Intracellular motility

The Role of Myosins in Cell Locomotion The Role of Actin-Binding Proteins in Cell Locomotion The Transduction of Extracellular Motility Signals to the Cytoskeleton Lipid Flow and Cell Locomotion The Role of Cell Locomotion in Metastasis Intracellular Motility Microtubule-Based Intracellular Motility... 

Microtubule-Based Motor Proteins The Meiotic and Mitotic Spindles Microfilament-Based Intracellular Motility Cytokinesis... 

Intracellular motility is also of vital importance in the lives of cells and the organisms they form. Material and organelles are transported within cells along microtubules and microfilaments an extreme example of this are the axons of nerve cells which transport materials to the synapses where they are secreted—another motile event. Other examples of intracellular motility include phagocytosis, pino-cytosis, the separating of chromosomes and cells in cell division, and maintenance of cell polarity. 

Kinesin and dynein are two microtubule-associated ATP-dependent motors responsible for intracellular motility. Gilbert et al made direct measurements of the dissociation kinetics of kinesin from microtubules (MTs), the release of orthophosphate and ADP, and the rebinding of this motor to MTs. They observed processivity in ATP hydrolysis amounting to 10 molecules ATP per site at low salt concentration and 1 molecule of ATP per site at a higher concentration of salt. After hydrolysis, the dissociation of kinesin from the MT is rate-limiting, and rebinding of kinesin-ADP to MTs is fast. The authors discuss how this behavior differs from that of skeletal myosin. 

Many biological effects have been observed by the cytochalasans. The most well-documented ones result from an influence on cellular processes, such as intracellular motility, exo- and endocytosis, and cytokinesis, and is based on the interference with actin filament network formation. This is due to interaction with actin (705), one of the key components of the cytoskeleton, leading to inhibition of cytokinesis (cell division) without any influence on karyokinesis (nuclear division). Thus, multinucleated cells were observed after treatment of proliferating cells with... 

Theriot et al., 1992] Theriot, J. A., Mitchison, T. J., Tilney, L. G., and Portnoi, D. A. The rate of actin-based motility of intracellular Listeria monocytogenes equals the rate of actin polymerization. Nature. 357 (1992) 257-260... 

Alexandrova, A.Y., Dugina, V.B., Paterson, H., Bershadsky, A.D., Vasiliev, J.M. (1993). Motility of intracellular particles in rat fibroblasts is greatly enhanced by photbol ester and by overexpression of normal p2l. Cell Mot. Cytoskel. 25, 254-266. 

The process of activation of neutrophils is essentially similar. They are activated, via specific receptors, by interaction with bacteria, binding of chemotactic factors, or antibody-antigen complexes. The resultant rise in intracellular Ca affects many processes in neutrophils, such as assembly of micrombules and the actin-myosin system. These processes are respectively involved in secretion of contents of granules and in motility, which enables neutrophils to seek out the invaders. The activated neutrophils are now ready to destroy the invaders by mechanisms that include production of active derivatives of oxygen. 

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