Bag Cell Peptides

Introduction

Bag cell peptides function in egg-laying by regulating the secretory activity of these cells, which also secrete a peptide egg-laying hormone (ELH). Bag cell peptides influence the electrophysiological properties of the bag cells and modulate cyclic adenosine monophosphate (cAMP) levels by influencing adenylyl cyclase activity. Bag cell peptides include α-bag cell peptides, β-bag cell peptides, and γ-bag cell peptides. The α-bag cell peptides contain three styles: (1-7), (1-8), and (1-9) and their amino acid sequences are Ala-Pro-Arg-Leu-Arg-Phe-Tyr, Ala-Pro-Arg-Leu-Arg-Phe-Tyr-Ser, and Ala-Pro-Arg-Leu-Arg-Phe-Tyr-Ser-Leu, respectively. The amino acid sequences of β-bag cell peptides and γ-bag cell peptides are -His and Arg-Leu-Arg-Phe-Asp. They all contain the Arg-Leu-Arg-Phe motif.

Mechanism of action

α-bag cell peptides were previously purified from bag cell extracts in three neuroactive forms: α-bag cell peptides (l-9), a nine amino acid peptide encoded on the ELH/bag cell peptides precursor protein, and two NH2-terminal fragments, α-bag cell peptides(l-8) and α-bag cell peptides (l -7). α-Bag cell peptide mimics the depolarization of bag cells induced during induction of inhibition of the upper left quadrant (LUQ) neurons and bag cell burst discharge by induced bag cells. β-Bag cell peptides depolarize and excite bag cells and stimulate bag cell adenylyl cyclase, but the effects of α-bag cell peptides and γ-bag cell peptides depend on temperature. At 15oC, a temperature at which Aplysia do not lay eggs, α-bag cell peptides hyperpolarize and inhibit these cells and inhibit adenylyl cyclase, whereas, at 20°C, which is permissive for egg laying, these peptides depolarize and excite and increase cAMP by stimulating adenylyl cyclase. γ-Bag cell peptides behave like α-bag cell peptides in that they regulate the cAMP system in a temperature-dependent fashion.

Application of Bag Cell Peptides

The bag cell peptide is secreted by Aplysia’s neuroendocrine bag cells and provides feedback regulation of bag cell excitability and cAMP levels. Therefore, bag cell peptides may be used to treat cancer and neurological related diseases.

Reference

1. Dudek, F. E., & Tobe, S. S. (1978). Bag cell peptide acts directly on ovotestis of Aplysia californica: basis for an in vitro bioassay. General and comparative endocrinology, 36(4), 618-627.