Crustacean hyperglycemic hormone from the tropical land crab, Gecarcinus lateralis: cloning, isoforms, and tissue expression.

Crustacean hyperglycemic hormone (CHH) regulates carbohydrate metabolism, molting, and ion and water transport. cDNAs encoding four CHH isoforms (designated EG-CHH-A, -B, -C, and -D) were cloned from eyestalk ganglia (EG) from land crab, Gecarcinus lateralis. The isoforms differed in the 3' region of the open reading frame and/or the length of the 3' untranslated region. All encoded essentially identical preprohormones containing a 28-amino acid (aa) signal peptide, a 42-aa precursor related peptide and a 72-aa mature CHH. All deduced aa sequences had the six cysteines, two arginines, one aspartate, one phenylalanine, and one arginine originally identified as characteristic of this neuropeptide family. There was a single aa difference between the EG-CHH-D mature hormone and the other three isoforms. The EG-CHH isoforms were expressed in EG, hindgut, and thoracic ganglion. A fifth CHH isoform, designated pericardial organ (PO)-CHH, was similar to the PO-CHH isoform described in green crab, Carcinus maenas. It was expressed in hindgut and testis, but not in eyestalk ganglia; its expression in PO was not determined. The deduced aa sequence of the PO-CHH was identical to that of the EG-CHH isoforms through aa #40 of the mature peptide. The divergent aa sequence between positions #41 and #73 was encoded by an insertion of a 111-bp sequence absent in EG-CHH cDNAs. The data suggest that EG-CHH and PO-CHH isoforms are generated by alternative splicing of at least two CHH genes.