In vitro functional studies of naturally occurring pathogenic PRKAR1A mutations that are not subject to nonsense mRNA decay.
Patients presenting with primary pigmented nodular adrenocortical disease (PPNAD), Carney complex (CNC), or sporadic tumors were previously found to carry germline mutations in the human type Ialpha regulatory subunit (RIalpha) of adenosine 3',5'-cyclic monophosphate (cyclic AMP [cAMP])-dependent protein kinase (PKA; PRKAR1A). Although about 90% of disease-causing PRKAR1A mutations lead to premature stop codon generation and subsequent degradation of the mutant message by nonsense-mediated mRNA decay (NMD), here we describe seven PRKAR1A mutations whose mRNAs do not seem to undergo NMD and instead result in an expressed mutant RIalpha protein. The expressed mutations (p.Ser9Asn, p.Glu60_Lys116del [Delta-exon 3], p.Arg74Cys, p.Arg146Ser, p.Asp183Tyr, p.Ala213Asp, and p.Gly289Trp) were spread over all the functional RIalpha domains, and all of them exhibited increased PKA activity, which we attribute to decreased binding to cAMP and/or the catalytic subunit. Our data further corroborate the previous finding that altered PRKAR1A function, not only haploinsufficiency, is enough to elevate PKA activity which is apparently associated with tumorigenesis in tissues affected by CNC. In some cases, as with the Delta-exon 3 mutation, we may even conclude that the presence of a mutant PRKAR1A protein may be more harmful than allelic loss.
Greene
Elizabeth L
EL
Section on Endocrinology & Genetics, Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Horvath
Anelia D
AD
Nesterova
Maria
M
Giatzakis
Christoforos
C
Bossis
Ioannis
I
Stratakis
Constantine A
CA
D001483:Base Sequence; D002460:Cell Line; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit / Q000235:genetics*; D017931:DNA Primers; D018095:Germ-Line Mutation; D006801:Humans; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics*
D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017931:DNA Primers; C517834:PRKAR1A protein, human; D012333:RNA, Messenger