EGF-DEPENDENT SIGNALING PATHWAYS ARE ACTIVATED UNDER HEAT STRESS IN A431 CARCINOMA
CELLS
A. L. Evdonin,1 N. V. Tsupkina, K. P. Vasilenko, N. D. Medvedeva
Institute of Cytology, RAS, St. Petersburg, Russia;
1 e-mail: evdonin@mail.ru
EGF receptor transactivation and activation of EGF-dependent signaling pathways under heat shock conditions
were studied. Heating A431 cells at 42 °C induced both EGF receptor tyrosine phosphorylation and appearance of phosphorylated
forms of key components of its downstream signaling pathways - phospholipase Ñγ1 (PLÑγ1), transcription factor STATS,
and ERK 1/2. It is suggested that EGF receptor is transactivated under heat shock in A431 cells. Pretreatment of heat-shocked
cells with a specific inhibitor of EGF receptor tyrosine kinase tyrphostin AG1478 does not prevent EGF receptor and ERK 1/2
tyrosine phosphorylation. In contrast, tyrphostin AG1478 abrogates tyrosine phosphorylation of PLÑγ1 and STATS. This suggested
that the intrinsic EGF receptor tyrosine kinase is not involved in EGF receptor transactivation, but is sufficient for
PLÑγ1 and STATS activation in stress conditions. The effect of a conditioned medium of heated cells was investigated to
check whether autocrine mechanism is involved in EGF receptor transactivation. The conditioned medium of heated cells induced
both tyrosine phosphorylation of EFG receptor and ERK 1/2. Simultaneously, neither PLÑγ1, not STATS phosphorylation were
detected. Here, for the first time, we demonstrated the involvement of autocrine mechanism in EGF receptor transactivation
under heat stress in A431 carcinoma cells, but additional intracellular events are essential for activation of EGF receptor
downstream signaling pathways.
Key words: heat shock, cell signaling, EGF receptor, EGF receptor transactivation, phospholipase C,
STAT3, ERK 1/2
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