How to make a lysosome

How to make a lysosome oated vesicles had been described as early as 1961. These small membranous structures were characterized by a highly organized layer of material on the cytoplasmic surface, “but no one knew their function,” says Marilyn Farquhar, whose lab at the time had become interested in how the Golgi complex helped produce enzymes. Roth and Porter (1964) had provided evidence that coated vesicles have specialized functions in the cellular uptake of proteins. But for Friend and Farquhar (1967), the simple idea of uptake was not enough. They helped cement the idea that cellular trafficking involved an intersecting set of cellular highways. They demonstrated that cells contain different types of coated vesicles, and that these vesicles are not only involved in protein uptake but also in the transport of lysosomal enzymes. The two pathways converged in multivesicular bodies (now known as endosomes), explaining how proteins could be endocytosed and then processed by cellular enzymes. The processing, we now know, takes places only after endosomes have either matured into or sent vesicles to lysosomes. C