Pyruvate Dehydrogenase A1 Phosphorylated by Insulin Associates with Pyruvate Kinase M2 and Induces LINC00273 through Histone Acetylation

Pyruvate Dehydrogenase-Dependent Metabolic Programming Affects the Oligodendrocyte Maturation and Remyelination

The metabolic needs of the premature/premyelinating oligodendrocytes (pre-OLs) and mature oligodendrocytes (OLs) are distinct. The metabolic control of oligodendrocyte maturation from the pre-OLs to the OLs is not fully understood. Here, we show that the terminal maturation and higher mitochondrial respiration in the OLs is an integrated process controlled through pyruvate dehydrogenase complex (Pdh). Combined bioenergetics and metabolic studies show that OLs show elevated mitochondrial respiration than the pre-OLs. Our signaling studies show that the increased mitochondrial respiration activity in the OLs is mediated by the activation of Pdh due to inhibition of the pyruvate dehydrogenase kinase-1 (Pdhk1) that phosphorylates and inhibits Pdh activity. Accordingly, when Pdhk1 is directly expressed in the pre-OLs, they fail to mature into the OLs. While Pdh converts pyruvate into the acetyl-CoA by its oxidative decarboxylation, our study shows that Pdh-dependent acetyl-CoA generation from pyruvate contributes to the acetylation of the bHLH family transcription factor, oligodendrocyte transcription factor 1 (Olig1) which is known to be involved in the OL maturation. Pdh inhibition via direct expression of Pdhk1 in the pre-OLs blocks the Olig1-acetylation and OL maturation. Using the cuprizone model of demyelination, we show that Pdh is deactivated during the demyelination phase, which is however reversed in the remyelination phase upon cuprizone withdrawal. In addition, Pdh activity status correlates with the Olig1-acetylation status in the cuprizone model. Hence, the Pdh metabolic node activation allows a robust mitochondrial respiration and activation of a molecular program necessary for the terminal maturation of oligodendrocytes. Our findings open a new dialogue in the developmental biology that links cellular development and metabolism. These findings have far-reaching implications in the development of therapies for a variety of demyelinating disorders including multiple sclerosis.

Extracellular pyruvate kinase M2 induces cell migration through p-Tyr42 RhoA-mediated superoxide generation and epithelial-mesenchymal transition

In the tumor microenvironment (TME), communication between cancer cells and tumor-associated macrophages (TAMs) through secreted extracellular proteins promotes cancer progression. Here, we observed that co-culturing cancer cells (4T1) and macrophage cells (Raw264.7) significantly enhanced superoxide production in both cell types. Using MALDI-TOF, we identified PKM2 as a highly secreted protein by Raw264.7 cells and bone marrow-derived monocytes. The extracellular recombinant PKM2 protein not only enhanced cancer cell migration and invasion but also increased superoxide production. Additionally, PKM2 was found to associate with the cell surface, and its binding to integrin α5/β1 receptor was inhibited by antibodies specifically targeting it. Furthermore, we investigated downstream signaling pathways involved in PKM2-induced superoxide production. We found that knock-down of RhoA and p47phox using siRNAs effectively abolished superoxide generation in response to extracellular PKM2. Notably, extracellular PKM2 triggered the phosphorylation of p47phox at Ser345 residue and RhoA at Tyr42 residue (p-Tyr42 RhoA). Moreover, extracellular PKM2 exerted regulatory control over the expression of key epithelial-mesenchymal transition (EMT) markers, including ZEB1, Snail1, vimentin, and E-cadherin. Interestingly, p-Tyr42 RhoA translocated to the nucleus, where it bound to the ZEB1 promoter region. In light of these findings, we propose that extracellular PKM2 within the TME plays a critical role in tumorigenesis by promoting cancer cell migration and invasion through RhoA/p47phox signaling pathway.

Association of Phosphorylated Pyruvate Dehydrogenase with Pyruvate Kinase M2 Promotes PKM2 Stability in Response to Insulin

Insulin is a crucial signalling molecule that primarily functions to reduce blood glucose levels through cellular uptake of glucose. In addition to its role in glucose homeostasis, insulin has been shown to regulate cell proliferation. Specifically, insulin enhances the phosphorylation of pyruvate dehydrogenase E1α (PDHA1) at the Ser293 residue and promotes the proliferation of HepG2 hepatocellular carcinoma cells. Furthermore, we previously observed that p-Ser293 PDHA1 bound with pyruvate kinase M2 (PKM2) as confirmed by coimmunoprecipitation. In this study, we used an in silico analysis to predict the structural conformation of the two binding proteins. However, the function of the protein complex remained unclear. To investigate further, we treated cells with si-PDHA1 and si-PKM2, which led to a reduction in PKM2 and p-Ser293 PDHA1 levels, respectively. Additionally, we found that the PDHA S293A dephospho-mimic reduced PKM2 levels and its associated enzyme activity. Treatment with MG132 and leupeptin impeded the PDHA1 S293A-mediated PKM2 reduction. These results suggest that the association between p-PDHA1 and PKM2 promotes their stability and protects them from protein degradation. Of interest, we observed that p-PDHA1 and PKM2 were localized in the nucleus in liver cancer patients. Under insulin stimulation, the knockdown of both PDHA1 and PKM2 led to a reduction in the expression of common genes, including KDMB1. These findings suggest that p-PDHA1 and PKM2 play a regulatory role in these proteins' expression and induce tumorigenesis in response to insulin.

Acylation of the Rat Brain Proteins is Affected by the Inhibition of Pyruvate Dehydrogenase in vivo

Organism adaptation to metabolic challenges requires coupling of metabolism to gene expression. In this regard, acylations of histones and metabolic proteins acquire significant interest. We hypothesize that adaptive response to inhibition of a key metabolic process, catalyzed by the acetyl-CoA-generating pyruvate dehydrogenase (PDH) complex, is mediated by changes in the protein acylations. The hypothesis is tested by intranasal administration to animals of PDH-specific inhibitors acetyl(methyl)phosphinate (AcMeP) or acetylphosphonate methyl ester (AcPMe), followed by the assessment of physiological parameters, brain protein acylation, and expression/phosphorylation of PDHA subunit. At the same dose, AcMeP, but not AcPMe, decreases acetylation and increases succinylation of the brain proteins with apparent molecular masses of 15-20 kDa. Regarding the proteins of 30-50 kDa, a strong inhibitor AcMeP affects acetylation only, while a less efficient AcPMe mostly increases succinylation. The unchanged succinylation of the 30-50 kDa proteins after the administration of AcMeP coincides with the upregulation of desuccinylase SIRT5. No significant differences between the levels of brain PDHA expression, PDHA phosphorylation, parameters of behavior or ECG are observed in the studied animal groups. The data indicate that the short-term inhibition of brain PDH affects acetylation and/or succinylation of the brain proteins, that depends on the inhibitor potency, protein molecular mass, and acylation type. The homeostatic nature of these changes is implied by the stability of physiological parameters after the PDH inhibition.

Phosphonate Inhibitors of Pyruvate Dehydrogenase Perturb Homeostasis of Amino Acids and Protein Succinylation in the Brain

Mitochondrial pyruvate dehydrogenase complex (PDHC) is essential for brain glucose and neurotransmitter metabolism, which is dysregulated in many pathologies. Using specific inhibitors of PDHC in vivo, we determine biochemical and physiological responses to PDHC dysfunction. Dose dependence of the responses to membrane-permeable dimethyl acetylphosphonate (AcPMe2) is non-monotonous. Primary decreases in glutathione and its redox potential, methionine, and ethanolamine are alleviated with increasing PDHC inhibition, the alleviation accompanied by physiological changes. A comparison of 39 brain biochemical parameters after administration of four phosphinate and phosphonate analogs of pyruvate at a fixed dose of 0.1 mmol/kg reveals no primary, but secondary changes, such as activation of 2-oxoglutarate dehydrogenase complex (OGDHC) and decreased levels of glutamate, isoleucine and leucine. The accompanying decreases in freezing time are most pronounced after administration of methyl acetylphosphinate and dimethyl acetylphosphonate. The PDHC inhibitors do not significantly change the levels of PDHA1 expression and phosphorylation, sirtuin 3 and total protein acetylation, but increase total protein succinylation and glutarylation, affecting sirtuin 5 expression. Thus, decreased production of the tricarboxylic acid cycle substrate acetyl-CoA by inhibited PDHC is compensated by increased degradation of amino acids through the activated OGDHC, increasing total protein succinylation/glutarylation. Simultaneously, parasympathetic activity and anxiety indicators decrease.