Prothoracicotropic hormone-regulated expression of a hsp 70 cognate protein in the insect prothoracic gland

In Manduca sexta, ecdysteroids coordinate molting and metamorphosis of insects and are produced by the prothoracic glands under the acute control of the brain neuropeptide prothoracicotropic hormone (PTTH). PTTH stimulates rapid ecdysteroidogenesis accompanied by specific increases in the synthesis and accumulation of three proteins, including one with M(r) = 70 kDa. This 70-kDa protein is a constitutively expressed member of the heat shock protein 70 family (hsc 70). Levels of this hsc 70 vary in a prothoracic gland-specific manner during development as does its PTTH-stimulated synthesis when assayed in vitro. The accumulation of hsc 70 may be regulated by abrupt changes in its turnover rate. The PTTH-stimulated increase in hsc 70 synthesis is dependent upon both translational and transcriptional events. Hsc 70 expression in the prothoracic gland may be required for changes in gland growth, e.g., protein content, that underlie alterations in ecdysteroid production.