甲狀腺激素(T3)作用於軟骨細胞和成骨細胞來控制骨骼發育和維護,但是調節這些功能的信號通路還不明確。近日,英國倫敦帝國理工學院Graham R. Williams等人研究發現突變的甲狀腺激素受體(TRβPV)在體內可以激活骨骼中Wnt信號,並闡明了在骨骼發育過程T3及Wnt信號通路相互作用。相關論文發表在3月22日的美國《生化周刊》(Journal of Biological Chemistry )上。
由於顯性負突變的T3受體(TRβPV)不能結合T3以幹擾野生型TR的功能,ThrbPV/PV老鼠的垂體甲狀腺軸嚴重受損,並有升高的甲狀腺激素水平。ThrbPV/PV老鼠通過不明機制加速了骨骼的發育。研究人員用微陣列研究了分別來自野生型老鼠及ThrbPV/PV老鼠的主要成骨細胞。由原位雜交分析骨骼Wnt目標基因的表達確認了ThrbPV/PV老鼠在產後生長期有激活的Wnt信號。與之相比,T3處理後會抑制成骨細胞Wnt信號,這表明T3通過促進蛋白酶體降解β-連環蛋白,阻止其在核內的積聚,以此抑制了Wnt信號通路。然而在ThrbPV/PV老鼠中,Wnt信號通路被活化,這起因於獲得功能的TRβPV穩定了β-連環蛋白。
這項研究就闡明了在調節骨骼發育與形成時,T3和Wnt信號通路之間的相互作用。(生物谷Deepblue編譯)
Advanced bone formation in mice with a dominant-negative mutation in the thyroid hormone receptor β gene due to activation of Wnt/β-catenin signaling
Patrick J. O Shea, Dong Wook Kim, John G. Logan, Sean Davis, Robert L. Walker, Paul S. Meltzer, Sheue-yann Cheng and Graham R. Williams.
Thyroid hormone (T3) acts in chondrocytes and bone-forming osteoblasts to control bone development and maintenance but the signaling pathways mediating these effects are poorly understood. ThrbPV/PV mice have a severely impaired pituitary-thyroid axis and elevated thyroid hormone levels due to a dominant-negative mutant T3-receptor (TRβPV) that cannot bind T3 and interferes with the actions of wild-type TR.ThrbPV/PV mice have accelerated skeletal development due to unknown mechanisms. We performed microarray studies in primary osteoblasts from wild-type mice and ThrbPV/PV mice. Activation of the canonical Wnt signaling in ThrbPV/PV mice was confirmed by in situ hybridization analysis of Wnt target gene expression in bone during post-natal growth.By contrast, T3 treatment inhibited Wnt signaling in osteoblastic cells, suggesting T3 inhibits the Wnt pathway by facilitating proteasomal degradation of β-catenin and preventing its accumulation in the nucleus.Activation of the Wnt pathway in ThrbPV/PV mice, however, results from a gain-of-function for TRβPV that stabilizes β-catenin despite the presence of increased thyroid hormone levels.These studies demonstrate novel interactions between T3 and Wnt signaling pathways in the regulation of skeletal development and bone formation..