Functional and Structural Characterization of Acrodysostosis Mutations of PKA RIα Reveals Mechanism Causing resistant to cAMP activation

Abstract

Acrodysostosis is a type of disease related to bone development which usually happened on gene PRKAR1A(PKA RIα) or PDE4D(PDE4D). Mutations in the PRKAR1A gene are linked to Carney complex disease (CNC) and Acrodysostosis‐1 (ACRDYS1) which show contrasting phenotypes. CNC mutations show increased protein kinase A (PKA) activity, whereas ACRDYS1 mutations result in decreased PKA activity and cAMP resistant holoenzymes. Here we characterize three ACRDYS1 mutants: Y371C, R366X and G198R biochemically and structurally to understand the molecular basis of Acrodysostosis disease mutants of PKA. The activation assay indicated that these three mutations show resistant to the cAMP activation, and almost complete loss of cooperativity for cAMP activation with a shift in the Hill coefficient from 1.7 in wild‐type to 1.2 in the mutants. The crystal structure of Y371C mutant at 3.36 Å resolution shows how PKA utilizes cyclic nucleotide‐binding (CNB) domains as building blocks to create a unique isoform‐specific homodimer interface, which agrees well with previously published wild‐type RIα structure. This structure also demonstrates the important role of Y371 which is essential for cAMP binding. The residues after Y371 are disordered in the mutant, and only one cyclic nucleotide ligand can be seen at its two CNB‐B sites. The molecular dynamics simulations show increased dynamics in Y371C mutant compared to wild type protein which agrees to the functional and structural results. These data allow us to better understand the molecular mechanism of Acrodysostosis and it might help the therapeutical and drugs development.Support or Funding InformationThis work was supported by NIH grant GM34921 (to S.S.T.).