RADIAL-ORGANIZED MICROTUBULES PROVIDE MAINTENANCE OF THE CELL SHAPE AND MORE EFFECTIVE INTERCELLULAR TRANSPORT
THAN IN THE CASE OF FREE MICROTUBULES
O. A. Chernobelskaya, I. B. Alieva, I. A. Vorobjev
A. N. Belozersky Institute of Physical-Chemical Biology, Moscow State University;
e-mail: irina_alieva@belozersky.msu.ru
Microtubules take part in very different cell processes including cell polarization and migration, intercellular transport and some others. Therefore the microtubules
spatial organization is crucial for normal cell behaviour. Fibroblasts have radial microtubule array consisting of microtubules running from the centrosome. This
microtubule array includes two components: 1) centrosomal microtubules with their minus ends attached to the centrosome and with their plus ends radiating to the
cell periphery and 2) free microtubules with the ends non-attached to the centrosome. Distinction in the dynamic properties, intercellular organization and structure of
centrosome-attached and free microtubules allow us to assume that their functions in the cell are also different. In order to investigate centrosome-attached and free
microtubules functions we used the cytoplasts - experimentally denucleated cellular fragments and under certain condition lacking of the centrosome as well - which
contain only free microtubules. Centrosome-containing cytoplasts do not differ significantly in the form, general morphology and the size from the intact cells. At the
same time centrosome-lacking cytoplasts keep extremely thinned out network of microtubules located in the central area of the cytoplast. These cytoplasts lose the
original cell shape usual for fibroblasts and get rough, with protrusions, lamella; the internal architecture of the cytoplasm and organoids arrangement is also broken.
Saltatory movements in the centrosome-containing cytoplasts are similar to those in the intact cells, and saltatory movements in centrosome-lacking cytoplasts
show half the speed and smaller distances compared with intact cells. Besides, the saltatory movements of granules in the centrosome-lacking cytoplasts occur
mainly in the central regions of the cytoplasts and they are less ordered than in the intact cells and in the cytoplasts kept the centrosome. We believe that radial
organization of the microtubules provide effective transport and dynamical interactions of microtubules plus ends with cortical structures of the cell, which are sufficient for maintenance of typical fibroblast-like shape, whereas
disorganized free microtubules by themselves cannot keep up the shape and intercellular organization characteristic of fibroblasts.
Key words: centrosome-attached microtubules, free microtubules, cytoplasts, saltatory movements of granules
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