Nielsen F C, Haselbacher G, Christiansen J, Lake M, Grønborg M, Gammeltoft S
Department of Clinical Biochemistry, University Hospital, Rigshospitalet, Copenhagen, Denmark.
Mol Cell Endocrinol. 1993 May;93(1):87-95. doi: 10.1016/0303-7207(93)90143-8.
In the present study we have analysed the expression of insulin-like growth factor II (IGF-II) in the human rhabdomyosarcoma cell line IN157.IN157 cells express high levels of three IGF-II mRNAs of 6.0 kb, 4.8 kb and 4.2 kb. In contrast, normal skeletal muscle expresses a negligible amount of IGF-II mRNA. Two forms of IGF-II with molecular masses of 7.5 kDa and 10 kDa, corresponding to the mature IGF-II and IGF-II with a C-terminal extension of 21 amino acids (IGF-IIE21), were secreted into the culture medium at amounts of 17 ng/ml (2.3 nM) and 15 ng/ml (1.5 nM), respectively. IN157 cells also produce IGF binding protein-2. The bioactivity of recombinant IGF-IIE21 was compared with human IGF-I and IGF-II. IGF-I, IGF-II and IGF-IIE21 bound with high affinity to human IGF-I receptors (Kd approximately 1 nM), whereas the human IGF-II/mannose 6-phosphate (IGF-II/Man 6-P) receptor bound IGF-II and IGF-IIE21 with Kd values of 0.5 nM and 2 nM, respectively, and IGF-I with about 500 times lower affinity. IGF-II and IGF-IIE21 stimulated DNA synthesis via the IGF-I receptor, whereas the IGF-II/Man 6-P receptor mediated their rapid internalization and inactivation. During culture of IN157 cells about 50% of their IGF-I receptors were occupied by endogenous IGF-II. We conclude that IN157 cells express high levels of bioactive 10 kDa IGF-II and 7.5 kDa IGF-II that may stimulate the proliferation of rhabdomyosarcomas by interaction with IGF-I receptors on the cells.
在本研究中，我们分析了胰岛素样生长因子II（IGF-II）在人横纹肌肉瘤细胞系IN157中的表达。IN157细胞表达高水平的三种IGF-II mRNA，大小分别为6.0 kb、4.8 kb和4.2 kb。相比之下，正常骨骼肌表达的IGF-II mRNA量可忽略不计。两种分子量分别为7.5 kDa和10 kDa的IGF-II形式，分别对应成熟的IGF-II和具有21个氨基酸C末端延伸的IGF-II（IGF-IIE21），以17 ng/ml（2.3 nM）和15 ng/ml（1.5 nM）的量分泌到培养基中。IN157细胞还产生IGF结合蛋白-2。将重组IGF-IIE21的生物活性与人IGF-I和IGF-II进行了比较。IGF-I、IGF-II和IGF-IIE21与人IGF-I受体具有高亲和力结合（Kd约为1 nM），而人IGF-II/甘露糖6-磷酸（IGF-II/Man 6-P）受体结合IGF-II和IGF-IIE21的Kd值分别为0.5 nM和2 nM，对IGF-I的亲和力约低500倍。IGF-II和IGF-IIE21通过IGF-I受体刺激DNA合成，而IGF-II/Man 6-P受体介导它们的快速内化和失活。在IN157细胞培养过程中，约50%的IGF-I受体被内源性IGF-II占据。我们得出结论，IN157细胞表达高水平的具有生物活性的10 kDa IGF-II和7.5 kDa IGF-II，它们可能通过与细胞上的IGF-I受体相互作用刺激横纹肌肉瘤的增殖。
