Glycolytic Enzyme Pyruvate Kinase M2 Research Articles

AKT1 phosphorylation of cytoplasmic ME2 induces a metabolic switch to glycolysis for tumorigenesis

Many types of tumors feature aerobic glycolysis for meeting their increased energetic and biosynthetic demands. However, it remains still unclear how this glycolytic phenomenon is achieved and coordinated with other metabolic pathways in tumor cells in response to growth stimuli. Here we report that activation of AKT1 induces a metabolic switch to glycolysis from the mitochondrial metabolism via phosphorylation of cytoplasmic malic enzyme 2 (ME2), named ME2fl (fl means full length), favoring an enhanced glycolytic phenotype. Mechanistically, in the cytoplasm, AKT1 phosphorylates ME2fl at serine 9 in the mitochondrial localization signal peptide at the N-terminus, preventing its mitochondrial translocation. Unlike mitochondrial ME2, which accounts for adjusting the tricarboxylic acid (TCA) cycle, ME2fl functions as a scaffold that brings together the key glycolytic enzymes phosphofructokinase (PFKL), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and pyruvate kinase M2 (PKM2), as well as Lactate dehydrogenase A (LDHA), to promote glycolysis in the cytosol. Thus, through phosphorylation of ME2fl, AKT1 enhances the glycolytic capacity of tumor cells in vitro and in vivo, revealing an unexpected role for subcellular translocation switching of ME2 mediated by AKT1 in the metabolic adaptation of tumor cells to growth stimuli.

Regulating lactate-related immunometabolism and EMT reversal for colorectal cancer liver metastases using shikonin targeted delivery

BackgroundThere are few effective medications for treating colorectal cancer and liver metastases (CRLM). The interactions among glycolysis, epithelial-mesenchymal transition (EMT), and immune microenvironment contribute to the progression of CRLM. A main glycolytic enzyme pyruvate Kinase M2 (PKM2) is highly expressed in colorectal cancer and CRLM, and thus can be a potential therapeutic target.MethodsA therapeutic strategy was proposed and the shikonin-loaded and hyaluronic acid-modified MPDA nanoparticles (SHK@HA-MPDA) were designed for CRLM therapy via PKM2 inhibition for immunometabolic reprogramming. The treatment efficacy was evaluated in various murine models with liver metastasis of colorectal tumor.ResultsSHK@HA-MPDA achieved tumor-targeted delivery via hyaluronic acid-mediated binding with the tumor-associated CD44, and efficiently arrested colorectal tumor growth. The inhibition of PKM2 by SHK@HA-MPDA led to the remodeling of the tumor immune microenvironment and reversing EMT by lactate abatement and the suppression of TGFβ signaling; the amount of cytotoxic effector CD8+ T cells was increased while the immunosuppressive MDSCs decreased.ConclusionThe work provided a promising targeted delivery strategy for CRLM treatment by regulating glycolysis, EMT, and anticancer immunity.Graphic abstractAn immunometabolic strategy for treating colorectal cancer liver metastases using the shikonin-loaded, hyaluronic acid-modified mesoporous polydopamine nanoparticles (SHK@HA-MPDA) via glycolysis inhibition, anticancer immunity activation, and EMT reversal. SHK@HA-MPDA can inhibit cytoplasmic PKM2 and glycolysis of the tumor and reduce lactate flux, and then activate the DCs and remodel the tumor immune microenvironment. The reduced lactate flux can reduce MDSC migration and suppress EMT.

Oral Squamous Cell Carcinoma Cells with Acquired Resistance to Erlotinib Are Sensitive to Anti-Cancer Effect of Quercetin via Pyruvate Kinase M2 (PKM2).

Oral squamous cell carcinoma (OSCC) frequently carries high epidermal growth factor receptor (EGFR) expression. Erlotinib, a small molecule tyrosine kinase inhibitor (TKI), is an effective inhibitor of EGFR activity; however, resistance to this drug can occur, limiting therapeutic outcomes. Therefore, in the current study, we aimed to unveil key intracellular molecules and adjuvant reagents to overcome erlotinib resistance. First, two HSC-3-derived erlotinib-resistant cell lines, ERL-R5 and ERL-R10, were established; both exhibited relatively higher growth rates, glucose utilization, epithelial-mesenchymal transition (EMT), and invasiveness compared with parental cells. Cancer aggressiveness-related proteins, such as N-cadherin, Vimentin, Twist, MMP-2, MMP-9, and MMP-13, and the glycolytic enzymes PKM2 and GLUT1 were upregulated in ERL-R cells. Notably, ERL-R cells were sensitive to quercetin, a naturally-existing flavonol phytochemical with anti-cancer properties against various cancer cells. At a concentration of 5 μM, quercetin effectively arrested cell growth, reduced glucose utilization, and inhibited cellular invasiveness. An ERL-R5-derived xenograft mouse model confirmed the growth-inhibitory efficacy of quercetin. Additionally, knock-down of PKM2 by siRNA mimicked the effect of quercetin and re-sensitized ERL-R cells to erlotinib. Furthermore, adding quercetin blocked the development of erlotinib-mediated resistance by enhancing apoptosis. In conclusion, our data support the application of quercetin in anti-erlotinib-resistant OSCC and indicate that PKM2 is a determinant factor in erlotinib resistance and quercetin sensitivity.

WZB117 enhanced the anti-tumor effect of apatinib against melanoma via blocking STAT3/PKM2 axis.

Background: Melanoma is the most lethal skin malignant tumor with a short survival once stepping into the metastatic status and poses a therapeutic challenge. Apatinib (a tyrosine kinase inhibitor) is a promising antiangiogenic agent for the treatment of metastatic melanoma. However, antiangiogenic monotherapy is prone to acquired drug resistance and has a limited therapeutic effect. The persistence dependence of glycolytic metabolism in antiangiogenic therapy-resistant cells provides evidence that glycolysis inhibitors may enhance the effect of antiangiogenic therapy. So, this study aimed to investigate whether WZB117 (a specific GLUT1 inhibitor) could enhance the anti-tumor effect of apatinib against melanoma and its potential mechanisms. Methods: We investigated the anti-tumor effects of apatinib alone or in combination with WZB117 on human melanoma cell lines (A375 and SK-MEL-28). The MTT assay determined cell viability and the half-maximal inhibitory concentration (IC50). Multiple drug effect/combination indexes (CI) analysis was conducted to assess interactions between apatinib and WZB117. Signal transducer and activator of transcription 3 (STAT3) pathway measured by western blotting and immunofluorescence staining. RNA expression analyses were performed using the reverse transcription-quantitative PCR method. Results: Apatinib and WZB117 showed dose and time-dependent growth inhibitory effects in both melanoma cells. The IC50 of apatinib at 48 h in A375 and SK-MEL-28 cells was 62.58 and 59.61 μM, respectively, while the IC50 of WZB117 was 116.85 and 113.91 μM, respectively. The CI values of the two drugs were 0.538 and 0.544, respectively, indicating a synergistic effect of apatinib combined with WZB117. We also found that glucose consumption and lactate production were suppressed by apatinib plus WZB117 in a dose-dependent manner, paralleled by reducing glycolytic enzyme pyruvate kinase M2 (PKM2). The potential mechanism of the combination was to suppress the phosphorylation of STAT3. Knockdown of STAT3 by siRNA inhibited the expression of PKM2, while the activation of STAT3 by IL-6 increased the expression of PKM2. The effects of IL-6 were attenuated by apatinib combined with WZB117 treatment. Conclusion: WZB117 enhanced the anti-tumor effect of apatinib against melanoma via modulating glycolysis by blocking the STAT3/PKM2 axis, which suggested the combination of apatinib with WZB117 could be a potential therapeutic candidate for melanoma.

Spatiotemporal feedforward between PKM2 tetramers and mTORC1 prompts mTORC1 activation

Most mammalian cells couple glucose availability to anabolic processes via the mTORC1 pathway. However, the mechanism by which fluctuations in glucose availability are rapidly translated into mTORC1 signals remains elusive. Here, we show that cells rapidly respond to changes in glucose availability through the spatial coupling of mTORC1 and tetramers of the key glycolytic enzyme pyruvate kinase M2 (PKM2) on lysosomal surfaces in the late G1/S phases. The lysosomal localization of PKM2 tetramers enables rapid increases in local ATP concentrations around lysosomes to activate mTORC1, while bypassing the need to elevate global ATP levels in the entire cell. In essence, this spatial coupling establishes a feedforward loop to enable mTORC1 to rapidly sense and respond to changes in glucose availability. We further demonstrate that this mechanism ensures robust cell proliferation upon fluctuating glucose availability. Thus, we present mechanistic insights into the rapid response of the mTORC1 pathway to changes in glucose availability. The underlying mechanism may be applicable to the control of other cellular processes.

The Antitumor Effect of Cinnamaldehyde Derivative CB-PIC in Hepatocellular Carcinoma Cells via Inhibition of Pyruvate and STAT3 Signaling.

Though cinnamaldehyde derivative (CB-PIC), a major compound of cinnamon, is known to have anticancer activity, its underlying mechanism is not fully understood. In the present study, the anticancer mechanism of CB-PIC was investigated in human hepatocellular carcinoma cells (HCCs) in association with signal transducer and activator of transcription 3 (STAT3) signaling. CB-PIC exerted cytotoxicity in HepG2 and Huh7 cells. CB-PIC increased the sub G1 population and attenuated the expression of pro-poly (ADP-ribose) polymerase (PARP) and pro-Caspase3 in HepG2 and Huh7 cells. Interestingly, CB-PIC significantly abrogated the expression of a glycolytic enzyme pyruvate kinase M2 (PKM2) in HepG2 cells more than in LNCaP, A549, and HCT-116 cells. Consistently, CB-PIC reduced the expression of hexokinase 2 (HK2) and PKM2, along with a reduced production of lactate in HepG2 and Huh7 cells. Notably, CB-PIC suppressed the phosphorylation of STAT3 in HepG2 and Huh7 cells and conversely STAT3 depletion enhanced the capacity of CB-PIC to suppress the expression of HK2, PKM2, and pro-caspase3 and to reduce the viability in Huh7 cells. Furthermore, CB-PIC activated the phosphorylation of AMPK and ERK and suppressed expression of IL-6 as STAT3-related genes in HepG2 and Huh7 cells. Conversely, pyruvate treatment reversed the inhibitory effect of CB-PIC on p-STAT3, HK2, PKM2, and pro-PARP in Huh7 cells. Overall, there findings suggest that CB-PIC exerts an apoptotic effect via inhibition of the Warburg effect mediated by p-STAT3 and pyruvate signaling.

Pyruvate Kinase M2: a novel regulator of adipogenesis

Obesity is the cornerstone of many other conditions, with far‐reaching impacts on numerous body systems and quality of life. Obesity is closely and likely causally associated with metabolic syndrome and consequent atherosclerosis, heart disease, stroke, and type 2 diabetes as well as diseases such as cancer and osteoarthritis. Recent studies suggest exploring the possibility of activating brown adipose tissue as a potential anti‐obesity strategy. However, understanding the mechanisms underlying the processes of brown adipogenesis and browning is foundational for effectively promoting this strategy as a primary, secondary, and/ or tertiary preventive measure against obesity. Additionally, recent studies have identified the glycolytic enzyme pyruvate kinase M2 (PKM2), as a novel regulator of white and brown adipogenesis. Yet, the molecular mechanisms remain to be elucidated. In the current study, we investigated the effects of PKM2 deficiency on white and brown fat adipogenesis using shRNA‐mediated lentiviral approach. We also investigated the underlying molecular mechanisms. Preliminary findings demonstrate that deletion of PKM2 enhances brown fat adipogenesis via modulation of the β‐catenin signaling pathway. Additionally, disruption of β‐catenin activity altered adipocytes differentiation and mimicked the effects of PKM2 deficiency on adipogenesis. Taken together, our study suggests that targeting PKM2/β‐catenin axis may serve as a strategy to promote brown fat adipogenesis, enhance whole body energy expenditure, and prevent obesity and its associated complications.

The Role of PKM2 in Diabetic Microangiopathy.

Diabetic microangiopathy is among the most common complications affecting patients with diabetes, and includes both diabetic retinopathy (DR) and diabetic nephropathy (DKD). Diabetic microangiopathy remains a persistent threat to the health and quality of life of affected patients. Mechanistically, the severity of DR and DKD is tied to mitochondrial and glucose metabolism abnormalities, with the activation of the glycolytic enzyme pyruvate kinase M2 (PKM2) contributing to mitochondrial and glomerular dysfunction, abnormal renal hemodynamics, and retinopathy. PKM2 can activate inflammatory bodies in macrophages to promote the release of inflammatory mediators, and serves as a key regulator of inflammatory factors, chemokines and adhesion molecules. As such, there is sufficient evidence that PKM2 can be used as a biomarker for the diagnosis of diabetes and diabetic microangiopathy. Here, we survey the mechanisms whereby PKM2 contributes to diabetes-related microvascular diseases, associated regulatory roles, post-translational modifications, and the potential utility of PKM2 as a therapeutic target. Through this literature review, we have determined that PKM2 offers promise as both a diagnostic marker and therapeutic target with direct relevance to research pertaining to diabetic microangiopathy.

Abstract 9528: Apical Resection in Newborn Pig Hearts Extends the Regenerative Window of Cardiomyocyte

Background: The neonatal porcine heart possesses proliferative cardiomyocyte capacity to recover heart function and structure after an acute myocardial injury during two days of birth. In this study, we have extended the myocardial regenerative window to postnatal day 28 (P28) by a double injury pig model (AR P1 MI P28 ), which performed apical resection at P1 (AR P1 ) followed by LAD ligation at P28 (MI P28 ). However, the molecular mechanism of regenerative window extension is unknown. Methods: The AR P1 MI P28 hearts showed no visible sign of myocardial damage or malfunction 4 weeks after LAD ligation. The nuclear RNA contents were isolated from hearts that received none, singe, and double injury hearts. They performed single nuclei RNA-seq to characterize the gene-expression profile of the AR P1 MI P28 in cardiomyocytes. Results: Gene-expression profiles revealed that regenerating AR P1 MI P28 hearts contained different subpopulations of cardiomyocytes early after 2 nd injury. Louvain clustering identified the six cardiomyocyte clusters (CM1-CM6). The CM6, CM3, and CM2 clusters have mainly comprised fetal (92.4%), CTL-P1 (95.7%), and CTL-P56 (96.2%) cardiomyocytes. In contrast, the CM1 cluster has comprised heterogeneous cardiomyocyte groups from all other animal groups, including less than 1% of fetal and CTL-P1 cardiomyocytes. The CM5 and CM4 clusters have mainly comprised AR P1 MI P28 -P35 (double injury hearts harvested at P35) cardiomyocytes, 97.8% and 68.6%, respectively. Sparse modeling analysis revealed that AR and MI injury, both alone and in combination, appeared to extend the regenerative capacity of cardiomyocytes and perturb cardiomyocyte maturation. Conclusion: We have demonstrated that the unique CM5 cluster appeared only after the 2 nd injury of AR P1 MI P28 -P35 hearts. This cell cluster was characterized by a highly expressed isoenzyme of the glycolytic enzyme pyruvate kinase M2 (Pkm2) and skeletal muscle filamentous gene Nebulin. Transient expression of the CM5 cluster induces by the AR P1 might contribute to the sustained remuscularization and myocardial function recovery following an acute MI in large mammals.

Role of PKM2-Mediated Immunometabolic Reprogramming on Development of Cytokine Storm.

The cytokine storm is a marker of severity of various diseases and increased mortality. The altered metabolic profile and energy generation of immune cells affects their activation, exacerbating the cytokine storm. Currently, the emerging field of immunometabolism has highlighted the importance of specific metabolic pathways in immune regulation. The glycolytic enzyme pyruvate kinase M2 (PKM2) is a key regulator of immunometabolism and bridges metabolic and inflammatory dysfunction. This enzyme changes its conformation thus walks in different fields including metabolism and inflammation and associates with various transcription factors. This review summarizes the vital role of PKM2 in mediating immunometabolic reprogramming and its role in inducing cytokine storm, with a focus on providing references for further understanding of its pathological functions and for proposing new targets for the treatment of related diseases.

Pyruvate Kinase M2 Deficiency Enhances Brown Fat Adipogenesis and Activity

In the last decade, development and regulation of brown adipose tissue (BAT) has gained traction due to its potential role in the protection against obesity and its associated disorders. Notably, BAT activity inversely correlates with overall adiposity. Brown fat-like adipocytes, that express the brown adipocyte-specific uncoupling protein 1, are interspersed in WAT of rodents and humans. These brown-like adipocytes exhibit many of the morphological and biochemical characteristics of classical brown adipocytes. Remarkably, brown-like transformation of WAT is associated with resistance to diet induced obesity in experimental mouse models. However, the mechanisms that regulate the browning of WAT remain incompletely understood. Recent studies have shown that inhibition of the glycolytic enzyme Pyruvate Kinase M2 (PKM2) promotes brown adipogenesis. Notably, PKM2 is an upstream regulator of the Wnt/β-catenin. Although the molecular mechanisms are yet to be determined, recent studies have shown that the Wnt/β-catenin regulates the differentiation of both, white and brown adipogenesis. Therefore, the main objective of the current study is to investigate the role of Wnt/β-catenin in mediating PKM2’s function in in brown adipogenesis and function. We demonstrate that PKM2 deficiency and pharmacological inhibition enhances brown fat activity via modulation of the Wnt/β-catenin signaling pathway. These findings identify PKM2 as a good target for therapeutic approaches aiming at overcoming the obesity epidemic and its comorbidities.

HMGCR inhibition stabilizes the glycolytic enzyme PKM2 to support the growth of renal cell carcinoma.

Renal cell carcinoma (RCC) is responsible for most cases of the kidney cancer. Previous research showed that low serum levels of cholesterol level positively correlate with poorer RCC-specific survival outcomes. However, the underlying mechanisms and functional significance of the role of cholesterol in the development of RCC remain obscure. 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) plays a pivotal role in RCC development as it is the key rate-limiting enzyme of the cholesterol biosynthetic pathway. In this study, we demonstrated that the inhibition of HMGCR could accelerate the development of RCC tumors by lactate accumulation and angiogenesis in animal models. We identified that the inhibition of HMGCR led to an increase in glycolysis via the regulated HSP90 expression levels, thus maintaining the levels of a glycolysis rate-limiting enzyme, pyruvate kinase M2 (PKM2). Based on these findings, we reversed the HMGCR inhibition-induced tumor growth acceleration in RCC xenograft mice by suppressing glycolysis. Furthermore, the coadministration of Shikonin, a potent PKM2 inhibitor, reverted the tumor development induced by the HMGCR signaling pathway.

Citrullination of pyruvate kinase M2 by PADI1 and PADI3 regulates glycolysis and cancer cell proliferation

Chromodomain helicase DNA binding protein 4 (CHD4) is an ATPase subunit of the Nucleosome Remodelling and Deacetylation (NuRD) complex that regulates gene expression. CHD4 is essential for growth of multiple patient derived melanoma xenografts and for breast cancer. Here we show that CHD4 regulates expression of PADI1 (Protein Arginine Deiminase 1) and PADI3 in multiple cancer cell types modulating citrullination of arginine residues of the allosterically-regulated glycolytic enzyme pyruvate kinase M2 (PKM2). Citrullination of PKM2 R106 reprogrammes cross-talk between PKM2 ligands lowering its sensitivity to the inhibitors Tryptophan, Alanine and Phenylalanine and promoting activation by Serine. Citrullination thus bypasses normal physiological regulation by low Serine levels to promote excessive glycolysis and reduced cell proliferation. We further show that PADI1 and PADI3 expression is up-regulated by hypoxia where PKM2 citrullination contributes to increased glycolysis. We provide insight as to how conversion of arginines to citrulline impacts key interactions within PKM2 that act in concert to reprogramme its activity as an additional mechanism regulating this important enzyme.

SEMG1/2 augment energy metabolism of tumor cells

SEMG1 and SEMG2 genes belong to the family of cancer-testis antigens (CTAs), whose expression normally is restricted to male germ cells but is often restored in various malignancies. High levels of SEMG1 and SEMG2 expression are detected in prostate, renal, and lung cancer as well as hemoblastosis. However, the functional importance of both SEMGs proteins in human neoplasms is still largely unknown. In this study, by using a combination of the bioinformatics and various cellular and molecular assays, we have demonstrated that SEMG1 and SEMG2 are frequently expressed in lung cancer clinical samples and cancer cell lines of different origins and are negatively associated with the survival rate of cancer patients. Using the pull-down assay followed by LC-MS/MS mass-spectrometry, we have identified 119 proteins associated with SEMG1 and SEMG2. Among the SEMGs interacting proteins we noticed two critical glycolytic enzymes-pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA). Importantly, we showed that SEMGs increased the protein level and activity of both PKM2 and LDHA. Further, both SEMGs increased the membrane mitochondrial potential (MMP), glycolysis, respiration, and ROS production in several cancer cell lines. Taken together, these data provide first evidence that SEMGs can up-regulate the energy metabolism of cancer cells, exemplifying their oncogenic features.

Abstract 1916: Targeting Warburg effect to overcome lapatinib resistance in esophageal adenocarcinoma

Abstract Background: A major target for esophageal adenocarcinoma (EAC) therapies is the human epidermal growth factor receptor 2 (HER2). EAC overexpresses HER2 and lapatinib, a dual tyrosine kinase inhibitor blocking HER1 and HER2 pathways fails to improve patient survival. Molecular mechanisms of this lapatinib resistance are still unclear. We therefore explored the role of glycolytic enzyme pyruvate kinase M2 (PKM2), a key regulator of Warburg effect in lapatinib resistance mechanism of EAC cells. Methods: First we established lapatinib-resistant OE19 (LPR-OE19) cells from OE19 EAC cells and characterized it. We then investigated the comparative cell growth inhibition, apoptotic and lactate production effects of HER2 inhibitor lapatinib and PKM2 inhibitor shikonin either alone or in combinations, both in OE19 and LPR-OE19 cells with and without knockdown of PKM2 and HSP40 by siRNAs. We then explored the antitumor efficacy following lapatinib and shikonin mono and combination therapies in murine subcutaneous xenograft model of human EAC. Results: Lapatinib-resistant OE19 (LPR-OE19) cells were established from OE19 cells by intermittent exposure to increasing concentrations of lapatinib for a period of total six months. Lapatinib resistant LPR-OE19 cells showed downregulation of HSP40 both at protein and mRNA levels whereas showed upregulation of PKM2 only at protein level. LPR-OE19 cells showed significantly reduced sensitivity to lapatinib induced cell growth inhibition, apoptosis and decreased cell migration compared to parent OE19 cells. Interestingly, augmented cell growth inhibition, apoptosis and decreased cell migration were observed in LPR-OE19 cells compared to parent OE19 cells when lapatinib was combined with shikonin. More interestingly, knockdown of PKM2 in LPR-OE19 cells abolished the reduced sensitivity of lapatinib induced cell growth inhibition and also abolished augmented cell growth inhibition response when lapatinib and shikonin were combined. Contrary to that, knockdown of HSP40 in OE19 cells enhanced PKM2 expression leading to significantly reduced sensitivity to lapatinib induced growth inhibition with augmented growth inhibition when lapatinib and shikonin were combined. Moreover, LPR-OE19 cells showed enhanced lactate production compared to parent OE19. Interestingly, PKM2 and HSP40 co-localize with each other in the cell nucleus suggesting that PKM2 bound to molecular chaperone HSP40. In subcutaneous xenografts using LPR-OE19 cells, average net tumor growth after two weeks in different therapy groups was 494.72 mm3 in control, 403.11 mm3 after lapatinib (p=0.241), 339.48 mm3 after shikonin (p=0.0478), and 141.59 mm3 after shikonin plus lapatinib (p=0.0003). Conclusions: In conclusion, these data suggest that combination therapy with lapatinib and glycolytic inhibitor shikonin should be tested as a potent option for lapatinib resistant HER2-positive EAC patients and could be a novel treatment strategy for specific EAC. In addition, it is suggested that targeting HSP40-PKM2 interaction as an innovative therapeutic approach to overcome lapatinib resistance in EAC. Citation Format: Md Sazzad Hassan, Samantha Holmes, Victoria Makuru, Chloe Johnson, Urs von Holzen. Targeting Warburg effect to overcome lapatinib resistance in esophageal adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1916.

Inhibiting Protein Kinase Activity of Pyruvate Kinase M2 by SIRT2 Deacetylase Attenuates Psoriasis

Signal transducer and activator of transcription 3 (STAT3) is crucial for the pathogenesis of psoriasis. Studies describe pleiotropic roles for a glycolytic enzyme pyruvate kinase M2 (PKM2) as a nuclear kinase of STAT3. However, little is known about the function of PKM2 in T helper type 17 cells in association with STAT3. In this study, we investigated whether and how SIRT2 deacetylase regulated the protein kinase function of PKM2 in T helper type 17 cell‒mediated inflammatory responses in psoriasis. Sirt2 knockout mice and wild-type littermates had psoriatic dermatitis induced by topical treatment of imiquimod or intradermal injection of recombinant IL-23. An initial downregulation of SIRT2 and an increase in PKM2 acetylation and STAT3 phosphorylation were observed in psoriasiform lesions of mice. SIRT2 directly interacted with and deacetylated PKM2 to suppress STAT3 phosphorylation. Consequently, psoriasiform skin inflammation was aggravated in Sirt2 knockout mice. Conversely, genetic re-expression of Sirt2 or pharmacological blockade of PKM2 decreased the disease severity. Flow cytometric analysis of skin tissues of Sirt2 knockout mice showed enhanced infiltration of T helper type 17 cells. Exvivo experiments showed that SIRT2 deficiency accelerated T helper type 17 cell differentiation with the concomitant production of IL-17A and IL-22. The results suggest SIRT2-mediated PKM2 deacetylation as an effective option for psoriasis therapy.

PKM2 Activator TEPP-46 Attenuates Thoracic Aortic Aneurysm and Dissection by Inhibiting NLRP3 Inflammasome-Mediated IL-1β Secretion.

The development of thoracic aortic aneurysm and dissection (TAAD) is mediated by inflammasome activation, which exacerbates the secretion of pro-inflammatory cytokines, chemokines, matrix metalloproteinases (MMPs), and reactive oxygen species (ROS). The glycolytic enzyme pyruvate kinase M2 (PKM2) has shown a protective role against various disorders with an inflammatory basis, such as sepsis, tumorigenesis, and diabetic nephropathy. However, its potential role in TAAD has not been investigated so far. We analyzed aortic tissues from TAAD patients and the β-aminopropionitrile fumarate (BAPN)-induced mouse model of TAAD and observed elevated levels of PKM2 in the aortic lesions of both. Treatment with the PKM2 activator TEPP-46 markedly attenuated the progression of TAAD in the mouse model as demonstrated by decreased morbidity and luminal diameter of the aorta. In addition, the thoracic aortas of the BAPN-induced mice showed reduced monocytes and macrophages infiltration and lower levels of IL-1β, MMPs, and ROS when treated with TEPP-46. Furthermore, TEPP-46 treatment also suppressed the activation of the NOD-like receptor (NLR) family and pyrin domain-containing protein 3 (NLRP3) inflammasome by downregulating p-STAT3 and HIF1-α. Pyruvate kinase M2 plays a protective role in TAAD development, and its activation is a promising therapeutic strategy against the progression of TAAD.

Pyruvate Kinase M2 Deficiency Promotes Brown Fat Adipogenesis in Vitro and Enhances Adaptive Thermogenesis in Vivo

The prevalence of obesity and its comorbidities has sparked a worldwide concern to address rates of adipose tissue accrual. Pharmacological approaches to combat obesity have met with limited success despite intensive investments in their development. Although many differing strategies are being explored in cellular and molecular studies, many have proven ineffective at achieving long‐term positive outcomes. Thus, the search for novel approaches and new target must continue. Brown adipocytes are specialized to dissipate chemical energy as heat and are associated with improved metabolic phenotypes. Herein we demonstrate that altered expression of the glycolytic enzyme pyruvate kinase M2 (PKM2) promotes adipogenesis of mouse and human brown adipocytes. Additionally, modulation of PKM2 expression results in increased lipolysis through modulation of the activity of protein kinase A and hormone‐sensitive lipase (HSL). Importantly, PKM2 deficiency in brown adipocytes increases ATP turnover, and enhances basal and maximal mitochondrial respiration. Furthermore, mice with specific deletion of PKM2 in brown adipose tissue exhibited increased energy expenditure and resistance to cold‐induced alteration in core body temperature. Collectively, these findings identify PKM2 as a novel component of the molecular circuit that contributes to brown fat adipogenesis and adaptive thermogenesis, which may have potential therapeutic implications.Support or Funding InformationThis work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases (R00DK100736) to A.B.

MYCN Regulates Metabolism Through Vesicular Transfer of Glycolytic Kinases

Amplification of the proto-oncogene MYCN is a key molecular aberration in high-risk neuroblastoma and predictive of poor outcome in this childhood malignancy. We investigated the role of MYCN in regulating the protein cargo of extracellular vesicles (EVs) secreted by tumour cells that can be internalized by recipient cells with functional consequences. Using a switchable MYCN system coupled to mass spectrometry analysis, we found that MYCN regulates distinct sets of proteins in the EVs secreted by neuroblastoma cells. EVs produced by MYCN expressing cells or isolated from neuroblastoma patients induced the Warburg effect, proliferation and c-MYC expression in target cells. Mechanistically, we linked the cancer promoting activity of extracellular vesicles to the glycolytic kinase pyruvate kinase M2 (PKM2) that was enriched in EVs secreted by MYCN expressing neuroblastoma cells. Importantly, the glycolytic enzymes PKM2 and Hexokinase II were detected in the EVs circulating in the blood stream of neuroblastoma patients, but not in those of non-cancer children. We conclude that MYC activated cancers might spread oncogenic signals to remote body locations through extracellular vesicles.

Metabolic modulation regulates cardiac wall morphogenesis in zebrafish.

During cardiac development, cardiomyocytes form complex inner wall structures called trabeculae. Despite significant investigation into this process, the potential role of metabolism has not been addressed. Using single cell resolution imaging in zebrafish, we find that cardiomyocytes seeding the trabecular layer actively change their shape while compact layer cardiomyocytes remain static. We show that Erbb2 signaling, which is required for trabeculation, activates glycolysis to support changes in cardiomyocyte shape and behavior. Pharmacological inhibition of glycolysis impairs cardiac trabeculation, and cardiomyocyte-specific loss- and gain-of-function manipulations of glycolysis decrease and increase trabeculation, respectively. In addition, loss of the glycolytic enzyme pyruvate kinase M2 impairs trabeculation. Experiments with rat neonatal cardiomyocytes in culture further support these observations. Our findings reveal new roles for glycolysis in regulating cardiomyocyte behavior during cardiac wall morphogenesis.