Crustacean hyperglycaemic hormone (CHH)-like peptides and CHH-precursor-related peptides from pericardial organ neurosecretory cells in the shore crab, Carcinus maenas, are putatively spliced and modified products of multiple genes

About 24 intrinsic neurosecretory neurons within the pericardial organs (PO s) of the crab Carcinus maenas produce a novel crustacean hyperglycaemic ho rmone (CHH)-like peptide (PO-CHH) and two CHH-precursor-related peptides (P O-CPRP I and II) as identified immunochemically and by peptide chemistry. E dman sequencing and MS revealed PO-CHH as a 73 amino acid peptide (8630 Da) with a free C-terminus, PO-CHH and sinus gland CHH (SG-CHH) share an ident ical N-terminal sequence, positions 1-40, but the remaining sequence, posit ions 41-73 or 41-72, differs considerably. PO-CHH may have different precur sors, as cDNA cloning of PO-derived mRNAs has revealed several similar form s, one exactly encoding the peptide. All PO-CHH cDNAs contain a nucleotide stretch coding fur the SG-CHH41-76 sequence in the 3'-untranslated region ( UTR). Cloning of crab testis genomic DNA revealed at least four CHH genes, the structure of which suggest that PO-CHH and SG-CHH arise by alternative splicing of precursors acid possibly post-transcriptional modification of P O-CHH. The genes encode four exons, separated by three variable introns, en coding part of a signal peptide (exon I), the remaining signal peptide resi dues. a CPRP, the PO-CHH1-40/SG-CHH1-40 sequences (exon II), the remaining PO-CHH residues (exon III) and the remaining SG-CHH residues acid a 3'-UTR (exon IV), Precursor and gene structures are more closely related to those encoding related insect ion-transport peptides than to penaeid shrimp CHH g enes. PO-CHH neither exhibits hyperglycaemic activity in vivo, nor does it inhibit Y-organ ecdysteroid synthesis in vitro. From the morphology of the neurons it seems likely that novel functions remain to be discovered.