Open AccessKinetics and inhibition studies of the L205R mutant of cAMP ‐dependent protein kinase involved in Cushing's syndrome
Author(s) -
Luzi Nicole M.,
Lyons Charles E.,
Peterson Darrell L.,
Ellis Keith C.
Publication year - 2018
Publication title -
febs open bio
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.718
H-Index - 31
ISSN - 2211-5463
DOI - 10.1002/2211-5463.12396
Subject(s) - mutant , potency , protein kinase a , kinase , adrenocorticotropic hormone , protein subunit , mutation , chemistry , biochemistry , pharmacology , medicine , endocrinology , hormone , biology , in vitro , gene
Overproduction of cortisol by the hypothalamus–pituitary–adrenal hormone system results in the clinical disorder known as Cushing's syndrome. Genomics studies have identified a key mutation (L205R) in the α‐isoform of the catalytic subunit of cAMP ‐dependent protein kinase ( PKAC α) in adrenal adenomas of patients with adrenocorticotropic hormone‐independent Cushing's syndrome. Here, we conducted kinetics and inhibition studies on the L205R‐ PKAC α mutant. We have found that the L205R mutation affects the kinetics of both Kemptide and ATP as substrates, decreasing the catalytic efficiency ( k cat / K M ) for each substrate by 12‐fold and 4.5‐fold, respectively. We have also determined the IC 50 and K i for the peptide substrate‐competitive inhibitor PKI (5–24) and the ATP ‐competitive inhibitor H89. The L205R mutation had no effect on the potency of H89, but causes a > 250‐fold loss in potency for PKI (5–24). Collectively, these data provide insights for the development of L205R‐ PKAC α inhibitors as potential therapeutics.