Department of Fundamental Oral Health Science, Institute of Health Biosciences, The University of Tokushima Graduate School, Kuramoto, Tokushima, Japan.
Mol Cell Endocrinol. 2012 Sep 25;361(1-2):99-105. doi: 10.1016/j.mce.2012.03.019. Epub 2012 Apr 5.
Double-stranded RNA-dependent protein kinase (PKR) is involved in various cellular functions. We previously reported that PKR regulates osteoblast differentiation, but the specific mechanisms by which this occurs remain unclear. In this study, we investigated the role of PKR in Glycogen synthase kinase 3β (GSK-3β) regulation of osteoblast differentiation. Lithium chloride (LiCl), a GSK-3β inhibitor, increased GSK-3β phosphorylation in MC3T3-E1 and MG-63 cells. LiCl also inhibited Runx2 and expression of its regulated genes, causing inhibition of Alkaline phosphatase activity and mineralization. LiCl injection to the calvaria in mice suppressed bone formation. Further, GSK-3β phosphorylation was increased in osteoblasts, by Akt-independent mechanisms, in which PKR was constitutively inactivated. A PKR inhibitor, 2-aminopurine, also induced GSK-3β phosphorylation in MC3T3-E1 and MG-63 cells. Further, Runx2 and its regulated genes were inhibited in PKR-inactivated osteoblasts, and differentiation was suppressed through a β-catenin-independent pathway. PKR positively regulates the differentiation of osteoblasts by mediating GSK-3β activity through a β-catenin-independent pathway.
双链 RNA 依赖的蛋白激酶（PKR）参与多种细胞功能。我们之前的研究表明，PKR 调节成骨细胞分化，但具体机制尚不清楚。在这项研究中，我们研究了 PKR 在糖原合酶激酶 3β（GSK-3β）调节成骨细胞分化中的作用。甘氨酸合成酶激酶 3β（GSK-3β）抑制剂氯化锂（LiCl）增加了 MC3T3-E1 和 MG-63 细胞中 GSK-3β的磷酸化。LiCl 还抑制了 Runx2 及其调控基因的表达，导致碱性磷酸酶活性和矿化的抑制。LiCl 注射到小鼠的颅骨中抑制了骨形成。此外，成骨细胞中 PKR 持续失活，通过 Akt 非依赖性机制增加了 GSK-3β的磷酸化。PKR 抑制剂 2-氨基嘌呤也诱导了 MC3T3-E1 和 MG-63 细胞中 GSK-3β的磷酸化。此外，PKR 失活的成骨细胞中 Runx2 及其调控基因受到抑制，通过非 β-连环蛋白途径抑制分化。PKR 通过介导 GSK-3β 活性，通过非 β-连环蛋白途径正向调节成骨细胞的分化。
