Stach R W, Rusenko K W
J Neurosci Res. 1984;11(3):215-29. doi: 10.1002/jnr.490110302.
When 125I-beta nerve growth factor binds to sympathetic and sensory neurons, some labeled ligand is sequestered (becomes inaccessible to the external milieu) in a time- and energy-dependent manner. It would appear that the higher affinity receptor (type I) participates in this process to a greater extent than does the lower affinity receptor (type II) [ Olender and Stach , 1980; Olender et al., 1981]. A small portion of the sequestered 125I-beta nerve growth factor is found as part of a high molecular weight complex. When cells, which have been incubated with 125I-beta nerve growth factor, are solubilized with Triton X-100 and subjected to sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis, a complex with an apparent molecular weight of approximately 240,000 is obtained. The formation of the covalent complex can be prevented by the prior addition of excess unlabeled beta nerve growth factor or sodium fluoride and dinitrophenol. The covalent 125I-beta nerve growth factor-receptor complex is dissociated in 50 mM dithiothreitol indicating that disulfide linkages are involved. At concentrations of beta nerve growth factor (3.8 X 10(-11) -3.8 X 10(-10) M) where maximal fiber outgrowth occurs in vitro, approximately 50-266 attomoles (0.3-1.6% of the type I receptors) of the covalent complex are formed per 10(7) nerve cells. These data suggest that a small portion of the 125I-beta nerve growth sequestered by sympathetic neurons becomes covalently attached to its receptor subsequent to its sequestration in a manner which appears to involve type I receptors.
当¹²⁵I-β神经生长因子与交感神经元和感觉神经元结合时，一些标记配体以时间和能量依赖的方式被隔离（变得无法接触外部环境）。似乎高亲和力受体（I型）比低亲和力受体（II型）在这一过程中参与程度更大[奥伦德和施塔赫，1980年；奥伦德等人，1981年]。隔离的¹²⁵I-β神经生长因子的一小部分以高分子量复合物的形式存在。当用¹²⁵I-β神经生长因子孵育过的细胞用曲拉通X-¹⁰⁰溶解并进行十二烷基硫酸钠（SDS）聚丙烯酰胺凝胶电泳时，可得到一种表观分子量约为240,000的复合物。预先加入过量未标记的β神经生长因子或氟化钠和二硝基苯酚可防止共价复合物的形成。共价的¹²⁵I-β神经生长因子-受体复合物在50 mM二硫苏糖醇中解离，表明涉及二硫键。在体外发生最大纤维生长的β神经生长因子浓度（3.8×10⁻¹¹ - 3.8×10⁻¹⁰ M）下，每10⁷个神经细胞形成约50 - 266阿托摩尔（I型受体的0.3 - 1.6%）的共价复合物。这些数据表明，交感神经元隔离的¹²⁵I-β神经生长因子的一小部分在被隔离后以一种似乎涉及I型受体 的方式与其受体共价结合。
