Pregnancy-associated plasma protein-A accounts for the insulin-like growth factor (IGF)-binding protein-4 (IGFBP-4) proteolytic activity in human pregnancy serum and enhances the mitogenic activity of IGF by degrading IGFBP-4 in vitro.
Pregnancy-associated plasma protein-A accounts for the insulin-like growth factor (IGF)-binding protein-4 (IGFBP-4) proteolytic activity in human pregnancy serum and enhances the mitogenic activity of IGF by degrading IGFBP-4 in vitro.
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DOI：
10.1210/jcem.86.2.7223
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发表时间：
2001-02
期刊：
影响因子：
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通讯作者：
D. Byun;S. Mohan;M. Yoo;C. Sexton;D. Baylink;X. Qin
中科院分区：
文献类型：
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作者：
D. Byun;S. Mohan;M. Yoo;C. Sexton;D. Baylink;X. Qin
妊娠相关血浆蛋白-A（PAPP-A）是由人成纤维细胞产生的胰岛素样生长因子（IGF）依赖性IGF结合蛋白-4（IGFBP-4）蛋白酶。最近，我们发现，在人类怀孕期间诱导的血清蛋白酶裂解IGFBP-4在IGF-II依赖和IGF-II独立的方式。本研究旨在确定PAPP-A是否是人妊娠血清（PS）中的主要IGFBP-4蛋白酶，并评估血清PAPP-A的体外作用。免疫沉淀与PAPP-A抗体有效地耗尽PAPP-A从PS和完全废除两个IGF-II依赖性和IGF-II非依赖性IGFBP-4蛋白水解活性在PS。将PAPP-A抗体直接加入到PS中完全阻断IGFBP-4的蛋白水解，部分阻断IGFBP-5的蛋白水解，但对IGFBP-3的蛋白水解没有影响。为了评估血清PAPP-A的作用，我们测试了PS中的PAPP-A是否调节IGFBP-4对人骨肉瘤MG 63细胞中IGF-II诱导的细胞增殖的抑制活性。野生型IGFBP-4（WTBP-4; 200 ng/mL）不能抑制单独用PS（0.1%或0.3%）或与IGF-II（40 ng/mL）组合处理的细胞的增殖，而在单独用非妊娠血清或与IGF-II组合处理的细胞中观察到WTBP-4的抑制作用（P < 0.05）。与WTBP-4相比，蛋白酶抗性的IGFBP-4能够抑制PS单独或与IGF-II联合处理的细胞的增殖（P < 0.05）。在PAPP-A中和抗体的存在下，WTBP-4对用IGF-II和PS处理的细胞的增殖的抑制作用得以恢复。总之，这些数据证明1）PAPP-A代表PS中的主要IGFBP-4蛋白酶; 2）PAPP-A可能部分地有助于PS中的IGFBP-5而不是IGFBP-3的蛋白水解活性;和3）PAPP-A通过降解IGFBP-4增强IGF的体外生物活性。
Pregnancy-associated plasma protein-A (PAPP-A) has been identified as the insulin-like growth factor (IGF)-dependent IGF-binding protein-4 (IGFBP-4) protease produced by human fibroblasts. Recently, we found that serum proteases induced during human pregnancy cleaved IGFBP-4 in both an IGF-II-dependent and an IGF-II-independent fashion. This study sought to determine whether PAPP-A is the predominant IGFBP-4 protease in human pregnancy serum (PS) and to assess the in vitro role of serum PAPP-A. Immunoprecipitation with PAPP-A antibody effectively depleted PAPP-A from the PS and completely abolished both IGF-II-dependent and IGF-II-independent IGFBP-4 proteolytic activity in PS. Direct addition of PAPP-A antibody to PS completely blocked IGFBP-4 proteolysis and partially blocked IGFBP-5 proteolysis, but had no effect on IGFBP-3 proteolysis. To evaluate the role of serum PAPP-A, we tested whether PAPP-A in PS modulated the inhibitory activity of IGFBP-4 on IGF-II-induced cell proliferation in human osteosarcoma MG63 cells. The wild-type IGFBP-4 (WTBP-4; 200 ng/mL) failed to inhibit proliferation of the cells treated with PS (0.1% or 0.3%) alone or in combination with IGF-II (40 ng/mL), whereas the inhibitory effect of WTBP-4 was observed in the cells treated with nonpregnancy serum alone or in combination with IGF-II (P < 0.05). In contrast to WTBP-4, a protease-resistant IGFBP-4 was able to inhibit proliferation of the cells treated with PS alone or in combination with IGF-II (P < 0.05). In the presence of PAPP-A neutralizing antibody, the inhibitory effect of WTBP-4 on proliferation of the cells treated with IGF-II and PS was restored. In summary, these data demonstrate 1) that PAPP-A represents the predominant IGFBP-4 protease in PS; 2) that PAPP-A may in part contribute to IGFBP-5, but not IGFBP-3, proteolytic activity in PS; and 3) that PAPP-A enhances the bioactivity of IGFs in vitro by degrading IGFBP-4.