Erythropoietin Prevents Hypoxia-Induced GATA-4 Ubiquitination <i>via</i> Phosphorylation of Serine 105 of GATA-4

Abstract

Erythropoietin (EPO), an essential hormone for erythropoiesis, can provide protection against myocardial ischemia/reperfusion (I/R) injury and hypoxic apoptosis. GATA-4 is a zinc finger transcription factor, and its activation and post-translational modification are essential components in the transcriptional response to hypoxia. GATA-4 has also been reported to play a role in the cellular mechanisms of EPO-induced myocardial protection against I/R injury. In this study, we aimed to investigate the influence of EPO on GATA-4 protein stability and post-translational modification under hypoxic conditions without reperfusion. EPO induced cell viability under long-term hypoxia. EPO significantly increased phosphorylation of GATA-4 via the extracellular signal-regulated kinase (ERK) signaling pathway and reduced hypoxia-induced GATA-4 ubiquitination, which enhanced GATA-4 stability under hypoxia. ERK activation by over-expression of constitutively active mitogen-activated protein kinase 1 (MEK1) strongly increased GATA-4 phosphorylation and its protein levels and decreased GATA-4 ubiquitination under hypoxia. Despite ERK activation, GATA-4 ubiquitination was not affected under hypoxia in a GATA-4-S105A mutant. Under hypoxic condition without reperfusion, EPO-induced ERK activation was associated with post-translational modification of GATA-4, mediated by enhancement of phosphorylation of GATA-4 at Ser-105. Subsequent attenuation of GATA-4 ubiquitination led to increases in GATA-4 protein stability, which resulted in increased cell viability under hypoxia.

Ovarian Carcinoma-Associated Mesenchymal Stem Cells Arise from Tissue-Specific Normal Stroma

“…One hallmark of the TME which impacts normal MSC morphology, proliferation, and differentiation is hypoxia . Hypoxia is known to increase TGF‐β signaling and GATA4 expression, genes upregulated in CA‐MSCs . CA‐MSCs demonstrated higher transcript and protein levels of hypoxia inducible factor alpha (HIF1α) and indirect cancer stimulation induced HIF1α expression in OM MSCs (Fig.…”

Downregulation of miR-200c protects cardiomyocytes from hypoxia-induced apoptosis by targeting GATA-4

“…The activity of GATA-4 is controlled by various post-translational modifications including ubiquitination, phosphorylation and acetylation (20,47). Hypoxia induces the ubiquitination of GATA-4 and the attenuation of GATA-4 ubiquitination by erythropoietin increases cell viability under hypoxia (48). Recent studies also showed that GATA-4 undergoes epigenetic regulation by miRNAs (49,50).…”

Erythropoietin protects myocardium against ischemia–reperfusion injury under moderate hyperglycemia

“…Ubiquitination is also an important PTM affecting the GATA-4 stability (Jun et al, 2013b). In contrast to the phosphorylation and acetylation, increased ubiquitination is associated with decreased protein stability (Seet et al, 2006).…”

“…After appropriate treatments, cells from each group underwent ubiquitination or immunoprecipitation assay as previously described (Jun et al, 2013a;Jun et al, 2013b). For ubiquitination assay under each condition, cells were pre-treated with 20 μM MG132 (a proteasome inhibitor, Sigma) and subjected to administration of 20 μM U0126 or 20 IU/ml EPO as indicated, for additional 6 h of hypoxiareoxygenation.…”

“…Since GATA-4 stability is related with ubiquitination (Jun et al, 2013b), we analyzed whether EPO-activated ERK phosphorylation affected endogenous GATA-4 ubiquitination. In the presence of MG132 (a proteasomal inhibitor), hypoxia/reoxygenation-induced GATA-4 ubiquitination was decreased by EPO treatment while U0126 pretreatment diminished this protective effect in H9c2 cells in HG (Fig.…”