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Corazonin receptor signaling in ecdysis initiation.

ABSTRACT: Corazonin is a highly conserved neuropeptide hormone of wide-spread occurrence in insects yet is associated with no universally recognized function. After discovery of the corazonin receptor in Drosophila, we identified its ortholog in the moth, Manduca sexta, as a prelude to physiological studies. The corazonin receptor cDNA in M. sexta encodes a protein of 436 amino acids with seven putative transmembrane domains and shares common ancestry with its Drosophila counterpart. The receptor exhibits high sensitivity and selectivity for corazonin when expressed in Xenopus oocytes (EC(50) approximately 200 pM) or Chinese hamster ovary cells (EC(50) approximately 75 pM). Northern blot analysis locates the receptor in peripheral endocrine Inka cells, the source of preecdysis- and ecdysis-triggering hormones. Injection of corazonin into pharate larvae elicits release of these peptides from Inka cells, which induce precocious preecdysis and ecdysis behaviors. In vitro exposure of isolated Inka cells to corazonin (25-100 pM) induces preecdysis- and ecdysis-triggering hormone secretion. Using corazonin receptor as a biosensor, we show that corazonin concentrations in the hemolymph 20 min before natural preecdysis onset range from 20 to 80 pM and then decline over the next 30-40 min. These findings support the role of corazonin signaling in initiation of the ecdysis behavioral sequence. We propose a model for peptide-mediated interactions between Inka cells and the CNS underlying this process in insect development.

SUBMITTER: Kim YJ

PROVIDER: S-EPMC404109 | biostudies-literature | 2004 Apr

REPOSITORIES: biostudies-literature

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Corazonin receptor signaling in ecdysis initiation.

Kim Young-Joon YJ Spalovská-Valachová Ivana I Cho Kook-Ho KH Zitnanova Inka I Park Yoonseong Y Adams Michael E ME Zitnan Dusan D

Proceedings of the National Academy of Sciences of the United States of America 20040419 17

Corazonin is a highly conserved neuropeptide hormone of wide-spread occurrence in insects yet is associated with no universally recognized function. After discovery of the corazonin receptor in Drosophila, we identified its ortholog in the moth, Manduca sexta, as a prelude to physiological studies. The corazonin receptor cDNA in M. sexta encodes a protein of 436 amino acids with seven putative transmembrane domains and shares common ancestry with its Drosophila counterpart. The receptor exhibits ...[more]

PMID: 15096620

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Project description:Insect ecdysis sequence is composed of pre-ecdysis, ecdysis and post-ecdysis behaviors controlled by a complex cascade of peptide hormones from endocrine Inka cells and neuropeptides in the central nervous system (CNS). Inka cells produce pre-ecdysis and ecdysis triggering hormones (ETH) which activate the ecdysis sequence through receptor-mediated actions on specific neurons in the CNS. Multiple experimental approaches have been used to determine mechanisms of ETH expression and release from Inka cells and its action on the CNS of moths and flies. During the preparatory phase 1-2 days prior to ecdysis, high ecdysteroid levels induce expression of ETH receptors in the CNS and increased ETH production in Inka cells, which coincides with expression of nuclear ecdysone receptor (EcR) and transcription factor cryptocephal (CRC). However, high ecdysteroid levels prevent ETH release from Inka cells. Acquisition of Inka cell competence to release ETH requires decline of ecdysteroid levels and beta-FTZ-F1 expression few hours prior to ecdysis. The behavioral phase is initiated by ETH secretion into the hemolymph, which is controlled by two brain neuropeptides-corazonin and eclosion hormone (EH). Corazonin acts on its receptor in Inka cells to elicit low level ETH secretion and initiation of pre-ecdysis, while EH induces cGMP-mediated ETH depletion and consequent activation of ecdysis. The activation of both behaviors is accomplished by ETH action on central neurons expressing ETH receptors A and B (ETHR-A and B). These neurons produce numerous excitatory or inhibitory neuropeptides which initiate or terminate different phases of the ecdysis sequence. Our data indicate that insect ecdysis is a very complex process characterized by two principal steps: (1) ecdysteroid-induced expression of receptors and transcription factors in the CNS and Inka cells. (2) Release and interaction of Inka cell peptide hormones and multiple central neuropeptides to control consecutive phases of the ecdysis sequence.

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Corazonin receptor signaling in ecdysis initiation.

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Corazonin receptor signaling in ecdysis initiation.

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