Voigt Carsten, Holzapfel Hans-Peter, Meyer Silke, Paschke Ralf
IIIrd Medical Department, University of Leipzig, Ph.-Rosenthal-Str. 27, D-04103 Leipzig, Germany.
J Endocrinol. 2004 Jul;182(1):173-82. doi: 10.1677/joe.0.1820173.
G-protein-coupled receptor kinases (GRKs) are implicated in the pathophysiology of human diseases such as arterial hypertension, heart failure and rheumatoid arthritis. While G-protein-coupled receptor kinases 2 and 5 have been shown to be involved in the desensitization of the rat thyrotropin receptor (TSHR), their role in the pathophysiology of hyperfunctioning thyroid nodules (HTNs) is unknown. Therefore, we analyzed the expression pattern of the known GRKs in human thyroid tissue and investigated their function in the pathology of HTNs. The expression of different GRKs in human thyroid and HTNs was measured by Western blotting. The influence of GRK expression on TSHR function was analyzed by coexpression experiments in HEK 293 cells. We demonstrate that in addition to GRKs 2, 5 and 6, GRKs 3 and 4 are also expressed in the human thyroid. GRKs 2, 3, 5 and 6 are able to desensitize the TSHR in vitro. This GRK-induced desensitization is amplified by the additional over-expression of beta-arrestin 1 or 2. We did not find any mutations in the GRKs 2, 3 and 5 from 14 HTNs without TSHR mutations and Gsalpha mutations. The expression of GRKs 3 and 4 was increased in HTNs independently from the existence of TSHR mutations or Gsalpha mutations. In conclusion, the increased expression of GRK 3 in HTNs and the ability of GRK 3 to desensitize the TSHR in vitro, suggest a potential role for GRK 3 as a negative feedback regulator for the constitutively activated cAMP pathway in HTNs.
G蛋白偶联受体激酶（GRKs）与动脉高血压、心力衰竭和类风湿关节炎等人类疾病的病理生理学有关。虽然已表明G蛋白偶联受体激酶2和5参与大鼠促甲状腺激素受体（TSHR）的脱敏过程，但其在功能亢进性甲状腺结节（HTNs）病理生理学中的作用尚不清楚。因此，我们分析了已知GRKs在人甲状腺组织中的表达模式，并研究了它们在HTNs病理学中的功能。通过蛋白质免疫印迹法检测不同GRKs在人甲状腺和HTNs中的表达。通过在HEK 293细胞中共表达实验分析GRK表达对TSHR功能的影响。我们证明，除了GRKs 2、5和6外，GRKs 3和4也在人甲状腺中表达。GRKs 2、3、5和6能够在体外使TSHR脱敏。β-抑制蛋白1或2的额外过表达会放大这种由GRK诱导的脱敏作用。我们在14个无TSHR突变和Gsα突变的HTNs中未发现GRKs 2、3和5有任何突变。GRKs 3和4的表达在HTNs中增加，与TSHR突变或Gsα突变的存在无关。总之，HTNs中GRK 3表达增加以及GRK 3在体外使TSHR脱敏的能力，提示GRK 3作为HTNs中组成性激活的cAMP途径的负反馈调节因子可能发挥作用。
