期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：7
DOI：10.1073/pnas.2113589119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Somatostatin (SS) and allatostatin-C (ASTC) are related neuropeptide hormones that act as inhibitory regulators of physiological processes in chordates (e.g., humans) and protostome invertebrates (e.g., insects), respectively. We have discovered that echinoderms (e.g., starfish) uniquely have both SS-type and ASTC-type neuropeptides, which act as inhibitory and excitatory regulators of muscle activity, respectively. Our findings suggest that SS-type and ASTC-type neuropeptides evolved by duplication of a common ancestral encoding gene. Then, one of the neuropeptides was lost in protostomes and chordates, probably because of their functional redundancy as inhibitory regulators. Conversely, the unique retention of both neuropeptide types in echinoderms may be explained by evolution of an excitatory role for ASTC-type neuropeptides mediated by yet-to-be-determined signaling mechanisms.
Somatostatin (SS) and allatostatin-C (ASTC) are inhibitory neuropeptides in chordates and protostomes, respectively, which hitherto were identified as orthologs. However, echinoderms have two SS/ASTC-type neuropeptides (SS1 and SS2), and here, our analysis of sequence data indicates that SS1 is an ortholog of ASTC and SS2 is an ortholog of SS. The occurrence of both SS-type and ASTC-type neuropeptides in echinoderms provides a unique context to compare their physiological roles. Investigation of the expression and actions of the ASTC-type neuropeptide ArSS1 in the starfish
Asterias rubens revealed that it causes muscle contraction (myoexcitation), contrasting with myoinhibitory effects of the SS-type neuropeptide ArSS2. Our findings suggest that SS-type and ASTC-type neuropeptides are paralogous and originated by gene duplication in a common ancestor of the Bilateria, with only one type being retained in chordates (SS) and protostomes (ASTC) but with both types being retained in echinoderms. Loss of ASTC-type and SS-type neuropeptides in chordates and protostomes, respectively, may have been due to their functional redundancy as inhibitory regulators of physiological processes. Conversely, the retention of both neuropeptide types in echinoderms may be a consequence of the evolution of a myoexcitatory role for ASTC-type neuropeptides mediated by as yet unknown signaling mechanisms.
