Neurohormone signal transduction for dual regulation of metabolism and gene expression in insects: Hypertrehalosemic hormone as a model

The hypertrehalosemic hormone of the cockroach, Blaberus discoidalis (Bld-HTH), stimulates trehalose biosynthesis by the fat body and is a member of the adipokinetic hormone/red pigment-concentrating hormone family of arthropods. Bld-HTH also stimulates expression of the gene for cytochrome P4504C1 (CYP4C1) in the fat body. The present studies were undertaken to determine if simultaneous stimulation of trehalose biosynthesis and CYP4C1 expression by Bld-HTH occurs in response to independent signal transduction cascades or if they are sequential events of a common cascade. The Bld-HTH signal transduction cascade does not involve cyclic nucleotides but appears to employ inositol 1,4,5-triphosphate (IP3) to release intracellular Ca2+ for activation of phosphorylase which increases trehalose biosynthesis and CYP4C1 expression. Trehalose-6-phosphate synthase activity was also stimulated by Bld-HTH. Both phosphorylase activation and CYP4C1 expression appear regulated by a common, IP3/Ca2+-based signal transduction cascade. (C) 1996 Wiley-Liss, Inc.