Matsubara Takuma, Kinbara Masayuki, Maeda Toshihiro, Yoshizawa Mitsuhiro, Kokabu Shoichiro, Takano Yamamoto Teruko
Dentofacial Orthopedics, Graduate School of Dentistry, Tohoku University, Sendai, Japan; Division of Molecular Signaling and Biochemistry, Department of Health Improvement, Kyushu Dental University, Fukuoka, Japan.
Dentofacial Orthopedics, Graduate School of Dentistry, Tohoku University, Sendai, Japan.
Biochem Biophys Res Commun. 2017 Aug 5;489(4):472-476. doi: 10.1016/j.bbrc.2017.05.174. Epub 2017 May 30.
Osteoclasts are cells that resorb the bone matrix and maintain bone and calcium homeostasis. An actin ring is a characteristic actin structure that is essential for bone resorption by osteoclasts. Tyrosine kinase Src deficient osteoclasts do not form actin rings; thus, Src is a key molecule for actin ring formation in osteoclasts. However, how Src regulates actin ring formation is not fully understood. We identified the cytolinker protein plectin as a Src-binding protein by immunoprecipitation and liquid chromatography tandem mass spectrometry. Plectin is a huge protein (>500 kDa) and regulates the cytoskeleton by binding to actin and tubulin. We assessed the expression and role of plectin in osteoclasts. Plectin was expressed and co-localized with Src close to the actin ring in osteoclasts. Moreover, plectin was tyrosine-phosphorylated by Src. Differentiation and actin ring formation were inhibited by downregulation of plectin. These results suggest an important role for plectin in osteoclast differentiation and actin ring formation through Src binding.
破骨细胞是一种能够吸收骨基质并维持骨骼和钙稳态的细胞。肌动蛋白环是一种特有的肌动蛋白结构，对于破骨细胞的骨吸收至关重要。酪氨酸激酶Src缺陷的破骨细胞不会形成肌动蛋白环；因此，Src是破骨细胞中肌动蛋白环形成的关键分子。然而，Src如何调节肌动蛋白环的形成尚未完全清楚。我们通过免疫沉淀和液相色谱串联质谱法鉴定出细胞连接蛋白网蛋白作为一种Src结合蛋白。网蛋白是一种巨大的蛋白质（>500 kDa），通过与肌动蛋白和微管蛋白结合来调节细胞骨架。我们评估了网蛋白在破骨细胞中的表达和作用。网蛋白在破骨细胞中表达，并与Src在靠近肌动蛋白环的位置共定位。此外，网蛋白被Src酪氨酸磷酸化。网蛋白的下调抑制了分化和肌动蛋白环的形成。这些结果表明网蛋白通过Src结合在破骨细胞分化和肌动蛋白环形成中起重要作用。
