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PPAR γ regulated CIDEA affects pro-apoptotic responses in glioblastoma

View Article: PubMed Central - PubMed

ABSTRACT

Refractoriness of glioblastoma multiforme (GBM) to current treatment paradigms has necessitated identification of new targets to better the existing therapeutic strategies. One such target is peroxisome proliferator-activated receptor gamma (PPARγ) – a transcription factor involved in regulation of lipid metabolism and inflammation. Expression of PPARγ, a known regulator of cell death-inducing DFFA-like effector (CIDEA), is modulated by hypoxia inducible factor (HIF-1α). While the involvement of CIDEA in lipid metabolism is known, its role in malignancies remains largely unknown. An elevated PPARγ and low CIDEA level was observed in GBM tumors as compared with surrounding non-neoplastic tissue. As reciprocal relation exists between PPAR and HIF-1α: and as HIF-1α is a key component in glioma progression, their role in regulating CIDEA expression in glioblastoma was investigated. Although HIF-1α inhibition had no effect on CIDEA expression, pharmacological inhibition of PPARγ elevated CIDEA levels. PPARγ mediated upregulation of CIDEA was accompanied by decreased recruitment of NFκB and SP1 to their predicted binding sites on CIDEA promoter. Ectopic expression of CIDEA triggered apoptosis, activated JNK, decreased HIF-1α activation and increased PPARγ levels in glioma cells. While CIDEA overexpression induced actin cytoskeletal disruption, cell cycle arrest, release of pro-inflammatory cytokine IL-6 in a JNK-dependent manner; CIDEA mediated apoptotic cell death, decreased STAT3 phosphorylation and increased p53 acetylation was JNK independent. This study highlights for the first time the existence of (i) PPARγ-CIDEA regulatory loop in glioma and (ii) novel function of CIDEA as regulator of glioma cell survival.

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JNK regulates CIDEA mediated actin cytoskeletal disruption. CIDEA overexpression alters the levels of phospho-VASP (a) and phospho-Cofilin (b) in glioma cell lines in a JNK dependent manner. A representative blot is shown from two independent experiments with identical results. Blots were re-probed with β-tubulin to establish loading control. (c) CIDEA overexpression affects actin cytoskeleton architecture in a JNK-dependent manner. Confocal imaging depicts that association between Cofilin (green, Alexa Fluor 488) and actin (red, rhodamine-phalloidin) observed in CIDEA overexpressing cells is reverted by JNK inhibition. Representative images from two independent experiments are shown for indicated conditions.
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fig6: JNK regulates CIDEA mediated actin cytoskeletal disruption. CIDEA overexpression alters the levels of phospho-VASP (a) and phospho-Cofilin (b) in glioma cell lines in a JNK dependent manner. A representative blot is shown from two independent experiments with identical results. Blots were re-probed with β-tubulin to establish loading control. (c) CIDEA overexpression affects actin cytoskeleton architecture in a JNK-dependent manner. Confocal imaging depicts that association between Cofilin (green, Alexa Fluor 488) and actin (red, rhodamine-phalloidin) observed in CIDEA overexpressing cells is reverted by JNK inhibition. Representative images from two independent experiments are shown for indicated conditions.

Mentions: CIDEA overexpression was accompanied by altered cell morphology, suggestive of disrupted cytoskeletal architecture (Supplementary Figure 3). Vasodilator-stimulated phosphoprotein (VASP) signaling is critical for dynamic actin reorganization, and VASP phosphorylation controls actin cytoskeleton remodeling.23 Inactivation of cofilin by its phosphorylation leads to accumulation of actin filaments.24 The elevated level of active phosphorylated VASP (Figure 6a) and non-phosphorylated Cofilin (Figure 6b) observed in CIDEA overexpressed cell was abrogated upon JNK inhibition. Immuno-cytochemical studies using antibodies directed against cofilin and direct labelling of actin using fluorophore-tagged Rhodamine further suggested that CIDEA over-expression disrupts polymerized F-actin structure in a JNK dependent manner (Figure 6c). Similar co-localization experiment performed in U87 and T98G glioma cells yielded identical results (data not shown).


PPAR γ regulated CIDEA affects pro-apoptotic responses in glioblastoma
JNK regulates CIDEA mediated actin cytoskeletal disruption. CIDEA overexpression alters the levels of phospho-VASP (a) and phospho-Cofilin (b) in glioma cell lines in a JNK dependent manner. A representative blot is shown from two independent experiments with identical results. Blots were re-probed with β-tubulin to establish loading control. (c) CIDEA overexpression affects actin cytoskeleton architecture in a JNK-dependent manner. Confocal imaging depicts that association between Cofilin (green, Alexa Fluor 488) and actin (red, rhodamine-phalloidin) observed in CIDEA overexpressing cells is reverted by JNK inhibition. Representative images from two independent experiments are shown for indicated conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4979534&req=5

fig6: JNK regulates CIDEA mediated actin cytoskeletal disruption. CIDEA overexpression alters the levels of phospho-VASP (a) and phospho-Cofilin (b) in glioma cell lines in a JNK dependent manner. A representative blot is shown from two independent experiments with identical results. Blots were re-probed with β-tubulin to establish loading control. (c) CIDEA overexpression affects actin cytoskeleton architecture in a JNK-dependent manner. Confocal imaging depicts that association between Cofilin (green, Alexa Fluor 488) and actin (red, rhodamine-phalloidin) observed in CIDEA overexpressing cells is reverted by JNK inhibition. Representative images from two independent experiments are shown for indicated conditions.
Mentions: CIDEA overexpression was accompanied by altered cell morphology, suggestive of disrupted cytoskeletal architecture (Supplementary Figure 3). Vasodilator-stimulated phosphoprotein (VASP) signaling is critical for dynamic actin reorganization, and VASP phosphorylation controls actin cytoskeleton remodeling.23 Inactivation of cofilin by its phosphorylation leads to accumulation of actin filaments.24 The elevated level of active phosphorylated VASP (Figure 6a) and non-phosphorylated Cofilin (Figure 6b) observed in CIDEA overexpressed cell was abrogated upon JNK inhibition. Immuno-cytochemical studies using antibodies directed against cofilin and direct labelling of actin using fluorophore-tagged Rhodamine further suggested that CIDEA over-expression disrupts polymerized F-actin structure in a JNK dependent manner (Figure 6c). Similar co-localization experiment performed in U87 and T98G glioma cells yielded identical results (data not shown).

View Article: PubMed Central - PubMed

ABSTRACT

Refractoriness of glioblastoma multiforme (GBM) to current treatment paradigms has necessitated identification of new targets to better the existing therapeutic strategies. One such target is peroxisome proliferator-activated receptor gamma (PPARγ) – a transcription factor involved in regulation of lipid metabolism and inflammation. Expression of PPARγ, a known regulator of cell death-inducing DFFA-like effector (CIDEA), is modulated by hypoxia inducible factor (HIF-1α). While the involvement of CIDEA in lipid metabolism is known, its role in malignancies remains largely unknown. An elevated PPARγ and low CIDEA level was observed in GBM tumors as compared with surrounding non-neoplastic tissue. As reciprocal relation exists between PPAR and HIF-1α: and as HIF-1α is a key component in glioma progression, their role in regulating CIDEA expression in glioblastoma was investigated. Although HIF-1α inhibition had no effect on CIDEA expression, pharmacological inhibition of PPARγ elevated CIDEA levels. PPARγ mediated upregulation of CIDEA was accompanied by decreased recruitment of NFκB and SP1 to their predicted binding sites on CIDEA promoter. Ectopic expression of CIDEA triggered apoptosis, activated JNK, decreased HIF-1α activation and increased PPARγ levels in glioma cells. While CIDEA overexpression induced actin cytoskeletal disruption, cell cycle arrest, release of pro-inflammatory cytokine IL-6 in a JNK-dependent manner; CIDEA mediated apoptotic cell death, decreased STAT3 phosphorylation and increased p53 acetylation was JNK independent. This study highlights for the first time the existence of (i) PPARγ-CIDEA regulatory loop in glioma and (ii) novel function of CIDEA as regulator of glioma cell survival.

No MeSH data available.


Related in: MedlinePlus