title: Structural insights into mis-regulation of protein kinase A in human tumors.
abstract: 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.
authors.affiliation: New York Structural Biology Center, New York, NY 10027; jcheung@nysbc.org wayne@xtl.cumc.columbia.edu.
authors.forename: Jonah
authors.initials: J
authors.lastname: Cheung
authors.affiliation: New York Structural Biology Center, New York, NY 10027;
authors.forename: Christopher
authors.initials: C
authors.lastname: Ginter
authors.affiliation: New York Structural Biology Center, New York, NY 10027;
authors.forename: Michael
authors.initials: M
authors.lastname: Cassidy
authors.affiliation: New York Structural Biology Center, New York, NY 10027;
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Franklin
authors.affiliation: New York Structural Biology Center, New York, NY 10027;
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rudolph
authors.affiliation: New York Genome Center, New York, NY 10013;
authors.forename: Nicolas
authors.initials: N
authors.lastname: Robine
authors.affiliation: New York Genome Center, New York, NY 10013; Howard Hughes Medical Institute and Laboratory of Molecular Neuro-Oncology, The Rockefeller University, New York, NY 10021; and.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Darnell
authors.affiliation: New York Structural Biology Center, New York, NY 10027; Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032 jcheung@nysbc.org wayne@xtl.cumc.columbia.edu.
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Hendrickson
mesh_terms: D020134:Catalytic Domain; D002850:Chromatography, Gel; D003460:Crystallization; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D009369:Neoplasms / Q000201:enzymology*; D011487:Protein Conformation; D020349:Surface Plasmon Resonance
chemical_list: D017868:Cyclic AMP-Dependent Protein Kinases
keywords: Cushing’s syndrome; cancer mutations; chimeric protein; fibrolamelllar hepatocellular carcinoma