Sea Slug Study Reveals Evolutionary Link Between Ancient Mollusk Peptides and Human Kisspeptin Signaling

The researchers used bioinformatics to identify candidate buccalin receptors in the Aplysia genome, then cloned the receptor and tested it in cell-based assays. They measured dose-response activation with all 19 buccalin peptides and tested cross-reactivity with fruit fly allatostatin A peptides and human kisspeptin and galanin. Phylogenetic and chromosomal analyses were used to map evolutionary relationships.

Understanding how neuropeptide signaling systems evolved across species helps researchers trace the origins of peptides that are important in human health. Kisspeptin controls reproduction and galanin influences appetite and pain — knowing their evolutionary roots in ancient mollusk peptides could reveal conserved mechanisms and potential new drug targets.

This work connects peptide signaling in invertebrates to clinically relevant peptide systems in humans. Kisspeptin is central to puberty and fertility, while galanin modulates pain, appetite, and cognition. Tracing their origins to ancient buccalin-type peptides in mollusks deepens our understanding of how these signaling systems arose and diversified — knowledge that could inform peptide drug design by revealing conserved receptor mechanisms.

This is a basic biology study in an invertebrate model (sea slug). The evolutionary connections to human kisspeptin and galanin systems, while supported by phylogenetic analysis, are inferred rather than functionally proven in mammalian systems. The KISSR-like receptor found in Aplysia could not be activated by any tested peptides, leaving its function unknown.