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Site-specific O -Glycosylation by Polypeptide N -Acetylgalactosaminyltransferase 2 (GalNAc-transferase T2) Co-regulates β 1 -Adrenergic Receptor N-terminal Cleavage.

Authors :
Goth CK
Tuhkanen HE
Khan H
Lackman JJ
Wang S
Narimatsu Y
Hansen LH
Overall CM
Clausen H
Schjoldager KT
Petäjä-Repo UE
Source :
The Journal of biological chemistry [J Biol Chem] 2017 Mar 17; Vol. 292 (11), pp. 4714-4726. Date of Electronic Publication: 2017 Feb 06.
Publication Year :
2017

Abstract

The β <subscript>1</subscript> -adrenergic receptor (β <subscript>1</subscript> AR) is a G protein-coupled receptor (GPCR) and the predominant adrenergic receptor subtype in the heart, where it mediates cardiac contractility and the force of contraction. Although it is the most important target for β-adrenergic antagonists, such as β-blockers, relatively little is yet known about its regulation. We have shown previously that β <subscript>1</subscript> AR undergoes constitutive and regulated N-terminal cleavage participating in receptor down-regulation and, moreover, that the receptor is modified by O -glycosylation. Here we demonstrate that the polypeptide GalNAc-transferase 2 (GalNAc-T2) specifically O -glycosylates β <subscript>1</subscript> AR at five residues in the extracellular N terminus, including the Ser-49 residue at the location of the common S49G single-nucleotide polymorphism. Using in vitro O -glycosylation and proteolytic cleavage assays, a cell line deficient in O -glycosylation, GalNAc-T-edited cell line model systems, and a GalNAc-T2 knock-out rat model, we show that GalNAc-T2 co-regulates the metalloproteinase-mediated limited proteolysis of β <subscript>1</subscript> AR. Furthermore, we demonstrate that impaired O -glycosylation and enhanced proteolysis lead to attenuated receptor signaling, because the maximal response elicited by the βAR agonist isoproterenol and its potency in a cAMP accumulation assay were decreased in HEK293 cells lacking GalNAc-T2. Our findings reveal, for the first time, a GPCR as a target for co-regulatory functions of site-specific O -glycosylation mediated by a unique GalNAc-T isoform. The results provide a new level of β <subscript>1</subscript> AR regulation that may open up possibilities for new therapeutic strategies for cardiovascular diseases.<br /> (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)

Details

Language :
English
ISSN :
1083-351X
Volume :
292
Issue :
11
Database :
MEDLINE
Journal :
The Journal of biological chemistry
Publication Type :
Academic Journal
Accession number :
28167537
Full Text :
https://doi.org/10.1074/jbc.M116.730614