Choi S J, Devlin R D, Menaa C, Chung H, Roodman G D, Reddy S V
Department of Medicine/Hematology, University of Texas Health Science Center, San Antonio, Texas 78284, USA.
J Clin Invest. 1998 Oct 1;102(7):1360-8. doi: 10.1172/JCI2667.
Increased osteoclast activity is responsible for the enhanced bone destruction in postmenopausal osteoporosis, Paget's disease, bone metastasis, and hypercalcemia of malignancy. However, the number of known inhibitory factors that block osteoclast formation and bone resorption are limited. Therefore, we used an expression-cloning approach to identify novel factors produced by osteoclasts that inhibit osteoclast activity. A candidate clone was identified and isolated from a human osteoclast-like multinucleated cell (MNC) cDNA library, named osteoclast inhibitory peptide-1 (OIP-1), and the cDNA sequence was determined. This sequence matched that of the recently identified human stem cell antigen, was structurally similar to the mouse Ly-6 gene family, and the sequence predicted it was a glycosyl phosphatidyl inositol (GPI)-anchored protein that had a cleavable COOH-terminal peptide. Western blot analysis of conditioned media from 293 cells transfected with the OIP-1 cDNA clone confirmed that OIP-1 was released into the media as a membrane-bound GPI-linked protein. Interestingly, both recombinant OIP-1 expressed in Escherichia coli (which does not have GPI linker) and OIP-1 expressed by mammalian cells significantly reduced osteoclast-like MNC formation induced by 1,25-dihydroxyvitamin D3 or PTH-related protein in mouse and human bone marrow cultures, and inhibited 45Ca release from prelabeled bone in fetal rat organ cultures. In contrast, recombinant OIP-1 did not inhibit the growth of a variety of other cell types. These data indicate that OIP-1 is a novel, specific inhibitor of osteoclast formation and bone resorption.
破骨细胞活性增加是绝经后骨质疏松症、佩吉特病、骨转移和恶性肿瘤高钙血症中骨破坏增强的原因。然而，已知的抑制破骨细胞形成和骨吸收的抑制因子数量有限。因此，我们采用表达克隆方法来鉴定由破骨细胞产生的抑制破骨细胞活性的新因子。从人破骨细胞样多核细胞（MNC）cDNA文库中鉴定并分离出一个候选克隆，命名为破骨细胞抑制肽-1（OIP-1），并确定了其cDNA序列。该序列与最近鉴定的人类干细胞抗原的序列匹配，在结构上与小鼠Ly-6基因家族相似，并且该序列预测它是一种糖基磷脂酰肌醇（GPI）锚定蛋白，具有可裂解的COOH末端肽。对用OIP-1 cDNA克隆转染的293细胞的条件培养基进行蛋白质印迹分析证实，OIP-1作为膜结合的GPI连接蛋白释放到培养基中。有趣的是，在大肠杆菌（不具有GPI连接体）中表达的重组OIP-1和哺乳动物细胞表达的OIP-1均显著减少了小鼠和人骨髓培养物中由1,25-二羟基维生素D3或甲状旁腺激素相关蛋白诱导的破骨细胞样MNC形成，并抑制了胎鼠器官培养物中预标记骨的45Ca释放。相比之下，重组OIP-1不抑制多种其他细胞类型的生长。这些数据表明，OIP-1是一种新型的、特异性的破骨细胞形成和骨吸收抑制剂。
