Control of autophagy with small molecules

Cho, Yoon Sun; Kwon, Ho Jeong

doi:10.1007/s12272-010-1201-6

Cited by 13 publications

(8 citation statements)

References 44 publications

(34 reference statements)

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“…The identification of autophagy regulators will not only advance our mechanistic understanding of autophagy but will also facilitate modulation of autophagy for practical applications. Although some chemical modulators of mammalian autophagy have been identified (24), these modulators are ineffective in plants. Therefore, the BRET-based AtAtg8 substrates described here will allow us to screen for autophagy regulators under in vitro and in vivo conditions in a high throughput manner.…”

Section: Discussionmentioning

confidence: 99%

Differential processing of Arabidopsis ubiquitin-like Atg8 autophagy proteins by Atg4 cysteine proteases

Woo¹,

Park

Dinesh‐Kumar³

2013

Proc. Natl. Acad. Sci. U.S.A.

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Significance Autophagy is a highly regulated biological process for recycling or degrading cellular contents in response to environmental stimuli. Atg4 cysteine protease-mediated processing of Atg8 proteins is required for formation of intracellular vesicles, autophagosomes, which carry cellular cargoes to the vacuole/lysosome. Because the Arabidopsis plant contains nine AtAtg8 and two AtAtg4 proteins, we have developed unique AtAtg8 synthetic substrates to determine AtAtg4s cleavage specificity. We show that AtAtg4a is more active and cleaves all AtAtg8s efficiently compared with AtAtg4b. The AtAtg8 synthetic substrate can be efficiently incorporated to autophagosomes in plant cells and this requires endogenous AtAtg4s. The AtAtg8 synthetic substrates described here are suitable to screen for in vitro and in vivo autophagy regulators.

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Section: Discussionmentioning

confidence: 99%

Differential processing of Arabidopsis ubiquitin-like Atg8 autophagy proteins by Atg4 cysteine proteases

Woo¹,

Park

Dinesh‐Kumar³

2013

Proc. Natl. Acad. Sci. U.S.A.

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“…A number of diverse signaling complexes have effects on the respective molecular steps in the regulation of the autophagic process [12], [13]. There are several pharmacological compounds, including rapamycin, a well-known specific inhibitor of mammalian target of rapamycin (mTOR), that have been found to induce the autophagic process [14]. Rapamycin has been used as a conventional reagent for autophagy activation since it was first discovered that its inhibition of mTOR strongly induced autophagy.…”

Section: Introductionmentioning

confidence: 99%

Inhibitory Effect of mTOR Activator MHY1485 on Autophagy: Suppression of Lysosomal Fusion

et al. 2012

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Autophagy is a major degradative process responsible for the disposal of cytoplasmic proteins and dysfunctional organelles via the lysosomal pathway. During the autophagic process, cells form double-membraned vesicles called autophagosomes that sequester disposable materials in the cytoplasm and finally fuse with lysosomes. In the present study, we investigated the inhibition of autophagy by a synthesized compound, MHY1485, in a culture system by using Ac2F rat hepatocytes. Autophagic flux was measured to evaluate the autophagic activity. Autophagosomes were visualized in Ac2F cells transfected with AdGFP-LC3 by live-cell confocal microscopy. In addition, activity of mTOR, a major regulatory protein of autophagy, was assessed by western blot and docking simulation using AutoDock 4.2. In the result, treatment with MHY1485 suppressed the basal autophagic flux, and this inhibitory effect was clearly confirmed in cells under starvation, a strong physiological inducer of autophagy. The levels of p62 and beclin-1 did not show significant change after treatment with MHY1485. Decreased co-localization of autophagosomes and lysosomes in confocal microscopic images revealed the inhibitory effect of MHY1485 on lysosomal fusion during starvation-induced autophagy. These effects of MHY1485 led to the accumulation of LC3II and enlargement of the autophagosomes in a dose- and time- dependent manner. Furthermore, MHY1485 induced mTOR activation and correspondingly showed a higher docking score than PP242, a well-known ATP-competitive mTOR inhibitor, in docking simulation. In conclusion, MHY1485 has an inhibitory effect on the autophagic process by inhibition of fusion between autophagosomes and lysosomes leading to the accumulation of LC3II protein and enlarged autophagosomes. MHY1485 also induces mTOR activity, providing a possibility for another regulatory mechanism of autophagy by the MHY compound. The significance of this study is the finding of a novel inhibitor of autophagy with an mTOR activating effect.

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“…Indeed, targeting autophagy may provide new opportunities for cancer drug discovery. Several small molecules which modulate autophagy have been already described [8,9,10]. Interestingly, promotion of cell death for cancer therapy has been observed not only with autophagy inducers, but also with autophagy inhibitors [11].…”

Section: Introductionmentioning

confidence: 99%

Modulation of Autophagy by a Thioxanthone Decreases the Viability of Melanoma Cells

et al. 2016

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(1) Background: Our previous studies unveiled the hit thioxanthone TXA1 as an inhibitor of P-glycoprotein (drug efflux pump) and of human tumor cells growth, namely of melanoma cells. Since TXA1 is structurally similar to lucanthone (an autophagy inhibitor and apoptosis inducer) and to N 10 -substituted phenoxazines (isosteres of thioxanthones, and autophagy inducers), this study aimed at further assessing its cytotoxic mechanism and evaluating its potential as an autophagy modulator in A375-C5 melanoma cells; (2) Methods: Flow cytometry with propidium iodide (PI) for cell cycle profile analysis; Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, flow cytometry with Annexin V/PI labeling and Western blot for apoptosis analysis were conducted. A pharmacophore approach was used for mapping TXA1 onto pharmacophores for autophagy induction. Autophagy analyses included transmission electron microscopy for visualization of autophagic structures, fluorescence microscopy for observation of monodansylcadaverine (MDC) staining, pattern of LC3 expression in the cells and acridine orange staining, and Western blot for autophagic proteins expression; (3) Results: TXA1 induced autophagy of melanoma cells at the GI 50 concentration (3.6 µM) and apoptosis at twice that concentration. Following treatment with TXA1, autophagic structures were observed, together with the accumulation of autophagosomes and the formation of autophagolysosomes. An increase in LC3-II levels was also observed, which was reverted by 3-methyladenine (3-MA) (an early stage autophagy-inhibitor) but further increased by E-64d/pepstatin (late-stage autophagy inhibitors). Finally, 3-MA also reverted the effect of TXA1 in cellular viability; (4) Conclusion: TXA1 decreases the viability of melanoma cells by modulation of autophagy and may, therefore, serve as a lead compound for the development of autophagy modulators with antitumor activity.

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Control of autophagy with small molecules

Cited by 13 publications

References 44 publications

Differential processing of Arabidopsis ubiquitin-like Atg8 autophagy proteins by Atg4 cysteine proteases

Differential processing of Arabidopsis ubiquitin-like Atg8 autophagy proteins by Atg4 cysteine proteases

Inhibitory Effect of mTOR Activator MHY1485 on Autophagy: Suppression of Lysosomal Fusion

Modulation of Autophagy by a Thioxanthone Decreases the Viability of Melanoma Cells

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