Kinetics of homophilic binding by embryonic and adult forms of the neural cell adhesion molecule.

作者：S Hoffman, Gerald M. Edelman · 发表于：Proceedings of the National Academy of Sciences · 年份：1983 · DOI：10.1073/pnas.80.18.5762 · 被引用次数：628 · 研究领域：Axon Guidance and Neuronal Signaling、Glycosylation and Glycoproteins Research、Lipid Membrane Structure and Behavior

The neural cell adhesion molecule, N-CAM, is a cell surface glycoprotein found on embryonic and adult neurons and on a variety of ectodermal and mesodermal tissues in very early embryos. During development, it shows local variations in prevalence at the cell surface as well as conversion from an embryonic form (E form) with high sialic acid content to an adult form (A form) with lesser amounts of this sugar. This E leads to A conversion occurs on different schedules in different brain regions, and it has been hypothesized that both the conversion and the prevalence changes are related to early regulation of pattern formation and connectivity. In order to identify precisely the consequences of these mechanisms of local cell surface modulation of N-CAM, an assay was developed to measure the rate of aggregation either of vesicles reconstituted from lipid and purified N-CAM or of native brain membrane vesicles. In both preparations, aggregation was greater than 95% inhibitable by specific anti-(N-CAM) Fab' fragments. The rates of aggregation of reconstituted N-CAM vesicles and native brain vesicles were found to be inversely related to the sialic acid content of their N-CAM molecules, with full desialylation resulting in about a 4-fold increase in rate over E-form N-CAM. Intermediate rates were obtained both with A-form N-CAM (which contains only one-third of the sialic acid content of E-form N-CAM) and with partially desialylated E-form N-CAM. The rate of coaggregation of recons...