Hikita Atsuhiko, Yana Ikuo, Wakeyama Hidetoshi, Nakamura Masaki, Kadono Yuho, Oshima Yasushi, Nakamura Kozo, Seiki Motoharu, Tanaka Sakae
Department of Orthopaedic Surgery, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, USA.
J Biol Chem. 2006 Dec 1;281(48):36846-55. doi: 10.1074/jbc.M606656200. Epub 2006 Oct 3.
Receptor activator of NF-kappaB ligand (RANKL) is a transmembrane glycoprotein that has an essential role in the development of osteoclasts. The extracellular portion of RANKL is cleaved proteolytically to produce soluble RANKL, but definite RANKL sheddase(s) and the physiologic function of RANKL shedding have not yet been determined. In the present study, we found that matrix metalloproteinase (MMP) 14 and a disintegrin and metalloproteinase (ADAM) 10 have strong RANKL shedding activity. In Western blot analysis, soluble RANKL was detected as two different molecular weight products, and RNA interference of MMP14 and ADAM10 resulted in a reduction of both the lower and higher molecular weight products. Suppression of MMP14 in primary osteoblasts increased membrane-bound RANKL and promoted osteoclastogenesis in cocultures with macrophages. Soluble RANKL produced by osteoblasts from MMP14-deficient mice was markedly reduced, and their osteoclastogenic activity was promoted, consistent with the findings of increased osteoclastogenesis in vivo. RANKL shedding is an important process that down-regulates local osteoclastogenesis.
核因子κB受体激活蛋白配体（RANKL）是一种跨膜糖蛋白，在破骨细胞的发育中起关键作用。RANKL的细胞外部分经蛋白水解切割产生可溶性RANKL，但确切的RANKL裂解酶及RANKL裂解的生理功能尚未确定。在本研究中，我们发现基质金属蛋白酶（MMP）14和去整合素金属蛋白酶（ADAM）10具有很强的RANKL裂解活性。在蛋白质印迹分析中，可溶性RANKL被检测为两种不同分子量的产物，MMP14和ADAM10的RNA干扰导致低分子量和高分子量产物均减少。在原代成骨细胞中抑制MMP14可增加膜结合型RANKL，并在与巨噬细胞共培养时促进破骨细胞生成。来自MMP14缺陷小鼠的成骨细胞产生的可溶性RANKL明显减少，且其破骨细胞生成活性增强，这与体内破骨细胞生成增加的结果一致。RANKL裂解是下调局部破骨细胞生成的重要过程。
