| Abstract | Since the initial characterization of the cardioexcitatory peptide FMRFamide in the bivalve
mollusk Macrocallista nimbosa, a great number of FMRFamide-like peptides (FLPs) have
been identified in mollusks. FLPs were initially isolated and molecularly characterized in
model mollusks using biochemical methods. The development of recombinant technologies
and, more recently, of genomics has boosted knowledge on their diversity in various
mollusk classes. Today, mollusk FLPs represent approximately 75 distinct RFamide peptides
that appear to result from the expression of only five genes: the FMRFamide-related
peptide gene, the LFRFamide gene, the luqin gene, the neuropeptide F gene, and the cholecystokinin/
sulfakinin gene. FLPs display a complex spatiotemporal pattern of expression
in the central and peripheral nervous system.Working as neurotransmitters, neuromodulators,
or neurohormones, FLPs are involved in the control of a great variety of biological
and physiological processes including cardiovascular regulation, osmoregulation, reproduction,
digestion, and feeding behavior. From an evolutionary viewpoint, the major challenge
will then logically concern the elucidation of the FLP repertoire of orphan mollusk classes
and the way they are functionally related. In this respect, deciphering FLP signaling pathways
by characterizing the specific receptors these peptides bind remains another exciting
objective.
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