Citation

  • Authors: Zhu J. et al.
  • Year: 2021
  • Journal: J Mol Cell Cardiol 154 70-79
  • Applications: in vitro / DNA / jetOPTIMUS
  • Cell types:
    1. Name: CHO-ldlD
    2. Name: CHO-pro5

Method

CHO-pro5 cells cultured in α-MEM + 5% FBS, 100 units/ml P-S and 100 mM glutamine. CHO-ldlD cells cultured in Ham's F-12 medium + 5% FBS, 100 units/ml P-S, 100 mM glutamine, either with or without Gal, 20 μM and GalNAc, 200 μM. Transfections were performed in 60 mm dishes with 1 μg cDNA of β1AR plasmid using jetOPTIMUS according to manufacturer's instructions.

Abstract

β1-adrenergic receptors (β1ARs) are the principle mediators of catecholamine action in cardiomyocytes. We previously showed that the β1AR extracellular N-terminus is a target for post-translational modifications that impact on signaling responses. Specifically, we showed that the β1AR N-terminus carries O-glycan modifications at Ser37/Ser41, that O-glycosylation prevents β1AR N-terminal cleavage, and that N-terminal truncation influences β1AR signaling to downstream effectors. However, the site(s) and mechanism for β1AR N-terminal cleavage in cells was not identified. This study shows that β1ARs are expressed in cardiomyocytes and other cells types as both full-length and N-terminally truncated species and that the truncated β1AR species is formed as a result of an O-glycan regulated N-terminal cleavage by ADAM17 at R31↓L32. We identify Ser41 as the major O-glycosylation site on the β1AR N-terminus and show that an O-glycan modification at Ser41 prevents ADAM17-dependent cleavage of the β1-AR N-terminus at S41↓L42, a second N-terminal cleavage site adjacent to this O-glycan modification (and it attenuates β1-AR N-terminal cleavage at R31↓L32). We previously reported that oxidative stress leads to a decrease in β1AR expression and catecholamine responsiveness in cardiomyocytes. This study shows that redox-inactivation of cardiomyocyte β1ARs is via a mechanism involving N-terminal truncation at R31↓L32 by ADAM17. In keeping with the previous observation that N-terminally truncated β1ARs constitutively activate an AKT pathway that affords protection against doxorubicin-dependent apoptosis, overexpression of a cleavage resistant β1AR mutant exacerbates doxorubicin-dependent apoptosis. These studies identify the β1AR N-terminus as a structural determinant of β1AR responses that can be targeted for therapeutic advantage.

Pubmed