PRKAR1A Mutations and protein kinase A interactions with other signaling pathways in the adrenal cortex.
BACKGROUND
Primary pigmented nodular adrenocortical disease, associated with Carney complex, is caused by mutations in PRKAR1A (mt-PRKAR1A), a gene that codes for the regulatory subunit type 1alpha (RIalpha) of cAMP-dependent protein kinase (PKA). PRKAR1A inactivation is associated with dysregulated PKA activity that is thought to result in tumorigenesis. mt-PRKAR1A-bearing lymphocytes from Carney complex patients exhibit enhanced cell proliferation associated with increased expression of the MAPK ERK1/2 pathway.


OBJECTIVE
The objective of the study was to determine how PKA and its subunits and ERK1/2 and their molecular partners change in the presence of PRKAR1A mutations in adrenocortical tissue.


METHODS
PKA activity and subunit expression, ERK1/2, other immunoassays, and immunohistochemistry on adrenocortical samples from patients with germline normal or mt-PRKAR1A were analyzed.


RESULTS
Increased cAMP-stimulated total kinase activity was associated with mt-PRKAR1A. PKA subunit expression analysis in mt-PRKAR1A tissues, by quantitative mRNA assay and immunoblotting, showed a 2.4-fold (P = 0.02) and 1.8-fold (P = 0.09) decrease in RIalpha's message and protein, respectively, and increases in other PKA subunits. Immunoassays showed 2-fold (P = 0.03) and 6-fold (P = 0.03) decreases in baseline ERK1/2, with corresponding increases in phosphorylated (p) ERK1/2 in mt-PRKAR1A samples. B-raf kinase, p-MEK1/2, and p-c-Myc, but not p-Akt/protein kinase B, were significantly increased. Immunohistochemistry studies supported these data.


CONCLUSIONS
mt-PRKAR1A causes increased total cAMP-stimulated kinase activity, likely the result of up-regulation of other PKA subunits caused by down-regulation of RIalpha, as seen in human lymphocytes and mouse animal models. These changes, associated with enhanced MAPK activity, may be, in part, responsible for the proliferative signals that result in primary pigmented nodular adrenocortical disease.
Section on Endocrinology and Genetics, and Pediatric Endocrinology Training Program, Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Audrey
A
Robinson-White
Elise
E
Meoli
Sotirios
S
Stergiopoulos
Anelia
A
Horvath
Sosipatros
S
Boikos
Ioannis
I
Bossis
Constantine A
CA
Stratakis
D000302:Adrenal Cortex / Q000378:metabolism*; D000328:Adult; D002648:Child; D002675:Child, Preschool; D000242:Cyclic AMP / Q000502:physiology; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000502:physiology*
D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; C517834:PRKAR1A protein, human; C517835:Prkar1a protein, mouse; D012333:RNA, Messenger; D000242:Cyclic AMP; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases