Structural and functional characterization of an egg-laying hormone signaling system in a lophotrochozoan – The pacific oyster (Crassostrea gigas)
Résumé
The egg-laying hormones (ELHs) of gastropod mollusks were characterized more than forty years ago. Yet, they
have remained little explored in other mollusks. To gain insights into the functionality of the ELH signaling
system in a bivalve mollusk – the oyster Crassostrea gigas, this study investigates the processing of its ELH pre-
cursor (Cragi-ELH) by mass spectrometry. Some of the ELH mature peptides identified in this study were sub-
sequently investigated by nuclear magnetic resonance and shown to adopt an extended alpha-helix structure in a
micellar medium mimicking the plasma membrane. To further characterize the ELH signaling system in C. gigas,
a G protein-coupled receptor phylogenetically related to ecdysozoan diuretic hormone DH44 and corticotropin-
releasing hormone (CRH) receptors named Cragi-ELHR was also characterized functionally and shown to be
specifically activated by the two predicted mature ELH peptides and their N-terminal fragments. Both Cragi-ELH
and Cragi-ELHR encoding genes were mostly expressed in the visceral ganglia (VG). Cragi-ELH expression was
significantly increased in the VG of both fully mature male and female oysters at the spawning stage. When the
oysters were submitted to a nutritional or hyposaline stress, no change in the expression of the ligand or receptor
genes was recorded, except for Cragi-ELHR only during a mild acclimation episode to brackish water. These
results suggest a role of Cragi-ELH signaling in the regulation of reproduction but not in mediating the stress
response in our experimental conditions.
Domaines
Sciences du Vivant [q-bio]Origine | Fichiers produits par l'(les) auteur(s) |
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