Regulation of IGFBP-4 levels in human intestinal muscle by an IGF-I-activated, confluence-dependent protease.
Regulation of IGFBP-4 levels in human intestinal muscle by an IGF-I-activated, confluence-dependent protease.
复制标题
IGF-I 激活的汇合依赖性蛋白酶调节人肠道肌肉中的 IGFBP-4 水平。
DOI：
10.1152/ajpgi.2000.279.5.g975
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Teng,B
中科院分区：
文献类型：
--
作者：
Kuemmerle,JF;Teng,B
Human intestinal smooth muscle cells in culture produce insulin-like growth factor-I (IGF-I), IGF binding protein-3 (IGFBP-3), IGFBP-4, and IGFBP-5, which can modulate the effects of IGF-I on growth. This study examined the role of IGFBP-4 on IGF-I-induced growth and the mechanisms regulating IGFBP-4 levels. IGFBP-4 inhibited IGF-I-induced [3H]thymidine incorporation. IGFBP-4 mRNA levels were not altered by IGF-I. IGF-I caused a concentration-dependent activation of an endogenous IGFBP-4 protease, resulting in time-dependent degradation of intact IGFBP-4 into inactive fragments. Protease activity was measured in a cell-free assay using smooth muscle cell conditioned medium containing the IGFBP-4 protease. The protease was inhibited by EDTA and benzamidine. Protease activity was highest in proliferating cells and lowest in postconfluent cells. The role of endogenous IGF-I in regulating IGFBP-4 degradation was confirmed by the ability of an IGF-I antagonist to inhibit IGF-I-activated IGFBP-4 proteolysis in intact cells. We conclude that in human intestinal smooth muscle cells levels of secreted IGFBP-4 are determined by the confluence-dependent production of a cation-dependent serine protease that is activated by endogenous IGF-I.
