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Autophagy provides nutrients but can lead to Chop-dependent induction of Bim to sensitize growth factor-deprived cells to apoptosis.

ABSTRACT: Tissue homeostasis is controlled by the availability of growth factors, which sustain exogenous nutrient uptake and prevent apoptosis. Although autophagy can provide an alternate intracellular nutrient source to support essential basal metabolism of apoptosis-resistant growth factor-withdrawn cells, antiapoptotic Bcl-2 family proteins can suppress autophagy in some settings. Thus, the role of autophagy and interactions between autophagy and apoptosis in growth factor-withdrawn cells expressing Bcl-2 or Bcl-xL were unclear. Here we show autophagy was rapidly induced in hematopoietic cells upon growth factor withdrawal regardless of Bcl-2 or Bcl-xL expression and led to increased mitochondrial lipid oxidation. Deficiency in autophagy-essential gene expression, however, did not lead to metabolic catastrophe and rapid death of growth factor-deprived cells. Rather, inhibition of autophagy enhanced survival of cells with moderate Bcl-2 expression for greater than 1 wk, indicating that autophagy promoted cell death in this time frame. Cell death was not autophagic, but apoptotic, and relied on Chop-dependent induction of the proapoptotic Bcl-2 family protein Bim. Therefore, although ultimately important, autophagy-derived nutrients appear initially nonessential after growth factor withdrawal. Instead, autophagy promotes tissue homeostasis by sensitizing cells to apoptosis to ensure only the most apoptosis-resistant cells survive long-term using autophagy-derived nutrients when growth factor deprived.

SUBMITTER: Altman BJ

PROVIDER: S-EPMC2642748 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature

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Autophagy provides nutrients but can lead to Chop-dependent induction of Bim to sensitize growth factor-deprived cells to apoptosis.

Altman Brian J BJ Wofford Jessica A JA Zhao Yuxing Y Coloff Jonathan L JL Ferguson Emily C EC Wieman Heather L HL Day Amanda E AE Ilkayeva Olga O Rathmell Jeffrey C JC

Molecular biology of the cell 20081224 4

Tissue homeostasis is controlled by the availability of growth factors, which sustain exogenous nutrient uptake and prevent apoptosis. Although autophagy can provide an alternate intracellular nutrient source to support essential basal metabolism of apoptosis-resistant growth factor-withdrawn cells, antiapoptotic Bcl-2 family proteins can suppress autophagy in some settings. Thus, the role of autophagy and interactions between autophagy and apoptosis in growth factor-withdrawn cells expressing B ...[more]

PMID: 19109422

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Project description:Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3, is a fatal neurodegenerative disease that causes loss of balance and motor co-ordination, eventually leading to paralysis. It is caused by the autosomal dominant inheritance of a long CAG trinucleotide repeat sequence within the ATXN3 gene, encoding for an expanded polyglutamine (polyQ) repeat sequence within the ataxin-3 protein. Ataxin-3 containing an expanded polyQ repeat is known to be highly prone to intraneuronal aggregation, and previous studies have demonstrated that protein quality control pathways, such as autophagy, are impaired in MJD patients and animal models of the disease. In this study, we tested the therapeutic potential of spermidine on zebrafish and rodent models of MJD to determine its capacity to induce autophagy and improve functional output. Spermidine treatment of transgenic MJD zebrafish induced autophagy and resulted in increased distances swum by the MJD zebrafish. Interestingly, treatment of the CMVMJD135 mouse model of MJD with spermidine added to drinking water did not produce any improvement in motor behaviour assays, neurological testing or neuropathology. In fact, wild type mice treated with spermidine were found to have decreased rotarod performance when compared to control animals. Immunoblot analysis of protein lysates extracted from mouse cerebellar tissue found little differences between the groups, except for an increased level of phospho-ULK1 in spermidine treated animals, suggesting that autophagy was indeed induced. As we detected decreased motor performance in wild type mice following treatment with spermidine, we conducted follow up studies into the effects of spermidine treatment in zebrafish. Interestingly, we found that in addition to inducing autophagy, spermidine treatment also induced apoptosis, particularly in wild type zebrafish. These findings suggest that spermidine treatment may not be therapeutically beneficial for the treatment of MJD, and in fact warrants caution due to the potential negative side effects caused by induction of apoptosis.

Dataset Information

Autophagy provides nutrients but can lead to Chop-dependent induction of Bim to sensitize growth factor-deprived cells to apoptosis.

Publications

Autophagy provides nutrients but can lead to Chop-dependent induction of Bim to sensitize growth factor-deprived cells to apoptosis.

Similar Datasets

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