scholarly journals Intermediate filaments exchange subunits along their length and elongate by end-to-end annealing

2009 ◽  
Vol 185 (5) ◽  
pp. 769-777 ◽  
Author(s):  
Gülsen Çolakoğlu ◽  
Anthony Brown
Keyword(s):  
Intermediate Filaments ◽  
Actin Filaments ◽  
Fusion Proteins ◽  
Cultured Cells ◽  
Intermediate Filament Proteins ◽  
Subunit Exchange ◽  
End To End ◽  
Vimentin Intermediate Filament ◽  
Vimentin Filaments

Actin filaments and microtubules lengthen and shorten by addition and loss of subunits at their ends, but it is not known whether this is also true for intermediate filaments. In fact, several studies suggest that in vivo, intermediate filaments may lengthen by end-to-end annealing and that addition and loss of subunits is not confined to the filament ends. To test these hypotheses, we investigated the assembly dynamics of neurofilament and vimentin intermediate filament proteins in cultured cells using cell fusion, photobleaching, and photoactivation strategies in combination with conventional and photoactivatable fluorescent fusion proteins. We show that neurofilaments and vimentin filaments lengthen by end-to-end annealing of assembled filaments. We also show that neurofilaments and vimentin filaments incorporate subunits along their length by intercalation into the filament wall with no preferential addition of subunits to the filament ends, a process which we term intercalary subunit exchange.

scholarly journals Assembly of type IV neuronal intermediate filaments in nonneuronal cells in the absence of preexisting cytoplasmic intermediate filaments

1993 ◽  
Vol 122 (6) ◽  
pp. 1323-1335 ◽  
Author(s):  
GY Ching ◽  
RK Liem
Keyword(s):  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Cultured Cells ◽  
Neuronal Cell ◽  
Intermediate Filament Protein ◽  
Amino Acid Residues ◽  
Intermediate Filament Proteins ◽  
Transfected Cells ◽  
Type Iv

We report here on the in vivo assembly of alpha-internexin, a type IV neuronal intermediate filament protein, in transfected cultured cells, comparing its assembly properties with those of the neurofilament triplet proteins (NF-L, NF-M, and NF-H). Like the neurofilament triplet proteins, alpha-internexin coassembles with vimentin into filaments. To study the assembly characteristics of these proteins in the absence of a preexisting filament network, transient transfection experiments were performed with a non-neuronal cell line lacking cytoplasmic intermediate filaments. The results showed that only alpha-internexin was able to self-assemble into extensive filamentous networks. In contrast, the neurofilament triplet proteins were incapable of homopolymeric assembly into filamentous arrays in vivo. NF-L coassembled with either NF-M or NF-H into filamentous structures in the transfected cells, but NF-M could not form filaments with NF-H. alpha-internexin could coassemble with each of the neurofilament triplet proteins in the transfected cells to form filaments. When all but 2 and 10 amino acid residues were removed from the tail domains of NF-L and NF-M, respectively, the resulting NF-L and NF-M deletion mutants retained the ability to coassemble with alpha-internexin into filamentous networks. These mutants were also capable of forming filaments with other wild-type neurofilament triplet protein subunits. These results suggest that the tail domains of NF-L and NF-M are dispensable for normal coassembly of each of these proteins with other type IV intermediate filament proteins to form filaments.

scholarly journals A Novel Interaction of the Golgi Complex with the Vimentin Intermediate Filament Cytoskeleton

2001 ◽  
Vol 152 (5) ◽  
pp. 877-894 ◽  
Author(s):  
Ya-sheng Gao ◽  
Elizabeth Sztul
Keyword(s):  
Golgi Complex ◽  
Intermediate Filament ◽  
Cultured Cells ◽  
Golgi Region ◽  
Golgi Compartment ◽  
Golgi Protein ◽  
Vimentin Intermediate Filament ◽  
Vimentin Filaments

The integration of the vimentin intermediate filament (IF) cytoskeleton and cellular organelles in vivo is an incompletely understood process, and the identities of proteins participating in such events are largely unknown. Here, we show that the Golgi complex interacts with the vimentin IF cytoskeleton, and that the Golgi protein formiminotransferase cyclodeaminase (FTCD) participates in this interaction. We show that the peripherally associated Golgi protein FTCD binds directly to vimentin subunits and to polymerized vimentin filaments in vivo and in vitro. Expression of FTCD in cultured cells results in the formation of extensive FTCD-containing fibers originating from the Golgi region, and is paralleled by a dramatic rearrangements of the vimentin IF cytoskeleton in a coordinate process in which vimentin filaments and FTCD integrate into chimeric fibers. Formation of the FTCD fibers is obligatorily coupled to vimentin assembly and does not occur in vim−/− cells. The FTCD-mediated regulation of vimentin IF is not a secondary effect of changes in the microtubule or the actin cytoskeletons, since those cytoskeletal systems appear unaffected by FTCD expression. The assembly of the FTCD/vimentin fibers causes a coordinate change in the structure of the Golgi complex and results in Golgi fragmentation into individual elements that are tethered to the FTCD/vimentin fibers. The observed interaction of Golgi elements with vimentin filaments and the ability of FTCD to specifically interacts with both Golgi membrane and vimentin filaments and promote their association suggest that FTCD might be a candidate protein integrating the Golgi compartment with the IF cytoskeleton.

scholarly journals Mechanism of interaction of Dictyostelium severin with actin filaments.

1982 ◽  
Vol 95 (3) ◽  
pp. 711-719 ◽  
Author(s):  
K Yamamoto ◽  
J D Pardee ◽  
J Reidler ◽  
L Stryer ◽  
J A Spudich
Keyword(s):  
Energy Transfer ◽  
Actin Filaments ◽  
Exchange Process ◽  
Molar Ratio ◽  
Fluorescence Energy Transfer ◽  
Dependent Manner ◽  
Emission Anisotropy ◽  
Subunit Exchange ◽  
Fluorescence Energy

Severin, a 40,000-dalton protein from Dictyostelium that disassembles actin filaments in a Ca2+ -dependent manner, was purified 500-fold to greater than 99% homogeneity by modifications of the procedure reported by Brown, Yamamoto, and Spudich (1982. J. Cell Biol. 93:205-210). Severin has a Stokes radius of 29 A and consists of a single polypeptide chain. It contains a single methionyl and five cysteinyl residues. We studied the action of severin on actin filaments by electron microscopy, viscometry, sedimentation, nanosecond emission anisotropy, and fluorescence energy transfer spectroscopy. Nanosecond emission anisotropy of fluoresence-labeled severin shows that this protein changes its conformation on binding Ca2+. Actin filaments are rapidly fragmented on addition of severin and Ca2+, but severin does not interact with actin filaments in the absence of Ca2+. Fluorescence energy transfer measurements indicate that fragmentation of actin filaments by severin leads to a partial depolymerization (t1/2 approximately equal to 30 s). Depolymerization is followed by exchange of a limited number of subunits in the filament fragments with the disassembled actin pool (t1/2 approximately equal to 5 min). Disassembly and exchange are probably restricted to the ends of the filament fragments since only a few subunits in each fragment participate in the disassembly or exchange process. Steady state hydrolysis of ATP by actin in the presence of Ca2+-severin is maximal at an actin: severin molar ratio of approximately 10:1, which further supports the inference that subunit exchange is limited to the ends of actin filaments. The observation of sequential depolymerization and subunit exchange following the fragmentation of actin by severin suggests that severin may regulate site-specific disassembly and turnover of actin filament arrays in vivo.

scholarly journals Type II Keratins Are Phosphorylated on a Unique Motif during Stress and Mitosis in Tissues and Cultured Cells

2002 ◽  
Vol 13 (6) ◽  
pp. 1857-1870 ◽  
Author(s):  
Diana M. Toivola ◽  
Qin Zhou ◽  
Luc S. English ◽  
M. Bishr Omary
Keyword(s):  
Cultured Cells ◽  
Uv Light ◽  
Ex Vivo ◽  
Psoriatic Skin ◽  
Type I ◽  
Type Ii ◽  
Intermediate Filament Proteins ◽  
Phosphatase Inhibitors

Epithelial cell keratins make up the type I (K9–K20) and type II (K1–K8) intermediate filament proteins. In glandular epithelia, K8 becomes phosphorylated on S73 (71LLpSPL) in human cultured cells and tissues during stress, apoptosis, and mitosis. Of all known proteins, the context of the K8 S73 motif (LLS/TPL) is unique to type II keratins and is conserved in epidermal K5/K6, esophageal K4, and type II hair keratins, except that serine is replaced by threonine. Because knowledge regarding epidermal and esophageal keratin regulation is limited, we tested whether K4–K6 are phosphorylated on the LLTPL motif. K5 and K6 become phosphorylated in vitro on threonine by the stress-activated kinase p38. Site-specific anti-phosphokeratin antibodies to LLpTPL were generated, which demonstrated negligible basal K4–K6 phosphorylation. In contrast, treatment of primary keratinocytes and other cultured cells, and ex vivo skin and esophagus cultures, with serine/threonine phosphatase inhibitors causes a dramatic increase in K4–K6 LLpTPL phosphorylation. This phosphorylation is accompanied by keratin solubilization, filament reorganization, and collapse. K5/K6 LLTPL phosphorylation occurs in vivo during mitosis and apoptosis induced by UV light or anisomycin, and in human psoriatic skin and squamous cell carcinoma. In conclusion, type II keratins of proliferating epithelia undergo phosphorylation at a unique and conserved motif as part of physiological mitotic and stress-related signals.

scholarly journals Distributions of vimentin and desmin in developing chick myotubes in vivo. II. Immunoelectron microscopic study.

1985 ◽  
Vol 100 (4) ◽  
pp. 1157-1166 ◽  
Author(s):  
K T Tokuyasu ◽  
P A Maher ◽  
S J Singer
Keyword(s):  
Intermediate Filaments ◽  
De Novo ◽  
Early Stage ◽  
Primary Role ◽  
Special Relationship ◽  
Frozen Sections ◽  
Intermediate Filament Proteins ◽  
Immunofluorescence Studies ◽  
Ultrathin Frozen Sections

The distribution of the intermediate filament proteins vimentin and desmin in developing and mature myotubes in vivo was studied by single and double immunoelectron microscopic labeling of ultrathin frozen sections of iliotibialis muscle in 7-21-d-old chick embryos, and neonatal and 1-d-old postnatal chicks. This work is an extension of our previous immunofluorescence studies of the same system (Tokuyasu, K. T., P. A. Maher and S. J. Singer, 1984, J. Cell Biol., 98:1961-1972). In immature myotubes of 7-11-d embryos, significant labeling for desmin and vimentin was found only in intermediate filaments, and these proteins coexisted in the same individual filaments. Each of the two proteins was present in irregular clusters along the entire length of a filament. No exclusively vimentin- or desmin-containing filaments were observed at this stage. In the early myotubes, the intermediate filaments were essentially all longitudinally oriented, even when they contained three times as much desmin as vimentin. No special relationship was recognized between the dispositions of the filaments and the organization of the myofibrils. Occasionally, several myofibrils were already aligned in lateral registry at this early stage, but labeling for desmin and vimentin was largely absent at the level of the Z bands. Instead, the Z bands appeared to be covered by elements of the sarcoplasmic reticulum. The confinement of intermediate filaments to the level of the Z bands occurred in the myotubes of later embryos after the extensive lateral registry of the Z bands. Thus, intermediate filaments are unlikely to play a primary role in producing the lateral registration of myofibrils during myogenesis, but may be important in determining the polarization of the early myotube and the alignment of its organelles. Throughout the development of myotubes, desmin and vimentin remained in the form of intermediate filaments, although the number of filaments per unit volume of myotube appeared to be reduced as myofibrils increased in number in maturing myotubes. This observation indicated that the transverse orientation of intermediate filaments in mature myotubes does not result from the de novo polymerization of subunits from Z band to Z band, but a continuous shifting of the positions and directions of intact filaments.

scholarly journals Neurofilaments are obligate heteropolymers in vivo

1993 ◽  
Vol 122 (6) ◽  
pp. 1337-1350 ◽  
Author(s):  
MK Lee ◽  
Z Xu ◽  
PC Wong ◽  
DW Cleveland
Keyword(s):  
Intermediate Filaments ◽  
Intermediate Filament ◽  
Cultured Cells ◽  
Dna Transfection ◽  
Tail Domain ◽  
In Vitro Assembly ◽  
Mature Neurons ◽  
Filament Network

Neurofilaments (NFs), composed of three distinct subunits NF-L, NF-M, and NF-H, are neuron-specific intermediate filaments present in most mature neurons. Using DNA transfection and mice expressing NF transgenes, we find that despite the ability of NF-L alone to assemble into short filaments in vitro NF-L cannot form filament arrays in vivo after expression either in cultured cells or in transgenic oligodendrocytes that otherwise do not contain a cytoplasmic intermediate filament (IF) array. Instead, NF-L aggregates into punctate or sheet like structures. Similar nonfilamentous structures are also formed when NF-M or NF-H is expressed alone. The competence of NF-L to assemble into filaments is fully restored by coexpression of NF-M or NF-H to a level approximately 10% of that of NF-L. Deletion of the head or tail domain of NF-M or substitution of the NF-H tail onto an NF-L subunit reveals that restoration of in vivo NF-L assembly competence requires an interaction provided by the NF-M or NF-H head domains. We conclude that, contrary to the expectation drawn from earlier in vitro assembly studies, NF-L is not sufficient to assemble an extended filament network in an in vivo context and that neurofilaments are obligate heteropolymers requiring NF-L and NF-M or NF-H.

scholarly journals Antibodies to neurofilament, glial filament, and fibroblast intermediate filament proteins bind to different cell types of the nervous system.

1981 ◽  
Vol 88 (1) ◽  
pp. 115-126 ◽  
Author(s):  
S H Yen ◽  
K L Fields
Keyword(s):  
Nervous System ◽  
Sciatic Nerve ◽  
Schwann Cells ◽  
Cell Cultures ◽  
Intermediate Filaments ◽  
Cultured Cells ◽  
Polyacrylamide Gel Electrophoresis ◽  
Cell Types ◽  
Intermediate Filament Proteins ◽  
Tissue Sections

Antisera were raised to the 210,000-dalton and the 49,000-dalton proteins of a fraction enriched in intermediate (10 nm) filaments from human brain. Proteins of the filament preparation were separated by SDS-polyacrylamide gel electrophoresis and used for immunization and subsequent analysis of the reactions of the sera by rocket immunoelectrophoresis. Anti-210,000-dalton serum precipitated proteins of molecular weights 210,000, 160,000, and 68,000, and, thus, reacted with all the neurofilament triplet components. Anti-49,000-dalton serum did not react with the triplet proteins but precipitated the 49,000-dalton protein. By immunofluorescence on tissue sections, anti-210,000-dalton serum bound to neuronal axons in sciatic nerve and cerebellum. In dissociated cell cultures, rat dorsal root ganglion cells and their processes bound the serum, whereas nonneuronal cells did not. Some cultured cerebellar neurons were also positive, whereas astrocytes were not. At the ultrastructural level, anti-210,000-dalton serum bound to intermediate filaments inside axonal processes. Anti-49,000-dalton serum bound to astrocytes in sections of the cerebellum, and cultured astrocytes had filaments that stained, whereas other cell types did not. In sciatic nerve sections, elements stained with this serum, but cultured cells from newborn sciatic nerve were negative. An antiserum against the 58,000-dalton protein of the cytoskeleton of NIL-8 fibroblasts strongly stained sciatic nerve sections, binding to Schwann cells but not to axons or to myelin. In cerebellar sections, astrocytes were positive, as were blood vessels and cells in the pia. In cell cultures, anti-58,000-dalton serum stained filaments inside Schwann cells, fibroblasts, and astrocytes, but neurons were negative. Cells in the cultures and tissue sections of the nervous system failed to react with antiserum to the 58,000-dalton protein of skin intermediate filaments. In these studies, astrocytes in vivo and in culture were the only cells which had antigens related to two classes of intermediate filaments.

Inositol 1,4,5-trisphosphate receptor-like protein in plasmalemmal caveolae is linked to actin filaments

1995 ◽  
Vol 108 (1) ◽  
pp. 7-15 ◽  
Author(s):  
T. Fujimoto ◽  
A. Miyawaki ◽  
K. Mikoshiba
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Cultured Cells ◽  
Contact Region ◽  
Epidermal Keratinocytes ◽  
Aortic Endothelial Cells ◽  
Cell Contacts ◽  
Inositol 1,4,5 Trisphosphate ◽  
Trisphosphate Receptor

We reported that a plasmalemmal inositol 1,4,5-trisphosphate receptor-like protein (PM InsP3R-L) is localized in caveolae of various non-neuronal cells in vivo (Fujimoto et al. (1992) J. Cell Biol. 119, 1507–1513). In the present study, we investigated the distribution of PM InsP3R-L in cultured cells. In mouse epidermal keratinocytes (Pam 212) cultured in standard Ca2+ (1.8 mM), PM InsP3R-L was distributed densely in the vicinity of cell-to-cell contacts. In contrast, when Pam cells were cultured in low Ca2+ (0.06 mM) without making cell-to-cell contacts, PM InsP3R-L was observed randomly; by restoring the Ca2+ concentration, the circumferential actin filaments became obvious and the density of PM InsP3R-L increased in the contact region. Treatment of Pam cells with cytochalasin D caused aggregation of caveolae where PM InsP3R-L as well as F-actin and fodrin were localized. In bovine aortic endothelial cells, PM InsP3R-L was aligned along actin filaments crossing the cytoplasm in various directions. PM InsP3R-L of Pam cells was hardly extracted by treatment with 0.5% Triton X-100 or 60 mM octyl-glucoside in a cytoskeleton-stabilizing buffer for 15 minutes at 4 degrees C. The results show that the distribution of caveolae bearing PM InsP3R-L changes when the actin cytoskeleton is modified. They also indicate that the association of PM InsP3R-L with actin filaments may mediate the redistribution of caveolae. Since caveolae are thought to be related to signal transduction, their location defined by the actin cytoskeleton may affect the site where cellular reaction is to occur in response to various stimuli.

Ultrastructural Correlations between Clonal Human Tumor Colonies and in Vivo Neoplasms

1982 ◽  
Vol 40 ◽  
pp. 210-211
Author(s):  
M.J. Murphy ◽  
R.R. Price ◽  
J.C. Sloman
Keyword(s):  
Cultured Cells ◽  
Human Tumor ◽  
Cell Type ◽  
Tumor Mass ◽  
Initial Cell ◽  
Cloning Assay ◽  
Human Tumor Cloning ◽  
The Relationship

The in vitro human tumor cloning assay originally described by Salmon and Hamburger has been applied recently to the investigation of differential anti-tumor drug sensitivities over a broad range of human neoplasms. A major problem in the acceptance of this technique has been the question of the relationship between the cultured cells and the original patient tumor, i.e., whether the colonies that develop derive from the neoplasm or from some other cell type within the initial cell population. A study of the ultrastructural morphology of the cultured cells vs. patient tumor has therefore been undertaken to resolve this question. Direct correlation was assured by division of a common tumor mass at surgical resection, one biopsy being fixed for TEM studies, the second being rapidly transported to the laboratory for culture.

The Infection of Cells by Bullet-Shaped Viruses

1969 ◽  
Vol 27 ◽  
pp. 372-373
Author(s):  
Frederick A. Murphy ◽  
Alyne K. Harrison ◽  
Sylvia G. Whitfield
Keyword(s):  
Electron Microscopy ◽  
Physical Properties ◽  
Host Cell ◽  
Thin Section ◽  
Cultured Cells ◽  
Cell Infection ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.

Sign in / Sign up

Export Citation Format

Share Document