Peptide Hormones, Steroid Hormones, and Puffs: Mechanisms and Models in Insect Development

Abstract

Publisher Summary This chapter describes the mechanisms and models of peptide hormones, steroid hormones, and puffs in insect development. The postnatal physical development of homeothermic animals is chiefly a period of increase in size, with a few final touches such as the appearance of secondary sexual characteristics or flight feathers. Perfection of motor and behavioral skills is often the dominant feature of this period. Ecdysteroids act as triggers for alterations in transcription, which, in turn, lead to subsequent cellular and organismal changes. Their action is modified by the juvenile hormone (JH) class of hormones. The classic paradigm of insect endocrinology states that high ecdysteroid titers in the presence of high JH titers lead to larval–larval molts. The cysteines involved in intra- and intermonomer cross-linking of bombyx prothoracicotropic hormone (PTTH) are conserved in the Antheraea and Samia sequences, suggesting very similar folding patterns. The PTTH-stimulated generation of cyclic AMP (cAMP) in prothoracic glands results in rapid activation of a cAMP-dependent protein kinase A (PKA), ∼ 90% of maximum within 5 minutes. The proteins phosphorylated directly by PTTH-activated PKA in the prothoracic glands are not known, it seems likely that PTTH stimulation results in the activation of several additional kinases.