Sit4 Phosphatase Is Functionally Linked to the Ubiquitin-Proteasome System

Singer, Thorsten; Haefner, Stefan; Hoffmann, Michael; Fischer, Michael B.; Ilyina, Julia; Hilt, Wolfgang

doi:10.1093/genetics/164.4.1305

Cited by 13 publications

(1 citation statement)

References 69 publications

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“…Furthermore, several pieces of evidence suggest that autophagy and the ubiquitin proteasome system are coordinated for proper control of protein homeostasis and housekeeping functions, and that the inhibition of autophagy can be compensated by the induction of the proteasome, and vice versa [101][102][103][104]. Although Sit4 does not regulate proteasome activity, Sit4 and proteasome are functionally linked as they act in concert in osmoregulation and nutrient sensing [105]. More studies are required to assess if the ubiquitin proteasome system contributes to sit4∆ lifespan extension.…”

Section: Discussionmentioning

confidence: 99%

Sit4 Genetically Interacts with Vps27 to Regulate Mitochondrial Function and Lifespan in Saccharomyces cerevisiae

Martins,

Correia,

Pinheiro

et al. 2024

Cells

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The Sit4 protein phosphatase plays a key role in orchestrating various cellular processes essential for maintaining cell viability during aging. We have previously shown that SIT4 deletion promotes vacuolar acidification, mitochondrial derepression, and oxidative stress resistance, increasing yeast chronological lifespan. In this study, we performed a proteomic analysis of isolated vacuoles and yeast genetic interaction analysis to unravel how Sit4 influences vacuolar and mitochondrial function. By employing high-resolution mass spectrometry, we show that sit4Δ vacuolar membranes were enriched in Vps27 and Hse1, two proteins that are part of the endosomal sorting complex required for transport-0. In addition, SIT4 exhibited a negative genetic interaction with VPS27, as sit4∆vps27∆ double mutants had a shortened lifespan compared to sit4∆ and vps27∆ single mutants. Our results also show that Vps27 did not increase sit4∆ lifespan by improving protein trafficking or vacuolar sorting pathways. However, Vps27 was critical for iron homeostasis and mitochondrial function in sit4∆ cells, as sit4∆vps27∆ double mutants exhibited high iron levels and impaired mitochondrial respiration. These findings show, for the first time, cross-talk between Sit4 and Vps27, providing new insights into the mechanisms governing chronological lifespan.

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Section: Discussionmentioning

confidence: 99%

Sit4 Genetically Interacts with Vps27 to Regulate Mitochondrial Function and Lifespan in Saccharomyces cerevisiae

Martins,

Correia,

Pinheiro

et al. 2024

Cells

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Oxidant resistance in a yeast mutant deficient in the Sit4 phosphatase

2008

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Resistance to thiol oxidation can arise from mutations altering redox homeostasis. A Saccharomyces cerevisiae sit4-110 mutant is here described, which was isolated as resistant to the thiol-specific oxidant dipyridyl disulfide (DPS) and which contains a single-residue substitution in the SIT4 gene. Sit4p is a protein phosphatase with multiple roles in signal transduction through the target-of-rapamycin (TOR) pathway. We found that sit4-110 elevates the levels of glutathione. However, this cannot be the (only) cause for the DPS-resistance, since sit4-110 also conferred DPS/H2O2-resistance in a glutathione-deficient strain. Of the known Sit4p substrates, only Tip41p is involved in DPS-resistance; both Delta tip41 deletion and overexpression of the Tip41p target Tap42p resulted in increased DPS-resistance. Thus, the role of Sit4p in DPS-tolerance differs from its role during TOR-inactivation and salt stress. In view of Tap42p's known involvement in actin homeostasis, sit4-110 could compensate for putative actin-related defects caused by DPS. However, sit4-110 has pronounced actin polarization defects under both absence and presence of DPS. A relation between actin homeostasis and DPS resistance of sit4-110 cannot be ruled out, but our results suggest that unknown pathways might be involved in DPS resistance through mechanisms involving the Sit4p and/or Tap42p function(s).

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Sit4p-mediated dephosphorylation of Atp2p regulates ATP synthase activity and mitochondrial function

Pereira

Osório

et al. 2018

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Sit4p is a type 2A-related protein phosphatase in Saccharomyces cerevisiae involved in a wide spectrum of cellular functions, including the glucose repression of mitochondrial transcription. Here we report that Sit4p is also involved in post-translational regulation of mitochondrial proteins and identified 9 potential targets. One of these, the ATP synthase (FoF1 complex) beta subunit Atp2p, was characterized and two phosphorylation sites, T124 and T317, were identified. Expression of Atp2p-T124 or T317 phosphoresistant versions in sit4Δ cells decreased Atp2p phosphorylation confirming these as Sit4p-regulated sites. Moreover, Sit4p and Atp2p interacted both physically and genetically. Mimicking phosphorylation at T124 or T317 increased Atp2p levels, resulting in higher abundance/activity of ATP synthase. Similar changes were observed in sit4Δ cells in which Atp2p is endogenously more phosphorylated. Expression of Atp2-T124 or T317 phosphomimetics also increased mitochondrial respiration and ATP levels and extended yeast lifespan. These results suggest that Sit4p-mediated dephosphorylation of Atp2p-T124/T317 downregulates Atp2p alongside with ATP synthase and mitochondrial function. Combination of transcriptional with post-translational regulation during fermentative growth may allow for a more efficient Sit4p repression of mitochondrial respiration.

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Sit4 Phosphatase Is Functionally Linked to the Ubiquitin-Proteasome System

Cited by 13 publications

References 69 publications

Sit4 Genetically Interacts with Vps27 to Regulate Mitochondrial Function and Lifespan in Saccharomyces cerevisiae

Sit4 Genetically Interacts with Vps27 to Regulate Mitochondrial Function and Lifespan in Saccharomyces cerevisiae

Oxidant resistance in a yeast mutant deficient in the Sit4 phosphatase

Sit4p-mediated dephosphorylation of Atp2p regulates ATP synthase activity and mitochondrial function

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