1. Termination of isoform-selective Vps21/Rab5 signaling at endolysosomal organelles by Msb3/Gyp3.
- Author
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Nickerson DP, Russell MRG, Lo SY, Chapin HC, Milnes J, and Merz AJ
- Subjects
- Calcineurin metabolism, DNA-Binding Proteins genetics, DNA-Binding Proteins metabolism, GTPase-Activating Proteins genetics, Multivesicular Bodies ultrastructure, Protein Isoforms metabolism, Protein Transport, Saccharomyces cerevisiae genetics, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins genetics, Transcription Factors genetics, Transcription Factors metabolism, rab GTP-Binding Proteins genetics, GTPase-Activating Proteins metabolism, Lysosomes metabolism, Multivesicular Bodies metabolism, Saccharomyces cerevisiae Proteins metabolism, rab GTP-Binding Proteins metabolism
- Abstract
Traffic through endosomes and lysosomes is controlled by small G-proteins of the Rab5 and Rab7 families. Like humans, Saccharomyces cerevisiae has three Rab5s (Vps21, Ypt52 and Ypt53) and one Rab7 (Ypt7). Here, we elucidate the functional roles and regulation of the yeast Rab5s. Using GFP-tagged cargoes, a novel quantitative multivesicular body (MVB) sorting assay, and electron microscopy, we show that MVB biogenesis and thus MVB cargo sorting is severely impaired in vps21Δ ypt52Δ double mutants. Ypt53, the third Rab5 paralog, is hardly expressed during normal growth but its transcription is strongly induced by cellular stress through the calcineurin-Crz1 pathway. The requirement for Rab5 activity in stress tolerance facilitated identification of Msb3/Gyp3 as the principal Rab5 GAP (GTPase accelerating protein). In vitro GAP assays verified that Vps21 is a preferred Gyp3 target. Moreover, we demonstrate that Gyp3 spatially restricts active Vps21 to intermediate endosomal compartments by preventing Vps21 accumulation on lysosomal vacuoles. Gyp3, therefore, operates as a compartmental insulator that helps to define the spatial domain of Vps21 signaling in the endolysosomal pathway., (© 2012 John Wiley & Sons A/S.)
- Published
- 2012
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