scholarly journals PKA Cα subunit mutation triggers caspase-dependent RIIβ subunit degradation via Ser114 phosphorylation

2021 ◽  
Vol 7 (8) ◽  
pp. eabd4176
Author(s):  
Isabel Weigand ◽  
Cristina L. Ronchi ◽  
Jens T. Vanselow ◽  
Kerstin Bathon ◽  
Kerstin Lenz ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cushing’S Syndrome ◽  
Molecular Mechanisms ◽  
Cushing's Syndrome ◽  
Regulatory Subunit ◽  
Cortisol Secretion ◽  
Adrenocortical Cells ◽  
Protein Levels ◽  
Adrenocortical Adenomas ◽  
Kinase A

Mutations in the PRKACA gene are the most frequent cause of cortisol-producing adrenocortical adenomas leading to Cushing’s syndrome. PRKACA encodes for the catalytic subunit α of protein kinase A (PKA). We already showed that PRKACA mutations lead to impairment of regulatory (R) subunit binding. Furthermore, PRKACA mutations are associated with reduced RIIβ protein levels; however, the mechanisms leading to reduced RIIβ levels are presently unknown. Here, we investigate the effects of the most frequent PRKACA mutation, L206R, on regulatory subunit stability. We find that Ser114 phosphorylation of RIIβ is required for its degradation, mediated by caspase 16. Last, we show that the resulting reduction in RIIβ protein levels leads to increased cortisol secretion in adrenocortical cells. These findings reveal the molecular mechanisms and pathophysiological relevance of the R subunit degradation caused by PRKACA mutations, adding another dimension to the deregulation of PKA signaling caused by PRKACA mutations in adrenal Cushing’s syndrome.

scholarly journals Structural insights into mis-regulation of protein kinase A in human tumors

2015 ◽  
Vol 112 (5) ◽  
pp. 1374-1379 ◽  
Author(s):  
Jonah Cheung ◽  
Christopher Ginter ◽  
Michael Cassidy ◽  
Matthew C. Franklin ◽  
Michael J. Rudolph ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Cushing’S Syndrome ◽  
Biochemical Characterization ◽  
Cushing's Syndrome ◽  
Regulatory Subunit ◽  
Recurrent Mutations ◽  
Distinct Disease ◽  
Genomic Studies ◽  
Kinase A

The extensively studied cAMP-dependent protein kinase A (PKA) is involved in the regulation of critical cell processes, including metabolism, gene expression, and cell proliferation; consequentially, mis-regulation of PKA signaling is implicated in tumorigenesis. Recent genomic studies have identified recurrent mutations in the catalytic subunit of PKA in tumors associated with Cushing’s syndrome, a kidney disorder leading to excessive cortisol production, and also in tumors associated with fibrolamellar hepatocellular carcinoma (FL-HCC), a rare liver cancer. Expression of a L205R point mutant and a DnaJ–PKA fusion protein were found to be linked to Cushing's syndrome and FL-HCC, respectively. Here we reveal contrasting mechanisms for increased PKA signaling at the molecular level through structural determination and biochemical characterization of the aberrant enzymes. In the Cushing’s syndrome disorder, we find that the L205R mutation abolishes regulatory-subunit binding, leading to constitutive, cAMP-independent signaling. In FL-HCC, the DnaJ–PKA chimera remains under regulatory subunit control; however, its overexpression from the DnaJ promoter leads to enhanced cAMP-dependent signaling. Our findings provide a structural understanding of the two distinct disease mechanisms and they offer a basis for designing effective drugs for their treatment.

scholarly journals Cushing’s syndrome driver mutation disrupts protein kinase A allosteric network, altering both regulation and substrate specificity

2019 ◽  
Vol 5 (8) ◽  
pp. eaaw9298 ◽  
Author(s):  
Caitlin Walker ◽  
Yingjie Wang ◽  
Cristina Olivieri ◽  
Adak Karamafrooz ◽  
Jordan Casby ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Substrate Specificity ◽  
Protein Kinase A ◽  
Cushing’S Syndrome ◽  
Genetic Alterations ◽  
Cushing's Syndrome ◽  
Single Mutation ◽  
Α Subunit ◽  
Adrenocortical Adenomas ◽  
Kinase A

Genetic alterations in the PRKACA gene coding for the catalytic α subunit of the cAMP-dependent protein kinase A (PKA-C) are linked to cortisol-secreting adrenocortical adenomas, resulting in Cushing’s syndrome. Among those, a single mutation (L205R) has been found in up to 67% of patients. Because the x-ray structures of the wild-type and mutant kinases are essentially identical, the mechanism explaining aberrant function of this mutant remains under active debate. Using NMR spectroscopy, thermodynamics, kinetic assays, and molecular dynamics simulations, we found that this single mutation causes global changes in the enzyme, disrupting the intramolecular allosteric network and eliciting losses in nucleotide/pseudo-substrate binding cooperativity. Remarkably, by rewiring its internal allosteric network, PKA-CL205R is able to bind and phosphorylate non-canonical substrates, explaining its changes in substrate specificity. Both the lack of regulation and change in substrate specificity reveal the complex role of this mutated kinase in the formation of cortisol-secreting adrenocortical adenomas.

scholarly journals PRKAR1A gene analysis and protein kinase A activity in endometrial tumors

2012 ◽  
Vol 19 (4) ◽  
pp. 457-462 ◽  
Author(s):  
A Tsigginou ◽  
E Bimpaki ◽  
M Nesterova ◽  
A Horvath ◽  
S Boikos ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Regulatory Subunit ◽  
Normal Endometrium ◽  
Protein Levels ◽  
Normal Tissues ◽  
Subunit Expression ◽  
Dependent Protein ◽  
Pka Regulatory Subunit ◽  
Kinase A

PRKAR1A codes for the type 1a regulatory subunit (RIα) of the cAMP-dependent protein kinase A (PKA), an enzyme with an important role in cell cycle regulation and proliferation. PKA dysregulation has been found in various tumors, and PRKAR1A-inactivating mutations have been reported in mostly endocrine neoplasias. In this study, we investigated PKA activity and the PRKAR1A gene in normal and tumor endometrium. Specimens were collected from 31 patients with endometrial cancer. We used as controls 41 samples of endometrium that were collected from surrounding normal tissues or from women undergoing gynecological operations for other reasons. In all samples, we sequenced the PRKAR1A-coding sequence and studied PKA subunit expression; we also determined PKA activity and cAMP binding. PRKAR1A mutations were not found. However, PKA regulatory subunit protein levels, both RIα and those of regulatory subunit type 2b (RIIβ), were lower in tumor samples; cAMP binding was also lower in tumors compared with normal endometrium (P<0.01). Free PKA activity was higher in tumor samples compared with that of control tissue (P<0.01). There are significant PKA enzymatic abnormalities in tumors of the endometrium compared with surrounding normal tissue; as these were not due to PRKAR1A mutations, other mechanisms affecting PKA function ought to be explored.

scholarly journals Noncanonical protein kinase A activation by oligomerization of regulatory subunits as revealed by inherited Carney complex mutations

2021 ◽  
Vol 118 (21) ◽  
pp. e2024716118
Author(s):  
Naeimeh Jafari ◽  
Jason Del Rio ◽  
Madoka Akimoto ◽  
Jung Ah Byun ◽  
Stephen Boulton ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Molecular Mechanisms ◽  
Carney Complex ◽  
Regulatory Subunit ◽  
Regulatory Subunits ◽  
Inhibitory Function ◽  
Wide Range ◽  
Liver Cancers ◽  
Kinase A

Familial mutations of the protein kinase A (PKA) R1α regulatory subunit lead to a generalized predisposition for a wide range of tumors, from pituitary adenomas to pancreatic and liver cancers, commonly referred to as Carney complex (CNC). CNC mutations are known to cause overactivation of PKA, but the molecular mechanisms underlying such kinase overactivity are not fully understood in the context of the canonical cAMP-dependent activation of PKA. Here, we show that oligomerization-induced sequestration of R1α from the catalytic subunit of PKA (C) is a viable mechanism of PKA activation that can explain the CNC phenotype. Our investigations focus on comparative analyses at the level of structure, unfolding, aggregation, and kinase inhibition profiles of wild-type (wt) PKA R1α, the A211D and G287W CNC mutants, as well as the cognate acrodysostosis type 1 (ACRDYS1) mutations A211T and G287E. The latter exhibit a phenotype opposite to CNC with suboptimal PKA activation compared with wt. Overall, our results show that CNC mutations not only perturb the classical cAMP-dependent allosteric activation pathway of PKA, but also amplify significantly more than the cognate ACRDYS1 mutations nonclassical and previously unappreciated activation pathways, such as oligomerization-induced losses of the PKA R1α inhibitory function.

Is disrupted nucleotide-substrate cooperativity a common trait for Cushing's syndrome driving mutations of protein kinase A?

2021 ◽  
pp. 167123
Author(s):  
Caitlin Walker ◽  
Yingjie Wang ◽  
Cristina Olivieri ◽  
Manu V.S ◽  
Jiali Gao ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Cushing’S Syndrome ◽  
Cushing's Syndrome ◽  
Kinase A
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