Coated vesicles were isolated from metabolically labeled human fibroblasts with the aid of affinity-purified antibodies against human brain clathrin and Staphylococcus aureus cells. The material adsorbed to the S. aureus cells was enriched in clathrin. When the S. aureus cells bearing the immunoadsorbed material were treated with 0.5% saponin, extracts containing the precursor form of cathepsin D were obtained. The extraction of the precursor was promoted in the presence of mannose 6-phosphate. Material adsorbed to S. aureus cells coated with control immunoglobulins was nearly free of clathrin and contained a small amount of the cathepsin D precursor (less than 20% of that adsorbed with anti-clathrin antibodies). The extraction of this cathepsin D precursor was independent of mannose 6-phosphate and was complete after a brief exposure to saponin. The amount of cathepsin D precursor in coated membranes varied between 0.4 and 2.5% of total precursor. Analysis of pulse chase-labeled fibroblasts revealed that cathepsin D was only transiently associated with coated membranes. The mean residence time of cathepsin D precursor in coated membranes was estimated to be 2 min. These observations support the view that coated membranes participate in the transfer of precursor forms of endogenous lysosomal enzymes to lysosomes.
Skip Nav Destination
Article| September 01 1985
Cathepsin D precursors in clathrin-coated organelles from human fibroblasts.
K von Figura
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1985) 101 (3): 824–829.
E Schulze-Lohoff, A Hasilik, K von Figura; Cathepsin D precursors in clathrin-coated organelles from human fibroblasts.. J Cell Biol 1 September 1985; 101 (3): 824–829. doi: https://doi.org/10.1083/jcb.101.3.824
Download citation file: