The non-induction of HSP70 in heat shocked Malpighian tubules of Drosophila larvae is not due to constitutive presence of HSP70 or HSC70

Abstract

To understand reasons for the earlier reported non-induction of any of the common heat shock polypeptides in Malpighian tubules of Drosophila larvae, we examined the levels of the 70 kDa heat shock polypeptide (HSP70) and of its cognates (HSC70) in control and heat shocked larval tissues, including the Malpighian tubules, by ³⁵S-methionine labelling in conjunction with Western blotting or by immunocytochemical localization using appropriate antibodies against the heat inducible and constitutively expressed members of the HSP70 family. The HSP70 was totally undetectable in western blots of control as well as heat shocked Malpighian tubules of Drosophila larvae; the levels of different HSC70 in un-treated Malpighian tubules were comparable to those in other larval tissues and also did not increase following heat shock. Immunocytochemical localization of HSP70 showed that none of the highly polytenized cells of Malpighian tubules showed induction of HSP70 after heat shock. The non-induction of the common heat shock proteins in Malpighian tubules of Drosophila larvae, therefore, is not due to auto regulation by constitutively high levels of HSP70 or HSC70.