THE ROLE OF PHOSPHATIDYLINOSITOL-3-KINASES P85/P110 AND HVPS34 IN ENDOCYTOSIS OF
EGF-RECEPTOR COMPLEXES
N. N. Zheleznova,1 M. S. Melikova, M. V. Kharchenko, N. N. Nikolsky, E. S. Kornilova
Institute of Cytology RAS, St. Petersburg;
1 e-mail: zheleznova@hotmail.com
The previous data (Zheleznova et al., 2001) did not enable the authors to conclude which particular wortmannin
sensitive PI-3-kinase - p85/ð110 (I class PI-3-K) or hVPS34 (III class PI-3-K) - may be involved in the regulation
of EGF-receptor endocytosis. In the present work, we have shown that upon stimulation of EGF-receptor endocytosis
additional structures stained with antibody against p85 appear in A431 cells, but the p85-positive compartment
never co-localized with EGF-receptor-containing compartments either in control or in wortmannin-treated cells.
At the same time, wortmannin treatment prevented association of hVPS34 with endosomal membranes. We have also
found that early endosomal markers - Rab5 and EEA1 (membrane association of the latter depends on Rab5 and hVPS34)
- co-localized with EGF-receptor in the juxtranuclear region during late stages of endocytosis, both in control
and upon wortmannin treatment. These observations favor our suggestions that the transition of EGF-receptors from
early to late endosomes may occur directly in this juxtranuclear region and be tightly associated with the
formation of so called multivesicular bodies (MVB), which are late endosomes per se. We suggest that wortmannin
may have no sffect on early ÅÅ À1-dependent stage of the receptor endocytosis but blocks a transition of
EGF-receptor complexes into the late endosomes by inhibiting activity of hVPS34 and removing it from membranes.
The hVPS34 product PI-3-K, according to the known data, is involved in the formation of internal vesicles of MVB.
Accumulation of EGF-receptors in these vesicles is believed to be necessary for the receptor degradation.
Key words: EOF receptor, A431 cells, endocytosis, early and late endosomes, multivesicular
endosomes, wortmannin, phosphatidylinositol-3-kinases p85/ð110 and hVPS34, Rab5, EEA1
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