Transient activation of fission yeast AMPK is required for cell proliferation during osmotic stress

Schutt, Katherine L.; Moseley, James B.

doi:10.1091/mbc.e17-04-0235

Cited by 16 publications

(19 citation statements)

References 75 publications

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“…At the same time (15-60 min), mTOR and S6 ribosomal protein showed decreased phosphorylation, which indicates that AMPK is not responsible for mTOR inhibition at this time. In line with this idea, a transient decrease in AMPK phosphorylation at phospho-T189 was also observed in yeast exposed to hyperosmotic stress [8]. We did find AMPK activation, however, at later times (3 and 6 h).…”

Section: Discussionsupporting

confidence: 88%

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Hyperosmotic Stress Initiates AMPK-Independent Autophagy and AMPK- and Autophagy-Independent Depletion of Thioredoxin 1 and Glyoxalase 2 in HT22 Nerve Cells

Dafre

Schmitz

Maher

2019

Oxidative Medicine and Cellular Longevity

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Background. Hyperosmotic stress is an important pathophysiologic condition in diabetes, severe trauma, dehydration, infection, and ischemia. Furthermore, brain neuronal cells face hyperosmotic stress in ageing and Alzheimer’s disease. Despite the enormous importance of knowing the homeostatic mechanisms underlying the responses of nerve cells to hyperosmotic stress, this topic has been underrepresented in the literature. Recent evidence points to autophagy induction as a hallmark of hyperosmotic stress, which has been proposed to be controlled by mTOR inhibition as a consequence of AMPK activation. We previously showed that methylglyoxal induced a decrease in the antioxidant proteins thioredoxin 1 (Trx1) and glyoxalase 2 (Glo2), which was mediated by AMPK-dependent autophagy. Thus, we hypothesized that hyperosmotic stress would have the same effect. Methods. HT22 hippocampal nerve cells were treated with NaCl (37, 75, or 150 mM), and the activation of the AMPK/mTOR pathway was investigated, as well as the levels of Trx1 and Glo2. To determine if autophagy was involved, the inhibitors bafilomycin (Baf) and chloroquine (CQ), as well as ATG5 siRNA, were used. To test for AMPK involvement, AMPK-deficient mouse embryonic fibroblasts (MEFs) were used. Results. Hyperosmotic stress induced a clear increase in autophagy, which was demonstrated by a decrease in p62 and an increase in LC3 lipidation. AMPK phosphorylation, linked to a decrease in mTOR and S6 ribosomal protein phosphorylation, was also observed. Deletion of AMPK in MEFs did not prevent autophagy induction by hyperosmotic stress, as detected by decreased p62 and increased LC3 II, or mTOR inhibition, inferred by decreased phosphorylation of P70 S6 kinase and S6 ribosomal protein. These data indicating that AMPK was not involved in autophagy activation by hyperosmotic stress were supported by a decrease in pS555-ULK1, an AMPK phosphorylation site. Trx1 and Glo2 levels were decreased at 6 and 18 h after treatment with 150 mM NaCl. However, this decrease in Trx1 and Glo2 in HT22 cells was not prevented by autophagy inhibition by Baf, CQ, or ATG5 siRNA. AMPK-deficient MEFs under hyperosmotic stress presented the same Trx1 and Glo2 decrease as wild-type cells. Conclusion. Hyperosmotic stress induced AMPK activation, but this was not responsible for its effects on mTOR activity or autophagy induction. Moreover, the decrease in Trx1 and Glo2 induced by hyperosmotic stress was independent of both autophagy and AMPK activation.

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Section: Discussionsupporting

confidence: 88%

“…Hyperosmotic stress has been shown to induce autophagy in several organisms, including yeast [8], fish [9], and a number of mammalian cells [9–12]. Autophagy and microtubule remodeling have been proposed to play a prominent role in the osmoprotective cell response [12].…”

Section: Introductionmentioning

confidence: 99%

Hyperosmotic Stress Initiates AMPK-Independent Autophagy and AMPK- and Autophagy-Independent Depletion of Thioredoxin 1 and Glyoxalase 2 in HT22 Nerve Cells

Dafre

Schmitz

Maher

2019

Oxidative Medicine and Cellular Longevity

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“…We tested the role of proteins that signal changes in glucose availability and cellular energy status. During glucose starvation, Pak1 still localized to RNP granules with Sum2 upon deletion of Ssp2, the catalytic subunit of AMP-activated protein kinase, and upon deletion of its upstream activator Ssp1 (Deng et al, 2017; Schutt and Moseley, 2017; Valbuena and Moreno, 2012) (Figure 6A). Similarly, Pak1 localized to RNP granules with Sum2 after deletion of Sds23 (Figure 6A), which regulates glucose-dependent phosphatase activity (Hanyu et al, 2009; Ishii et al, 1996).…”

Section: Resultsmentioning

confidence: 99%

Pak1 kinase controls cell shape through ribonucleoprotein granules

Magliozzi

Moseley

2021

Preprint

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Fission yeast cells maintain a rod shape due to conserved signaling pathways that organize the cytoskeleton for polarized growth. We discovered a mechanism linking the conserved protein kinase Pak1 with cell shape through the RNA-binding protein Sts5. Pak1 prevents Sts5 association with P bodies by directly phosphorylating its intrinsically disordered region (IDR). Pak1 and the cell polarity kinase Orb6 both phosphorylate the Sts5 IDR but at distinct residues. Mutations preventing phosphorylation in the Sts5 IDR cause increase P body formation and defects in cell shape and polarity. Unexpectedly, when cells encounter glucose starvation, PKA signaling triggers Pak1 recruitment to P bodies with Sts5. Through retargeting experiments, we reveal that Pak1 localizes to these ribonucleoprotein (RNP) granules to promote rapid dissolution of Sts5 upon glucose addition. Our work reveals a new role for Pak1 in regulating cell shape through RNPs during normal and stressed growth conditions.

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“…We tested the role of proteins that signal changes in glucose availability and cellular energy status. During glucose starvation, Pak1 still colocalized with Sum2 upon deletion of Ssp2, the catalytic subunit of AMP-activated protein kinase, and upon deletion of its upstream activator Ssp1 (Deng et al, 2017;Schutt and Moseley, 2017;Valbuena and Moreno, 2012) (Figure 7A). Similarly, Pak1 co-localized with Sum2 after deletion of Sds23 (Figure 7A), which regulates glucose-dependent phosphatase activity (Hanyu et al, 2009;Ishii et al, 1996).…”

Section: Pka Signaling Is Required For Pak1 Stress Granule Localizationmentioning

confidence: 99%

Pak1 kinase controls cell shape through ribonucleoprotein granules

Magliozzi

Moseley

2021

eLife

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Fission yeast cells maintain a rod shape due to conserved signaling pathways that organize the cytoskeleton for polarized growth. We discovered a mechanism linking the conserved protein kinase Pak1 with cell shape through the RNA-binding protein Sts5. Pak1 (also called Shk1 and Orb2) prevents Sts5 association with P bodies by directly phosphorylating its intrinsically disordered region (IDR). Pak1 and the cell polarity kinase Orb6 both phosphorylate the Sts5 IDR but at distinct residues. Mutations preventing phosphorylation in the Sts5 IDR cause increased P body formation and defects in cell shape and polarity. Unexpectedly, when cells encounter glucose starvation, PKA signaling triggers Pak1 recruitment to stress granules with Sts5. Through retargeting experiments, we reveal that Pak1 localizes to stress granules to promote rapid dissolution of Sts5 upon glucose addition. Our work reveals a new role for Pak1 in regulating cell shape through ribonucleoprotein granules during normal and stressed growth conditions.

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Transient activation of fission yeast AMPK is required for cell proliferation during osmotic stress

Abstract: Transient activation of the cellular energy sensor AMPK during osmotic stress requires its energy-sensing subunit. Cellular ATP levels decrease during osmotic stress, which triggers energy stress, which in turn requires dynamic activation of AMPK.

Cited by 16 publications

References 75 publications

Hyperosmotic Stress Initiates AMPK-Independent Autophagy and AMPK- and Autophagy-Independent Depletion of Thioredoxin 1 and Glyoxalase 2 in HT22 Nerve Cells

Hyperosmotic Stress Initiates AMPK-Independent Autophagy and AMPK- and Autophagy-Independent Depletion of Thioredoxin 1 and Glyoxalase 2 in HT22 Nerve Cells

Pak1 kinase controls cell shape through ribonucleoprotein granules

Pak1 kinase controls cell shape through ribonucleoprotein granules

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