Redistribution of microfilament-associated proteins during the formation of focal contacts and adhesions in chick fibroblasts

1983 ◽  
Vol 4 (6) ◽  
pp. 647-661 ◽  
Author(s):  
J. R. Couchman ◽  
R. A. Badley ◽  
D. A. Rees
Keyword(s):  
Focal Contacts ◽  
Associated Proteins

scholarly journals Actin-independent association of vinculin with the cytoplasmic aspect of the plasma membrane in cell-contact areas.

1983 ◽  
Vol 96 (6) ◽  
pp. 1622-1630 ◽  
Author(s):  
Z Avnur ◽  
J V Small ◽  
B Geiger
Keyword(s):  
Actin Filaments ◽  
Molecular Mechanisms ◽  
Cell Contact ◽  
Membrane Association ◽  
Focal Contact ◽  
Permeabilized Cells ◽  
Focal Contacts ◽  
Microfilament Bundles ◽  
Associated Proteins ◽  
Independent Association

We investigated the mode of association of vinculin with areas of contact between the termini of microfilament bundles and the cell membrane in sites of focal contact with the substrate by selective removal of actin from these areas. Opened-up substrate-attached membranes of chick fibroblasts as well as detergent-permeabilized cells were treated with fragmin from Physarum in the presence of Ca+2. This treatment removed actin filaments from the cytoplasmic faces of the membranes, along with several actin-associated proteins (alpha-actinin, tropomyosin, myosin, and filamin). Vinculin distribution was not affected by treatment. Moreover, rhodamine- or fluorescein-conjugated vinculin, when added to these preparations, became specifically associated with the focal contacts regardless of whether the latter were pretreated with fragmin or not. We conclude that the association of vinculin with focal contacts is largely actin-independent. We discuss the implications of these findings in the molecular mechanisms of microfilament membrane association in areas of cell contact.

scholarly journals Microfilament-organizing centers in areas of cell contact: cytoskeletal interactions during cell attachment and locomotion.

1984 ◽  
Vol 99 (1) ◽  
pp. 83s-91s ◽  
Author(s):  
B Geiger ◽  
Z Avnur ◽  
G Rinnerthaler ◽  
H Hinssen ◽  
V J Small
Keyword(s):  
Dynamic Equilibrium ◽  
Cell Attachment ◽  
Dynamic Properties ◽  
Leading Edge ◽  
Stress Fibers ◽  
Cell Contact ◽  
Molecular Architecture ◽  
Contact Areas ◽  
Focal Contacts ◽  
Associated Proteins

In this article we discuss three aspects of cell contact formation: (a) the molecular architecture of the cytomatrix in cell-to-substrate focal contacts, (b) the dynamic properties of membrane- and microfilament-associated proteins in the contact areas, and (c) the involvement of microtubules in the coordinated and directed formation of new substrate contacts during cell locomotion. We show that different microfilament-associated proteins exhibit distinct patterns of association with focal contacts: some proteins are specifically associated with focal contacts (vinculin and talin); alpha-actinin is enriched in the contact areas but also is present along the stress fibers and in the lamellipodium; actin and filamin are detected throughout the contact areas but in apparently reduced amounts compared with the associated stress fibers; and tropomyosin, myosin, and spectrin are either absent from the endofacial surfaces of contact areas or are present in only very small amounts. Fluorescence photobleaching recovery analyses performed with living cells microinjected with fluorescently labeled actin, vinculin, and alpha-actinin indicate that each of these proteins maintains a dynamic equilibrium between a soluble cytoplasmic pool and a membrane-bound fraction. Correlation of the distribution of vinculin and tubulin in motile fibroblasts to local movements of the leading edge of the same cells indicates that free-end microtubules extend into actively ruffling areas along the lamellipodium and that new vinculin-containing contacts are preferentially formed in these protruding regions.

Photoreceptor disk membrane substructures by means of the complementary freeze-fracture-replica methods

1978 ◽  
Vol 36 (2) ◽  
pp. 156-157
Author(s):  
A. Tonosaki ◽  
M. Yamasaki ◽  
H. Washioka ◽  
J. Mizoguchi
Keyword(s):  
Cell Membranes ◽  
Freeze Fracture ◽  
Purple Membrane ◽  
Remarkable Case ◽  
Single Face ◽  
Disk Membrane ◽  
Associated Proteins ◽  
Photoreceptor Membranes

A vertebrate disk membrane is composed of 40 % lipids and 60 % proteins. Its fracture faces have been classed into the plasmic (PF) and exoplasmic faces (EF), complementary with each other, like those of most other types of cell membranes. The hypothesis assuming the PF particles as representing membrane-associated proteins has been challenged by serious questions if they in fact emerge from the crystalline formation or decoration effects during freezing and shadowing processes. This problem seems to be yet unanswered, despite the remarkable case of the purple membrane of Halobacterium, partly because most observations have been made on the replicas from a single face of specimen, and partly because, in the case of photoreceptor membranes, the conformation of a rhodopsin and its relatives remains yet uncertain. The former defect seems to be partially fulfilled with complementary replica methods.

Fibronexus-Like Adhesion Sites are Present at the Invasive Zones of Human Epidermoid Carcinomas

1982 ◽  
Vol 40 ◽  
pp. 106-109
Author(s):  
Irwin I. Singer
Keyword(s):  
Cell Cycle ◽  
Serum Concentration ◽  
Substrate Binding ◽  
High Serum ◽  
Adhesion Sites ◽  
Substrate Adhesion ◽  
Focal Contacts ◽  
Adhesion Complex ◽  
Low Serum

Our previous results indicate that two types of fibronectin-cytoskeletal associations may be formed at the fibroblast surface: dorsal matrixbinding fibronexuses generated in high serum (5% FBS) cultures, and ventral substrate-adhering units formed in low serum (0.3% FBS) cultures. The substrate-adhering fibronexus consists of at least vinculin (VN) and actin in its cytoplasmic leg, and fibronectin (FN) as one of its major extracellular components. This substrate-adhesion complex is localized in focal contacts, the sites of closest substratum approach visualized with interference reflection microscopy, which appear to be the major points of cell-tosubstrate adhesion. In fibroblasts, the latter substrate-binding complex is characteristic of cultures that are arrested at the G1 phase of the cell cycle due to the low serum concentration in their medium. These arrested fibroblasts are very well spread, flattened, and immobile.

Characterization of microtubules by dark-field STEM and replication

1991 ◽  
Vol 49 ◽  
pp. 152-153
Author(s):  
S.B. Andrews ◽  
R.D. Leapman ◽  
P.E. Gallant ◽  
T.S. Reese
Keyword(s):  
Protein Interactions ◽  
Low Dose ◽  
Unit Length ◽  
Dark Field ◽  
Carbon Films ◽  
Microtubule Associated Proteins ◽  
Molecular Weights ◽  
Freeze Dried ◽  
Protein Motors ◽  
Associated Proteins

As part of a study on protein interactions involved in microtubule (MT)-based transport, we used the VG HB501 field-emission STEM to obtain low-dose dark-field mass maps of isolated, taxol-stabilized MTs and correlated these micrographs with detailed stereo images from replicas of the same MTs. This approach promises to be useful for determining how protein motors interact with MTs. MTs prepared from bovine and squid brain tubulin were purified and free from microtubule-associated proteins (MAPs). These MTs (0.1-1 mg/ml tubulin) were adsorbed to 3-nm evaporated carbon films supported over Formvar nets on 600-m copper grids. Following adsorption, the grids were washed twice in buffer and then in either distilled water or in isotonic or hypotonic ammonium acetate, blotted, and plunge-frozen in ethane/propane cryogen (ca. -185 C). After cryotransfer into the STEM, specimens were freeze-dried and recooled to ca.-160 C for low-dose (<3000 e/nm2) dark-field mapping. The molecular weights per unit length of MT were determined relative to tobacco mosaic virus standards from elastic scattering intensities. Parallel grids were freeze-dried and rotary shadowed with Pt/C at 14°.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules

1988 ◽  
Vol 46 ◽  
pp. 122-123
Author(s):  
R.A Walker ◽  
S. Inoue ◽  
E.D. Salmon
Keyword(s):  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Gtp Hydrolysis ◽  
Abrupt Transition ◽  
Microtubule Associated Proteins ◽  
Asymmetrical Structure ◽  
Associated Proteins

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).

Alzheimer's Paired Helical Filaments Contain Insoluble Cytoskeletal Elements

1985 ◽  
Vol 43 ◽  
pp. 748-751
Author(s):  
P. Gambetti ◽  
G. Perry ◽  
L. Autillo-Gambetti
Keyword(s):  
Paired Helical Filaments ◽  
Microscope Level ◽  
Antigenic Determinants ◽  
Light Microscope Level ◽  
Neuronal Cytoskeleton ◽  
Ionic Detergent ◽  
Associated Proteins ◽  
Pathologic Lesions ◽  
10 Nm Filaments ◽  
Cytoskeletal Elements

Neurofibrillary tangles (NFT) are one of the major pathologic lesions of Alzheimer's disease. These neuronal inclusions are predominantly composed of paired helical filaments (PHF), which consist of two 10 nm filaments winding around each other with an approximately 80 nm periodicity. Besides PHF, NFT comprise also 15 nm filaments, 10 nm filaments which are probably neurofilaments, microtubules and granular material. At variance with the neuronal cytoskeleton, PHF are insoluble in ionic detergent.Studies at the light microscope level have shown that NFT have unique antigenic determinants as well as determinants in common with elements of the normal neuronal cytoskeleton such as neurofilaments and microtubule-associated proteins. The present study uses immunocytochemistry and cytochemistry at the electron microscope level to assess which NFT component contains these determinants and whether these antigenic determinants are soluble in an ionic detergent.

Molecular architecture and functions of the neuronal cytoskeleton

1990 ◽  
Vol 48 (3) ◽  
pp. 2-3
Author(s):  
Nobutaka Hirokawa
Keyword(s):  
Major Elements ◽  
Molecular Structures ◽  
Organelle Transport ◽  
Molecular Architecture ◽  
Neuronal Morphogenesis ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
And Function ◽  
Small Clusters

In this symposium I will present our studies about the molecular architecture and function of the cytomatrix of the nerve cells. The nerve cell is a highly polarized cell composed of highly branched dendrites, cell body, and a single long axon along the direction of the impulse propagation. Each part of the neuron takes characteristic shapes for which the cytoskeleton provides the framework. The neuronal cytoskeletons play important roles on neuronal morphogenesis, organelle transport and the synaptic transmission. In the axon neurofilaments (NF) form dense arrays, while microtubules (MT) are arranged as small clusters among the NFs. On the other hand, MTs are distributed uniformly, whereas NFs tend to run solitarily or form small fascicles in the dendrites Quick freeze deep etch electron microscopy revealed various kinds of strands among MTs, NFs and membranous organelles (MO). These structures form major elements of the cytomatrix in the neuron. To investigate molecular nature and function of these filaments first we studied molecular structures of microtubule associated proteins (MAP1A, MAP1B, MAP2, MAP2C and tau), and microtubules reconstituted from MAPs and tubulin in vitro. These MAPs were all fibrous molecules with different length and formed arm like projections from the microtubule surface.

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

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