Microtubules distribution

Oda T (2006) Effects of 2 -Demethoxy-2 -propoxygriseofulvin on Microtubule Distribution in Chinese Hamster V79 Cells. J Antibiot 59 114... 

Neely MD, Boekelheide K. 1988. Sertoli cell processes have axoplasmic features an ordered microtubule distribution and an abundant high molecular weight microtubule-associated protein (cytoplasmic dynein). J. Cell Biol. 107 1767-76... 

In this chapter we describe the distribution, assembly, and interaction of microfilaments and microtubules and their functional roles in cell movement and in the maintenance of the spatial organization of the cytoplasm. Also, the relative roles... 

Nagasaki, T., Chapin, C.J., Gundersen, G.G. (1992). Distribution of detyrosinated microtubules in motile NRK fibroblasts is rapidly altered upon cell-cell contact Implications for contact inhibition of locomotion. Cell Mot. Cytoskel. 23,45-60. 

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.

FIG. 5. Distribution of microtubules during anaphase in wild-type and %yg-8 t165G) mutant embryos as revealed by staining with anti-tubulin antibodies. White contour marks the anterior cortex. In wild-type, astral microtubules are long, extending all the way to the cell cortex. Astral microtubules in %yg-8 mutant embryos are shorter, and do not reach the vicinity of the cell cortex. Bar=10/tm. 

TABLE 8-1 Major microtubule cytoskeletal proteins of the nervous system Protein Expression pattern and distribution... 

Schoenfeld, T. A. and Obar, R. A. Diverse distribution and function of fibrous microtubule-associated proteins in the nervous system. Int. Rev. Cytol. 151 67-137,1994. 

However, not all proteins proceed directly to their eventual destination. Some proteins relocate from one plasma membrane compartment to another by means of trans-cytosis. Transcytosis involves endocytosis of selected proteins in one membrane compartment, followed by subsequent transport through early endosomes to recycling endosomes and finally translocation to a different membrane compartment, for example from the apical to the basolateral surfaces. Sorting at the TGN and endo-some recycling steps appear to have a primary role in the steady state distribution of proteins in different plasma membrane domains [47], However, selective retention of proteins at the plasma membrane by scaffolding proteins or selective removal may also contribute to normal distributions. Finally, microtubule-motor regulatory mechanisms have been discovered that might explain the specific delivery of membrane proteins to discrete plasma membrane domains [48]. 

Akner G, Wikstrom AC, Gustafsson JA (1995) Subcellular distribution of the glucocorticoid receptor and evidence for its association with microtubules J Steroid Biochem Mol Biol 52 1... 

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. 

Fig. 5. Kinetics of brain microtubule depolymerization following rapid dilution. (A) Time course of the disassembly reaction with experimental data represented by the data points and the theoretical progress curve indicated by the solid line. (The inset to A shows that the process can be fitted to a simple decaying exponential for part of the depolymerization reaction.) (B) Microtubule length distribution for the sample subjected to rapid dilution in A. (Reproduced from Karr et al. (1980)./. Biol. Chm. 255, 8560-8566.)...

Fig. 7. Steady-state microtubule length distribution under idealized conditions. The concentrations of microtubule species at the dip in the distribution, at the maximum, and at the longest point are indicated by c/, c , and c , respiectively. [Reproduced from Kristof-ferson and Purich (1981). Arch. Biochem. Biophys. 211, 222-226.]...

Fig. 8. Experimental length distribution changes for bovine brain microtubule protein at 1 and 4 hours after initiation of assembly. Plots A and B correspond to unsheared samples, and give average length values of 11.3 and 12.1 /um, respectively. Plots C and D correspond to the sheared samples at 1 and 4 hours after assembly was induced, and polymer length values averaged 3.1 and 5.2 jam, respectively. [Reproduced from Kristofferson and Purich (1981). Arch. Biochem. Biaphys. 211, 222-226.]...

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. 

Figure 1. Mixing device for microtubule depolymerization kinetic studies requiring prompt dilution while minimizing shearing forces that may alter the polymer length distribution.

Figure 2. Progress curve for dilution-induced microtubule depolymerization. Inset Polymer length distribution prior to dilution-induced disassembly. The data points are experimentally determined, and the solid line is based on the theoretical treatmenF. ...

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