Cloning and expression of the recombinant crustacean hyperglycemic hormone isoform B2 (rCHH-B2) and its effects on the metabolism and osmoregulation of the Pacific white shrimp Litopenaeus vannamei.

Crustacean hyperglycemic hormones (CHHs) are multifunctional neuropeptides ubiquitous in crustaceans. In Litopenaeus vannamei, CHH-B2 is a CHH eyestalk isoform whose expression has been shown to vary with enviromental conditions, suggesting its relevance for ecophysiological performance of shrimp, controlling processes related to metabolism and osmo-ionic regulation. To study the involvement of CHH-B2 in these processes, we cloned and expressed a recombinant version with a free C-terminal glycine (rCHH-B2-Gly) in the methylotrophic yeast Pichia pastoris. The rCHH-B2-Gly peptide secreted to the culture medium was purified by RP-HPLC and used for in vivo glucose, triglyceride, and osmoregulation dose-response analyses with juvenile shrimp. The peptide was also amidated at the C-terminus using an α-amidating enzyme to produce rCHH-B2-amide. The shrimp showed a dose-dependent effect of rCHH-B2-Gly to hemolymph glucose and triglyceride levels, inducing maximal increases by injecting 500 and 1000pmol of hormone, respectively. Additionally, 10pmol of hormone was sufficient to reduce the hypo-osmoregulatory capacity of shrimp at 35‰. These findings suggest that CHH-B2 has regulatory roles in carbohydrate and lipid metabolism, and a potential involvement in osmoregulation of L. vannamei. Injection of 100pmol of rCHH-B2-amide increased glucose and triglyceride levels by 15 and 28%, respectively in comparison with rCHH-B2-Gly, suggesting an important role for the C-terminal amidation. Additionally, an in silico structural analysis done with the CHH-B1 and rCHH-B2-Gly peptides suggests that the C-terminal region may be relevant for the activity of the L. vannamei isoforms and explain the functional divergence from other crustacean CHH/CHH-like peptides.

Hyperglycemic activity of the recombinant crustacean hyperglycemic hormone B1 isoform (CHH-B1) of the Pacific white shrimp Litopenaeus vannamei.

Crustacean hyperglycemic hormone (CHH) is the most abundant neuropeptide produced by the X-organ/sinus gland (XO/SG) complex in the crustacean eyestalk. CHH plays a principal role in the control of glucose metabolism. The CHH-B1 isoform is produced in the eyestalk of Litopenaeus vannamei by alternative splicing of the chhB gene and its cDNA sequence has revealed that this isoform has a non-amidated C-terminal residue (CHH-like peptide). In this work, a recombinant CHH-B1 (rCHH-B1) with a sequence identical to the native hormone was expressed in the methylotrophic yeast Pichia pastoris X-33 and purified from the culture medium by RP-HPLC. The identity of the purified rCHH-B1 was confirmed by N-terminal sequencing and by using an anti-CHH-B1 polyclonal antibody. An in vivo assay showed that the hyperglycemic effect was dependant of the dosage of rCHH-B1, and the maximal hyperglycemic response was obtained with 250pmol treatment. These results suggest that the amino acid sequence of the C-terminus and its correct structure are both important for the hyperglycemic activity of naturally occurring non-amidated CHH peptides, such as CHH-B1. CHH-B1 appears to be the first reported CHH-like peptide with significant hyperglycemic activity produced in the sinus gland of a penaeid shrimp.