Newly Identified Aplysia SPTR-Gene Family-Derived Peptides: Localization and Function

Area of Science:

• Neuroscience
• Molecular Biology
• Peptide Signaling

Background:

• Individual neurons can release multiple neuropeptides, providing flexibility in neural circuits.
• The cerebral-buccal interneuron-12 (CBI-12) in Aplysia is known to contain peptides FCAP/CP2, which modulate feeding motor programs.

Purpose of the Study:

• To identify and characterize a novel family of neuropeptides, Aplysia SPTR-Gene Family-Derived peptides (apSPTR-GF-DPs).
• To investigate the role of apSPTR-GF-DP2, a member of this novel family, in modulating feeding motor programs in Aplysia.

Main Methods:

• Immunohistochemistry and MALDI-TOF MS were used to detect apSPTR-GF-DPs in the Aplysia central nervous system (CNS).
• Electrophysiological recordings were performed to assess the effects of apSPTR-GF-DP2 on the excitability of specific interneurons (B64 and B20).

Main Results:

• Novel apSPTR-GF-DPs, including apSPTR-GF-DP2, are expressed in the Aplysia CNS and found in projection neurons like CBI-12.
• Both FCAP and apSPTR-GF-DP2 were found to shorten the protraction phase of motor programs.
• apSPTR-GF-DP2 modulates feeding by increasing B20 interneuron excitability, rather than affecting B64 interneuron excitability.

Conclusions:

• The study provides the first evidence for the role of SPTR-GF peptides in feeding modulation.
• Different peptides co-released by a single neuron (CBI-12) can target distinct sets of pattern-generating interneurons to achieve similar modulatory outcomes.
• This demonstrates molecular degeneracy, where multiple peptide cotransmitters in single identified neurons contribute to functional flexibility in neural circuits.