β1-adrenergic receptor N-terminal cleavage by ADAM17; the mechanism for redox-dependent downregulation of cardiomyocyte β1-adrenergic receptors

J Mol Cell Cardiol. 2021 May:154:70-79. doi: 10.1016/j.yjmcc.2021.01.012. Epub 2021 Feb 6.

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.

Keywords: ADAM17; Cardiomyocytes; Glycosylation; Oxidant stress; β-Adrenergic receptor.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • ADAM17 Protein / metabolism*
  • Gene Expression
  • Glycosylation
  • Humans
  • Myocytes, Cardiac / metabolism*
  • Oxidation-Reduction*
  • Oxidative Stress
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Processing, Post-Translational
  • Proteolysis
  • Receptors, Adrenergic, beta-1 / chemistry
  • Receptors, Adrenergic, beta-1 / genetics
  • Receptors, Adrenergic, beta-1 / metabolism*

Substances

  • Receptors, Adrenergic, beta-1
  • ADAM17 Protein
  • ADAM17 protein, human