Ubiquitin-mediated targeting of a mutant plasma membrane ATPase, Pma1-7, to the endosomal/vacuolar system in yeast.
Pma1-7 is a mutant plasma membrane ATPase that is impaired in targeting to the cell surface at 37 degrees C and is delivered instead to the endosomal/vacuolar pathway for degradation. We have proposed that Pma1-7 is a substrate for a Golgibased quality control mechanism. By contrast with wild-type Pma1, Pma1-7 is ubiquitinated. Ubiquitination and endosomal targeting of Pma1-7 is dependent on the Rsp5-Bul1-Bul2 ubiquitin ligase protein complex but not the transmembrane ubiquitin ligase Tul1. Analysis of Pma1-7 ubiquitination in mutants blocked in protein transport at various steps of the secretory pathway suggests that ubiquitination occurs after ER exit but before endosomal entry. In the absence of ubiquitination in rsp5-1 cells, Pma1-7 is delivered to the cell surface and remains stable. Nevertheless, Pma1-7 remains impaired in association with detergent-insoluble glycolipid-enriched complexes in rsp5-1 cells, suggesting that ubiquitination is not the cause of Pma1-7 exclusion from rafts. In vps1 cells in which protein transport into the endosomal pathway is blocked, Pma1-7 is routed to the cell surface. On arrival at the plasma membrane in vps1 cells, Pma1-7 remains stable and its ubiquitination disappears, suggesting deubiquitination activity at the cell surface. We suggest that Pma1-7 sorting and fate are regulated by ubiquitination.
Pizzirusso
Maddalena
M
Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
Chang
Amy
A
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000502:physiology; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000201:enzymology* / Q000502:physiology; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology; D006056:Golgi Apparatus / Q000378:metabolism / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D021382:Protein Sorting Signals; D021381:Protein Transport; D006180:Proton-Translocating ATPases / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism / Q000502:physiology*; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000502:physiology; D014617:Vacuoles / Q000201:enzymology* / Q000502:physiology; D033921:Vesicular Transport Proteins
D048868:Adaptor Proteins, Signal Transducing; C099939:BUL1 protein, S cerevisiae; C117205:BUL2 protein, S cerevisiae; D056827:Endosomal Sorting Complexes Required for Transport; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D033921:Vesicular Transport Proteins; D043743:Ubiquitin-Protein Ligase Complexes; C461959:TUL1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D019204:GTP-Binding Proteins; C092477:PMA1 protein, S cerevisiae; C064553:VPS1 protein, S cerevisiae; D006180:Proton-Translocating ATPases; C469287:RSP5 protein, S cerevisiae