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PubMed1993

Microtubules, centrosomes and intermediate filaments in directed cell movement.

Cell movement involves the coordinated interaction of probably hundreds of components. The contractile apparatus based on actin, myosin and their associated proteins is involved in cell protrusion and force generation. Microtubules and intermediate filaments affect the distribution of membranous organelles and are also believed to determine cell shape and cell polarity. This review examines the way in which the distinct polarity of moving cells is influenced by microtubules, the microtubule-organizing centre and intermediate filaments. The observations summarized here suggest a broad spectrum of cell-type-specific differences in how these cytoskeletal components contribute to directional cell movement.

Journal Article↗
PubMed2001

Fully functional, naturally occurring and C-terminally truncated variant human immunodeficiency virus (HIV) Vif does not bind to HIV Gag but influences intermediate filament structure.

A variant human immunodeficiency virus type 1 (HIV-1) vif gene, vifA45-2, which encodes a protein lacking 19 amino acids at the C terminus but which is fully functional in supporting HIV replication in non-permissive cells has been described previously. By employing newly generated anti-VifA45 serum, further properties of VifA45 and its full-length counterpart, VifA45open, in comparison to Vif from HIV strain BH10 are reported in permissive HeLa and COS-7 cells. The results obtained using confocal microscopic localization studies and in vitro binding assays do not support a requirement for the direct interaction of HIV Gag with Vif. Furthermore and in contrast to previous conclusions, detergent solubility analyses do not demonstrate a role for the C terminus of Vif in mediating localization to the fraction containing cellular membrane proteins. Localization of Vif from HIV strain BH10 to perinuclear aggregates in a small fraction (about 10%) of transfected HeLa cells has been previously reported. The intermediate filament protein vimentin colocalizes to these structures. In contrast, VifA45 and VifA45open form perinuclear aggregates in nearly all transfected HeLa cells; vimentin as well as the cytoskeletal-bridging protein plectin, but not the microtubular protein tubulin, become relocalized to these structures. Interestingly, in COS-7 cells, all of the functional Vif proteins tested (Vif from strain BH10, VifA45 and VifA45open) predominantly localize in the cytoplasm but still induce dramatic aggregation of vimentin and plectin, i.e. in these cells the respective Vif proteins are influencing intermediate filament structure in the absence of colocalization.

Animals↗
PubMed1991

Morphological differentiation of hybrids of human mammary epithelial cell lines is dominant and correlates with the pattern of expression of intermediate filaments.

Hybrids have been developed from two cell lines originally derived from human mammary epithelial cells. MTSV1-7 (hygro), developed from cultured milk epithelial cells, shows a cuboidal morphology, expresses high levels of keratins (but no vimentin), and forms ball-like three-dimensional structures in collagen gels. 5.3.1E (neo), derived from a cell cultured from tissue taken from a primary breast cancer, shows an elongated morphology, expresses high levels of vimentin and low levels of keratins, and does not form structures on collagen gels. An examination of the hybrids formed by fusion of MTSV1-7 cells and 5.3.1E cells showed that while all could form three-dimensional structures in collagen gels, the type of structures formed resembled either ductal or alveolar-ball-like structures depending on the individual hybrid. Nine hybrids were examined and a clear correlation was observed between cell shape as seen on plastic, intermediate filament expression, and the form of the structures as seen in collagen gels. All the hybrids resembling the parent MTSV1-7 cells by showing a cuboidal morphology and high level of keratin expression formed ball-like structures; on the other hand, hybrids resembling 5.3.1E by showing an elongated morphology and a high level of vimentin expression formed duct-like structures in collagen gels. The results show that the ability to form structures in collagen gels was inherited in a dominant fashion from the MTSV1-7 parent. They also suggest that the profile of intermediate filament expression in the hybrids may influence both cell shape on plastic and the morphology of the three-dimensional structures formed in collagen gels.

Blotting, Southern↗
PubMed2004

The genome of the early chordate Ciona intestinalis encodes only five cytoplasmic intermediate filament proteins including a single type I and type II keratin and a unique IF-annexin fusion protein.

We screened the recently established draft genome of the early chordate Ciona intestinalis for genes encoding cytoplasmic intermediate filament (IF) proteins. The draft of the tunicate/urochordate genome contains only the five genes (IF-A, IF-B, IF-C, IF-D and IF-F) previously established by cDNA cloning. Three of these IF proteins (IF-D, IF-C, IF-A) were shown to be orthologs of vertebrate IF subfamilies I to III while two proteins (IF-B, IF-F) seemed tunicate specific. This is now firmly established for protein IF-F since the genomic data show that it arises as a fusion protein with a C-terminal annexin domain, a feature not found before in the very large collection of metazoan IF proteins. The results also confirm the previous proposal that urochordates lack orthologs of vertebrate type IV IF proteins. We discuss the striking increase of IF complexity from 5 tunicate to 65 human genes during chordate evolution. Thus the tunicate has a single keratin pair, which is expressed in the epidermis, while the human genome has at least 25 genes each for keratins I and keratins II. Finally there are four normal Ciona annexin genes in addition to the gene encoding the IF-annexin fusion proteins (IF-F).

Amino Acid Sequence↗
PubMed2003

Tropomodulin binds to filensin intermediate filaments.

Tropomodulin (Tmod) is an actin filament pointed end capping protein found in the membrane skeleton of lens fiber cells. We demonstrate that Tmod4 is able to bind the lens-specific intermediate filament protein, filensin, in either co-sedimentation or solid phase binding assays in a saturable fashion, but with low affinity and stoichiometry. Furthermore, Tmod4 does not bind the 53 kDa rod domain of filensin, nor to CP49, the obligate assembly partner of filensin. Finally, the binding of filensin to Tmod4 does not inhibit the actin capping activity of Tmod4 in vitro, suggesting that the two functions are not mutually exclusive.

Actin Cytoskeleton↗
PubMed1995

Intermediate filament typing of the human embryonic and fetal notochord.

In order to characterize human notochordal tissue we investigated notochords from 32 human embryos and fetuses ranging between the 5th and 13th gestational week, using immunohistochemistry to detect intermediate filament proteins cytokeratin, vimentin and desmin, the cytokeratin subtypes 7, 8, 18, 19 and 20, epithelial membrane antigen (EMA), and adhesion molecules pan-cadherin and E-cadherin. Strong immunoreactions could be demonstrated for pan-cytokeratin, but not for desmin or EMA. Staining for pan-cadherin and weak staining for E-cadherin was found on cell membranes of notochordal cells. Also it was demonstrated that notochordal cells of all developmental stages contain the cytokeratins 8, 18 and 19, but not 7 or 20. Some cells in the embryonic notochord also contained some vimentin. Vimentin reactivity increased between the 8th and 13th gestational week parallel to morphological changes leading from an epithelial phenotype to the chorda reticulum which represents a mesenchymal tissue within the intervertebral disc anlagen. This coexpression reflects the epithelial-mesenchymal transformation of the notochord, which also loses E-cadherin expression during later stages. Our findings cannot elucidate a histogenetic germ layer origin of the human notochord but demonstrate its epithelial character. Thus, morphogenetic inductive processes between the human notochord and its surrounding vertebral column anlagen can be classified as epithelial-mesenchymal interactions.

Antibodies, Monoclonal↗
PubMed1990

Intermediate filaments in DMBA-induced mammary adenocarcinomas in rats.

Experimental DMBA (7,12-dimethylbenzanthracene)-induced mammary tumours in rats were studied. Microscopic examination revealed a high rate of adenocarcinomas (95.3% in 148 mammary tumours studied). An immunohistochemical study of cytoskeleton intermediate filaments (I.F.) showed cytokeratins in neoplastic epithelial cells; myoepithelial cells expressed cytokeratins, vimentin and desmin. Finally we propose the immunocytochemical localization of desmin as a useful method to recognize myoepithelial proliferation areas in mammary tumours.

Adenocarcinoma↗
PubMed1998

Cell adhesion molecules and intermediate filaments on embryonal childhood tumors.

We describe the expression of 18 different cell adhesion molecules, intermediate filaments and Ki-67 antigen in embryonal childhood tumors. 5 microns frozen sections from 15 nephroblastomas, 13 neuroblastomas, six rhabdomyosarcomas, one Ewing sarcoma and one pulmonary blastoma were analyzed by the alkaline phosphatase anti-alkaline phosphatase (APAAP) method using murine monoclonal antibodies. All tumors exhibited high proliferation rates as did, surprisingly, the nephroblastoma specimens despite pre-treatment with chemotherapy. Polysialylated NCAM was demonstrated on all tumor types, but Ewing sarcoma and expression correlated inversely with cell differentiation. In contrast, E-cadherin was present solely on tubulus like cells in nephroblastomas. This cell type showed a coexpression of cytokeratin and vimentin, giving evidence of its intermediate position between the mesenchyme and epithelium. In neuroblastomas, CD44s (hyaluronate receptor) expression was increased with cell differentiation. ICAM-1, VCAM-1 and E-selectin were mostly expressed in regressive areas of pretreated nephroblastoma specimens where a considerable infiltration of leukocytes was noted as well. Since endothelial and leukocyte adhesion molecules were distinctly less expressed in all other tumors investigated, these findings may indicate immunological processes as a consequence of or as supplement to the chemotherapeutical effect on nephroblastoma cells. Integrin receptors were not found on the surface of tumor cells, and therefore, at least those investigated seem to be of secondary importance to the biology of the tumors studied herein. In conclusion, our investigations demonstrate that, besides achieving a secure and prompt differentiation between various embryonal tumors, applying the panel of monoclonal antibodies proposed herein gives interesting insights into the histogenesis, biology and metastatic potential of pediatric malignancies.

Antibodies, Monoclonal↗
PubMedDate not supplied

[The effect of low doses of ionizing radiation on the intermediate filaments and the Ca2+-activated proteolysis system in the rat brain].

The immunochemical methods were used to study the effect of low-level radiation (0.00645 C/kg and 0.0129 C/kg) on the content and polypeptide composition of glial intermediate filament proteins (GIFP) in different rat brain areas. Changes in glial fibrillar acidic protein (GFAP) concentration were more significant with the dose of 0.0129 C/kg than 0.00645 C/kg. It is suggested that soluble GIFP is more susceptible to the effect of Ca(2+)-dependent proteinases, calpains, than the filament one is, and degrades as early as the first few hours following irradiation. However, low radiation doses were ineffective with respect to calpains activity in the animal brain. The increased Ca2+ concentration enhances considerably GFAP degradation under the effect of calpains I and II. It is suggested that with low radiation doses the rearrangements of glial intermediate filaments may occur due to activation of calpains by releasing Ca ions.

Animals↗
PubMed1993

Familial desminopathy: myopathy with accumulation of desmin-type intermediate filaments.

Two siblings developed cardiomyopathy several years before slowly progressive muscle weakness. Skeletal muscle biopsy specimens showed subsarcolemmal crescents of dark eosinophilic material in both type I and type II fibres. Immunohistochemically the subsarcolemmal material stained positively for the intermediate filament protein desmin and for the heat shock protein ubiquitin but for no other cytoskeletal proteins. Ultrastructurally the subsarcolemmal deposits consisted of aggregates of granular and filamentous material arising from Z-bands. Follow up muscle biopsies six years later showed an increased number of the muscle fibres that contained subsarcolemmal aggregates that stained positively for desmin and ubiquitin. These clinical and pathological features characterise a rare familial myopathy associated with an unusual distribution of desmin intermediate filament proteins in skeletal and probably also cardiac muscle.

Child, Preschool↗
PubMed1989

Immunocytochemical localization of the intermediate filament protein peripherin in adult mouse adrenal chromaffin cells in culture.

Peripherin is the main intermediate filament protein in sympathetic neurons. Immunoreactivity to peripherin was studied in mouse adrenal chromaffin cells after 6 days in culture, and compared to immunoreactivity to tyrosine hydroxylase used as a general marker of chromaffin cells in culture. Most of the cells immunoreactive to tyrosine hydroxylase were rounded, with a glandular phenotype and a few of them had processes. The cells reactive to peripherin only constituted a small proportion of the chromaffin cells (2%), and most of them sent out processes. However, not all the cells with processes were reactive for peripherin. These results did not change in the presence of nerve growth factor. The discussion focuses on the significance of the sub-population of cells reactive to peripherin. We suggest that these cells resemble the small granule chromaffin cells, regarded as an intermediate cell type between glandular cells and neurons. The cells that expressed peripherin here are compared to those selected to form the PC12 clone. The presence of peripherin in only a few of the cells sending out neurite-like processes is discussed in relation to the expression of other neurofilament proteins in developing cells and to the influence of non-chromaffin cells.

Adrenal Medulla↗
PubMed1991

Effect of pepstatin A on structure and polymerization of intermediate filament subunit proteins in vitro.

Pepstatin A, a pentapeptide aspartyl protease inhibitor, can interact with intermediate filament (IF) subunit proteins and induce their polymerization in the absence of salt into long filaments with a rough surface and a diameter of 15-17 nm. This polymerization appears to be driven primarily by non-ionic interactions between pepstatin A and polymerization-competent forms of IF proteins, resulting in a composite filament. Proteolytic fragments of vimentin, lacking portions of only the head domain or of both the head and tail domains, failed to copolymerize with pepstatin A into long filaments under these conditions. Rather, these peptides, as well as control proteins like bovine serum albumin, were found to decorate pepstatin A polymers (filaments, ribbons, and sheets) by sticking to their surfaces. In addition to the electron microscopy experiments, UV difference spectra, ultracentrifugation, and SDS-PAGE analysis of in vitro cleavage products of vimentin obtained with HIV-1 protease all provided independent evidence for a direct association of pepstatin A with IF subunit proteins, with subsequent alterations in the IF subunit protein conformation. These data show that non-ionic interactions can substitute for the effect of salt and effectively drive the higher-order polymerization of IF subunit proteins.

Amino Acid Sequence↗
PubMed1993

Changes in the ovarian intermediate filament desmin during the luteal phase of the adult pseudopregnant rat.

The occurrence of the intermediate filament desmin in ovary and corpus luteum of pseudopregnant rats was studied using Western blot analysis and immunohistochemistry. The luteal phase was induced by mating with vasectomized male rats and ovaries were studied after 6, 11 and 19 days. The findings from the Western blot analysis showed that desmin was present in the corpus luteum. Immunohistochemical localization of desmin showed two types of localization in the corpus luteum. The arteries around the corpus luteum, as well as arteries elsewhere in the ovary, had a high content of desmin in their muscle layer. Dispersed in the corpus luteum was an immunohistochemical staining of desmin that was localized mainly adjacent to the luteal cells. In the other part of the ovary a weak staining was registered in the theca layer, no staining in the granulosa layer and a streaky staining in the hilar region of the ovary. Desmin filaments are found in muscle cells of all types, including vascular smooth muscle cells. Probably, all desmin in the ovary is localized to smooth muscle cells with the possible exception of the corpus luteum where very few muscle cells have been identified. Localization to other vascular cells as endothelial is possible. In this study we found an increase in desmin content in the corpus luteum after day 6. If desmin is related to vascular resistance, our finding is consistent with the decrease in blood flow that occurs after day 6.

Animals↗
PubMed2003

Embryonic intermediate filaments, nestin and vimentin, expression in the spinal cords of rats with experimental autoimmune encephalomyelitis.

Intermediate filaments, including nestin and vimentin, are found in specific cell types in central nervous system (CNS) tissues, particularly immature glial cells and multipotent progenitor cells. In the present study, the expression patterns of nestin and vimentin in the spinal cords of rats with experimental autoimmune encephalomyelitis (EAE) and the response of cells containing filaments against acute autoimmune injury were examined by immunohistochemistry. Nestin immunostaining was only weakly detected in vascular endothelial cells but not in any cell types in the spinal cord in normal and adjuvant-immunized rats. At the peak stage of EAE, nestin-immunoreativity was recognized in some astrocytes in the gray matter and white matter. Vimentin was immunopositive in some astrocytes and macrophages in EAE lesions, while vimentin was normally detected in ependymal cells of central canals in the rat spinal cords.We postulate that normal animals may contain multipotent progenitor cells in the spinal cord parenchyma as well as in the subpial lesion and ependyma. Multipotent progenitor cells may activate to transform into necessary cells, including neurons, astrocytes or oligodendrocytes, depending on CNS needs. Appropriate control of progenitor cells in the injured CNS is an alternative choice for CNS remodeling.

Animals↗
PubMedDate not supplied

Neuronal intermediate filaments in the developing tongue of the frog Rana esculenta.

The expression of several neuronal intermediate filament (NIF) proteins was investigated in the tongue of metamorphosing tadpoles (stage 38-45 of Gosner) and in adult individuals of the frog, Rana esculenta by means of immunohistochemistry. Results showed that nerve fibres at early stages of tongue development expressed peripherin (a NIF protein usually found in differentiating neurones) as well as the light- and medium molecular weight NIF polypeptide subunits (NF-L and NF-M, respectively); in the adult frog, peripherin was still found in nerve fibres reaching the fungiform papilla together with NF-M, but NF-L immunoreactivity was absent therein. Clusters of epithelial cells expressing peripherin were found in the early developing tongue before differentiation of taste organs, and NF-L and NF-H immunoreactivities were present in basal (Merkel) cells of the adult frog taste disc. Results indicate that neurones innervating the adult frog's taste disc maintain a certain plasticity in their cytoskeleton and that neuronal-like cells are present in the undifferentiated and differentiated tongue epithelium possibly playing a role in the developing and mature taste organ.

Animals↗
PubMed1988

Changes in the organization and antigenic determinants of intermediate filaments of rat hepatocytes after infusion of cytochalasin B in vivo.

The changes in cytokeratin intermedial filaments (IFs) after cytochalasin B (CB) infusion of rat liver in vivo were studied by light and electron microscopy, immunofluorescent staining (IMF), and immunoelectron microscopy (IEM). The CB treatment caused a change in the IFs at the cell border associated with a change in the distribution of microfilaments. The IFs at the cell border were partially disrupted. Actin aggregates were localized at points where IFs had condensed together. The pericanalicular sheath was intact but very dilated. These results indicated that the CB treatment caused an irregular distribution of the microfilaments at the cell periphery but spared the actin at the bile canaliculus. Cytokeratin staining by IMF was markedly decreased or absent; however, IEM clearly showed the presence of nonstaining IFs after CB treatment. These results indicated that the antigenic determinant of normal cytokeratin IFs became masked after CB treatment. The results indicate that F-actin disassembly induced by CB affects both the organization and conformation of cytokeratins associated with loss of integrity of the plasma membrane and vesicular uptake of plasma proteins by hepatocytes.

Actin Cytoskeleton↗
PubMed1989

Phosphorylation and disassembly of intermediate filaments in mitotic cells.

As baby hamster kidney (BHK-21) cells enter mitosis, networks of intermediate filaments (IFs) are transformed into cytoplasmic aggregates of protofilaments. Coincident with this morphological change, the phosphate content of vimentin increases from 0.3 mol of Pi per mol of protein in interphase to 1.9 mol of Pi per mol of protein in mitosis. A similar increase in phosphate content is observed with desmin, from 0.5 mol of Pi per mol of protein to 1.5 mol of Pi per mol of protein. Fractionation of mitotic cell lysates by hydroxylapatite column chromatography reveals the presence of two IF protein kinase activities, designated as IF protein kinase I and IF protein kinase II. Comparison of two-dimensional 32P-labeled phosphopeptide maps of vimentin and desmin phosphorylated in vivo in mitosis, and in vitro using partially purified kinase fractions, reveals extensive similarity in the two sets of phosphorylation sites. Phosphorylation of in vitro polymerized IFs by IF protein kinase II induces complete disassembly as determined by negative-stain electron microscopy. The results support the idea that the disassembly of IFs in mitosis is regulated by the phosphorylation of its subunit proteins.

Animals↗
PubMed2002

Expression of intermediate filaments in conjunctival melanocytic lesions.

BACKGROUND: To our knowledge there have been no studies on intermediate filament (IF) expression in conjunctival melanocytic tumors to date. Melanocytic lesions occurring at various body sites are known to express, in addition to the predominant IF protein vimentin, the epithelial-specific cytokeratins (CKs) and the neuronal IF peripherin. The present study was therefore carried out to assess the expression of IF proteins in conjunctival melanocytic lesions. METHODS: Paraffin-embedded material from 34 tumors - 16 conjunctival nevi, nine specimens of primary acquired melanosis (PAM; eight with and one without atypia), and nine conjunctival melanomas - was assessed after the application of a panel of antibodies directed against diverse IF proteins, including vimentin, CKs and peripherin. RESULTS: The most significant finding of this study was that all the tumors investigated expressed vimentin exclusively. While simple-epithelium CKs were found in epithelial cysts of nevi and in pseudoglandular portions adjacent to the melanoma, they were not identified in the tumor cells themselves. Similarly, peripherin and neurofilaments were not detected within any of the tumor cells. CONCLUSION: The IF expression pattern of conjunctival melanocytic lesions differs from that seen in melanocytic tumors of other body sites (including uveal melanomas), in that it includes neither CKs nor peripherin.

Conjunctiva↗