Molecular cloning of a cDNA encoding proglucagon from goldfish, Carassius auratus

Abstract

Proglucagon is the precursor for a number of peptides: glucagon and at least one glucagon-like peptide (GLP1 and GLP2). The production of these peptides is regulated by tissue-specific proteolytic processing. A cDNA encoding the proglucagon in goldfish was characterized using rapid amplification of the cDNA ends. Goldfish proglucagon cDNA was found to be 660 base pair long, encoding a putative 121-residue prepro-hormone. Goldfish glucagon and GLP do not terminate with two basic residues, as is common in vertebrates as specific endopeptidase cleavage recognition site. Instead, only one basic residue is found at these positions. It is not known whether goldfish glucagon and GLP have adopted an alternate processing pathway, or whether they remained unprocessed to yield C-terminal-extended peptides. By reverse transcriptase-polymerase chain reaction, the proglucagon mRNA was found to be expressed mainly in the gall bladder region and the proximal intestine, and less in the spleen and distal intestine.