Gates R E, King L E
Research Service, Department of Veterans Affairs, Nashville, TN.
J Recept Res. 1993;13(5):829-47. doi: 10.3109/10799899309073696.
Unlike EGF, concanavalin A and wheat germ agglutinin do not increase EGF receptor-kinase activity in intact A-431 membranes. However, they increase both autophosphorylation and phosphorylation of exogenous substrates about twice as much as EGF if the membranes are solubilized in detergent. Following solubilization, autophosphorylation due to the combined presence of a lectin and EGF is additive suggesting that each increases kinase activity by a different mechanism. These different mechanisms were studied by autophosphorylating membranes at increasing detergent concentrations after they had been permeabilized to [gamma-32P]ATP with alamethicin. As the detergent concentration increased, EGF stimulated autophosphorylation decreased 3-fold and 6-fold for the native 170 kDa receptor and for a protease-generated 150 kDa receptor form, respectively. However, in the presence of either lectin the same increase in detergent concentration only slightly altered the autophosphorylation rates which never exceeded the rate measured in the absence of EGF and detergent. Hence, the lectins increase kinase activity in solubilized membranes by preventing the adverse effects of detergent on the receptor-kinase and may not be useful models for how EGF activates its receptor.
与表皮生长因子（EGF）不同，伴刀豆球蛋白A和麦胚凝集素不会增加完整的A - 431细胞膜中EGF受体激酶的活性。然而，如果将细胞膜用去污剂溶解，它们使自身磷酸化和外源底物磷酸化的程度约为EGF的两倍。溶解后，由于凝集素和EGF共同存在导致的自身磷酸化具有加和性，这表明它们各自通过不同的机制增加激酶活性。在用阿拉霉素使细胞膜对[γ-32P]ATP通透后，通过在不断增加去污剂浓度的情况下使细胞膜自身磷酸化来研究这些不同的机制。随着去污剂浓度的增加，对于天然的170 kDa受体和蛋白酶产生的150 kDa受体形式，EGF刺激的自身磷酸化分别下降了3倍和6倍。然而，在存在任何一种凝集素的情况下，相同程度的去污剂浓度增加只会轻微改变自身磷酸化速率，且该速率从未超过在不存在EGF和去污剂时测得的速率。因此，凝集素通过防止去污剂对受体激酶的不利影响来增加溶解细胞膜中的激酶活性，可能不是EGF激活其受体方式的有用模型。
