Nicolson G L
Adv Exp Med Biol. 1975;55:153-72. doi: 10.1007/978-1-4684-0949-9_8.
Concanavalin A (Con A) has been popularly used as a cell surface probe for normal and neoplastic cells. Differences between normal fibroblasts and their transformed derivatives were examined using Con A agglutination, quantitative labeling with 125I-Con A and ultrastructural labeling with fluorescent- or ferritin-Con A. Con A agglutinates confluent-SV3T3 and 3T3 cells at midpoints of 20-60 and greater than, 500-2,000 mug/ml, respectively, and sparse cells at 5-15 and 1,200-1,500 mg/ml, respectively. Quantitative binding of 125I-Con A at 4 degrees C (10 or 15 min) with saturating lectin concentrations does not indicate a difference in the number of Con A receptors on sparse or confluent 3T3 and SV3T3 cells similar to many publications, but contrary to Noonan and Burger (1973). Under these conditions of labeling, ferritin-Con A is not internalized, indicating absence of endocytosis. The lateral mobility of Con A receptors and their relative ability to be aggregated on the cell surface by Con A was investigated with fluorescent- and ferritin-Con A. The initial distribution of Con A receptors on 3T3, SV3T3 and MSV3T3 cells under conditions of labeling at low temperature (0-5 degrees C) or to fixed cells was essentially randomly dispersed, but changes quickly to aggregated on SV3T3 and MSV3T3 (but not 3T3) after shifting the temperature to 20-37 degrees C, indicating, in general, a greater relative mobility of Con A receptors on SV3T3 and MSV3T3 cells. The aggregated Con A receptors seem to be directly involved in cell agglutination because they are usually found at the sites of cell-to-cell contact during 10 min agglutination experiments with ferritin-Con A. When confluent-3T3 cells are labeled on monolayer with ferritin-Con A at 0-4 degrees C, washed and then shifted to 20-37 degrees C for 10-15 min prior to in situ embedding, two classes of Con A receptors can be identified. One class appears to have low relative mobility and is associated with the 3T3 cell's extensive subplasma membrane microfilament network, while the other is capable of being aggregated and eventually endocytosed. On confluent-SV3T3 cells, only the latter class of receptors appears to be present, indicating a possible loss of cytoplasmic control over the distribution and mobility of lectin-binding sites on transformed cell surfaces.
刀豆球蛋白A（Con A）一直被广泛用作正常细胞和肿瘤细胞的细胞表面探针。使用Con A凝集、用125I-Con A进行定量标记以及用荧光或铁蛋白-Con A进行超微结构标记，研究了正常成纤维细胞与其转化衍生物之间的差异。Con A分别在20 - 60μg/ml和大于500 - 2000μg/ml的中点凝集汇合的SV3T3和3T3细胞，在5 - 15μg/ml和1200 - 1500μg/ml凝集稀疏细胞。与许多出版物类似，但与努南和伯格（1973年）的研究结果相反，在4℃（10或15分钟）用饱和凝集素浓度进行125I-Con A的定量结合，未显示稀疏或汇合的3T3和SV3T3细胞上Con A受体数量的差异。在这些标记条件下，铁蛋白-Con A未被内化，表明不存在内吞作用。用荧光和铁蛋白-Con A研究了Con A受体的侧向流动性及其在细胞表面被Con A聚集的相对能力。在低温（0 - 5℃）标记条件下或对固定细胞而言，3T3、SV3T3和MSV3T3细胞上Con A受体的初始分布基本随机分散，但温度升至20 - 37℃后，SV3T3和MSV3T3（但不是3T3）细胞上的受体迅速变为聚集状态，这总体上表明Con A受体在SV3T3和MSV3T3细胞上具有更大的相对流动性。聚集的Con A受体似乎直接参与细胞凝集，因为在使用铁蛋白-Con A进行10分钟凝集实验期间，它们通常出现在细胞间接触部位。当汇合的3T3细胞在单层上于0 - 4℃用铁蛋白-Con A标记、洗涤，然后在原位包埋前转移至20 - 37℃ 10 - 15分钟时，可鉴定出两类Con A受体。一类似乎相对流动性较低，与3T3细胞广泛的质膜下微丝网络相关，而另一类能够聚集并最终被内吞。在汇合的SV3T3细胞上，似乎只存在后一类受体，这表明转化细胞表面凝集素结合位点的分布和流动性可能丧失了细胞质控制。
