Bioactivity of the putative apelin proprotein expands the repertoire of apelin receptor ligands. Biochim Biophys Acta Gen Subj 2017 Aug;1861(8):1901-1912
Date
05/27/2017Pubmed ID
28546009Pubmed Central ID
PMC5770203DOI
10.1016/j.bbagen.2017.05.017Scopus ID
2-s2.0-85019764185 (requires institutional sign-in at Scopus site) 24 CitationsAbstract
BACKGROUND: Apelin is a peptide ligand for a class A G-protein coupled receptor called the apelin receptor (AR or APJ) that regulates angiogenesis, the adipoinsular axis, and cardiovascular functions. Apelin has been shown to be bioactive as 13, 17, and 36 amino acid isoforms, C-terminal fragments of the putatively inactive 55-residue proprotein (proapelin or apelin-55). Although intracellular proprotein processing has been proposed, isolation of apelin-55 from colostrum and milk demonstrates potential for secretion prior to processing and the possibility of proapelin-AR interaction.
METHODS: Apelin isoform activity and potency were compared by an In-Cell Western™ assay for ERK phosphorylation using a stably AR-transfected HEK293A cell line. Conformational comparison of apelin isoforms was carried out by circular dichroism and heteronuclear solution-state nuclear magnetic resonance spectroscopy.
RESULTS: Apelin-55 is shown to activate the AR, with similar maximum ERK phophorylation response and potency to the shorter isoforms except for apelin-13, which exhibited a greater potency. Correlating to this shared activity, highly similar conformations are exhibited in all apelin isoforms for the shared C-terminal region responsible for receptor binding and activation.
CONCLUSIONS: AR activation by all apelin isoforms likely hinges upon shared conformation and dynamics in the C-terminus, with apelin-55 providing an alternative bioactive isoform despite the addition of 19N-terminal residues relative to apelin-36.
GENERAL SIGNIFICANCE: Beyond providing novel insight into the physiology of this system, re-annotation of proapelin to the bioactive apelin-55 isoform adds to the molecular toolkit for dissection of apelin-AR interactions and expands the repertoire of therapeutic targets for the apelinergic system.
Author List
Shin K, Chapman NA, Sarker M, Kenward C, Huang SK, Weatherbee-Martin N, Pandey A, Dupré DJ, Rainey JKAuthor
Kyungsoo Shin PhD Assistant Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
ApelinApelin Receptors
Extracellular Signal-Regulated MAP Kinases
HEK293 Cells
Humans
Intercellular Signaling Peptides and Proteins
Ligands
Magnetic Resonance Spectroscopy
Phosphorylation
Protein Conformation
Protein Isoforms
Protein Precursors
Receptors, G-Protein-Coupled
Structure-Activity Relationship
