CELL-SURFACE SHEDDING - PHENOMENON AND ITS POSSIBLE SIGNIFICANCE

Surface membrane biosynthesis and turnover is reviewed focusing mainly on the fate of cell surface constituents after they terminated their sojourn as part of a functional cell structure. Different experimental approaches to this problem are described and original data are presented on the turnover of surface membrane constituents of chicken embryo cells in culture. As a consequence of surface membrane turnover, certain surface macromolecules are probably continuously shed from cells. The size and charge of these molecules was identical to molecules released from cells by mild trypsin treatment. The term shedding is proposed for this process which is assumed to occur both in vitro and in vivo. Many systems in which shedding of cell surface constituents is clearly demonstrated or can be tentatively suggested are described. The biological significance of cell surface carbohydrate containing macromolecules and the possible role of these shed cellular entities is discussed.