TY - JOUR
T1 - Induction of specific phosphodiesterase isoforms by constitutive activation of the cAMP pathway in autonomous thyroid adenomas
AU - Persani, Luca
AU - Lania, Andrea
AU - Alberti, Luisella
AU - Romoli, Roberto
AU - Mantovani, Giovanna
AU - Filetti, Sebastiano
AU - Spada, Anna
AU - Conti, Marco
PY - 2000
Y1 - 2000
N2 - Thyrocytes largely depend on cAMP signaling for replication and differentiation. This pathway may be constitutively activated by mutations of the TSH receptor (TSHR) and Gsα in autonomous thyroid adenomas (ATAs). Because steady state cAMP results from production by adenylyl cyclase and degradation by phosphodiesterases (PDEs), we evaluated PDE activity and expression in ATAs with wild-type and mutant TSHR and Gsα. Activating mutations of TSHR and Gsα were identified in 7 and 1 of 18 ATAs, respectively. No difference was observed in the cAMP content in ATAs with or without activating mutants. In the surrounding normal thyroid tissue (NTs), PDE activity was 80% isobutylmethylxanthine sensitive, with the major contribution by PDE1 and a minor contribution by PDE4. No differences were observed in PDE activities between NTs and ATAs with wild-type TSHR and Gsα. In contrast, in the presence of mutant TSHRs or Gsα, total PDE activity was higher. This increase was primarily due to PDE4 induction (917 ± 116% over NTs), associated with a minor PDE1 increase only in ATAs with mutant TSHR. By RT-PCR, increments of PDE4D and 4C messenger ribonucleic acids were found in the ATAs with mutant TSHR or Gsα, whereas messenger ribonucleic acids encoding other cAMP-specific PDEs were not significantly increased. This study provides a characterization of the PDEs expressed in human thyroid and demonstrates a dramatic PDE4 induction in the ATAs bearing mutant TSHR or Gsα genes. The increase in cAMP-degrading activity may represent a marker of constitutive adenylyl cyclase activation and constitutes an intracellular feedback mechanism with significant impact on the phenotypic expression of the activating mutations.
AB - Thyrocytes largely depend on cAMP signaling for replication and differentiation. This pathway may be constitutively activated by mutations of the TSH receptor (TSHR) and Gsα in autonomous thyroid adenomas (ATAs). Because steady state cAMP results from production by adenylyl cyclase and degradation by phosphodiesterases (PDEs), we evaluated PDE activity and expression in ATAs with wild-type and mutant TSHR and Gsα. Activating mutations of TSHR and Gsα were identified in 7 and 1 of 18 ATAs, respectively. No difference was observed in the cAMP content in ATAs with or without activating mutants. In the surrounding normal thyroid tissue (NTs), PDE activity was 80% isobutylmethylxanthine sensitive, with the major contribution by PDE1 and a minor contribution by PDE4. No differences were observed in PDE activities between NTs and ATAs with wild-type TSHR and Gsα. In contrast, in the presence of mutant TSHRs or Gsα, total PDE activity was higher. This increase was primarily due to PDE4 induction (917 ± 116% over NTs), associated with a minor PDE1 increase only in ATAs with mutant TSHR. By RT-PCR, increments of PDE4D and 4C messenger ribonucleic acids were found in the ATAs with mutant TSHR or Gsα, whereas messenger ribonucleic acids encoding other cAMP-specific PDEs were not significantly increased. This study provides a characterization of the PDEs expressed in human thyroid and demonstrates a dramatic PDE4 induction in the ATAs bearing mutant TSHR or Gsα genes. The increase in cAMP-degrading activity may represent a marker of constitutive adenylyl cyclase activation and constitutes an intracellular feedback mechanism with significant impact on the phenotypic expression of the activating mutations.
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U2 - 10.1210/jc.85.8.2872
DO - 10.1210/jc.85.8.2872
M3 - Article
C2 - 10946896
AN - SCOPUS:0034458407
VL - 85
SP - 2872
EP - 2878
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
SN - 0021-972X
IS - 8
ER -