REMODELING OF MICROTUBULE SYSTEM DURING EGF RECEPTOR ENDOCYTOSIS
M. V. Kharchenko, E. S. Kornilova, M. S. Melikova 1
Institute of Cytology RAS, St. Petersburg;
1 e-mail: melikova@mail.cytspb.rssi.ru
The idea of microtubules (MTs) as of passive railway tracks, along which transport vesicles travel by use of motor
proteins, is widely accepted. In the present work the organization of MT system during EGF-receptor endocytosis was
investigated by indirect double immunofluorescence in HeLa and A431 cell lines. Stimulation of cells with EGF
resulted in formation of EGF receptor-containing peripheral vesicular endosomes. During time course of endocytosis
the endosomes tended to concentrate in juxtranuclear region close to MTOC. This translocation was dependent on MTs
since nocodazole treatment resulted in endosomes' scattering throughout the cytoplasm. Parallel staining of the cells
with tubulin antibody has revealed significant remodeling of MTs organization during endocytosis. At early stages
MTs demonstrated slight retraction at the cell periphery and the increasing intensity of tubulin fluorescence in the
juxtranuclear region. Later on, long individual MTs disappeared and peripheral cytoplasm show diffuse staining in
combination with a meshwork of short MT fragments. This stage correlated with EGFR localization in juxtranuclear
endosomes. Disappearance of EGFR-positive staining due to its lysosomal degradation occurred in parallel to
reestablishment of radial MT system. Possible functional significance of described alterations in organization of
tubulin cytoskeleton is discussed.
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