Identification of the fnx1+ and fnx2+ genes for vacuolar amino acid transporters in Schizosaccharomyces pombe

Chardwiriyapreecha, Soracom; Shimazu, Masamitsu; Morita, Tomotake; Sekito, Takayuki; Akiyama, Koichi; Takegawa, Kaoru; Kakinuma, Yoshihiko

doi:10.1016/j.febslet.2008.05.017

Cited by 21 publications

(36 citation statements)

References 28 publications

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“…We recently reported that the fission yeast fnx1 + and fnx2 + genes, which are homologous to the budding yeast VBA (vacuolar transporter for basic amino acids) genes, are involved in vacuolar amino acid uptake in Sch. pombe (Chardwiriyapreecha et al, 2008). We tested sporulation of fnx1D and fnx2D cells, and found that they sporulate normally during nitrogen starvation (unpublished results).…”

Section: Discussionmentioning

confidence: 99%

Autophagy-deficient Schizosaccharomyces pombe mutants undergo partial sporulation during nitrogen starvation

et al. 2009

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Autophagy is triggered when organisms sense radical environmental changes, including nutritional starvation. During autophagy, cytoplasmic components, including organelles, are enclosed within autophagosomes and are degraded upon lysosome-vacuole fusion. In this study, we show that processing of GFP-tagged Atg8 can serve as a marker for autophagy in the fission yeast Schizosaccharomyces pombe. Using this marker, 13 Atg homologues were also found to be required for autophagy in fission yeast. In budding yeast, autophagy-deficient mutants are known to be sterile, whereas in fission yeast we found that up to 30 % of autophagy-defective cells with amino acid auxotrophy were able to recover sporulation when an excess of required amino acids was supplied. Furthermore, we found that approximately 15 % of the autophagydefective cells were also able to sporulate when a prototrophic strain was subjected to nitrogen starvation, which suggested that fission yeast may store sufficient intracellular nitrogen to allow partial sporulation under nitrogen-limiting conditions, although the majority of the nitrogen source is supplied by autophagy. Monitoring of the sporulation process revealed that the process was blocked non-specifically at various stages in the atg1D and atg12D mutants, possibly due to a shortage of amino acids. Taking advantage of this partial sporulation ability of fission yeast, we sought evidence for the existence of a recycling system for nitrogen sources during starvation. INTRODUCTIONAutophagy is a degradative pathway conserved among eukaryotic cells, and is responsible for turnover of damaged organelles and long-lived proteins. When living organisms are exposed to radical environmental changes such as nutrient starvation, differentiation or development, autophagy is rapidly induced and inner cell components are reorganized. In the budding yeast Saccharomyces cerevisiae, autophagy is triggered by starvation for nitrogen or carbon, after which endogenous proteins and organelles are enclosed within isolated membranes called autophagosomes. The outer membrane of the autophagosome then fuses with the vacuole, allowing the contents of the autophagosome, designated autophagic bodies, to be released and degraded in the vacuole. The molecular mechanisms involved in the process of autophagy have been subjected to detailed genetic analysis and more than 20 AuTophaGy-related (ATG) genes essential for autophagy have been identified in Sac. cerevisiae Kamada et al., 2000;Mizushima et al., 1998).One of the most striking findings with respect to function of the Atg proteins was the discovery of two ubiquitin-like conjugation systems involving Atg12p and Atg8p (Ohsumi, 2001). Atg12p, which has no apparent homology to ubiquitin, covalently attaches to Atg5p in a manner analogous to ubiquitination, and then forms a complex with Atg16p. Atg8p also lacks similarity to ubiquitin, but Abbreviations: DAPI, 49,6-diamidino-2-phenylindole; DIC, differential interference contrast; FSM, forespore membrane.Two supplementary tables a...

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Section: Discussionmentioning

confidence: 99%

Autophagy-deficient Schizosaccharomyces pombe mutants undergo partial sporulation during nitrogen starvation

et al. 2009

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“…After 15 min, 0.5 ml aliquots were withdrawn, filtered on cellulose acetate membrane filters (0.45 mm; ADVANTEC) and washed with cold 10 mM HEPES (pH 6.4). Radioactivity was measured using a liquid scintillation counter with xylene scintillator (Chardwiriyapreecha et al, 2008).…”

Section: The Gga22mentioning

confidence: 99%

Intracellular trafficking and ubiquitination of the Schizosaccharomyces pombe amino acid permease Aat1p

Nakase

Chardwiriyapreecha

et al. 2012

Microbiology

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In Schizosaccharomyces pombe, neither intracellular sorting nor ubiquitination of amino acid permeases is well understood. In the present study, we show that intracellular sorting of the amino acid permease Aat1p in S. pombe depends on the presence of a nitrogen source in the growth medium. Under nitrogen-sufficient conditions, Aat1p appeared to be stably localized at the Golgi apparatus. In contrast, under nitrogen-insufficient conditions, Aat1p was sorted to the plasma membrane. Over time, plasma membrane-localized Aat1p was internalized and sorted to the lumen of the vacuole, where it was degraded. Sorting of Aat1p to the vacuolar lumen was dependent on the ESCRT (endosomal sorting complex required for transport) complex, which is required for formation of the multivesicular body. S. pombe has three genes (pub1 + , pub2 + and pub3 + ) that are homologous to the ubiquitin ligase RSP5. Under nitrogen-sufficient conditions, Aat1-GFP was missorted to the plasma membrane in pub1D cells and ubiquitinated Aat1p was not detected. These results suggest that Pub1p-mediated ubiquitination is required for retention of Aat1 at the Golgi under nitrogen-sufficient conditions. The Aat1p lysine mutant Aat1 K18, 26, 27 was completely missorted to the plasma membrane under nitrogen-rich conditions. Furthermore, Aat1 K4, 18R , Aat1 K4, 26, 27R and Aat1 K18, 26, 27K mutants were severely blocked in endocytosis.These results indicate that ubiquitination is an important determinant for localization and regulation of the Aat1p permease in S. pombe.

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“…Amino acid uptake by intact yeast cells involves active transport into vacuoles. 12,15,16) Therefore, it is possible that the uptake activity of amino acids into vacuoles is critical for an increase in the cytosolic concentration. The primary step for the maintenance of intracellular amino acid concentration is a transport across the cell membrane.…”

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Loss of ATP-dependent lysine uptake in the vacuolar membrane vesicles of Saccharomyces cerevisiae ypq1∆ mutant

Sekito

Nakamura

Manabe

et al. 2014

Bioscience, Biotechnology, and Biochemistry

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Identification of the fnx1⁺ and fnx2⁺ genes for vacuolar amino acid transporters in Schizosaccharomyces pombe

Cited by 21 publications

References 28 publications

Autophagy-deficient Schizosaccharomyces pombe mutants undergo partial sporulation during nitrogen starvation

Autophagy-deficient Schizosaccharomyces pombe mutants undergo partial sporulation during nitrogen starvation

Intracellular trafficking and ubiquitination of the Schizosaccharomyces pombe amino acid permease Aat1p

Loss of ATP-dependent lysine uptake in the vacuolar membrane vesicles of Saccharomyces cerevisiae ypq1∆ mutant

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