Yogo Keiichiro, Mizutamari Megumi, Mishima Kazuta, Takenouchi Hiromi, Ishida-Kitagawa Norihiro, Sasaki Takehiko, Takeya Tatsuo
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan.
Endocrinology. 2006 Jul;147(7):3307-17. doi: 10.1210/en.2005-1309. Epub 2006 Apr 6.
c-Src plays an important role in bone resorption by osteoclasts. Here, we show using wild-type and ship(-/-) osteoclasts that Src homology 2 (SH2)-containing 5'-inositol phosphatase (SHIP) appeared to negatively regulate bone resorption activated by c-Src. SHIP was found to localize to podosomes under the influence of c-Src, and the presence of either the amino-terminal region comprising the SH2 domain or the carboxyl-terminal region was sufficient for its localization. Although SHIP lacking a functional SH2 domain was still found in podosomes, it could not rescue the hyper-bone resorbing activity and hypersensitivity to receptor activator of nuclear factor-kappaB ligand in ship(-/-) osteoclasts, suggesting that the localization of SHIP to podosomes per se was not sufficient and the SH2 domain was indispensable for its function. Cas and c-Cbl, known to function in podosomes of osteoclasts, were identified as novel proteins binding to the SHIP SH2 domain by mass spectrometric analysis, and this interaction appeared to be dependent on the Src kinase activity. These results demonstrate that c-Src enhances the translocation of SHIP to podosomes and regulates its function there through the SH2 domain, leading to an attenuation of bone resorption.
c-Src在破骨细胞的骨吸收过程中发挥着重要作用。在此，我们利用野生型和SHIP基因敲除（ship(-/-)）的破骨细胞表明，含Src同源2（SH2）结构域的5'-肌醇磷酸酶（SHIP）似乎对c-Src激活的骨吸收起负向调节作用。研究发现，在c-Src的影响下，SHIP定位于足体，并且包含SH2结构域的氨基末端区域或羧基末端区域的存在足以使其定位。尽管缺乏功能性SH2结构域的SHIP仍存在于足体中，但它无法挽救ship(-/-)破骨细胞中过度的骨吸收活性以及对核因子κB受体激活剂配体的超敏反应，这表明SHIP定位于足体本身并不足够，且SH2结构域对其功能不可或缺。通过质谱分析鉴定出已知在破骨细胞足体中发挥作用的Cas和c-Cbl是与SHIP的SH2结构域结合的新蛋白，并且这种相互作用似乎依赖于Src激酶活性。这些结果表明，c-Src增强了SHIP向足体的转位，并通过SH2结构域在那里调节其功能，从而导致骨吸收减弱。
