Classification of Cushing's syndrome PKAc mutants based upon their ability to bind PKI

Omar, Mitchell H, Kihiu, Maryanne, Byrne, Dominic P, Lee, Kyung-Soon, Lakey, Tyler M, Butcher, Erik, Eyers, Patrick A ORCID: 0000-0002-9220-2966 and Scott, John D (2023) Classification of Cushing's syndrome PKAc mutants based upon their ability to bind PKI. BIOCHEMICAL JOURNAL, 480 (12). pp. 875-890.

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Abstract

Cushing's syndrome is an endocrine disorder caused by excess production of the stress hormone cortisol. Precision medicine strategies have identified single allele mutations within the PRKACA gene that drive adrenal Cushing's syndrome. These mutations promote perturbations in the catalytic core of protein kinase A (PKAc) that impair autoinhibition by regulatory subunits and compartmentalization via recruitment into AKAP signaling islands. PKAcL205R is found in ∼45% of patients, whereas PKAcE31V, PKAcW196R, and L198insW and C199insV insertion mutants are less prevalent. Mass spectrometry, cellular, and biochemical data indicate that Cushing's PKAc variants fall into two categories: those that interact with the heat-stable protein kinase inhibitor PKI, and those that do not. In vitro activity measurements show that wild-type PKAc and W196R activities are strongly inhibited by PKI (IC50 < 1 nM). In contrast, PKAcL205R activity is not blocked by the inhibitor. Immunofluorescent analyses show that the PKI-binding variants wild-type PKAc, E31V, and W196R are excluded from the nucleus and protected against proteolytic processing. Thermal stability measurements reveal that upon co-incubation with PKI and metal-bound nucleotide, the W196R variant tolerates melting temperatures 10°C higher than PKAcL205. Structural modeling maps PKI-interfering mutations to a ∼20 Å diameter area at the active site of the catalytic domain that interfaces with the pseudosubstrate of PKI. Thus, Cushing's kinases are individually controlled, compartmentalized, and processed through their differential association with PKI.

Item Type:	Article
Uncontrolled Keywords:	Humans, Cushing Syndrome, Cyclic AMP-Dependent Protein Kinases, Catalytic Domain, Mutation
Divisions:	Faculty of Health and Life Sciences Faculty of Health and Life Sciences > Institute of Systems, Molecular and Integrative Biology
Depositing User:	Symplectic Admin
Date Deposited:	02 Oct 2023 09:24
Last Modified:	02 Oct 2023 09:25
DOI:	10.1042/BCJ20230183
Open Access URL:	https://doi.org/10.1042/BCJ20230183
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3173273