title: Apela exhibits isoform- and headgroup-dependent modulation of micelle binding, peptide conformation and dynamics.
abstract: Apela (also referred to as ELABELA and toddler) is a peptide hormone that activates the apelin receptor (AR or APJ) to regulate cardiovascular system development and function. Here, we report the first biophysical characterization of three apela isoforms, apela-54, -32, and -11, alongside a monomeric C1S-apela-11 mutant, using circular dichroism (CD) spectropolarimetry and nuclear magnetic resonance (NMR) spectroscopy. The behaviour of apela-54 is consistent with a preprotein containing a hydrophobic, N-terminal signal peptide. The potential for apela-membrane binding, leading to membrane catalyzed interactions with AR, was tested comprehensively for apela-32 and -11 in the presence of membrane-mimetic dodecylphosphocholine (DPC), sodium dodecyl sulfate (SDS), and 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LPPG) micelles. According to pulsed-field gradient diffusion NMR experiments, apela-32 interacts with all three micelles. Chemical shift perturbations indicate widespread interactions along apela, with DPC and LPPG micelles inducing short segments with α-helical character at distinct regions. Consistent with these data, ps-ns dynamics along the peptide backbone appear decreased in the presence of micelles. Apela-11 and C1S-apela-11, alternatively, interact preferentially with SDS and LPPG micelles, promoting β-turn character observable by CD. Distinct differences in membrane-interaction propensity are therefore apparent both as a function of apela isoform and of detergent headgroup. These results imply the potential for cell membrane involvement in apela-AR recognition and binding, with the implication that membrane catalysis has distinct functional and regulatory roles throughout the apelinergic system.
authors.affiliation: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Shuya K
authors.initials: SK
authors.lastname: Huang
authors.affiliation: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Kyungsoo
authors.initials: K
authors.lastname: Shin
authors.affiliation: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Muzaddid
authors.initials: M
authors.lastname: Sarker
authors.affiliation: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. Electronic address: jan.rainey@dal.ca.
authors.forename: Jan K
authors.initials: JK
authors.lastname: Rainey
mesh_terms: D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D036361:Peptide Hormones / Q000737:chemistry*; D011487:Protein Conformation; D020033:Protein Isoforms; D017433:Protein Structure, Secondary
chemical_list: C000601133:APELA protein, human; D008823:Micelles; D036361:Peptide Hormones; D020033:Protein Isoforms
keywords: Apela; Apelin receptor (APJ); Class A GPCR; Membrane catalysis; NMR spectroscopy; Peptide-micelle interactions