Relaxin-like Gonad-Stimulating Peptides in Asteroidea

Area of Science:

• Marine biology
• Endocrinology
• Evolutionary biology

Background:

• Starfish relaxin-like gonad-stimulating peptide (RGP) is the first identified invertebrate peptide hormone with gonadotropin-like activity.
• RGP is a heterodimeric peptide hormone, structurally related to the relaxin family, crucial for starfish reproduction.

Purpose of the Study:

• To review the identification, evolution, and function of starfish RGP.
• To explore the molecular mechanisms and potential new physiological roles of RGP.

Main Methods:

• Literature review of identified RGP orthologs across starfish orders.
• Analysis of RGP localization within starfish tissues.
• Investigation of RGP's role in inducing 1-methyladenine (1-MeAde) production and its downstream effects.

Main Results:

• Twenty-four RGP orthologs are identified, with molecular evolution aligning with starfish phylogeny.
• RGP is localized in nerve cords, gonoducts, and coelomocytes, acting on gonadal cells to stimulate 1-MeAde production.
• RGP-induced 1-MeAde triggers oocyte maturation and gamete shedding, potentially via cyclic AMP and acetylcholine pathways.

Conclusions:

• Starfish RGP is a vital reproductive hormone, with its evolution mirroring starfish taxonomy.
• RGP's mechanism of action involves stimulating 1-MeAde production, likely through G protein-coupled receptors.
• Further research may uncover novel physiological functions of RGP, particularly in larval stages.