Structure and functions of spexin as a new neuroendocrine signal

Abstract

Spexin (SPX) is a recently discovered endogenous peptide consisting of 14 amino acids. It was found that SPX, kisspeptin (KISS), and galanin (GAL) peptides belong to the same gene family and are also endogenous ligands of GAL2 and GAL3 receptors. The amino acid sequence of the SPX peptide is relatively conserved in vertebrates and invertebrates. The mRNA and protein of SPX are highly expressed both in peripheral organs and in the peripheral/central nervous system of mammals, birds, and fishes. Many biological roles of SPX has been found in non-mammal/mammals, including food intake, energy metabolism, reproduction, nociception, gastrointestinal motility, stress, and endocrine functions. This review collectively mentions the peptide structure of SPX, its receptors and distribution in tissues, and the biological activities of SPX on various organs.