Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
J Biol Chem. 2010 May 7;285(19):14756-63. doi: 10.1074/jbc.M110.102970. Epub 2010 Mar 8.
Bone growth and remodeling depend upon the opposing rates of bone formation and resorption. These functions are regulated by intrinsic seven transmembrane-spanning receptors, the parathyroid hormone receptor (PTH1R) and frizzled (FZD), through their respective ligands, parathyroid hormone (PTH) and Wnt. FZD activation of canonical beta-catenin signaling requires the adapter protein Dishevelled (Dvl). We identified a Dvl-binding motif in the PTH1R. Here, we report that the PTH1R activates the beta-catenin pathway by directly recruiting Dvl, independent of Wnt or LRP5/6. PTH1R coimmunoprecipitated with Dvl. Deleting the carboxyl-terminal PTH1R PDZ-recognition domain did not abrogate PTH1R-Dvl interactions; nor did truncating the receptor at position 480. However, further deletion eliminating the putative Dvl recognition domain abolished PTH1R interactions with Dvl. PTH activated beta-catenin in a time- and concentration-dependent manner and translocated beta-catenin to the nucleus. beta-Catenin activation was inhibited by Dvl2 dominant negatives and by short hairpin RNA sequences targeted against Dvl2. PTH-induced osteoclastogenesis was also inhibited by Dvl2 dominant negative mutants. These findings demonstrate that G protein-coupled receptors other than FZD directly activate beta-catenin signaling, thereby mimicking many of the functions of the canonical Wnt-FZD pathway. The distinct modes whereby FZD and PTH1R activate beta-catenin control convergent or divergent effects on osteoblast differentiation, and osteoclastogenesis may arise from PTH1R-induced second messenger phosphorylation.
骨骼的生长和重塑依赖于骨形成和吸收的相对速率。这些功能受内在的跨膜 7 次受体、甲状旁腺激素受体 (PTH1R) 和卷曲 (FZD) 的调节,通过它们各自的配体甲状旁腺激素 (PTH) 和 Wnt。FZD 激活经典的β-连环蛋白信号需要衔接蛋白 Dvl。我们在 PTH1R 中鉴定了一个 Dvl 结合基序。在这里,我们报告 PTH1R 通过直接招募 Dvl 来激活β-连环蛋白途径,而不依赖于 Wnt 或 LRP5/6。PTH1R 与 Dvl 共免疫沉淀。删除 PTH1R PDZ 识别结构域的羧基末端不会消除 PTH1R-Dvl 相互作用;在位置 480 截断受体也不会。然而,进一步删除消除潜在的 Dvl 识别域会使 PTH1R 与 Dvl 失去相互作用。PTH 以时间和浓度依赖的方式激活β-连环蛋白,并将β-连环蛋白转位到细胞核。Dvl2 显性阴性和针对 Dvl2 的短发夹 RNA 序列抑制了β-连环蛋白的激活。PTH 诱导的破骨细胞发生也被 Dvl2 显性负突变体抑制。这些发现表明,除了 FZD 之外,G 蛋白偶联受体还直接激活β-连环蛋白信号,从而模拟了经典 Wnt-FZD 途径的许多功能。FZD 和 PTH1R 激活β-连环蛋白的不同模式控制着成骨细胞分化的趋同或发散效应,破骨细胞的发生可能源于 PTH1R 诱导的第二信使磷酸化。
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