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PubMed1989

Malignant fibrous histiocytoma. Heterogeneous patterns of intermediate filament proteins by immunohistochemistry.

Patterns of intermediate filament expression of 10 malignant fibrous histiocytomas (MFHs) were immunohistochemically evaluated using acetone-fixed frozen sections. Seven cases represented the storiform-pleomorphic subtype, 2 were of myxoid type, and 1 was of giant-cell type. All cases had been studied by electron microscopy, and no proof for the diagnoses of liposarcoma, rhabdomyosarcoma, and leiomyosarcoma could be obtained. All tumors showed prominent vimentin immunoreactivity in the tumor cells. Cytokeratin-positive neoplastic cells were found in 2 cases, and in the majority of tumor cells in 1 of these. The 68k neurofilament-positive cells were found in 2 cases. Desmin was not found beyond doubt in the neoplastic cells in any cases, and all cases were negative for glial fibrillary acidic protein. The expression of several types of intermediate filament indicates divergent differentiation properties in MFH and may suggest the heterogeneity of this entity, but more cases should be studied to elaborate any possible consistent patterns of intermediate filament expression in different types of MFH. The expression of multiple types of intermediate filament proteins in MFH can alternatively signify random activation of the corresponding genes in the primitive tumor cells. The complex patterns of intermediate filament proteins in morphologically defined MFHs should be taken into account in the practical immunohistologic analysis of tumors.

Cell Differentiation↗
PubMed1987

The mesonephric (wolffian) and paramesonephric (müllerian) ducts of golden hamsters express different intermediate-filament proteins during development.

We analysed the expression of intermediate-filament proteins in the developing mesonephric duct (the precursor of the male genital ducts) and the paramesonephric duct (the precursor of the female genital ducts) of golden-hamster embryos using immunohistochemical methods. Embryos were investigated from the early stages of duct development, i.e. at 9.5 days post conceptionem (dpc), through sexual differentiation, until birth (15.5 dpc). Monospecific antibodies to vimentin or keratins 7, 8, 18 or 19 as well as two keratin antibodies that are pan-epithelial in human tissues were tested. Both ducts expressed vimentin to some degree from their early stages (mesonephric duct from 9.5 dpc onwards; paramesonephric duct from 10.5 dpc onwards) until birth. No keratins were detectable at these earliest stages. In the mesonephric duct, keratins 7, 18 and 19 appeared simultaneously at 10.5 dpc and persisted until birth. In the paramesonephric duct, only keratin 18 was detectable at first (at 12.0 dpc), with the expression of keratins 7 and 19 being delayed until 14.5 dpc. This feature was irrespective of sexual differentiation, which begins at 11.0 dpc, so that, in males, these keratins appeared on cue, even though the paramesonephric duct was regressing at this time. The expression of keratin 8 could not be demonstrated in either duct using the antibodies tested in our study. By 14.5 dpc, the differentiated male mesonephric duct and the differentiated female paramesonephric duct exhibited the same intermediate-filament protein pattern (weak vimentin expression and strong expression of keratins 7, 18 and 19), in spite of differences in the intermediate-filament protein patterns exhibited by the two ducts during early development. These different programmes of intermediate-filament protein regulation do not support the concept that the mesonephric duct makes a cellular contribution to the paramesonephric duct during the development of the latter.

Animals↗
PubMed2000

Plasticin, a type III neuronal intermediate filament protein, assembles as an obligate heteropolymer: implications for axonal flexibility.

The assembly characteristics of the neuronal intermediate filament protein plasticin were studied in SW13 cells in the presence and absence of a cytoplasmic filament network. Full-length plasticin cannot polymerize into homopolymers in filament-less SW13c1.2Vim(-) cells but efficiently coassembles with vimentin in SW13c1.1Vim(-) cells. By cotransfecting plasticin and vimentin in SW13c1.1Vim(-) cells, we show that plasticin assembly requires vimentin in noncatalytic amounts. Differing effects on assembly were seen with point mutations of plasticin monomers that were analogous to the keratin mutations that cause epidermolysis bullosa simplex (EBS). In particular, plasticin monomers with point mutations analogous to those in EBS do not uniformly inhibit neurofilament (NF) network formation. A point mutation in the helix termination sequence resulted in complete filament aggregation when coexpressed with vimentin but showed limited coassembly with low- and medium-molecular-weight NF proteins (NF-L and NF-M, respectively). In transfected SW13c1.1Vim(+) cells, a point mutation in the first heptad of the alpha-helical coil region formed equal amounts of filaments, aggregates, and a mixture of filaments and aggregates. Furthermore, coexpression of this point mutation with NF-L and NF-M was associated with a shift toward increased numbers of aggregates. These results suggest that there are important structural differences in assembly properties between homologous fish and mammalian intermediate filament proteins. These structural differences may contribute to the distinctive growth characteristics of the teleost visual pathway.

Amino Acid Substitution↗
PubMed1993

The 47-kD lens-specific protein phakinin is a tailless intermediate filament protein and an assembly partner of filensin.

In previous studies we have characterized a lens-specific intermediate filament (IF) protein, termed filensin. Filensin does not self-assemble into regular IFs but is known to associate with another 47-kD lens-specific protein which has been suggested to represent its assembly partner. To address this possibility, we cloned and sequenced the cDNA coding for the bovine 47-kD protein which we have termed phakinin (from the greek phi alpha kappa omicron sigma = phakos = lens). The predicted sequence comprises 406 amino acids and shows significant similarity (31.3% identity over 358 residues) to type I cytokeratins. Phakinin possesses a 95-residue, non-helical domain (head) and a 311 amino acid long alpha-helical domain punctuated with heptad repeats (rod). Similar to cytokeratin 19, phakinin lacks a COOH-terminal tail domain and it therefore represents the second known example of a naturally tailless IF protein. Confocal microscopy on frozen lens sections reveals that phakinin colocalizes with filensin and is distributed along the periphery of the lens fiber cells. Quantitative immunoblotting with whole lens fiber cell preparations and fractions of washed lens membranes suggest that the natural stoichiometry of phakinin to filensin is approximately 3:1. Under in vitro conditions, phakinin self-assembles into metastable filamentous structures which tend to aggregate into thick bundles. However, mixing of phakinin and filensin at an optimal ratio of 3:1 yields stable 10-nm filaments which have a smooth surface and are ultrastructurally indistinguishable from "mainstream" IFs. Immunolabeling with specific antibodies shows that these filaments represent phakinin/filensin heteropolymers. Despite its homology to the cytokeratins, phakinin does not coassemble with acidic (type I), or basic (type II) cytokeratins. From these data we conclude that filensin and phakinin are obligate heteropolymers which constitute a new membrane-associated, lens-specific filament system related to, but distinct from the known classes of IFs.

Amino Acid Sequence↗
PubMed1986

Homology and diversity between intermediate filament proteins of neuronal and nonneuronal origin in goldfish optic nerve.

The predominant intermediate filament proteins of the goldfish optic nerve have molecular weights of 58K. They can be separated into a series of four major isoelectric variants of neuronal (ON1 and ON2) and nonneuronal (ON3 and ON4) origin. The extent of homology between the goldfish 58K intermediate filament proteins themselves and to rat optic nerve vimentin and glial fibrillary acidic protein (GFAP) was investigated. Unlabeled and [32P]orthophosphate-labeled proteins were subjected to partial hydrolysis by V8 protease, chymotrypsin, and CNBr. The results show that the goldfish intermediate filament proteins share with vimentin and GFAP a 40K chymotrypsin-resistant core fragment. Phosphorylated moieties appear to be located outside the core region since they are preferentially cleaved off by chymotrypsin and not found associated with the 40K core. In addition, the goldfish ON proteins contain the antigenic site within the core that is common to most intermediate filaments. V8 or CNBr digestion indicates that many fragments that are common to ON1 and ON2 are clearly distinct from fragments that are common to ON3 and ON4. In addition, structural variability is observed between the goldfish intermediate filament proteins and vimentin and GFAP. The results are discussed in terms of intermediate filament structure and their possible role in nerve growth.

Animals↗
PubMedDate not supplied

Monoclonal antibodies to intermediate filament proteins: diagnostic specificity in orbital pathology.

Intermediate filaments derived from different cell types are antigenically distinct. Monoclonal antibodies to human intermediate filament proteins can, therefore, be used as tissue-specific reagents capable of distinguishing cell type in poorly differentiated neoplasms. We report a case demonstrating the specificity of antiintermediate filament protein antibodies in establishing a difficult orbital diagnosis of esthesioneuroblastoma.

Antibodies, Monoclonal↗
PubMed1982

Intermediate filament proteins in nonfilamentous structures: transient disintegration and inclusion of subunit proteins in granular aggregates.

The intermediate filament cytoskeleton of cultured bovine kidney epithelial cells and human HeLa cells changes dramatically during mitosis. The bundles of cytokeratin and vimentin filaments progressively unravel into protofilament-like threads of 2-4 nm diameter, and intermediate filament protein is included in numerous, variously sized (0.2-1.5 microns) spheroidal aggregates containing densely stained granular particles of 5-16 nm diameter. We describe these mitotic bodies in intact cells and in isolated cytoskeletons. In metaphase to anaphase of normal mitosis and after colcemid arrest of mitotic stages, many cells contain all their detectable cytokeratin and vimentin material in the form of such spheroidal aggregate bodies, whereas in other mitotic cells such bodies occur simultaneously with bundles of residual intermediate filaments. In telophase, the extended normal arrays of intermediate filament bundles are gradually reestablished. We find that vimentin and cytokeratins can be organized in structures other than intermediate filaments. Thus, at least during mitosis of some cell types, factors occur that promote unraveling of intermediate filaments into protofilament-like threads and organization of intermediate filament proteins into distinct granules that form large aggregate bodies. Some cells, at least certain epithelial and carcinoma cells, may contain factors effective in structural modulation and reorganization of intermediate filaments.

Anaphase↗
PubMed1996

Intermediate filament protein domain interactions as revealed by two-hybrid screens.

All intermediate filament proteins possess three distinct domains: heads, rod and tail, and subdomains within the rod called helices 1A, 1B, 2A, and 2B. Subunit packing within a filament is a consequence of interactions among these domains. Several such interactions are known, but probably many more contribute to stabilizing filament structure. We examined a number of such potential interactions using the yeast two-hybrid system. Domains or subdomains of murine vimentin, a Type III intermediate filament protein, were fused with either the DNA-binding or trans-activating domain of GAL4, a transcription factor. Interaction between the vimentin domains/subdomains functionally reconstituted GAL4, thereby activating transcription of a GAL1-LacZ reporter gene. The oligomeric state at which the interactions took place, i.e. whether the domains/subdomains were dimeric or tetrameric as they interacted, was also determined. These studies revealed a number of interesting interactions, among which was a strong homotypic binding to helix 2B to form tetramers. They also demonstrated a lack of interaction among others expected to do so based on current structural models. From these results we deduced which of the candidates for interactions, suggested by current models, were true protein-protein interactions and which represented nearest-neighbors only. Thus, the A11 and A22 modes of molecular alignment identified by Steinert et al. (Steinert, P. M., Marekov, L. N., Fraser, R. D. B., and Parry, D. A. D. (1993) J. Mol. Biol. 230, 436-452) are probably true interactions, whereas the A12 and ACN modes may describe adjacent but non-interacting molecules.

Animals↗
PubMed1996

[Neuronal intermediate filament proteins].

The characteristics of the seven intermediate filament proteins expressed during the development of neurons are reviewed. The most extensively studied have been neurofilament proteins (NFP) and peripherin. The relative plasticity of the peripherin network can account for its possible role during development when the axons of the neurons in which this protein is expressed have to find their targets crossing a non-neural environment probably in answer to signals from this environment and from their respective targets. Peripherin may assume a similar role when axons regenerate. NFP are considered as maintaining the axonal caliber, thus ensuring a normal axonal transport. Their network is highly disrupted in several diseases, particularly in motor neuron diseases. Mice transgenic for human NFP or in which mouse NFP are overexpressed have been obtained and are considered as animal models for these diseases.

Animals↗
PubMed1994

Myogenesis and the intermediate filament protein, nestin.

We show that the intermediate filament protein nestin is expressed in myogenic cells and that multiple mechanisms regulate nestin expression at different stages of myogenesis. Cultured embryonic, fetal, and neonatal mouse limb myoblasts initially expressed nestin in the absence of the four muscle regulatory factors (MRFs) of the MyoD family, whereas nestin and MRFs became coexpressed by myoblasts as culture duration was lengthened. Upon differentiation, nestin was commonly concentrated at the ends, and reduced or absent in the middles, of myotubes formed by mouse limb cells. Nestin was expressed by C2C12 and L6 myoblasts and was distributed throughout C2C12 myotubes, but was entirely absent in myotubes formed by L6 cells, suggesting that nestin is dispensable for fusion and terminal differentiation. Nestin was expressed in C3H10T1/2 cells, but was not expressed in 3T3-L1 cells until transfected with MyoD or myogenin. In mouse somites, nestin was found in both myotomal and dermatomal cells. Thus, nestin is expressed by dermatomal cells and by myoblasts during the earliest stages of myogenesis, and nestin expression can be activated upon MRF transfection. Additional MRF-independent mechanisms must, however, regulate nestin expression, because nestin is found in MRF-negative cells and, conversely, nestin is not uniformly distributed in MRF-expressing myotubes.

3T3 Cells↗
PubMed2002

Cytoplasmic intermediate filament protein expression in tunicate development: a specific marker for the test cells.

The urochordate Ciona intestinalis is a well established system for embryological studies, and large scale EST sequences begin to emerge. We cloned five cytoplasmic intennediate filament (IF) cDNAs and made specific antibodies to the recombinant proteins. Self-assembly studies and immunofluorescence microscopy were used to study these proteins and their distribution. Confirming and extending previous studies in Styela, we found that Ciona protein IF-A is expressed in muscle and forms homopolymeric filaments while proteins IF-C and IF-D, which form only obligatory heteropolymeric filaments, resemble a keratin pair exclusively found in the entire epidermis. Protein IF-B and the new protein IF-F potentially reflect tunicate-specific IF proteins. They are found in the entire internal epithelia including the neural gland. We also extended the analysis to earlier developmental stages of Ciona. Protein IF-A is expressed in muscle from larval stages, whereas proteins IF-C and IF-D are found only in the tail epidermis. Protein IF-F is detected abundantly in the test cells of eggs, embryos and premetamorphic larvae. Our studies show that IF proteins could prove very useful markers in the study of cell fate determination in Ciona. They also support previous findings on the evolutionary relationships of different IF proteins. Non-vertebrate chordates have IF proteins which represent orthologs of vertebrate type I to III proteins, but also IF proteins that do not seem to fit into these classes. However, the intron positions of all tunicate IF genes are conserved with vertebrate type I to III genes, pointing to a common evolutionary origin.

Amino Acid Sequence↗
PubMed1985

Variable expression of intermediate filament proteins during embryonic development of human optic nerve.

The intermediate filament protein composition of human optic nerve and tract was analyzed by two-dimensional gel electrophoresis. Optic nerves were analyzed at 15, 19, 22, and 24 weeks of embryonic development and the results were compared with the composition of adult optic nerve. The optic tract was analyzed at the later stages of development. The proteins were visualized by Coomassie blue staining and immunoblotting with specific antibodies to glial fibrillary acidic protein (GFAP) and vimentin. The 70K and 150K neurofilament proteins were first observed at 24 weeks. At 15 weeks of development, only trace amounts of GFAP were observed and vimentin was the predominant intermediate filament protein. In contrast, there was more than twice as much GFAP as vimentin in the adult optic nerve. The results also showed that the ratio of GFAP to vimentin is higher in the optic tract than in the optic nerve during development, whereas in adult tissue, the ratio is the same for the two regions. In pathological situations with axonal dropout, a complete loss of neurofilament proteins was observed. The amounts of both GFAP and vimentin were the same for both the normal and involved optic nerve. These results are discussed in terms of the development of the optic nerve.

Glial Fibrillary Acidic Protein↗
PubMed1998

Molecular phylogeny of metazoan intermediate filament proteins.

We have cloned cytoplasmic intermediate filament (IF) proteins from a large number of invertebrate phyla using cDNA probes, the monoclonal antibody IFA, peptide sequence information, and various RT-PCR procedures. Novel IF protein sequences reported here include the urochordata and nine protostomic phyla, i.e., Annelida, Brachiopoda, Chaetognatha, Echiura, Nematomorpha, Nemertea, Platyhelminthes, Phoronida, and Sipuncula. Taken together with the wealth of data on IF proteins of vertebrates and the results on IF proteins of Cephalochordata, Mollusca, Annelida, and Nematoda, two IF prototypes emerge. The L-type, which includes 35 sequences from 11 protostomic phyla, shares with the nuclear lamins the long version of the coil 1b subdomain and, in most cases, a homology segment of some 120 residues in the carboxyterminal tail domain. The S-type, which includes all four subfamilies (types I to IV) of vertebrate IF proteins, lacks 42 residues in the coil 1b subdomain and the carboxyterminal lamin homology segment. Since IF proteins from all three phyla of the chordates have the 42-residue deletion, this deletion arose in a progenitor prior to the divergence of the chordates into the urochordate, cephalochordate, and vertebrate lineages, possibly already at the origin of the deuterostomic branch. Four phyla recently placed into the protostomia on grounds of their 18S rDNA sequences (Brachiopoda, Nemertea, Phoronida, and Platyhelminthes) show IF proteins of the L-type and fit by sequence identity criteria into the lophotrochozoic branch of the protostomia.

Amino Acid Sequence↗
PubMed2001

Association of syncoilin and desmin: linking intermediate filament proteins to the dystrophin-associated protein complex.

We recently identified a novel protein called syncoilin, a putative intermediate filament protein that interacts with alpha-dystrobrevin, a member of the dystrophin-associated protein complex. Syncoilin is found at the neuromuscular junction, sarcolemma, and Z-lines and is thought to be important for muscle fiber integrity. Based on the similar protein structure and cellular localization of syncoilin and desmin, we proposed that these proteins interact in vivo. The data presented confirm an interaction between syncoilin and desmin and demonstrate their co-localization in skeletal muscle. Intriguingly, whereas these proteins interact, COS-7 cell expression studies show that desmin and syncoilin do not assemble into heterofilaments. Furthermore, fractionation assay and immunofluorescence study of H2K myoblasts and myotubes suggest that, unlike typical intermediate filament proteins, syncoilin does not participate in filament formation with any protein. However, it is possible that syncoilin is involved in the anchoring of the desmin intermediate filament network at the sarcolemma and the neuromuscular junction. This interaction is likely to be important for maintaining muscle fiber integrity and may also link the dystrophin-associated protein complex to the cytoskeleton. The dysfunction or absence of syncoilin may result in the disruption of the intermediate filament network leading to muscle necrosis. Syncoilin is therefore an ideal candidate gene for muscular dystrophies and desmin-related myopathies.

Animals↗
PubMed1992

Structure of the mouse gene encoding peripherin: a neuronal intermediate filament protein.

The gene encoding mouse peripherin, a neuronal intermediate filament protein, has been cloned. Its sequence, through 1021 nucleotides composing the 5'-flanking region, nine exons, eight introns and 547 nucleotides of the 3'-flanking region, as well as its transcription initiation site have been determined. The amino acid coding sequence differs from that of the rat peripherin gene. The mouse gene has an additional histidine near the N-terminal end, and shows three conservative and two non-conservative changes. The promoter sequence, containing the binding sites for transcription factors as well as other sequences is homologous to promoter regions of other type III intermediate filament protein genes and other neuronal-specific genes.

Amino Acid Sequence↗
PubMed1985

Efficient detection of intermediate filament proteins using a panspecific monoclonal antibody: anti-IFA.

Anti-IFA, a panspecific monoclonal antibody which was raised against human glial fibrillary acidic protein (GFAP), recognizes a determinant common to GFAP and all other intermediate filament proteins. This antibody can be used to identify intermediate filament proteins from both vertebrate and invertebrate tissues. Its utility in immunoblot studies of intermediate filament proteins is enhanced by using cytoskeleton extracts and protease treatment to facilitate the transfer of high molecular weight (greater than 70 000) proteins from gels to nitrocellulose membranes.

Animals↗
PubMed1985

Assembly of glial intermediate filament protein is initiated in the centriolar region.

Assembly of glial intermediate filament protein (GFP) into intermediate filaments (IF) was first detected by immunofluorescence in the perinuclear region of astrocytes differentiating in colony cultures before the rest of the cytoplasm was labeled. Double labeling with antisera specific for centrioles indicated that this site corresponds to the centriolar region. These studies suggest that the centriolar region plays an important role in the assembly of some types of IF as well as microtubules.

Animals↗