RESUMO
The regulation of cellular membrane dynamics is crucial for maintaining proper cell growth and division. The Cdc48-Npl4-Ufd1 complex is required for several regulated membrane-associated processes as part of the ubiquitin-proteasome system, including ER-associated degradation and the control of lipid composition in yeast. In this study we report the results of a genetic screen in Saccharomyces cerevisiae for extragenic suppressors of a temperature-sensitive npl4 allele and the subsequent analysis of one suppressor, GET3/ARR4. The GET3 gene encodes an ATPase with homology to the regulatory component of the bacterial arsenic pump. Mutants of GET3 rescue several phenotypes of the npl4 mutant and transcription of GET3 is coregulated with the proteasome, illustrating a functional relationship between GET3 and NPL4 in the ubiquitin-proteasome system. We have further found that Get3 biochemically interacts with the trans-membrane domain proteins Get1/Mdm39 and Get2/Rmd7 and that Deltaget3 is able to suppress phenotypes of get1 and get2 mutants, including sporulation defects. In combination, our characterization of GET3 genetic and biochemical interactions with NPL4, GET1, and GET2 implicates Get3 in multiple membrane-dependent pathways.
Assuntos
Adenosina Trifosfatases/metabolismo , Proteínas de Arabidopsis/metabolismo , Proteínas de Membrana/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas Adaptadoras de Transporte Vesicular , Proteínas de Arabidopsis/genética , Proteínas de Ciclo Celular/metabolismo , Regulação Fúngica da Expressão Gênica , Proteínas de Membrana/genética , Proteínas de Membrana/fisiologia , Complexos Multiproteicos/metabolismo , Mutação , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Proteínas de Transporte Nucleocitoplasmático , Fenótipo , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/fisiologia , Esporos Fúngicos/genética , Supressão Genética/fisiologia , Distribuição Tecidual , Proteína com Valosina , Proteínas de Transporte VesicularAssuntos
Proteínas de Fluorescência Verde/genética , Saccharomyces cerevisiae/fisiologia , Schizosaccharomyces/fisiologia , Transporte Biológico , Candida albicans/genética , Ciclo Celular , Evolução Molecular , Regulação Fúngica da Expressão Gênica , Genes Reporter , Proteínas de Fluorescência Verde/análise , Proteínas Luminescentes/análise , Proteínas Luminescentes/genética , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética , Schizosaccharomyces/citologia , Schizosaccharomyces/genética , Proteína Vermelha FluorescenteRESUMO
Ubiquitination of membrane-associated proteins can direct their proteasome-mediated degradation or activation at the endoplasmic reticulum (ER), as well as their endocytosis and intracellular sorting. However, the full spectrum of ubiquitinated membrane proteins has not been determined. Here we combined proteomic analysis with yeast genetics to identify 211 ubiquitinated membrane-associated proteins in Saccharomyces cerevisiae and map >30 precise sites of ubiquitination. Major classes of identified ubiquitinated proteins include ER-resident membrane proteins, plasma membrane-localized permeases, receptors, and enzymes, and surprisingly, components of the actin cytoskeleton. By determining the differential abundance of ubiquitinated proteins in yeast mutated for NPL4 and UBC7, which are major components of ER-associated degradation (ERAD), we furthermore were able to classify 83 of these identified ubiquitinated membrane proteins as potential endogenous substrates of the ERAD pathway. These substrates are highly enriched for proteins that localize to or transit through the ER. Interestingly, we also identified novel membrane-bound transcription factors that may be subject to ubiquitin/proteasome-mediated cleavage and activation at the ER membrane.
