Selective modulation of protein kinase A I and II reveals distinct roles in thyroid cell gene expression and growth.
A global gene expression profiling of TSH stimulation on differentiated (FRTL5) and partially dedifferentiated [FRT/TSHR (TSH receptor)] rat thyroid cells was performed. A total of 123 TSH-regulated genes (95 newly described) were identified in FRTL5, whereas no significant transcriptional modifications were seen in FRT/TSHR cells. Because regulatory subunit IIbeta (RIIbeta) of protein kinase A (PKA), a key element downstream of cAMP, was expressed in FRTL5 but not in cAMP-refractory FRT/TSHR cells, we hypothesized that this gene may play an important role in TSH signaling. We therefore performed a series of experiments to investigate the involvement of RIIbeta and the different PKA isoforms. A positive effect of PKA II- but not of PKA I-selective activation on gene transcription and proliferation in FRTL5 cells, as well as an impairment of TSH nuclear effects after RIIbeta silencing were observed, suggesting that PKA II plays an essential role in TSH signaling. This view was supported by the restoration of TSH nuclear effects after reexpression of RIIbeta in FRT/TSHR cells. Because PKA I stimulation could increase iodide uptake in FRTL5 cells without affecting gene transcription, PKA I may mediate TSH actions at posttranscriptional levels. Analyses on three human cancer cell lines confirmed the possible loss of RIIbeta expression and antiproliferative activity of PKA I-selective cAMP analogs ( approximately 60% at 200 microm in BRAF-mutated cells). The inhibitory effect of PKA I apparently required constitutive MAPK activation and was associated with an inhibition of ERK phosphorylation. These findings may open new therapeutic perspectives in patients with thyroid cancer.
Calebiro
Davide
D
Department of Medical Sciences, University of Milan, Milan, Italy.
de Filippis
Tiziana
T
Lucchi
Simona
S
Martinez
Fernando
F
Porazzi
Patrizia
P
Trivellato
Roberta
R
Locati
Massimo
M
Beck-Peccoz
Paolo
P
Persani
Luca
L
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000502:physiology*; D004789:Enzyme Activation; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
D054754:Cyclic AMP-Dependent Protein Kinase RIIalpha Subunit; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; C517834:PRKAR1A protein, human; C517819:PRKAR2A protein, human; C517837:PRKAR2B protein, human; C517836:Prkar1a protein, rat; C517822:Prkar2a protein, rat; C517839:Prkar2b protein, rat; D011506:Proteins; D013972:Thyrotropin; D017868:Cyclic AMP-Dependent Protein Kinases