Amino acid sensing by Ssy1

Poulsen, Peter Noe; Wu, Bolin; Gaber, Richard F.; Ottow, Kim Ekelund; Andersen, H.A.; Kielland‐Brandt, Morten C.

doi:10.1042/bst0330261

Cited by 23 publications

(43 citation statements)

References 26 publications

(40 reference statements)

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“…In yeast, an AA-sensing protein, Ssy1, has been identified. While it is not definite that this protein actually transports AAs, it is necessary for detection and is structurally related to other AA transporters (Poulsen et al, 2005). The second possibility is that AAs flowing into and other solutes flowing out of the cell results in physiological changes in membrane polarity, cellular volume, pH and salt concentrations, which are then detected by the cell.…”

Section: Discussionmentioning

confidence: 99%

Identification of two cationic amino acid transporters required for nutritional signaling during mosquito reproduction

Attardo

Hansen

Shiao

et al. 2006

Journal of Experimental Biology

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The defining characteristic of anautogenous mosquitoes is their requirement for a blood meal to initiate reproduction. The need for blood drives the association of vector and host, and is the primary reason why anautogenous mosquitoes are effective disease vectors. During mosquito vitellogenesis, a key process in reproduction, yolk protein precursor (YPP) gene expression is activated specifically in the fat body, the insect analogue of the vertebrate liver. We have demonstrated that blood meal derived amino acids (AAs) activate YPP genes via the target of rapamycin (TOR)-signal transduction pathway. Here we show, by stimulating fat bodies with balanced AA solutions lacking individual AAs, that specific cationic and branched AAs are essential for activation of the vitellogenin (vg) gene, the major YPP gene. Treatment of fat bodies with AA uptake inhibitors results in a strong inhibition of AA-induced vg gene expression proving that an active transport mechanism is necessary to transduce the AA signal. We identified two cationic AA transporters (CATs) in the fat body of Aedes aegypti females -Aa slimfast and iCAT2. RNAi knockdown of slimfast and iCAT2 results in a strong decrease in the response to AAs by the vg gene similar to that seen due to TOR inhibition. These data demonstrate that active uptake of specific AAs plays a key role in nutritional signaling during the onset of vitellogenic gene expression in mosquitoes and it is mediated by two cationic AA transporters.

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Section: Discussionmentioning

confidence: 99%

Identification of two cationic amino acid transporters required for nutritional signaling during mosquito reproduction

Attardo

Hansen

Shiao

et al. 2006

Journal of Experimental Biology

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“…Ssy1p possesses the distinctive structural features of permeases of the YAT family but has no significant transport function per se. Instead, it interacts with two peripheral membrane proteins, namely Ptr3p and Ssy5p, to form the SPS sensor system that detects extracellular amino acids and regulates the transcription of an array of genes related to nitrogen metabolism (57). A similar role for Agp2p as a plasma membrane sensor of extracellular signals would provide an explanation for the complete lack of competition for transport between the various substrates found to be under the control of an active AGP2 gene (Fig.…”

Section: Enhancement Of Spermidine Uptake In Endocytosis-deficient Mumentioning

confidence: 99%

AGP2 Encodes the Major Permease for High Affinity Polyamine Import in Saccharomyces cerevisiae

Aouida

Leduc

Poulin³

et al. 2005

Journal of Biological Chemistry

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Polyamines play essential functions in many aspects of cell biology. Plasma membrane transport systems for the specific uptake of polyamines exist in most eukaryotic cells but have been very recently identified at the molecular level only in the parasite Leishmania. We now report that the high affinity polyamine permease in Saccharomyces cerevisiae is identical to Agp2p, a member of the yeast amino acid transporter family that was previously identified as a carnitine transporter. Deletion of AGP2 dramatically reduces the initial velocity of spermidine and putrescine uptake and confers strong resistance to the toxicity of exogenous polyamines, and transformation with an AGP2 expression vector restored polyamine transport in agp2⌬ mutants. Yeast mutants deficient in polyamine biosynthesis required >10-fold higher concentrations of exogenous putrescine to restore cell proliferation upon deletion of the AGP2 gene. Disruption of END3, a gene required for an early step of endocytosis, increased the abundance of Agp2p, an effect that was paralleled by a marked up-regulation of spermidine transport velocity. Thus, AGP2 encodes the first eukaryotic permease that preferentially uses spermidine over putrescine as a high affinity substrate and plays a central role in the uptake of polyamines in yeast.

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“…Extracellular amino acid sensing via the SPS amino acid sensing pathway is best characterized in the budding yeast Saccharomyces cerevisiae (1)(2)(3)(4)(5). The SPS amino acid sensing pathway includes Ssy1, a plasma membrane-localized sensor for extracellular amino acids, and two downstream factors, Ptr3 and Ssy5 (1-3, 6, 7).…”

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confidence: 99%

Differential Regulation of Transcription Factors Stp1 and Stp2 in the Ssy1-Ptr3-Ssy5 Amino Acid Sensing Pathway

Tumusiime

Zhang

Overstreet

et al. 2011

Journal of Biological Chemistry

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Stp1 and Stp2 are two homologous transcription factors activated in response to extracellular amino acid stimuli. Here we show that both ubiquitin-dependent degradation of Stp1 and Stp2 and their intracellular localization are differentially regulated. We have found that the E2 ubiquitinconjugating enzyme Cdc34 is required for degradation of both full-length and processed Stp1, but not Stp2. We have also found that Grr1, the F-box component of the SCF Grr1 E3 ubiquitin ligase, is the primary factor in degradation of full-length Stp1, whereas both Grr1 and Cdc4 are required for degradation of processed Stp1. Our localization studies showed that full-length Stp1 is localized both in the cytoplasm and at the cell periphery, whereas full-length Stp2 is localized only diffusely in the cytoplasm. We identified two nuclear localization signals of Stp1 and found that the Nterminal domain of Stp1 is required for localization of fulllength Stp1 to the cell periphery. We also found that Stp2 is the primary factor involved in basal activation of target gene expression. Our results indicate that the functions of two seemingly redundant transcription factors can be separated by differential degradation and distinct cellular localization.

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Amino acid sensing by Ssy1

Cited by 23 publications

References 26 publications

Identification of two cationic amino acid transporters required for nutritional signaling during mosquito reproduction

Identification of two cationic amino acid transporters required for nutritional signaling during mosquito reproduction

AGP2 Encodes the Major Permease for High Affinity Polyamine Import in Saccharomyces cerevisiae

Differential Regulation of Transcription Factors Stp1 and Stp2 in the Ssy1-Ptr3-Ssy5 Amino Acid Sensing Pathway

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