Molecular biological approaches to protein sorting

The use of recombinant DNA technology to introduce specifically altered genes into epithelial cells has passed through its introductory phase. Enough data have accumulated to indicate the major problems and opportunities for this approach. The greatest opportunity is for locating the features of glycoproteins that are recognized during sorting through the expression of specifically altered proteins in epithelial cells. The results of experiments of this kind briefly summarized here emphasize the need for detailed analyses of the effects of specific mutations on the structure of the mutant proteins. In addition, progress will require quantitative results that have been difficult to obtain to date. To accomplish this, the level of expression of mutant proteins in polarized cells must be higher than previously has been the case. This in turn requires that an effort be made to identify vectors specifically adapted for use in epithelial cells.