Differential expression of pyruvate dehydrogenase E1A and its inactive phosphorylated form among breast cancer subtypes

Pak1 dysregulates pyruvate metabolism in PDAC cells by exerting a phosphorylation-mediated regulatory effect on PDHA1

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive form of pancreatic cancer with the worst prognosis. Treating PDAC poses significant challenges, as tumor cells adapt metabolic alterations to thrive in the hypoxic environment created by desmoplasia surrounding the tumor cells. p21-activated kinase (Pak1), a serine-threonine kinase is found to be upregulated in many solid tumors and promotes tumor progression via diverse signaling pathways. In this study, we focused on exploring the role of Pak1 in mediating tumor cell metabolism. Deletion of the Pak1 gene reduced the tumorigenic potential of PDAC cells. Also, Pak1 regulated both glycolysis and mitochondrial respiration in PDAC cells, contributing to the Warburg phenomenon. Untargeted metabolomic analysis revealed that Pak1 was strongly associated with pyruvate metabolism. Interestingly, we found that Pak1 interacted and phosphorylated pyruvate dehydrogenase E1α (PDHA1) at serine 152. This phosphorylation negatively regulates PDHA1 activity, implying the direct regulatory role of Pak1 in pyruvate metabolism. Moreover, deleting the Pak1 gene altered the expression and activity of PDHA1 and LDHA, as both are involved in regulating the direction of pyruvate flux inside the cells. Our study demonstrated that Pak1 plays a significant role in PDAC metabolism and Warburg effect, partly by phosphorylating PDHA1.

Effect and mechanism of Dichloroacetate in the treatment of stroke and the resolution strategy for side effect

Stroke is a serious disease that leads to high morbidity and mortality, and ischemic stroke accounts for more than 80% of strokes. At present, the only effective drug recombinant tissue plasminogen activator is limited by its indications, and its clinical application rate is not high. Therefore, it is urgent to develop effective new drugs according to the pathological mechanism. In the hypoxic state after ischemic stroke, anaerobic glycolysis has become the main way to provide energy to the brain. This process is essential for the maintenance of important brain functions and has important implications for recovery after stroke. However, acidosis caused by anaerobic glycolysis and lactic acid accumulation is an important pathological process after ischemic stroke. Dichloroacetate (DCA) is an orphan drug that has been used for decades to treat children with genetic mitochondrial diseases. Some studies have confirmed the role of DCA in stroke, but the conclusions are conflicting because some believe that DCA is not effective for ischemic stroke and may aggravate hemorrhagic stroke. This study reviews these studies and finds that DCA has a good effect on ischemic stroke. DCA can protect ischemic stroke by improving oxidative stress, reducing neuroinflammation, inhibiting apoptosis, protecting blood-brain barrier, and regulating metabolism. We also describe the differences in the outcomes of DCA in the treatment of ischemic stroke and the reasons why DCA aggravate hemorrhagic stroke. In addition, DCA, as a water disinfection byproduct, has been concerned about its toxicity. We describe the causes and solutions of peripheral neuropathy caused by DCA. In summary, this study analyzes the neuroprotective mechanism of DCA in ischemic stroke and the contradiction of the different research results, and discusses the causes and solutions of its adverse effects.

Evaluation of IP3R3 Gene Silencing Effect on Pyruvate Dehydrogenase (PDH) Enzyme Activity in Breast Cancer Cells with and Without Estrogen Receptor

Background

Inositol 1,4,5-trisphosphate receptor (IP3R), a critical calcium ion (Ca2+) regulator, plays a vital role in breast cancer (BC) metabolism. Dysregulated IP3R in BC cells can drive abnormal growth or cell death. Estradiol increases IP3R type 3 (IP3R3) levels in BC, promoting cell proliferation and metabolic changes, including enhanced pyruvate dehydrogenase (PDH) activity, which, when reduced, leads to cell apoptosis. The study silenced IP3R3 to assess its impact on PDH.

Materials and Methods

The study used IP3R3 small interfering RNA (siRNA) to target Michigan Cancer Foundation-7 (MCF-7) and MDA-MB-231 cell lines. Transfection success was confirmed by flow cytometry. Cell viability and gene silencing were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and real-time quantitative polymerase chain reaction (PCR) assays. Protein expression and cellular activity were analyzed through western blotting and PDH activity measurement.

Results

Transfecting MCF-7 and MDA-MB-231 cells with IP3R3 siRNA achieved a 65% transfection rate without significant toxicity. IP3R3 gene silencing effectively reduced IP3R3 messenger RNA (mRNA) and protein levels in both cell lines, leading to decreased PDH enzyme activity, especially in MDA-MB-231 cells.

Conclusion

The study highlights a link between high IP3R3 gene silencing and reduced PDH activity, with higher IP3R3 expression in estrogen-independent (MDA-MB-231) compared to estrogen-dependent (MCF-7) cell lines. This suggests a potential impact on BC metabolism and tumor growth via regulation of PDH activity.

ERN1 dependent impact of glutamine and glucose deprivations on the pyruvate dehydrogenase genes expression in glioma cells

Objective. The aim of the present study was to investigate the expression of pyruvate dehydrogenase genes such as PDHA1, PDHB, DLAT, DLD, and PDHX in U87 glioma cells in response to glutamine and glucose deprivations in control glioma cells and endoplasmic reticulum to nucleus signaling 1 (ERN1) knockdown cells, the major endoplasmic reticulum (ER) stress signaling pathway, to find out whether there exists a possible dependence of these important regulatory genes expression on both glutamine and glucose supply as well as ERN1 signaling.

Methods. The expression level of PDHA1, PDHB, DLAT, DLD, and PDHX genes was studied by real-time quantitative polymerase chain reaction in control U87 glioma cells (transfected by empty vector) and cells with inhibition of ERN1(transfected by dnERN1) after cells exposure to glucose and glutamine deprivations.

Results. The data showed that the expression level of PDHA1, PDHB, DLAT, and DLD genes was down-regulated (more profound in PDHB gene) in control glioma cells treated with glutamine deprivation. At the same time, ERN1 knockdown modified the impact of glutamine deprivation on the expression level of all these genes in glioma cells: suppressed the sensitivity of PDHB and DLD genes expression and removed the impact of glutamine deprivation on the expression of PDHA1 and DLAT genes. Glucose deprivation did not significantly change the expression level of all studied genes in control glioma cells, but ERN1 knockdown is suppressed the impact of glucose deprivation on PDHX and DLD genes expression and significantly enhanced the expression of PDHA1 and PDHB genes. No significant changes were observed in the sensitivity of PDHX gene expression to glutamine deprivation neither in control nor ERN1 knock-down glioma cells. The knock-down of ERN1 removed the sensitivity of DLAT gene expression to glucose deprivation.

Conclusion. The results of this investigation demonstrate that the exposure of control U87 glioma cells under glutamine deprivation significantly affected the expression of PDHA1, PDHB, DLAT, and DLD genes in a gene specific manner and that impact of glutamine deprivation was modified by inhibition of the ER stress signaling mediated by ERN1. At the same time, glucose deprivation affected the expression of PDHA1, PDHB, PDHX, and DLD genes in ERN1 knockdown glioma cells only. Thus, the expression of pyruvate dehydrogenase genes under glutamine and glucose deprivation conditions appears to be controlled by the ER stress signaling through ERN1.

GLUTAMINE DEPRIVATION AFFECTS THE EXPRESSION OF GENES WHICH CONTROL PYRUVATE DEHYDROGENASE ACTIVITY: THE IMPACT OF ERN1 KNOCKDOWN

The aim of the current investigation was to study the expression of genes encoded pyruvate dehydrogenase subunits (PDHA1, PDHB, PDHX, DLAT, and DLD) in U87 glioma cells in response to glutamine deprivation in U87 glioma cells in relation to knockdown of ERN1 for evaluation of a possible dependence of the expression of these important regulatory genes from glutamine supply and ERN1 signaling. Methods. The expression of PDHA1, PDHB, PDHX, DLAT, and DLD genes was studied by real-time qPCR in control U87 glioma cells (transfected by vector) and cells with knockdown of ERN1 (transfected by dnERN1) after exposure to glutamine deprivation condition. Total RNA was extracted from glioma cells using TRIZOL reagent. An RNA quantity as well as spectral characteristics was measured using NanoDrop One. For reverse transcription of mRNAs we used Thermo Scientific Verso cDNA Synthesis Kit (Germany). The values of mRNA expressions were normalized to the level of ACTB mRNA and represented as percent of control (100 %). Results. It was shown that the expression level of PDH1, PDHB, DLAT, and DLD genes was down-regulated in control glioma cells treated by glutamine deprivation. At the same time, ERN1 knockdown is suppressed the effect of glutamine deprivation on PDHB and DLD gene expressions in glioma cells, but did not change significantly the impact of glutamine deprivation on the expression of PDHA1, DLAT, and PDHX genes. Conclusions. The results of this investigation demonstrated that the expression of PDH1, PDHB, PDHX, DLAT, and DLD genes was significantly affected by exposure of U87 glioma cells under glutamine deprivation condition and that the effect of glutamine deprivation on the expression of most these genes was modified in cells with knockdown of ERN1, a major signaling pathway of the endoplasmic reticulum stress.