Characterization of a novel LFRFamide neuropeptide in the cephalopod Sepia officinalis.

From a single LC-MS/MS analysis, a new C-terminally extended RFamide neuropeptide was characterized in Sepia officinalis. The experimental strategy was based on the specific neutral loss associated with RFamide breakdown. Mass losses of 17 Da (C-terminally amide) and 320 Da (RFamide) have been observed for three known peaks of m/z 581.7 (FLRFamide), 599.8 (FMRFamide), 1096.3 (ALSGDAFLRFamide) and one unknown of m/z 752.8. The primary sequence of the peptide of m/z 752.8 was GNLFRFamide. MS/MS analyses revealed that this novel neuropeptide, called sepFRF1, is largely distributed in the central nervous system of cuttlefish of both sexes. Probably transported in the visceral nerve from the subesophageal mass (the peptide was not detected in the hemolymph), this neuropeptide targeted the rectum in agreement with its peripheral distribution. From concentrations as low as 10(-9)M, sepFRF1 increased the frequency, tonus and amplitude of rectal contractions. SepFRF1 is the first RFamide peptide identified in Sepia officinalis that is not derived from the FaRPs precursor. SepFRF1 could belong to a RFamide subfamily identified in gastropods and may be involved in feeding behavior.