins are primarily present in ectodermally derived tissues. Developmental control of the expression of some IF proteins is observed, but three keratins (k1, Y1, D1) and an additional IF protein (X1) detected at the gastrula stage are expressed throughout the life cycle.

Amino Acid Sequence↗
PubMed1997

Phosphorylation-dependent control of structures of intermediate filaments: a novel approach using site- and phosphorylation state-specific antibodies.

Site-specific phosphorylation of intermediate filament (IF) proteins on serine and threonine residues leads to dynamic alterations in filament structure. Site- and phosphorylation state-specific antibodies for IF proteins can visualize spatial and temporal distribution of site-specific IF protein phosphorylations in the cell. These antibodies are also useful to identity IF kinases involved in cellular events, including cell signaling and cell cycle.

Antibodies↗
PubMed1981

Expression of keratin and vimentin intermediate filaments in rabbit bladder epithelial cells at different stages of benzo[a]pyrene-induced neoplastic progression.

Rabbit bladder epithelium, grown on collagen gels and exposed to the chemical carcinogen benzo[a]pyrene, produced nontumorigenic altered foci as well as tumorigenic epithelial cell lines during 120-180 d in culture. Immunofluorescence studies revealed extensive keratin filaments in both primary epithelial cells and benzo[a]pyrene-induced altered epithelial foci but showed no detectable vimentin filaments. The absence of vimentin expression in these cells was confirmed by two-dimensional gel electrophoresis. In contrast, immunofluorescence staining of the cloned benzo[a]pyrene-transformed rabbit bladder epithelial cell line, RBC-1, revealed a reduction in filamentous keratin concomitant with the expression of vimentin filaments. The epithelial nature of this cell line was established by the observation that cells injected into nude mice formed well-differentiated adenocarcinomas. Frozen sections of such tumors showed strong staining with antikeratins antibodies, but no detectable staining with antivimentin antibodies. These results demonstrated a differential expression of intermediate filament type in cells at different stages of neoplastic progression and in cells maintained in different growth environments. It is apparent that the expression of intermediate filaments throughout neoplastic progression is best studied by use of an in vivo model system in parallel with culture studies.

Animals↗
PubMed1993

Confocal microscopy immunofluorescence localization of desmin and other intermediate filament proteins in fetal rat livers.

Immunolocalization of desmin in fetal rat livers shows that on day 12 of gestation a high number of liver cells express desmin. This number decreases from day 14 onward. On day 20 about the same density of desmin-containing cells is found in fetal rat livers as is found in adult rat livers. Desmin-containing cells show two types of labeling patterns, especially on days 12 and 13 of gestation: (a) a basketlike network of intermediate filaments throughout the whole cell, similar to the labeling pattern of cytokeratin in hepatocytes; and (b) more strongly labeled intermediate filaments developing long and slender processes between adjacent cells, close to the labeling pattern of Ito cells in adult rats. From day 14 of gestation, the first type becomes rare, and from day 18 only the second type remains. Double-labeling experiments show that coexpression of desmin and cytokeratin is found in cells of the first type on days 12, 13 and 14 of gestation. Cells containing desmin with the labeling pattern of the second type never express cytokeratin. Coexpression of vimentin and cytokeratin is never found in fetal hepatocytes, even on day 12 of gestation. Numerous nonhepatocyte cells coexpress desmin and vimentin, but some cells contain vimentin or desmin alone. In desmin-containing cells the labeling pattern is of the first type (basketlike network). These results suggest that in early stages of fetal liver development, desmin is found in two different types of liver cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

[Comparative expression of 2 intermediate filament proteins, peripherin and the 68 kDa neurofilament protein, during embryonal development of the rat].

Peripherin, an intermediate filament protein, was originally detected by biochemical methods in the neurons of the peripheral nervous system. We now studied its expression and cellular localization by immunocytochemical methods in the developing rat embryo, and compared them with the expression and localization of the 68 kDa neurofilament protein. It appears that peripherin is expressed not only in the neurons of the peripheral nervous system, but also in some well defined neuronal populations of the central nervous system. These results focus on the questions of the phylogenetic origin and of the function of peripherin.

Animals↗