title: The nutrient stress-induced small GTPase Rab5 contributes to the activation of vesicle trafficking and vacuolar activity.
abstract: Rab family small GTPases regulate membrane trafficking by spatiotemporal recruitment of various effectors. However, it remains largely unclear how the expression and functions of Rab proteins are regulated in response to extracellular or intracellular stimuli. Here we show that Ypt53, one isoform of Rab5 in Saccharomyces cerevisiae, is up-regulated significantly under nutrient stress. Under non-stress conditions, Vps21, a constitutively expressed Rab5 isoform, is crucial to Golgi-vacuole trafficking and to vacuolar hydrolase activity. However, when cells are exposed to nutrient stress for an extended period of time, the up-regulated Ypt53 and the constitutive Vps21 function redundantly to maintain these activities, which, in turn, prevent the accumulation of reactive oxygen species and maintain mitochondrial respiration. Together, our results clarify the relative roles of these constitutive and nutrient stress-inducible Rab5 proteins that ensure adaptable vesicle trafficking and vacuolar hydrolase activity, thereby allowing cells to adapt to environmental changes.
authors.forename: Kunio
authors.initials: K
authors.lastname: Nakatsukasa
authors.forename: Akira
authors.initials: A
authors.lastname: Kanada
authors.forename: Mariko
authors.initials: M
authors.lastname: Matsuzaki
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Byrne
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Okumura
authors.forename: Takumi
authors.initials: T
authors.lastname: Kamura
mesh_terms: D001693:Biological Transport, Active / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological / Q000502:physiology*; D015854:Up-Regulation / Q000502:physiology; D014617:Vacuoles / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D029701:Saccharomyces cerevisiae Proteins; C086866:VPS21 protein, S cerevisiae; C086868:YPT53 protein, S cerevisiae; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins