Identification, Synthesis, Conformation and Activity of an Insulin-like Peptide from a Sea Anemone.

Michela L Mitchell,Briony E Forbes,Carlie Delaine,Feng Lin,Steve Peigneur,Ernesto L Pinheiro-Junior,Andrew J Blyth,Raymond S Norton,Mohammed Akhter Hossain,John D Wade,Dorothy C C Wai,Jan Tytgat

doi:10.3390/biom11121785

Abstract

The role of insulin and insulin-like peptides (ILPs) in vertebrate animals is well studied. Numerous ILPs are also found in invertebrates, although there is uncertainty as to the function and role of many of these peptides. We have identified transcripts with similarity to the insulin family in the tentacle transcriptomes of the sea anemone Oulactis sp. (Actiniaria: Actiniidae). The translated transcripts showed that these insulin-like peptides have highly conserved A- and B-chains among individuals of this species, as well as other Anthozoa. An Oulactis sp. ILP sequence (IlO1_i1) was synthesized using Fmoc solid-phase peptide synthesis of the individual chains, followed by regioselective disulfide bond formation of the intra-A and two interchain disulfide bonds. Bioactivity studies of IlO1_i1 were conducted on human insulin and insulin-like growth factor receptors, and on voltage-gated potassium, sodium, and calcium channels. IlO1_i1 did not bind to the insulin or insulin-like growth factor receptors, but showed weak activity against KV1.2, 1.3, 3.1, and 11.1 (hERG) channels, as well as NaV1.4 channels. Further functional studies are required to determine the role of this peptide in the sea anemone.

Highlights

The role of insulin as a key anabolic hormone that promotes the absorption of glucose from the blood into liver, fat, and skeletal muscle cells in vertebrates is well documented [1,2,3]
The characterized invertebrate insulin-like peptides (ILPs) perform an array of functions, which vary depending upon their tissue of origin
In this study we describe the synthesis of a representative ILP from this sea anemone and the results of activity assays against human insulin and insulin-like growth factor receptors, as well as a range of ion channels

Summary

Introduction

The role of insulin as a key anabolic hormone that promotes the absorption of glucose from the blood into liver, fat, and skeletal muscle cells in vertebrates is well documented [1,2,3]. The presence and role of insulin-like peptides (ILPs) in invertebrates, especially those found in the marine environment, are less well understood. The characterized invertebrate ILPs perform an array of functions, which vary depending upon their tissue of origin. Insect ILPs (e.g., from Drosophila melanogaster) are implicated in multiple functions, including regulating metabolism, growth, reproduction, and longevity [4,5,6,7]. Bombyxin A-1, a silk moth (Bombyx mori) ILP, is produced in the brain to activate the prothoracic glands to produce ecdysone (a moulting hormone) for growth development [8].

Methods

Results

Conclusion