Actin distribution

Howard, T. H. and Oresajo, C. O. (1985) The kinetics of chemotactic peptide-induced changes in F-actin content, F-actin distribution, and the shape of neutrophil. J. Cell Biol. 101,1078-1085. 

Intracellular RNA expression inhibits binding of cells to ICAM-I and induces reorganization of actin distribution in vitro. 

On the side adjacent to the endothelium the cytoplasm contains a dense meshwork of fine filaments, whereas on the outer surface numerous pi-nocytotic vesicles are observed (Weibel 1974). Pulmonary pericytes influenced the actin distribution of pulmonary microvascular endothelial cells (Shepro and Morel 1993). Pericytes enhanced the formation of a distinct dense peripheral band at microvascular endothelial cell periphery and promoted close apposition of adjacent endothelial cells. Transforming growth factor-P appears to mediate this pericyte-endothehal interaction. The role played by TGF-P is supported by the finding that this agonist modulates extracellular matrix organisation and the formation of tubelike structures with apparent tight junctions in three-dimensional cultures of rat epididymal fat pad microvascular en-dothehal cells (Merwin et al. 1990). 

Duther, P. W., Peng. H. B., and Din, J., Changes in cell shape and actin distribution induced by constant electric field.s. Nature, 303, 61-64 (1983). 

Endocytic ability Disruption of actin distribution patterns ... 

De Biasio, R.L., Wang, L.-L., Fisher, G.W., Taylor, D.L. (1988). The dynamic distribution of fluorescent analogs of actin and myosin in protrusions at the leading edge of migrating Swiss 3T3 fibroblasts. J. Cell Biol. 107,2631-2645. 

Redmond, T., Zigmond, S.H. (1993). Distribution of F-actin elongation sites in lysed polymorphonuclear leukocytes parallels the distribution of endogenous F-actin. Cell Mot. Cytoskel. 26, 7-28. 

First, in the striated muscles, the cross-sectional organization of filaments is highly ordered in a hexagonal pattern commensurate with the ratio of actin to myosin filaments and the distribution of active myosin heads, S-1 segments, helically every 60 degrees around the myosin filament. In smooth muscle, with perhaps 13 actin filaments per myosin filament, many actin filaments appear to be ranked in layers around myosin filaments. It is not known how the more distant actin filaments participate in contraction. 

Correlated with the wide distribution of the actin-myosin system found in smooth muscle, MLCK is also found in neural, epithelial, connective, and blood... 

In striated muscle, there are two other proteins that are minor in terms of their mass but important in terms of their function. Tropomyosin is a fibrous molecule that consists of two chains, alpha and beta, that attach to F-actin in the groove between its filaments (Figure 49-3). Tropomyosin is present in all muscular and muscle-fike structures. The troponin complex is unique to striated muscle and consists of three polypeptides. Troponin T (TpT) binds to tropomyosin as well as to the other two troponin components. Troponin I (Tpl) inhibits the F-actin-myosin interaction and also binds to the other components of troponin. Troponin C (TpC) is a calcium-binding polypeptide that is structurally and functionally analogous to calmodulin, an important calcium-binding protein widely distributed in nature. Four molecules of calcium ion are bound per molecule of troponin C or calmodulin, and both molecules have a molecular mass of 17 kDa. 

Fig. 2.3 The development of polarity and asymmetric division in Saccharomyces cerevisiae. The diagram is reproduced in a slightly simplified form from the work of Lew Reed (1995) with the permission of Current Opinion in Genetics and Development, (a) The F-actin cytoskeleton strands = actin cables ( ) cortical actin patches, (b) The polarity of growth is indicated by the direction of the arrows (arrows in many directions signifies isotropic growth), (c) 10-nm filaments which are assembled to form a ring at the neck between mother and bud. (d) Construction of the cap at the pre-bud site. Notice that the proteins of the cap become dispersed at the apical/isotropic switch, first over the whole surface of the bud, then more widely. Finally, secretion becomes refocussed at the neck in time for cytokinesis, (e) The status and distribution of the nucleus and microtubules of the spindle. Notice how the spindle pole body ( ) plays an important part in orientation of the mitotic spindle.

Glacy, S. (1983) Subcellular distribution of rhodamine-actin microinjected into living fibroblastic cells. Cell Biol. 97, 1207. 

Many MF-associated proteins [28] have been described in the nervous system (Table 8-3). In general, a good deal is known about their distribution and function in primary cultures of neurons and glia, but less is known about their role in the mature nervous system. Two that have been characterized more extensively are the major non-actin... 

Adams AE, Pringle PR. Relationship of actin and tubulin distribution to bud growth in wild-type and morphogenetic-mutant Saccharomyces cerevisiae. J Cell Biol 1984 98 934-945. 

The microtrabecular lattice is part of the cytoskeleton and is comprised of an intricate network of fine strands of variable (7-18-nm) diameter. This lattice is made up of many (perhaps up to 400) polypeptides, of which actin is the major component. The cytoplasmic granules appear to be distributed at different depths within this lattice, an organisation that may allow phagosome and granule fusion to occur more efficiently. 

The calcium mediated contraction of smooth muscle, which unlike striated muscle does not contain troponin, is quite different and requires a particular calcium-binding protein called calmodulin. Calmodulin (CM) is a widely distributed regulatory protein able to bind, with high affinity, four Ca2+ per protein molecule. The calcium—calmodulin (CaCM) complex associates with, and activates, regulatory proteins, usually enzymes, in many different cell types in smooth muscle the target regulatory proteins are caldesmon (CDM) and the enzyme myosin light chain kinase (MLCK). As described below, CaCM impacts on both actin and myosin filaments. 

This theory clearly predicts that the shape of the polymer length distribution curve determines the shape of the time course of depolymerization. For example Kristofferson et al. (1980) were able to show that apparent first-order depolymerization kinetics arise from length distributions which are nearly exponential. It should also be noted that the above theory helps one to gain a better feeling for the time course of cytoskeleton or mitotic apparatus disassembly upon cooling cells to temperatures which destabilize microtubules and effect unidirectional depolymerization. Likewise, the linear depolymerization kinetic model could be applied to the disassembly of bacterial flagella, muscle and nonmuscle F-actin, tobacco mosaic virus, hemoglobin S fibers, and other linear polymers to elucidate important rate parameters and to test the sufficiency of the end-wise depolymerization assumption in such cases. 

The principal cytoskeletal proteins in non-muscle cells are actin, tubulin, and the components of intermediate filaments. Actin can exist either as monomers ( G-actin ) or polymerized into 70 A diameter double filament ( F-actin ). Polymerized actin usually is localized at the margins of the cells, linked by other proteins to the cell membrane. In contrast, tubulin forms hollow filaments, approximately 250 A in diameter, that are distributed within a cell in association, generally, with cell organelles. Stabilized microtubule structures are found in the flagella and cilia of eucaryotic cells however, in other instances - examples being the mitotic apparatus and the cytoskeletal elements arising in directed cell locomotion - the microtubules are temporal entities. Intermediate filaments, which are composed of keratin-like proteins, are approximately 100 A thick and form stable structural elements that impart rigidity, for example, to nerve axons and epithelial cells. 

Fig. 13a and b. Intensity contour maps around the 5.9-nm and 5.1-nm actin layer lines (indicated by arrows) a resting state b contracting state. Z is the reciprocal-space axial coordinate from the equator. M5 to M9 are myosin meridional reflections indexed to the fifth to ninth orders of a 42.9-nm repeat, (c) intensity profiles (in arbitrary units) of the 5.9- and 5.1-nm actin reflections. Dashed curves, resting state solid curves, contracting state. Intensity distributions were measured by scanning the intensity data perpendicular to the layer lines at intervals of 0.4 mm. The area of the peak above the background was adopted as an integrated intensity and plotted as a function of the reciprocal coordinate (R) from the meridian... 

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