Figure 7.

Rap1 does not play a role in the processing or targeting of α-mannosidase to lysosomes. Growing cells were pulsed with [³⁵S]methionine in HL5 medium for 20 min and chased in unlabeled medium for the times indicated. After centrifugation, both the cell pellet and the extracellular medium were incubated with a monoclonal antibody specific for α-mannosidase (Mierendorf et al., 1983). The immunoprecipitated proteins were separated by SDS-PAGE, and autoradiography was used to visualize the labeled proteins. None of the Rap1 overexpressing cell lines examined displayed a defect in the processing kinetics, targeting, or secretion of α-mannosidase.