Abstract
Neuropeptides control many physiological and endocrinological processes in animals, acting as neuroactive chemicals within the central and peripheral nervous systems. Corazonin (CRZ) is one such neuropeptide that has a variety of physiological roles associated with control of heartbeat, ecdysis behavior initiation, and cuticle coloration. These physiological effects are mediated by the CRZ receptor (CRZR). In order to understand the role of the CRZ-signaling pathway in Rhodnius prolixus, the cDNA sequence encoding the Rhopr-CRZR was isolated and cloned revealing two splice variants (Rhopr-CRZR-α and β). Sequence analysis revealed characteristics of rhodopsin-like GPCRs. Rhopr-CRZR-α and β were dose-dependently activated by Rhopr-CRZ with EC50 values of 2.7 and 1 nM, respectively, when tested in a functional receptor assay using CHOKI-aeq cells. Neither receptors were activated by the evolutionarily-related peptides, Rhopr-AKH, or Rhopr-ACP. For 5th instars, qPCR revealed expression of Rhopr-CRZR transcript in the CNS, the dorsal vessel, abdominal dorsal epidermis, and prothoracic glands with associated fat body. Interestingly, transcript expression was also found in the female and male reproductive tissues. Rhopr-CRZR transcript was reduced after injection of dsCRZR into adult R. prolixus. In these insects, the basal heartbeat rate was reduced in vivo, and the increase in heartbeat frequency normally produced by CRZ on dorsal vessel in vitro was much reduced. No effect of dsCRZR injection was seen on ecdysis or coloration of the cuticle.
Highlights
Fundamental questions in physiology revolve around understanding the means by which the nervous system communicates information throughout the organism
The use of model organisms to study these signaling pathways is advantageous since the genomes of a variety of organisms have been sequenced, The Corazonin-Signaling Pathway in Rhodnius prolixus allowing for the use of molecular tools to examine these pathways and their messengers; the most diverse messengers being via neuropeptides
It has been proposed that this signaling pathway arose during protostome evolution alongside two other insect signaling pathways, the adipokinetic hormone (AKH), and the AKH/CRZrelated peptide (ACP) pathways (Hauser and Grimmelikhuijzen, 2014; Roch et al, 2014)
Summary
Fundamental questions in physiology revolve around understanding the means by which the nervous system communicates information (messages) throughout the organism. The use of model organisms to study these signaling pathways is advantageous since the genomes of a variety of organisms have been sequenced, The Corazonin-Signaling Pathway in Rhodnius prolixus allowing for the use of molecular tools to examine these pathways and their messengers; the most diverse messengers being via neuropeptides. These neuropeptides are often associated with distinct behaviors, piecing together the overall integration of such behaviors is a challenge in neurobiology (Orchard et al, 2001). Before the emergence of the Arthropoda, the AKH-signaling system duplicated leading to AKH and ACP systems along with the CRZ-signaling system (Roch et al, 2014)
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