Dynamics of biosynthesis and release of crustacean hyperglycemic hormone isoforms in the X‐organ–sinus gland complex of the crayfish Orconectes limosus

The crustacean hyperglycemic hormone (CHH) is the major neuropeptide produced by the X-organ–sinus gland neurosecretory system of the crayfish, Orconectes limosus. This hormone is synthesized by two different cell types, as two isomers (CHH and d-Phe3-CHH) which display different activities The aim of this report is to analyze and compare the synthetic and secretory activities of these specialized cells. In vitro pulse–chase incubations and time–course experiments were conducted on isolated X-organ–sinus gland (XO–SG) complexes, followed by analysis of the labeled peptides. The different steps of the post-translational processing of the CHH precursor, including proteolytic cleavage of the propeptide, C-terminal amidation and N-terminal pyroglutamylation were characterized and the kinetics of CHHs maturation were estimated in the different parts of the neuroendocrine complex. Furthermore, synthesis of CHHs in XO–SG complexes and release in incubation media were investigated using combined HPLC/immunoassay. Under basal conditions, i.e. without stimulation, similar dynamics for both isomers were found and results indicate that newly synthesized CHHs are preferentially released.