title: Depletion of type IA regulatory subunit (RIalpha) of protein kinase A (PKA) in mammalian cells and tissues activates mTOR and causes autophagic deficiency.
abstract: The human PRKAR1A gene encodes the regulatory subunit 1-alpha (RIalpha) of the cAMP-dependent protein kinase A (PKA) holoenzyme. Regulation of the catalytic activity of PKA is the only well-studied function of RIalpha. Inactivating PRKAR1A mutations cause primary pigmented nodular adrenocortical disease (PPNAD) or Carney complex (CNC), an inherited syndrome associated with abnormal skin pigmentation and multiple neoplasias, including PPNAD. Histochemistry of tissues from CNC patients is indicative of autophagic deficiency and this led us to investigate the relationship between RIalpha and mammalian autophagy. We found that fluorescently tagged RIalpha associates with late endosomes and autophagosomes in cultured cells. The number of autophagosomes in prkar1a-/- mouse embryonic fibroblasts (MEFs) was reduced compared with wild-type MEFs. RIalpha co-immunoprecipitated with mTOR kinase, a major regulator of autophagy. Phosphorylated-mTOR levels and mTOR activity were dramatically increased in prkar1a-/- mouse cells, and in HEK 293 cells with RIalpha levels reduced by siRNA. Finally, phosphorylated-mTOR levels and mTOR activity were increased in CNC cells and in PPNAD tissues. These data suggest that RIalpha deficiency decreases autophagy by the activation of mTOR, providing a molecular basis to autophagic deficiency in PPNAD.
authors.affiliation: Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA. mavrakim@mail.nih.gov
authors.forename: Manos
authors.initials: M
authors.lastname: Mavrakis
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lippincott-Schwartz
authors.forename: Constantine A
authors.initials: CA
authors.lastname: Stratakis
authors.forename: Ioannis
authors.initials: I
authors.lastname: Bossis
mesh_terms: D000303:Adrenal Cortex Diseases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001343:Autophagy / Q000502:physiology*; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000172:deficiency* / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D010588:Phagosomes / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D058570:TOR Serine-Threonine Kinases
chemical_list: D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D018076:DNA, Complementary; C517834:PRKAR1A protein, human; C517835:Prkar1a protein, mouse; D011506:Proteins; D034741:RNA, Small Interfering; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases