RESUMO
An innovative method, direct peptide profiling of small samples of nervous tissue by matrix-assisted laser desorption ionization mass spectrometry, in combination with peptide characterization, immunocytochemistry in conjunction with specific neuronal labeling by backfilling of the penis nerve, and bioassay of peptides was used to study the intrinsic neuronal expression patterns of distinct sets of related FMRFa peptides and their significance for the organization of male copulation behavior in the mollusk, Lymnaea stagnalis. Previous studies indicate that the sets of FMRFa-related and GDPFLRFa-related peptides are encoded by two alternatively spliced transcripts of the single FMRFa gene. Direct mass spectrometry revealed that both FMRFa-related and GDPFLRFa-related peptides are present in the penis nerve, the sole nerve that innervates the penis complex. Accordingly, authentic FMRFa, GDPFLRFa, and related peptides were purified from the penis complex. The loci of synthesis of FMRFa and related peptides could be traced to the right cerebral ventral lobe, those of GDPFLRFa and related peptides to the B group neurons in the right parietal ganglion and to a few unidentified neurons in the right pleural ganglion. Notwithstanding their related structures, the two sets of peptides have distinctly different actions on the penis retractor muscle.
Assuntos
Processamento Alternativo , Expressão Gênica , Lymnaea/fisiologia , Neurônios/metabolismo , Neuropeptídeos/biossíntese , Sequência de Aminoácidos , Animais , Bioensaio , Copulação , FMRFamida , Feminino , Hormônios de Invertebrado/biossíntese , Lymnaea/genética , Masculino , Dados de Sequência Molecular , Contração Muscular/efeitos dos fármacos , Neuropeptídeos/genética , Neuropeptídeos/farmacologia , Pênis , Peptídeos/síntese química , Peptídeos/farmacologia , Precursores de Proteínas/biossíntese , Relação Estrutura-AtividadeRESUMO
Peptide messengers are crucial for the execution of male copulatory processes in the snail Lymnaea stagnalis. In this study, we report the purification of a novel peptide from the penis complex of L. stagnalis. This peptide enhances the contraction frequency and contraction amplitude of the vas deferens. Amino acid sequencing and mass spectrometry indicate that the primary structure is GLTPNMNSLFF-NH2. We propose that this amide peptide modulates the transfer rate of semen in the vas deferens.