RELATIONSHIP BETWEEN MEMBRANE LIPID MOBILITY AND SPECTRIN DISTRIBUTION IN LYMPHOCYTES

We have previously established that T and B lymphocytes in situ are remarkably heterogeneous with respect to the cytoskeletal protein spectrin. Since in erythrocytes spectrin is known to play an important role in the regulation of membrane fluidity, lipid organization and lateral mobility of membrane proteins, we have sought to determine if the heterogeneous patterns of spectrin distribution that we have observed are related to possible differences in membrane lipid organization in these various subsets. To this end, we have utilized a fluorescent pyrene-labelled phospholipid as a probe of the lipid lateral mobility and have examined two related T cell systems maintained in vitro, DO.11.10 cells and a spontaneously arising variant, DO.11.10V. In these (and other cloned in vitro systems) we have previously observed that the cells homogeneously express one of the kinds of spectrin distribution patterns observed in situ. Thus the uniformity of staining of these systems permits us to address whether the various patterns of spectrin distribution may be predictive of differences in membrane lipid properties. Here we show that in cells in which there is little or no spectrin at the plasma membrane (DO.11.10) that the lipids in the plasma membrane are considerably less mobile than in its related variant in which spectrin is diffusely distributed within the cell and at the plasma membrane. From this and previous results, we conclude that differences in the distribution of the cytoskeletal protein spectrin among lymphocytes may be a useful parameter in helping to predict the status of membrane lipid organization.