Heat stress induces a glycosylation of membrane sterol in myxoamoebae of a true slime mold, Physarum polycephalum.

To know the very early events occurring after heat shock, the changes of membrane lipids were examined. Heat stress induced the production of a certain glycolipid in the myxoamoebae of Physarum polycephalum in a few minutes. The purified glycolipid was determined to be a poriferasterol monoglucoside by structural studies that was previously reported to be expressed during the differentiation of Physarum cells from haploid myxoamoebae to diploid plasmodia (Murakami-Murofushi, K., Nakamura, K., Ohta, J., Suzuki, M., Suzuki, A., Murofushi, H., and Yokota, T. (1987) J. Biol. Chem. 262, 16719-16723). The activity of UDP-glucose:poriferasterol glucosyltransferase (Murakami-Murofushi, K., and Ohta, J. (1989) Biochim. Biophys. Acta 992, 412-415) was also expressed rapidly after heat shock. Thus, the activation of sterol glucosyltransferase and the production of sterol-glucoside were considered to be important events that were involved in the signal transduction system to induce some succeeding heat-shock responses, such as the synthesis of heat-shock proteins.