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Endocrine Abstracts (2018) 56 OC5.3 | DOI: 10.1530/endoabs.56.OC5.3

1Division of Endocrinology and Diabetes, University Hospital, Würzburg, Germany; 2Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK; 3Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany; 4Central Laboratory, University Hospital, Würzburg, Germany; 5Institute of Pharmacology and Toxicology and Bioimaging Center, University of Würzburg, Würzburg, Germany; 6Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Birmingham, Nottingham, UK.


Protein Kinase A (PKA) consists of two catalytic and two regulatory subunits with several isoforms (Cα, β, γ and RIα, IIα, Iβ, IIβ, respectively). Type II regulatory subunits are phosphorylated by PKA in their inhibitory sites, while type I are not. Somatic activating mutations in the gene encoding the catalytic subunit α (Cα) of PKA (PRKACA) have been found in 30–40% of cortisol-producing adrenocortical adenomas (CPA). We recently described reduced levels of RIIβ in PRKACA-mutated CPA compared to PRKACA WT CPA. In NCI-H295R cells co-transfected with RIIβ and CαWT or CαL206R, the L206R mutation led to a full degradation of RIIβ and this degradation could not be reversed by proteasome and lysosome inhibition but by caspase inhibition. Same co-transfections with RIα did not lead to its degradation. When the inhibitory site of RIIβ was replaced by the corresponding amino acids of RIα, CαL206R did not lead to RIIβ degradation, while it was able to degrade RIα when its inhibitory site was replaced by the corresponding amino acids of RIIβ. Same results were observed when point mutations were introduced into RIIβ or RIα in order to delete or introduce a serine into the inhibitory site (serine 114). In addition, a protein interacting with RIIβ only in CαL206R–transfected cells was identified by performing nanoLC-MS/MS analysis and interestingly, this protein is known to interact with caspases. Furthermore, a knockdown of RIIβ led to increased cortisol secretion in NCI-H295R cells. These results show that the phosphorylation of serine 114 in the inhibitory site of RIIβ plays a fundamental role in RIIβ stability and makes RIIβ susceptible for degradation in the presence of CαL206R, which is likely mediated by caspases. The resulting decreased levels of RIIβ could additionally contribute to increased cortisol levels in Cushing adenoma patients.

Volume 56

20th European Congress of Endocrinology

Barcelona, Spain
19 May 2018 - 22 May 2018

European Society of Endocrinology 

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