EGTA Treatment Causes the Synthesis of Heat Shock Proteins in Sea Urchin Embryos

Paracentrotus lividus embryos, at post-blastular stage, when subjected to a rise in temperature from physiologic (20°C) to 31°C, synthesize a large group of heat shock proteins (hsps), and show a severe inhibition of bulk protein synthesis. We show, by mono- and two-dimensional electrophoresis, that also EGTA (ethylene glycol-bis[β-aminoethyl ether] tetraacetic acid) treatment induces in sea urchin embryos both marked inhibition of bulk protein synthesis and the synthesis of the entire set of hsps. Furthermore, EGTA-treated sea urchin embryos are able to survive at a temperature otherwise lethal (35°C) becoming thermotolerant. Because incubation with a different calcium-chelator, EDTA (ethylenediaminetetraacetic acid), or in calcium-free medium did not induce hsps synthesis we conclude that the stress response caused by EGTA is not related to its calcium chelator function.