Abstract
C-type allatostatins (C-type ASTs) are a family of structurally related neuropeptides found in a wide range of insects and crustaceans. To date, the C-type allatostatin receptor in crustaceans has not been deorphaned, and little is known about its physiological functions. In this study, we aimed to functionally define a C-type ASTs receptor in the mud crab, Scylla paramamosian. We showed that C-type ASTs receptor can be activated by ScypaAST-C peptide in a dose-independent manner and by ScypaAST-CCC peptide in a dose-dependent manner with an IC50 value of 6.683 nM. Subsequently, in vivo and in vitro experiments were performed to investigate the potential roles of ScypaAST-C and ScypaAST-CCC peptides in the regulation of ecdysone (20E) and methyl farnesoate (MF) biosynthesis. The results indicated that ScypaAST-C inhibited biosynthesis of 20E in the Y-organ, whereas ScypaAST-CCC had no effect on the production of 20E. In addition, qRT-PCR showed that both ScypaAST-C and ScypaAST-CCC significantly decreased the level of expression of the MF biosynthetic enzyme gene in the mandibular organ, suggesting that the two neuropeptides have a negative effect on the MF biosynthesis in mandibular organs. In conclusion, this study provided new insight into the physiological roles of AST-C in inhibiting ecdysone biosynthesis. Furthermore, it was revealed that AST-C family peptides might inhibit MF biosynthesis in crustaceans.
Highlights
Allatostatins (ASTs), a class of peptides found in insects, have a potent effect on the production of juvenile hormone (JH) in corpora allata (Stay and Tobe, 2007)
We assessed the functionality of ScypaAST-CR by assaying cAMP accumulation in response to ScypaAST-C or ScypaAST-CCC stimulation
A potent eukaryotic adenylate cyclase (AC) activator, can rapidly increase intracellular cAMP levels without receptors, so it was commonly used in receptor assay (Alasbahi and Melzig, 2012)
Summary
Allatostatins (ASTs), a class of peptides found in insects, have a potent effect on the production of juvenile hormone (JH) in corpora allata (Stay and Tobe, 2007). Three distinct families of allatostatin peptides known as A-type, B-type, and C-type ASTs, have been identified in arthropods based on structural difference (Verlinden et al, 2015). Three members of C-type ASTs, including AST-C peptide, AST-CC peptide, and AST-CCC peptide, have been recorded in arthropods. AST-C and AST-CC are unblocked peptides whereas AST-CCC has an amidated C-terminus in most insect species, but AST-CCC peptides in Hemiptera are not amidated (Veenstra, 2009, 2016). The allatostatic role was initially assigned to allatostatin neuropeptides, but further research revealed pleiotropic roles in different species, such as inhibition of the spontaneous foregut contractions in the tomato moth (Lacanobia oleracea)
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