Dynamics of low-density lipoprotein receptors in the plasma membrane of cultured human skin fibroblasts as visualized by colloidal gold in conjunction with surface replicas.

The aim of this study was to characterize further the human skin fibroblast membrane receptor for LDL. We herein report that LDL particles bound to colloidal gold in conjunction with the surface replication technique can be used to visualize steps in the movement of their receptors in the plane of the lipid bilayer and provide the first clear demonstration of the sequential clustering of LDL-receptors into coated pits. Competition experiments have shown that recycled LDL-receptors are inserted in plaques and not at random into unspecialized regions of the plasma membrane. The site of replacement of LDL-receptors into the plasma membrane corresponds to the site of formation of coated pits and their subsequent internalization.