Methods for visualization of the LDL pathway in cultured human fibroblasts.

A number of different light and electron microscopic probes have been developed for visualizing the LDL pathway. These probes give a consistent picture of the endocytic process and allow the identification of various cellular organelles through which ligand traffics on the way to the lysosome. Moreover, the pathway, with some variation, appears to be the same for other ligands that are taken up by receptor-mediated endocytosis. These methodologies have been the foundation for studying such issues as the role of coated pits in endocytosis, the route of receptor recycling during endocytosis, and the role of coated pits in clustering of receptors on the cell surface. These reagents should prove useful in future studies to understand better the cell biology of receptor-mediated endocytosis.