McCusker R H, Kaleko M, Sackett R L
Department of Animal Sciences, The University of Illinois, Urbana, USA.
J Cell Physiol. 1998 Aug;176(2):392-401. doi: 10.1002/(SICI)1097-4652(199808)176:2<392::AID-JCP18>3.0.CO;2-5.
Mouse P2A2-LISN myoblasts are transfected cells that overexpress the human type 1 insulin-like growth factor (IGF) receptor. Because the type 1 IGF receptor is the major binding site for both IGF-I and IGF-II, this cell line is an excellent model to determine the effect of multivalent cations on ligand binding specifically to this type of receptor. Competitive binding assays were performed to characterize IGF binding and Scatchard analysis to quantify affinity (Ka). 125I-IGF-I, 125I-IGF-II, and 125I-R3-IGF-I bind only to the type 1 IGF receptor on these cells. Zn2+ increased binding of the three ligands to the type 1 IGF receptor by 17 to 35%. Cd2+ significantly increased binding of 125I-IGF-I, although by only 8%. La3+ and Cr3+ did not effect binding. Au3+ decreased IGF binding by approximately 56%. Scatchard analysis produced nonlinear concave-down plots yielding binding constants for high and low affinity sites. Zn2+ increased the strength of only the high affinity sites. Au3+ decreased the affinity of both high and low affinity sites. Zn2+ increased binding with a half-maximal effect between 40 microM and 60 microM. Half-maximal dose of Au3+ was >130 microM. Zinc, gold, and cadmium bind to similar regions within proteins (a zinc-binding motif) and only these cations were found to affect receptor binding indicating similar mechanisms of action. Thus, multivalent cations may alter IGF binding to cell surface receptors ultimately controlling growth. Physiologically this may be especially important for the growth promoting effects of Zn2+.
小鼠P2A2-LISN成肌细胞是过表达人1型胰岛素样生长因子（IGF）受体的转染细胞。由于1型IGF受体是IGF-I和IGF-II的主要结合位点，该细胞系是确定多价阳离子对特异性结合此类受体的配体的影响的极佳模型。进行竞争性结合试验以表征IGF结合，并进行Scatchard分析以量化亲和力（Ka）。125I-IGF-I、125I-IGF-II和125I-R3-IGF-I仅与这些细胞上的1型IGF受体结合。Zn2+使三种配体与1型IGF受体的结合增加了17%至35%。Cd2+显著增加了125I-IGF-I的结合，尽管仅增加了8%。La3+和Cr3+不影响结合。Au3+使IGF结合减少了约56%。Scatchard分析产生了向下凹的非线性图，得出了高亲和力和低亲和力位点的结合常数。Zn2+仅增加了高亲和力位点的强度。Au3+降低了高亲和力和低亲和力位点的亲和力。Zn2+在40 microM至60 microM之间以半最大效应增加结合。Au3+的半最大剂量>130 microM。锌、金和镉与蛋白质内的相似区域（锌结合基序）结合，并且仅发现这些阳离子影响受体结合，表明作用机制相似。因此，多价阳离子可能会改变IGF与细胞表面受体的结合，最终控制生长。在生理上，这对于Zn2+的生长促进作用可能尤为重要。
