Endogenous protein kinase inhibitor gamma terminates immediate-early gene expression induced by cAMP-dependent protein kinase (PKA) signaling: termination depends on PKA inactivation rather than PKA export from the nucleus.
Expression of many genes induced by cAMP-dependent protein kinase (PKA) signaling is rapidly terminated. Although many mechanisms contribute to regulation of PKA signaling, members of the endogenous protein kinase inhibitor (PKI) family may be particularly important for terminating nuclear PKA activity and gene expression. Here we used both siRNA and antisense knockdown strategies to examine PKA signaling activated by parathyroid hormone or the beta-adrenergic agonist, isoproterenol. We found that endogenous PKIgamma is required for efficient termination of nuclear PKA activity, transcription factor phosphorylation, and immediate-early genes. Moreover, PKIgamma is required for export of PKA catalytic subunits from the nucleus back to the cytoplasm following activation of PKA signaling because this is also inhibited by PKIgamma knockdown. Leptomycin B blocks PKA nuclear export but has little or no effect on nuclear PKA activity or immediate-early gene expression. Thus, inactivation of PKA activity in the nucleus is sufficient to terminate signaling, and nuclear export is not required. These results were the first in any cell type showing that endogenous levels of PKI regulate PKA signaling.
Chen
Xin
X
Orthopaedics, Pediatrics, Physiology and Biophysics, and Pathology, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, Ohio 44106-5000, USA.
Dai
Jia-Chun
JC
Orellana
Stephanie A
SA
Greenfield
Edward M
EM
D021581:Active Transport, Cell Nucleus; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D015153:Blotting, Western; D002384:Catalysis; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003470:Culture Media / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D016376:Oligonucleotides, Antisense / Q000737:chemistry; D010281:Parathyroid Hormone / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic
D000935:Antifungal Agents; D003470:Culture Media; D018076:DNA, Complementary; D005231:Fatty Acids, Unsaturated; D047908:Intracellular Signaling Peptides and Proteins; D016376:Oligonucleotides, Antisense; C107592:PKIG protein, human; D010281:Parathyroid Hormone; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; C038753:leptomycin B