Membrane dynamics of the phosphatidylinositol-anchored form and the transmembrane form of the cell adhesion protein LFA-3.

The cell adhesion glycoprotein LFA-3 is expressed on the cell surface of nucleated cells in both a membrane-spanning form and a glycosyl phosphatidylinositol-anchored form. To determine whether distinct membrane anchors direct the dynamics of a given protein, the turnover of biosynthetically 35S-labeled and biotin surface-labeled LFA-3 molecules was followed. It is shown here that (a) expression of the two LFA-3 forms is regenerated with similar kinetics after enzymatic removal from the cell surface; (b) neither of the distinct LFA-3 molecules undergoes constitutive internalization; and (c) transmembrane and glycosyl phosphatidylinositol-anchored LFA-3 have an unusually long life span with an identical half-life of 50 h. Thus, the type of membrane anchor is not affecting turnover characteristics of a particular cell surface glycoprotein.