Phosphorylation of the deubiquitinase USP20 by Protein Kinase A regulates post-endocytic trafficking of {beta} 2 adrenergic receptors to autophagosomes during physiological stress [Cell Biology]

February 9th, 2015 by Kommaddi, R. P., Jean-Charles, P.-Y., Shenoy, S. K.

Ubiquitination by the E3 ligase Nedd4 and deubiquitination by deubiquitinases (DUBs) USP20 and USP33 have been shown to regulate the lysosomal trafficking and recycling of agonist-activated β2ARs. In this work, we demonstrate that in cells subjected to physiological stress by nutrient starvation, agonist-activated ubiquitinated β2ARs traffic to autophagosomes to colocalize with the autophagy marker protein LC3-II. Furthermore, this trafficking is synchronized by dynamic post-translational modifications of USP20, which in turn are induced in a β2AR-dependent manner. Upon β2AR activation, a specific isoform of the second-messenger cAMP-dependent protein kinase A (PKAα) rapidly phosphorylates USP20 on serine333 located in its unique insertion domain. This phosphorylation of USP20 correlates with a characteristic SDS-PAGE mobility shift of the protein, blocks its deubiquitinase activity, promotes its dissociation from the activated β2AR complex and facilitates trafficking of the ubiquitinated β2AR to autophagosomes, which fuse with lysosomes to form autolysosomes where receptors are degraded. Dephosphorylation of USP20 has reciprocal effects and blocks trafficking of the β2AR to autophagosomes, while promoting plasma membrane recycling of internalized β2AR. Our findings reveal dynamic regulation of USP20 by site-specific phosphorylation as well as the interdependence of signal transduction and trafficking pathways in balancing adrenergic stimulation and maintaining cellular homeostasis.
  • Posted in Journal of Biological Chemistry, Publications
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