Sumoylation of the β₂ARinfluences receptor internalisation, desensitisation and downstream signaling

J. Ling¹, L. Wills², G. Baillie¹. ¹Institute of Cardiovascular and Medical Science, Glasgow, United Kingdom, ²Cardiovascular research center mount sinai, New York.

Introduction: Beta 2 adrenergic receptor (β₂AR) signalling can be modulated by a variety of post-translational modifications (PTMs) which include phosphorylation, ubiquitination, palmitoylation and glycosylation [1]. Following sequence analysis of the β₂AR, we discovered a putative site for SUMOylation, a previously unknown type of modification for this receptor. Our aim was to verify whether the β₂AR can be SUMOylated and how this modification affects receptor signaling and desensitization.

Method: Using peptide array we have delineated a putative SUMO site on β₂AR. Using both wild type and SUMO-null β₂AR mutants we have investigated downstream signaling of the β₂AR using western blotting. We have “forced” SUMOylation of the receptor via overexpression of the SUMO E3 ligase PIASy.

Results: We have identified a novel site of SUMOylation on the β₂AR and shown that this modification robustly alters downstream signaling in a model cell-line. Specifically, we have demonstrated that SUMOylation reduces β₂AR phosphorylation by PKA, altering the receptor driven phospho-ERK response, inhibits β₂AR ubiquitination and degradation, and delays β₂AR internalisation.

Conclusion: 10.0pt;We report for the first time that the β₂AR can be SUMOylated and that this retards desensitization and receptor degradation. We speculate that this mechanism may be relevant to heart disease and have developed a β₂AR SUMO-site specific antibody to investigate this possibility.

References:

1. Shenoy S et al. (2006). J Bio Chem 1261-1273.