PKM2, function and expression and regulation

TIPE drives a cancer stem-like phenotype by promoting glycolysis via PKM2/HIF-1α axis in melanoma

TIPE (TNFAIP8) has been identified as an oncogene and participates in tumor biology. However, how its role in the metabolism of tumor cells during melanoma development remains unclear. Here, we demonstrated that TIPE promoted glycolysis by interacting with pyruvate kinase M2 (PKM2) in melanoma. We found that TIPE-induced PKM2 dimerization, thereby facilitating its translocation from the cytoplasm to the nucleus. TIPE-mediated PKM2 dimerization consequently promoted HIF-1α activation and glycolysis, which contributed to melanoma progression and increased its stemness features. Notably, TIPE specifically phosphorylated PKM2 at Ser 37 in an extracellular signal-regulated kinase (ERK)-dependent manner. Consistently, the expression of TIPE was positively correlated with the levels of PKM2 Ser37 phosphorylation and cancer stem cell (CSC) markers in melanoma tissues from clinical samples and tumor bearing mice. In summary, our findings indicate that the TIPE/PKM2/HIF-1α signaling pathway plays a pivotal role in promoting CSC properties by facilitating the glycolysis, which would provide a promising therapeutic target for melanoma intervention.

Identification of a distinctive immunogenomic gene signature in stage-matched colorectal cancer

BACKGROUND

Colorectal cancer (CRC) remains one of the leading causes of cancer-related mortality worldwide. Despite advances in diagnosis and treatment, including surgery, chemotherapy, and immunotherapy, accurate clinical markers are still lacking. The development of prognostic and predictive indicators, particularly in the context of personalized medicine, could significantly improve CRC patient management.

METHOD

In this retrospective study, we used FFPE blocks of tissue samples from CRC patients at Augusta University (AU) to quantify a custom 15-gene panel. To differentiate the tumor and adjacent normal regions (NAT), H&E staining was utilized. For the quantification of transcripts, we used the NanoString nCounter platform. Kaplan-Meier and Log-rank tests were used to perform survival analyses. Several independent datasets were explored to validate the gene signature. Orthogonal analyses included single-cell profiling, differential gene expression, immune cell deconvolution, neoantigen prediction, and biological pathway assessment.

RESULTS

A 3-gene signature (GTF3A, PKM, and VEGFA) was found to be associated with overall survival in the AU cohort (HR = 2.26, 95% CI 1.05-4.84, p = 0.02, 93 patients), TCGA cohort (HR = 1.57, 95% CI 1.05-2.35, p < 0.02, 435 patients) and four other GEO datasets. Independent single-cell analysis identified relatively higher expression of the 3-gene signature in the tumor region. Differential analysis revealed dysregulated tissue inflammation, immune dysfunction, and neoantigen load of cell cycle processes among high-risk patients compared to low-risk patients.

CONCLUSION

We developed a 3-gene signature with the potential for prognostic and predictive clinical assessment of CRC patients. This gene-based stratification offers a cost-effective approach to personalized cancer management. Further research using similar methods could identify therapy-specific gene signatures to strengthen the development of personalized medicine for CRC patients.

The impact of glucose metabolism on inflammatory processes in sepsis-induced acute lung injury

Acute lung injury (ALI) is a prevalent and critical complication of sepsis, marked by high incidence and mortality rates, with its pathogenesis still not being fully elucidated. Recent research has revealed a significant correlation between the metabolic reprogramming of glucose and sepsis-associated ALI (S-ALI). Throughout the course of S-ALI, immune cells, including macrophages and dendritic cells, undergo metabolic shifts to accommodate the intricate demands of immune function that emerge as sepsis advances. Indeed, glucose metabolic reprogramming in S-ALI serves as a double-edged sword, fueling inflammatory immune responses in the initial stages and subsequently initiating anti-inflammatory responses as the disease evolves. In this review, we delineate the current research progress concerning the pathogenic mechanisms linked to glucose metabolic reprogramming in S-ALI, with a focus on the pertinent immune cells implicated. We encapsulate the impact of glucose metabolic reprogramming on the onset, progression, and prognosis of S-ALI. Ultimately, by examining key regulatory factors within metabolic intermediates and enzymes, We have identified potential therapeutic targets linked to metabolic reprogramming, striving to tackle the inherent challenges in diagnosing and treating Severe Acute Lung Injury (S-ALI) with greater efficacy.

Development of novel tetrazole-based pyruvate kinase M2 inhibitors targeting U87MG glioblastoma cells

Glioblastoma (GB), the most aggressive and life-threatening primary brain tumor in adults, poses significant therapeutic challenges. Tumor pyruvate kinase M2 (PKM2) has been implicated in the proliferation and survival of glioma cells. In this study, we designed and synthesized a series of 23 novel tetrazole-based derivatives. The compounds were thoroughly characterized using 1H, 13C, 19F NMR, along with HRMS analysis. Among them, 1-(imidazo[1,2-a]pyrimidin-3-yl)-2-(5-(naphthalen-2-yl)-2H-tetrazol-2-yl)ethan-1-one (9b) exhibited potent and selective antiproliferative activity against U87MG glioma cells, with minimal effects on bEnd (brain endothelial cell line) non-glioma cells. It emerged as a potent PKM2 inhibitor, with an IC50 of 0.307 µM. Apoptosis assays and cell cycle analysis revealed that compound 9b induced early apoptosis and caused G1 phase arrest. A significant decrease in pyruvate concentration further suggested PKM2 inhibition. In silico studies confirmed the binding affinity to the PKM2 inhibitory site, and RT-PCR data demonstrated its inhibitory activity against PKM2. Additionally, it reduced lactate levels, indicating its potential impact on cellular metabolism. Collectively, these findings suggest that the most potent compound holds promise as a therapeutic candidate against GB.

Hsa_Circ_002144 Promotes Glycolysis and Immune Escape of Breast Cancer Through miR-326/PKM Axis

Background: Breast cancer is a leading cause of cancer-related deaths in women worldwide, posing a significant threat to female health. Therefore, it is crucial to search for new therapeutic targets and prognostic biomarkers for breast cancer patients. Method: Bioinformatics analysis, quantitative real-time PCR (qRT-PCR), and fluorescence in situ hybridization (FISH) were employed to investigate the expression of hsa_circ_002144 in breast cancer. Transwell assay, Western blotting, and cell viability assay were utilized to assess the impact of hsa_circ_002144 on the proliferation, migration, and invasion of breast cancer cells. Additionally, a mouse model was established to validate its functionality. Flow cytometry, WB analysis, enzyme-linked immunosorbent assay (ELISA), qRT-PCR, exosomes isolation, and co-culture system were employed to elucidate the molecular mechanism underlying macrophage polarization. Result: we have discovered for the first time that hsa_circ_002144 is highly expressed in breast cancer. It affected tumor growth and metastasis and could influence macrophage polarization through the glycolytic pathway. Conclusion: This finding provides a new direction for breast cancer treatment and prognosis assessment.

Transition from fetal to postnatal state in the heart: Crosstalk between metabolism and regeneration

Cardiovascular disease is the leading cause of mortality worldwide. Myocardial injury resulting from ischemia can be fatal because of the limited regenerative capacity of adult myocardium. Mammalian cardiomyocytes rapidly lose their proliferative capacities, with only a small fraction of adult myocardium remaining proliferative, which is insufficient to support post-injury recovery. Recent investigations have revealed that this decline in myocardial proliferative capacity is closely linked to perinatal metabolic shifts. Predominantly glycolytic fetal myocardial metabolism transitions towards mitochondrial fatty acid oxidation postnatally, which not only enables efficient production of ATP but also causes a dramatic reduction in cardiomyocyte proliferative capacity. Extensive research has elucidated the mechanisms behind this metabolic shift, as well as methods to modulate these metabolic pathways. Some of these methods have been successfully applied to enhance metabolic reprogramming and myocardial regeneration. This review discusses recently acquired insights into the interplay between metabolism and myocardial proliferation, emphasizing postnatal metabolic transitions.

Dihydroartemisinin enhances the anti-tumour effect of photodynamic therapy by targeting PKM2-mediated glycolysis in oesophageal cancer cell

Photodynamic therapy (PDT) has been demonstrated to provide immediate relief of oesophageal cancer patients' re-obstruction and extend their lifespan. However, tumour regrowth may occur after PDT due to enhanced aerobic glycolysis. Previous research has confirmed the inhibitory effect of Dihydroartemisinin (DHA) on aerobic glycolysis. Therefore, the current study intends to investigate the function and molecular mechanism of DHA targeting tumour cell aerobic glycolysis in synergia PDT. The combined treatment significantly suppressed glycolysis in vitro and in vivo compared to either monotherapy. Exploration of the mechanism through corresponding experiments revealed that pyruvate kinase M2 (PKM2) was downregulated in treated cells, whereas overexpression of PKM2 nullified the inhibitory effects of DHA and PDT. This study proposes a novel therapeutic strategy for oesophageal cancer through DHA-synergized PDT treatment, targeting inhibit PKM2 to reduce tumour cell proliferation and metastasis.

PAK5-mediated PKM2 phosphorylation is critical for anaerobic glycolysis in endometriosis

P21-activated kinase 5 (PAK5) belongs to the PAK-II subfamily, which is an important regulator of cell survival, adhesion, and motility. However, the functions of PAK5 in endometriosis remain unclear. Here, PAK5 is strikingly upregulated in endometriosis. Furthermore, the knockdown of PAK5 or its inhibitor GNE 2861 blocks the development of endometriosis, which is equally demonstrated in PAK5-knockout mice. In addition, PAK5 promotes glycolysis by enhancing the protein stability of pyruvate kinase 2 (PKM2) in endometriotic cells, which is a key enzyme for glucose metabolism. Moreover, the phosphorylation of PKM2 at Ser519 by PAK5 mediates endometriosis cell proliferation and metastasis. Collectively, PAK5 plays an indispensable role in endometriosis. Our findings demonstrate that PAK5 is an important target for the treatment of endometriosis.

p53 induces circFRMD4A to suppress cancer development through glycolytic reprogramming and cuproptosis

Cuproptosis is a type of copper-induced cell death that mainly impacts cells relying on mitochondrial metabolism. Although p53 regulates glycolytic metabolism, its role in cuproptosis remains unclear. Here, we report that the circular RNA, circFRMD4A, is crucial for p53-mediated metabolic reprogramming and cuproptosis. CircFRMD4A originates from the transcript of FRMD4A, which is transcriptionally activated by p53, and the formation of circFRMD4A is facilitated by the RNA-binding protein EWSR1. CircFRMD4A functions as a tumor suppressor and enhances the sensitivity of cancer cells to elesclomol-induced cuproptosis. Mechanistic analysis reveals that circFRMD4A interacts with and inactivates the pyruvate kinase PKM2, leading to a decrease in lactate production and a redirection of glycolytic flux toward the tricarboxylic acid cycle. Finally, p53 agonists and elesclomol coordinately suppress the growth of cancer in a xenograft mouse model. Altogether, our study uncovers that p53 promotes glycolytic reprogramming and cuproptosis via circFRMD4A and suggests a potential combination strategy against cancers with wild-type p53.

Bilateral transcranial direct-current stimulation confers neuroprotection through suppression of PKM2 after mouse cerebral ischemia injury

BACKGROUND

In its tetrameric form, pyruvate kinase M2 isoform (PKM2) catalyzes the last step of glycolysis and plays a key role in the metabolic reprogramming via regulating the signaling of pentose phosphate pathway (PPP). But the role of PKM2 in cerebral ischemia-reperfusion (I/R) injury remains unknown.

METHODS

Mice model of middle cerebral artery occlusion (MCAO) and model of oxygen-glucose deprivation (OGD) injury in cultured neurons were established. PKM2 activator or inhibitor were used to test the effects of PKM2 in wild-type and PKM2 (-/-) mice after I/R injury. Biochemical and molecular approach were used to detect the level of PKM2 tetramers and PPP metabolites.

RESULTS

We showed for the first time that ischemia-induced increase of PKM2 activity promoted neuronal death via the suppression of PPP-dependent antioxidant capacity. To identify therapeutic approach that suppresses ischemia-induced increase of PKM2 activity, we tested the effect of bilateral transcranial direct-current stimulation (BtDCS), a newly established BtDCS approach by us, on PKM2 activity after mouse I/R. Our data demonstrated that BtDCS inhibited PKM2 activity in the ischemic neurons. BtDCS also reduced the cerebral infarct volume and the neurological deficits in stroke mice. We found that BtDCS-induced neuroprotection was mediated through the suppression of PKM2 activity after I/R.

CONCLUSIONS

Together, this study provided novel evidence that supported PKM2 as a crucial regulator of neuronal metabolism after cerebral I/R injury, and revealed the molecular mechanism by which BtDCS protects against mouse cerebral I/R injury through regulating PKM2-mediated metabolic reprogramming.

Pralatrexate represses the resistance of HCC cells to molecular targeted agents via the miRNA-34a/Notch pathway

Metabolism-related pathways are important targets for intervention in the treatment of hepatocellular carcinoma (HCC), but few studies have reported on the combination of inhibitors of folate metabolism-related enzymes and molecularly targeted drugs for HCC. The results of the present work are the first to reveal the effects of an inhibitor of dihydrofolate reductase (DHFR), pralatrexate, on the sensitivity of HCC cells to molecularly targeted agents examined using multiple assays. In HCC cells, knockdown of DHFR or treatment with pralatrexate enhanced the sensitivity of HCC cells to molecularly targeted agents, such as sorafenib, regorafenib, lenvatinib, cabozantinib, or anlotinib. Mechanically, pralatrexate decreased the methylation rates of miRNA-34a's promoter region to enhance the expression of miRNA-34a. Treatment with pralatrexate inhibited the expression of Notch and its downstream factors by enhancing the expression of miRNA-34a in HCC cells. In clinical specimens, the expression of miRNA-34a was negatively correlated with DHFR expression, while DHFR expression was positively correlated with the Notch intracellular domain (NICD) and downstream factors of the Notch pathway. The expression of miRNA-34a was negatively correlated with DHFR expression, while the methylation rates of miRNA-34a's promoter were positively related to DHFR. The effect of pralatrexate on the metabolic profile of HCC cells is very different from that of small molecule inhibitors related to glycolipid metabolism. Therefore, pralatrexate upregulates the sensitivity of HCC cells to molecularly targeted drugs. These results expand our understanding of folate metabolism and HCC and can help provide more options for HCC treatment.

The role of PI3K-Akt-mTOR axis in Warburg effect and its modification by specific protein kinase inhibitors in human and rat inflammatory macrophages

The Warburg effect occurs both in cancer cells and in inflammatory macrophages. The aim of our work was to demonstrate the role of PI3K-Akt-mTOR axis in the Warburg effect in HL-60 derived, rat peritoneal and human blood macrophages and to investigate the potential of selected inhibitors of this pathway to antagonize it. M1 polarization in HL-60-derived and human blood monocyte-derived macrophages was supported by the increased expression of NOS2 and inflammatory cytokines. All M1 polarized and inflammatory macrophages investigated expressed higher levels of HIF-1α and NOS2, which were reduced by selected kinase inhibitors, supporting the role of PI3K-Akt-mTOR axis. Using Seahorse XF plates, we found that in HL-60-derived and human blood-derived macrophages, glucose loading reduced oxygen consumption (OCR) and increased glycolysis (ECAR) in M1 polarization, which was antagonized by selected kinase inhibitors and by dichloroacetate. In rat peritoneal macrophages, the changes in oxidative and glycolytic metabolism were less marked and the NOS2 inhibitor decreased OCR and increased ECAR. Non-mitochondrial oxygen consumption and ROS production were likely due to NADPH oxidase, expressed in each macrophage type, independently of PI3K-Akt-mTOR axis. Our results suggest that inflammation changed the metabolism in each macrophage model, but a clear relationship between polarization and Warburg effect was confirmed only after glucose loading in HL-60 and human blood derived macrophages. The effect of kinase inhibitors on Warburg effect was variable in different cell types, whereas dichloroacetate caused a shift toward oxidative metabolism. Our findings suggest that these originally anti-cancer inhibitors may also be candidates for anti-inflammatory therapy.

Lactylation and Ischemic Stroke: Research Progress and Potential Relationship

Ischemic stroke is caused by interrupted cerebral blood flow and is a leading cause of mortality and disability worldwide. Significant advancements have been achieved in comprehending the pathophysiology of stroke and the fundamental mechanisms responsible for ischemic damage. Lactylation, as a newly discovered post-translational modification, has been reported to participate in several physiological and pathological processes. However, research on lactylation and ischemic stroke is scarce. This review summarized the current function of protein lactylation in other diseases or normal physiological processes and explored their potential link with the pathophysiological process and the reparative mechanism of ischemic stroke. We proposed that neuroinflammation, regulation of metabolism, regulation of messenger RNA translation, angiogenesis, and neurogenesis might be the bridge linking lactylation and ischemic stroke. Our study provided a novel perspective for comprehending the role of protein lactylation in the pathophysiological processes underlying ischemic stroke. Lactylation might be a promising target in drug development of ischemic stroke.

Probing Selenium-Deficient Chicken Spleen Th1/Th17 Differentiation Based on Selenoprotein W Targeting of PKM2/HIF1α

Selenium regulates the differentiation and function of immune cells mainly through selenoproteins. Selenoprotein W (SelW) has been shown to mitigate inflammatory bowel disease in mice by modulating the differentiation of helper T (CD4+ T) cell. Previous studies by our team have underscored SelW's critical role in safeguarding chicken spleens and splenic lymphocytes against inflammatory injury. However, research examining SelW's involvement in regulating CD4+ T cell differentiation in avian spleens remains scarce. Therefore, the selenium-deficient chicken model was constructed in this study. It was found that the spleen of selenium-deficient chickens showed significant inflammatory damage, accompanied by decreased SelW expression, diminished antioxidant capacity, heightened glycolysis, and an elevated count of Th1/Th17 cells. To elucidate the specific mechanism of SelW regulating Th1/Th17 cell differentiation, this study used molecular docking technology, fluorescence colocalization, and co-immunoprecipitation and initially confirmed the targeting relationship between SelW and pyruvate kinase M2 (PKM2). Subsequently, an in vitro model of SelW overexpression, knockdown, and TEPP-46 (PKM2 tetramer activator) cotreatment of chicken primary splenic lymphocytes was replicated. Our findings revealed that selenium deficiency triggers oxidative stress and promotes PKM2 nuclear translocation via SelW downregulation, which stabilizes HIF1α transcription in the nucleus, enhancing glycolysis and skewing chicken splenic CD4+ T cells toward the Th1/Th17 phenotype. Our study, for the first time, demonstrates the existence of an interaction between SelW and PKM2 in poultry, emphasizing SelW's paramount significance in CD4+ T cell differentiation, providing fresh perspectives on the contributions of selenoproteins to T cell biology and immune processes.

Macrophage polarization and metabolic reprogramming in abdominal aortic aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) is a macrovascular disease with high morbidity and mortality in the elderly. The limitation of the current management is that most patients can only be followed up until the AAA diameter increases to a threshold, and surgical intervention is recommended. The development of preventive and curative drugs for AAA is urgently needed. Macrophage-mediated immune inflammation is one of the key pathological links in the occurrence and development of AAA.

AIMS

This review article aims to evaluate the impact of immunometabolism on macrophage biology and its role in AAA.

METHODS

We analyze publications focusing on the polarization and metabolic reprogramming in macrophages as well as their potential impact on AAA, and summarize the potential interventions that are currently available to regulate these processes.

RESULTS

The phenotypic and functional changes in macrophages are accompanied by significant alterations in metabolic pathways. The interaction between macrophage polarization and metabolic pathways significantly influences the progression of AAA.

CONCLUSION

Macrophage polarization is a manifestation of the gross dichotomy of macrophage function into pro-inflammatory killing and tissue repair, that is, classically activated M1 macrophages and alternatively activated M2 macrophages. Macrophage functions are closely linked to metabolic changes, and the emerging field of immunometabolism is providing unique insights into the role of macrophages in AAA. It is essential to further investigate the precise metabolic changes and their functional consequences in AAA-associated macrophages.

Nuclear-localized pyruvate kinases control phosphorylation of histone H3 on threonine 11

Phosphorylation of histone H3 at threonine 11 (H3T11ph) affects transcription and chromosome stability. However, the enzymes responsible for depositing H3T11ph and the functions of H3T11ph in plants remain unknown. Here we report that in Arabidopsis thaliana, PYRUVATE KINASE 6 (PK6), PK7 and PK8 enter the nucleus under conditions of sufficient glucose and light exposure, where they interact with SWI2/SNF2-RELATED 1 COMPLEX 4 (SWC4) and phosphorylate H3 at threonine 11. Mutations in these kinases or knockdown of SWC4 resulted in FLC-dependent early flowering, short hypocotyls and short pedicels. Genome-wide, H3T11ph is highly enriched at transcription start sites and transcription termination sites, and positively correlated with gene transcript levels. PK6 and SWC4 targeted FLC, MYB73, PRE1, TCP4 and TCP10, depositing H3T11ph at these loci and promoting their transcription, and PK6 occupancy at these loci requires SWC4. Together, our results reveal that nuclear-localized PK6, PK7 and PK8 modulate H3T11ph and plant growth.

Enhanced Tissue Regeneration Through Immunomodulatory Extracellular Vesicles Encapsulated in Diversified Silk-Based Injectable Hydrogels

Mesenchymal stem cells (MSCs) immunologically trained using lipopolysaccharide (LPS) display enhanced immunomodulatory capabilities. Extracellular vesicles (EVs) derived from MSCs are widely used in regenerative medicine owing to their bioactive properties without the drawbacks of cell therapy. However, it remains unclear whether EVs derived from LPS-stimulated (trained) MSCs (L-EVs) inherit the enhanced reparative potential from their parent cells. Thus, this study first aims to explore the effect of immunological training on the bioactivity of L-EVs. LPS-trained bone marrow-derived MSCs (BMSCs) secrete more EVs, and these EVs significantly promote M2 macrophage polarization. Subsequently, hydrogel systems based on thixotropic injectable silk fibroin are prepared for in vivo EV delivery. These hydrogels have controllable gelation time and exhibit outstanding reparative effects on rat skin wounds and alveolar bone defects. Finally, it is revealed that L-EVs promote M2 macrophage polarization by inhibiting the nuclear translocation of PKM2. Overall, this study shows that the immunological training of BMSCs effectively improves the therapeutic effects of their EVs and provides a convenient and diversified EV delivery strategy using an injectable silk fibroin hydrogel. This strategy has broad clinical application prospects for tissue regeneration.

Sirtuin 1/sirtuin 3 are robust lysine delactylases and sirtuin 1-mediated delactylation regulates glycolysis

Lysine lactylation (Kla), an epigenetic mark triggered by lactate during glycolysis, including the Warburg effect, bridges metabolism and gene regulation. Enzymes such as p300 and HDAC1/3 have been pivotal in deciphering the regulatory dynamics of Kla, though questions about additional regulatory enzymes, their specific Kla substrates, and the underlying functional mechanisms persist. Here, we identify SIRT1 and SIRT3 as key "erasers" of Kla, shedding light on their selective regulation of both histone and non-histone proteins. Proteomic analysis in SIRT1/SIRT3 knockout HepG2 cells reveals distinct substrate specificities toward Kla, highlighting their unique roles in cellular signaling. Notably, we highlight the role of specific Kla modifications, such as those on the M2 splice isoform of pyruvate kinase (PKM2), in modulating metabolic pathways and cell proliferation, thereby expanding Kla's recognized functions beyond epigenetics. Therefore, this study deepens our understanding of Kla's functional mechanisms and broadens its biological significance.

Cabozantinib-encapsulated and maytansine-conjugated high-density lipoprotein for immunotherapy in colorectal cancer

Advanced colorectal cancer (CRC) responds poorly to current adjuvant therapies, partially due to its immunosuppressive intestinal microenvironment. We found that myeloid-derived suppressor cells (MDSCs) were enriched in orthotopic tumors due to treatment-induced succinate release, which activated tuft cells and upregulated interleukin 25 (IL-25) and interleukin 13 (IL-13). We engineered a cabozantinib (Cabo)-encapsulated and maytansine (DM1)-conjugated synthetic high-density lipoprotein (ECCD-sHDL) to modulate the tumor microenvironment. DM1 induced immunogenic cell death and promoted the maturation of dendritic cells. Meanwhile, Cabo alleviated DM1-induced succinate release, preventing tuft cell activation, downregulating IL-25 and IL-13 secretion, and reducing intratumoral MDSC infiltration. ECCD-sHDL increased the densities of active cytotoxic T lymphocytes (CTLs) and M1 macrophages in the tumors, effectively inhibiting tumor growth and metastasis, thereby prolonging survival in murine CRC models. Our study sheds light on the mechanism of treatment-induced immunosuppression in orthotopic CRC and demonstrates that this combinatorial therapy could be an effective treatment for CRC.

SLC45A4 is involved in malignant progression of ovarian cancer through glycolytic metabolic reprogramming

Tumor cells promote malignant behaviors such as proliferation, invasion, and metastasis of cancer cells through glucose metabolic reprogramming, but the role of the H-dependent sugar cotransporter SLC45A4 in regulating metabolic reprogramming in ovarian cancer (OC) remains largely unknown. This study aimed to investigate the effects of SLC45A4 silencing on the transcriptome spectrum of ovarian cancer cells (OCC), glucose uptake, lactic acid production, intracellular ATP levels, and the expression and activity of HIF-α glycolysis signaling pathway. The results showed that SLC45A4 is overexpressed in OC and its elevated expression correlates with adverse clinical outcomes in OC patients. Silencing of SLC45A4 significantly inhibited the proliferation, invasion, and metastasis of OCC by suppressing glucose uptake and glycolysis, and it also reduced the expression of HIF-α glycolysis signaling pathway in OC tissues. In vivo experiments using shRNA to knock down SLC45A4 in xenograft models in nude mice demonstrated a significant inhibition of tumor growth. These findings suggest that SLC45A4 silencing can restrain the malignant progression of OC by inhibiting glucose uptake in OCC and affecting the reprogramming of glycolytic energy metabolism, indicating that SLC45A4 may serve as a potential therapeutic target for OC intervention.

Hsa_Circ_0008035 drives immune evasion of gastric cancer via promoting EXT1-mediated nuclear translocation of PKM2

Circular RNAs (circRNAs) have been reported to be associated with the malignant phenotypes of cancer. However, the role and underlying mechanism of hsa_Circ_0008035 in colorectal cancer (CRC) remains unclear. In this study, we elucidated the pivotal role of hsa_circ_0008035 in gastric cancer progression and immune evasion. Elevated hsa_circ_0008035 levels in gastric cancer patient serum correlated positively with disease advancement, including tumor stages and lymph node metastasis. Functional analyses revealed a negative association between hsa_circ_0008035 and CD8+ T cell number and function. Mechanistically, hsa_circ_0008035 encoded the novel protein EXT1-219aa, suppressing EXT1 phosphorylation and expression. Additionally, hsa_circ_0008035 regulated pyruvate metabolism by influencing the nucleus localization of PKM2. The identified EXT1/PKM2 axis further underscored the intricate regulatory mechanisms orchestrated by hsa_circ_0008035 in gastric cancer, offering potential diagnostic and therapeutic implications in the ongoing pursuit of targeted therapies for gastric cancer patients.

Tetrameric, active PKM2 inhibits IP3 receptors, potentially requiring GRP75 as an additional interaction partner

Pyruvate kinase M2 (PKM2) is a key glycolytic enzyme interacting with the inositol 1,4,5-trisphosphate receptor (IP3R). This interaction suppresses IP3R-mediated cytosolic [Ca2+] rises. As PKM2 exists in monomeric, dimeric and tetrameric forms displaying different properties including catalytic activity, we investigated the molecular determinants of PKM2 enabling its interaction with IP3Rs. Treatment of HeLa cells with TEPP-46, a compound stabilizing the tetrameric form of PKM2, increased both its catalytic activity and the suppression of IP3R-mediated Ca2+ signals. Consistently, in PKM2 knock-out HeLa cells, PKM2C424L, a tetrameric, highly active PKM2 mutant, but not inactive PKM2K270M or the less active PKM2K305Q, suppressed IP3R-mediated Ca2+ release. Surprisingly, however, in vitro assays did not reveal a direct interaction between purified PKM2 and either the purified Fragment 5 of IP3R1 (a.a. 1932-2216) or the therein located D5SD peptide (a.a. 2078-2098 of IP3R1), the presumed interaction sites of PKM2 on the IP3R. Moreover, on-nucleus patch clamp of heterologously expressed IP3R1 in DT40 cells devoid of endogenous IP3Rs did not reveal any functional effect of purified wild-type PKM2, mutant PKM2 or PKM1 proteins. These results indicate that an additional factor mediates the regulation of the IP3R by PKM2 in cellulo. Immunoprecipitation of GRP75 using HeLa cell lysates co-precipitated IP3R1, IP3R3 and PKM2. Moreover, the D5SD peptide not only disrupted PKM2:IP3R, but also PKM2:GRP75 and GRP75:IP3R interactions. Our data therefore support a model in which catalytically active, tetrameric PKM2 suppresses Ca2+ signaling via the IP3R through a multiprotein complex involving GRP75.

The Activation of PKM2 Induces Pyroptosis in Hippocampal Neurons via the NLRP3/Caspase-1/GSDMD Pathway in Neonatal Rats With Hypoxic-Ischemic Brain Injury

INTRODUCTION

The presence of hypoxic-ischemic brain damage (HIBD) in neonates triggers a strong neuroinflammatory reaction. Pyroptosis, a programmed cell death mechanism associated with inflammation, plays a crucial role in HIBD. Pyruvate kinase M2 (PKM2) plays a significant role in connecting metabolic processes and inflammatory responses, but whether it affects hippocampus pyroptosis in HIBD is unclear. The aim of this study is to elucidate the role of PKM2 in HIBD and to propose a novel therapeutic approach for neonatal ischemic-hypoxic encephalopathy.

METHODS

In this study, we employed neonatal 7-day-old Sprague Dawley rats to establish a model of HIBD using the Rice-Vannucci surgical technique and a hypoxia device. To inhibit the elevation of PKM2, we utilized the PKM2 inhibitor shikonin. The rats were categorized into four groups: Sham, Shikonin, HIBD, and Shikonin + HIBD. Behavioral tests, hematoxylin eosin staining, immunofluorescence staining, ELISA (IL-1β, IL-18), and LDH were conducted in each group to evaluate neurological function, hippocampal damage, the occurrence of neuronal pyroptosis, and the neuroinflammation. Western blot was used to assess the expression levels of PKM2, NLRP3, Caspase-1, Cleaved Caspase-1, GSDMD, GSDMDN, and IL-1β.

RESULTS

The expression of PKM2 elevated in hippocampal tissues of the HIBD model and the localization of PKM2 in the hippocampus was activated in neurons instead of microglia during the HIBD. Meanwhile, the inhibition of PKM2 improved the behavioral test scores and the body weight of rats, the neuronal damage in the CA1 region of hippocampal tissue was also attenuated. In addition, inhibiting PKM2 alleviated neuronal pyroptosis by decreasing the expression of PKM2, NLRP3, Caspase-1, Cleaved Caspase-1, GSDMD, GSDMDN. Furthermore, serum levels of LDH and inflammatory factors IL-1β and IL-18 decrease with PKM2 inhibition.

CONCLUSIONS

Based on these findings, we can conclude that PKM2 plays a crucial role in regulating hippocampal neuronal pyroptosis of HIBD rats via NLRP3/Caspase-1/GSDMD pathway. Therefore, inhibiting PKM2 could be a promising therapeutic strategy for the treatment of neonatal ischemic-hypoxic encephalopathy.

Non-metabolic enzyme function of pyruvate kinase M2 in breast cancer

Breast cancer (BC) is a prevalent malignant tumor in women, and its incidence has been steadily increasing in recent years. Compared with other types of cancer, it has the highest mortality and morbidity rates in women. So, it is crucial to investigate the underlying mechanisms of BC development and identify specific therapeutic targets. Pyruvate kinase M2 (PKM2), an important metabolic enzyme in glycolysis, has been found to be highly expressed in BC. It can also move to the nucleus and interact with various transcription factors and proteins, including hypoxia-inducible factor-1α (HIF-1α), signal transducer and activator of transcription 3 (STAT3), β-catenin, cellular-myelocytomatosis oncogene (c-Myc), nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), and mammalian sterile 20-like kinase 1 (MST1). This interaction leads to non-metabolic functions that control the cell cycle, proliferation, apoptosis, migration, invasion, angiogenesis, and tumor microenvironment in BC. This review provides an overview of the latest advancements in understanding the interactions between PKM2 and different transcription factors and proteins that influence the initiation and progression of BC. It also examined how natural drugs and noncoding RNAs affect various biological processes in BC cells through the regulation of the non-metabolic enzyme functions of PKM2. The findings provide valuable insights for improving the prognosis and developing targeted therapies for BC in the coming years.

Mass Spectrometry Structural Proteomics Enabled by Limited Proteolysis and Cross-Linking

The exploration of protein structure and function stands at the forefront of life science and represents an ever-expanding focus in the development of proteomics. As mass spectrometry (MS) offers readout of protein conformational changes at both the protein and peptide levels, MS-based structural proteomics is making significant strides in the realms of structural and molecular biology, complementing traditional structural biology techniques. This review focuses on two powerful MS-based techniques for peptide-level readout, namely limited proteolysis-mass spectrometry (LiP-MS) and cross-linking mass spectrometry (XL-MS). First, we discuss the principles, features, and different workflows of these two methods. Subsequently, we delve into the bioinformatics strategies and software tools used for interpreting data associated with these protein conformation readouts and how the data can be integrated with other computational tools. Furthermore, we provide a comprehensive summary of the noteworthy applications of LiP-MS and XL-MS in diverse areas including neurodegenerative diseases, interactome studies, membrane proteins, and artificial intelligence-based structural analysis. Finally, we discuss the factors that modulate protein conformational changes. We also highlight the remaining challenges in understanding the intricacies of protein conformational changes by LiP-MS and XL-MS technologies.

Deciphering the role of PLCD3 in lung cancer: A gateway to glycolytic reprogramming via PKC-Rap1 activation

PLCD3 belongs to the phospholipase C delta group and is involved in numerous biological functions, including cell growth, programmed cell death, and specialization. However, the role of PLCD3 in lung cancer still needs further investigation. This research aimed to investigate if PLCD3 influences glycolytic reprogramming and lung cancer development through the PKC-dependent Rap1 signaling pathway. This study found that PLCD3 was increased in lung cancer tissues. PLCD3 promotes the proliferation and invasion of lung cancer cells by activating the PKC-dependent Rap1 pathway. The detailed process involves PLCD3 triggering PKC, which subsequently stimulates the Rap1 pathway, leading to glycolytic reprogramming that supplies adequate energy and metabolic substrates necessary for the growth and spread of lung cancer cells. Moreover, PLCD3 can also promote the metastasis and invasion of lung cancer cells by activating the Rap1 pathway. This study reveals the mechanism of PLCD3 in lung cancer and provides new ideas for the treatment of lung cancer. Inhibiting PLCD3, PKC, and the Rap1 pathway may be an effective strategy for treating lung cancer.

Glucose metabolism in glioma: an emerging sight with ncRNAs

Glioma is a primary brain tumor that grows quickly, has an unfavorable prognosis, and can spread intracerebrally. Glioma cells rely on glucose as the major energy source, and glycolysis plays a critical role in tumorigenesis and progression. Substrate utilization shifts throughout glioma progression to facilitate energy generation and biomass accumulation. This metabolic reprogramming promotes glioma cell proliferation and metastasis and ultimately decreases the efficacy of conventional treatments. Non-coding RNAs (ncRNAs) are involved in several glucose metabolism pathways during tumor initiation and progression. These RNAs influence cell viability and glucose metabolism by modulating the expression of key genes of the glycolytic pathway. They can directly or indirectly affect glycolysis in glioma cells by influencing the transcription and post-transcriptional regulation of oncogenes and suppressor genes. In this review, we discussed the role of ncRNAs in the metabolic reprogramming of glioma cells and tumor microenvironments and their abnormal expression in the glucometabolic pathway in glioma. In addition, we consolidated the existing theoretical knowledge to facilitate the use of this emerging class of biomarkers as biological indicators and potential therapeutic targets for glioma.

Neurotoxic effects of triclosan in adolescent mice: Pyruvate kinase M2 dimer regulated Signal transducer and activator of transcription 3 phosphorylation mediated microglia activation and neuroinflammation

Triclosan (TCS), a commonly used antibacterial agent, is associated with various harmful effects on mammalian neurodevelopment, particularly when exposed prenatally. This study investigated the impact of long-term exposure to TCS on the prefrontal cortex development in adolescent mice. We evaluated the motor ability, motor coordination, and anxiety behavior of mice using open field tests (OFT) and elevated cross maze tests (EPM). An increase in movement distance, number of passes through the central area, and open arm retention time was observed in mice treated with TCS. Hematoxylin eosin staining and Nissl staining also showed significant adverse reactions in the brain tissue of TCS-exposed group. TCS induced microglia activation and increased inflammatory factors expression in the prefrontal cortex. TCS also increased the expression of pyruvate kinase M2 (PKM2), thereby elevating the levels of PKM2 dimer, which entered the nucleus. Treatment with TEPP46 (PKM2 dimer nuclear translocation inhibitor) blocked the expression of inflammatory factors induced by TCS. TCS induced the phosphorylation of nuclear signal transducer and activator of transcription 3 (STAT3) in vivo and in vitro, upregulating the levels of inflammatory cytokines. The results also demonstrated the binding of PKM2 to STAT3, which promoted STAT3 phosphorylation at the Tyr705 site, thereby regulating the expression of inflammatory factors. These findings highlight the role of PKM2-regulated STAT3 phosphorylation in TCS-induced behavioral disorders in adolescents and propose a reliable treatment target for TCS.

LysR-type transcriptional regulators: state of the art

The LysR-type transcriptional regulators (LTTRs) are DNA-binding proteins present in bacteria, archaea, and in algae. Knowledge about their distribution, abundance, evolution, structural organization, transcriptional regulation, fundamental roles in free life, pathogenesis, and bacteria-plant interaction has been generated. This review focuses on these aspects and provides a current picture of LTTR biology.

Reduced bioenergetics and mitochondrial fragmentation in human primary cytotrophoblasts induced by an EGFR-targeting chemical mixture

Exposures to complex environmental chemical mixtures during pregnancy reach and target the feto-placental unit. This study investigates the influence of environmental chemical mixtures on placental bioenergetics. Recognizing the essential role of the epidermal growth factor receptor (EGFR) in placental development and its role in stimulating glycolysis and mitochondrial respiration in trophoblast cells, we explored the effects of chemicals known to disrupt EGFR signaling on cellular energy production. Human primary cytotrophoblasts (hCTBs) and a first-trimester extravillous trophoblast cell line (HTR-8/SVneo) were exposed to a mixture of EGFR-interfering chemicals, including atrazine, bisphenol S, niclosamide, PCB-126, PCB-153, and trans-nonachlor. An RNA sequencing approach revealed that the mixture altered the transcriptional signature of genes involved in cellular energetics. Next, the impact of the mixture on cellular bioenergetics was evaluated using a combination of mitochondrial and glycolytic stress tests, ATP production, glucose consumption, lactate synthesis, and super-resolution imaging. The chemical mixture did not alter basal oxygen consumption but diminished the maximum respiratory capacity in a dose-dependent manner, indicating a disruption of mitochondrial function. The respiratory capacity and ATP production were increased by EGF, while the Chem-Mix reduced both EGF- and non-EGF-mediated oxygen consumption rate in hCTBs. A similar pattern was observed in the glycolytic medium acidification, with EGF increasing the acidification, and the Chem-Mix blocking EGF-induced glycolytic acidification. Furthermore, direct stochastic optical reconstruction microscopy (dSTORM) imaging demonstrated that the Chem-Mix led to a reduction of the mitochondrial network architecture, with findings supported by a decrease in the abundance of OPA1, a mitochondrial membrane GTPase involved in mitochondrial fusion. In conclusion, we demonstrated that a mixture of EGFR-disrupting chemicals alters mitochondrial remodeling, resulting in disturbed cellular bioenergetics, reducing the capacity of human cytotrophoblast cells to generate energy. Future studies should investigate the mechanism by which mitochondrial dynamics are disrupted and the pathological significance of these findings.

Inhibition of heterogeneous nuclear ribonucleoproteins A1 and oxidative stress reduces glycolysis via pyruvate kinase M2 in chronic thromboembolic pulmonary hypertension

Background and Objective

Chronic thromboembolic pulmonary hypertension (CTEPH) is a lethal complication of pulmonary embolism involving pulmonary artery occlusion and microvascular disease. The glucose metabolism and reactive oxygen species (ROS) production may be perturbed in CTEPH, but the precise mechanisms are unclear. This study investigated glucose metabolism in CTEPH employing pulmonary endarterectomy (PEA)-derived pulmonary artery smooth muscle cells (PASMCs) and characterized the roles of pyruvate kinase M2 (PKM2) and its regulation by heterogeneous nuclear ribonucleoproteins A1 (hnRNPA1) and ROS in CTEPH.

Methods

PEA tissues and blood samples of CTEPH patients were collected to study the levels of PKM2. Primary PASMCs were isolated from PEA tissues. We used small interfering RNAs to knock down PKM2 and hnRNPAI, and applied antioxidant N-acetylcysteine (NAC) and mito-TEMPO to reduce ROS production. The expression of glucometabolic genes, ROS production, glycolysis rate and proliferative and migratory activities were analyzed in PEA-derived PASMCs.

Results

PKM2 levels in serum and PEA tissues of CTEPH patients were higher than that of the healthy controls. Compared to the control PASMCs, PEA-derived PASMCs showed increased PKM2 expression and ROS production. The rates of glycolysis, proliferation and migration were increased in PEA-PASMCs and could be mitigated by PKM2 downregulation through hnRNPA1 or ROS inhibition.

Conclusions

Increased glycolysis and PKM2 expression were found in PEA-PASMCs. Inhibition of hnRNPA1 or ROS corrected the aberrant glycolysis, cell proliferation and migration by downregulating PKM2. Regulation of the hnRNPA1/PKM2 axis represents a potential therapeutic target for the treatment of CTEPH.

ETV4 promotes the progression of cholangiocarcinoma by regulating glycolysis via the TGF-β signaling

BACKGROUND

Considerable studies show that ETS variant 4 (ETV4) plays an important roles in multitudinous tumor. This study investigated its function in cholangiocarcinoma (CCA) progression and revealed the underlying mechanisms.

METHODS

The expression of ETV4 in CCA was evaluated using TCGA database and the single-cell analysis based on GSE189903 dataset. ETV4 expression in CCA human specimens was detected by reverse transcription-quantitative PCR, immunohistochemistry, and western blot. Cell Counting Kit-8, EdU, colony formation, wound healing, and Transwell assays were used to analyze the effects of ETV4. Extracellular acidification rate, oxygen consumption rate, glucose uptake, and lactate production were used to measure glycolysis in CAA cells. Western blot was performed to explore glycolysis-related proteins. Tumor growth was evaluated in mice xenograft tumors.

RESULTS

ETV4 was up-regulated in CCA epithelial cells. The high-expression of ETV4 was associated with poor prognosis of patients with CCA. ETV4 overexpression enhanced the proliferation, migration, invasion, and glycolysis of CCA cells; ETV4 silencing led to the contrary effects. Mechanistically, ETV4 activates TGF-β/Smad2/3 signaling pathway. In mice xenograft mode, ETV4 silencing inhibits the tumor growth, the expression of glycolysis-related proteins and TGF-β/Smad2/3 pathway proteins.

CONCLUSIONS

ETV4 functions as an essential factor in the roles of TGF-β1 in CCA cells, and may be a promising target for TGF-β1-mediated CCA progression.

Hydrogen sulfide coordinates glucose metabolism switch through destabilizing tetrameric pyruvate kinase M2

Most cancer cells reprogram their glucose metabolic pathway from oxidative phosphorylation to aerobic glycolysis for energy production. By reducing enzyme activity of pyruvate kinase M2 (PKM2), cancer cells attain a greater fraction of glycolytic metabolites for macromolecule synthesis needed for rapid proliferation. Here we demonstrate that hydrogen sulfide (H2S) destabilizes the PKM2 tetramer into monomer/dimer through sulfhydration at cysteines, notably at C326, leading to reduced PKM2 enzyme activity and increased PKM2-mediated transcriptional activation. Blocking PKM2 sulfhydration at C326 through amino acid mutation stabilizes the PKM2 tetramer and crystal structure further revealing the tetramer organization of PKM2-C326S. The PKM2-C326S mutant in cancer cells rewires glucose metabolism to mitochondrial respiration, significantly inhibiting tumor growth. In this work, we demonstrate that PKM2 sulfhydration by H2S inactivates PKM2 activity to promote tumorigenesis and inhibiting this process could be a potential therapeutic approach for targeting cancer metabolism.

Tetramerization of PKM2 Alleviates Traumatic Brain Injury by Ameliorating Mitochondrial Damage in Microglia

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Microglial activation and neuroinflammation are key cellular events that determine the outcome of TBI, especially neuronal and cognitive function. Studies have suggested that the metabolic characteristics of microglia dictate their inflammatory response. The pyruvate kinase isoform M2 (PKM2), a key glycolytic enzyme, is involved in the regulation of various cellular metabolic processes, including mitochondrial metabolism. This suggests that PKM2 may also participate in the regulation of microglial activation during TBI. Therefore, the present study aimed to evaluate the role of PKM2 in regulating microglial activation and neuroinflammation and its effects on cognitive function following TBI. A controlled cortical impact (CCI) mouse model and inflammation-induced primary mouse microglial cells in vitro were used to investigate the potential effects of PKM2 inhibition and regulation. PKM2 was significantly increased during the acute and subacute phases of TBI and was predominantly detected in microglia rather than in neurons. Our results demonstrate that shikonin and TEPP-46 can inhibit microglial inflammation, improving mitochondria, improving mouse behavior, reducing brain defect volume, and alleviating pathological changes after TBI. There is a difference in the intervention of shikonin and TEPP-46 on PKM2. Shikonin directly inhibits General PKM2; TEPP-46 can promote the expression of PKM2 tetramer. In vitro experiments, TEPP-46 can promote the expression of PKM2 tetramer, enhance the interaction between PKM2 and MFN2, improve mitochondria, alleviate neuroinflammation. General inhibition and tetramerization activation of PKM2 attenuated cognitive function caused by TBI, whereas PKM2 tetramerization exhibited a better treatment effect. Our experiments demonstrated the non-metabolic role of PKM2 in the regulation of microglial activation following TBI. Both shikonin and TEPP-46 can inhibit pro-inflammatory factors, but only TEPP-46 can promote PKM2 tetramerization and upregulate the release of anti-inflammatory factors from microglia.

A sperm-enriched 5'fragment of tRNA-Valine regulates preimplantation embryonic transcriptome and development

Sperm small RNAs have been implicated in intergenerational epigenetic inheritance of paternal environmental effects; however, their biogenesis and functions remain poorly understood. We previously identified a 5' fragment of tRNA-Valine-CAC-2 (tRFValCAC) as one of the most abundant small RNA in mature sperm. tRFValCAC is specifically enriched in sperm during post-testicular maturation in the epididymis, and we found that it is delivered to sperm from epididymis epithelial cells via extracellular vesicles. Here, we investigated the mechanistic basis of tRFValCAC delivery to sperm and its functions in the early embryo. We show that tRFValCAC interacts with an RNA binding protein, heterogeneous nuclear ribonucleoprotein A/B (hnRNPAB), in the epididymis, and this interaction regulates the sorting and packing of tRFValCAC into extracellular vesicles. In the embryo, we found that tRFValCAC regulates early embryonic mRNA processing and splicing. Inhibition of tRFValCAC in preimplantation embryos altered the transcript abundance of genes involved in RNA splicing and mRNA processing. Importantly, tRFValCAC-inhibited embryos showed altered mRNA splicing, including alternative splicing of various splicing factors and genes important for proper preimplantation embryonic development. Finally, we find that inhibition of tRFValCAC in zygotes delayed preimplantation embryonic development. Together, our results reveal a novel function of a sperm-enriched tRF in regulating alternating splicing and preimplantation embryonic development and shed light on the mechanism of sperm small RNA-mediated epigenetic inheritance.

Youthful small extracellular vesicles restore the function and reparative capacity of inflammatory-impaired periodontal ligament stem cells via delivering protein biglycan for bone regeneration

Regenerating inflamed bone defects represents a severe clinical challenge due to the undesirable inflammatory microenvironment. The inflammatory stimulus poses a weighty threat to the regenerative capacity of endogenously derived mesenchymal stem cells (MSCs), which are mainly responsible for osteogenic differentiation, thereby resulting in compromised endogenous bone formation. Consequently, alleviating the biological characteristics of inflammatory-impaired MSCs is crucial for promoting inflamed bone regeneration. Nano-sized small extracellular vesicles (sEVs) have emerged as promising therapeutic tools to orchestrate MSCs fate due to their intrinsic biocompatibility and encapsulated bioactive contents. In the present study, we extracted sEVs from youthful and adult dental pulp MSCs and explored their ability to recover inflammation-compromised periodontal ligament stem cells (IPDLSCs). The results indicated that both types of sEVs were capable of facilitating IPDLSCs osteogenesis. However, young sEVs exhibited a more robust potential at a lower concentration compared to adult sEVs. Mechanically, young sEVs enhanced the expression of bone morphogenetic protein 4 (BMP4) via delivering the protein Biglycan, which correspondingly promoted the osteogenic capability of IPDLSCs. Collectively, our findings emphasized that young sEVs hold enormous potential to rescue the inherent function and regenerative competence of inflammation-impaired MSCs, shedding light on their promising therapeutic prospects for infected bone regeneration.

iTRAQ-Based Serum Proteomic Analysis Reveals Multifactorial Cellular Function Impairment and Aggravated Systematic Inflammation in Drug-free Obsessive-Compulsive Disorders

Obsessive-compulsive disorder (OCD) is a debilitating mental disorder with obvious difficulties in treatment. Its pathogenesis has not been fully elucidated. Further understanding of etiology and mechanism needs to be explored further. We employed the isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis to compare serum proteome profile between OCD patients and healthy controls, in order to find out the possible mechanism of OCD in the downstream biological process. Eighty-one drug-free OCD patients and 78 healthy controls were enrolled. A total of 475 proteins were identified. Totally, 80 proteins with p < 0.05 were selected for gene set enrichment analysis (GSEA), and only those with a fold change ≥1.2 and q value <0.2 between groups were accepted as differentially expressed proteins (DEPs). We observed a significant enrichment of immuno-inflammation-related pathways, along with intriguing expression trends that immuno-inflammation-related proteins were upregulated in GSEA. After that, 2 up-regulated proteins and 13 down-regulated ones were accepted as DEP. According to the available literature, most of the DEPs have not been reported in OCD. These DEPs were enriched in 121 gene ontology (GO) terms, including hepatocyte growth factor receptor activity, angiogenin-PRI complex, and so on. DEPs were enriched in pathways including adherens junction in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Alterations in DEPs including STXBP5L, GRN, and ANG were validated in OCD animal models. Our study suggested that OCD patients manifested multifactorial impairment in neuronal or non-neuronal cellular function under the inflammatory background. Further research employing larger sample sizes, longitudinal design, stratified analysis, and multiomics methodology will be needed. Experiments in laboratories were essential in illuminating the mechanism.

TIPE1 limits virus replication by disrupting PKM2/ HIF-1α/ glycolysis feedback loop

OBJECTIVE

Virus infection is a major threat to human health and remains a significant cause of death to date. Macrophages are important innate immune cells that exhibit indispensable roles in controlling virus replication. It was recently reported that metabolic adaption determines the functional state of macrophages. Thus, to further unravel the crucial factors involving in metabolic adaption of macrophages might provide the potential candidates for optimizing their anti-viral capabilities.

METHODS

RT-PCR, Western blotting, virus plaque assay and HE were used to evaluate the viral load in virus-infected Tipe1M-KO and Tipe1f/f mice or cultured macrophages. RNA sequencing were performed with Tipe1M-KOor Tipe1f/f BMDMs upon virus infection. Extracellular acidification rate (ECAR) was applied for analyzing glycolysis rate in virus-infected BMDMs. Co-immunoprecipitation (Co-IP) assay and LC-MS/MS were used to determine the potential interacting proteins of TIPE1.

RESULTS

TIPE1 level was significantly reduced in BMDMs infected with either RNA viruses or DNA virus. Deficiency of Tipe1 in macrophages increased viral load and aggravated tissue damage. Mechanistically, TIPE1 suppressed the glycolytic capacity of macrophages through interacting with PKM2 and promoting its ubiquitination degradation, which in turn decreased HIF1α transcription and viral replication in macrophages.

CONCLUSIONS

TIPE1 functions as a novel regulator for metabolic reprogramming and virus infection in macrophages.

Targeted suppression of oral squamous cell carcinoma by pyrimidine-tethered quinoxaline derivatives

Oral cancer (OC) stands as a prominent cause of global mortality. Despite numerous efforts in recent decades, the efficacy of novel therapies to extend the lifespan of OC patients remains disappointingly low. Consequently, the demand for innovative therapeutic agents has become all the more pressing. In this context, we present our work on the design and synthesis of twenty-five novel quinoxaline-tethered imidazopyri(mi)dine derivatives. This was followed by comprehensive investigations into the impact of these molecules on the OC cell line. The in vitro cytotoxicity studies performed in CAL-27 and normal oral epithelial (NOE) cell lines revealed that some of the synthesized molecules like 12d have potent antiproliferative activity specifically towards OC cells with an IC50 of 0.79 μM and show negligible cytotoxicity over NOE cells. Further, 12d arrested cell growth in the S phase of the cell cycle and induced cell death by early apoptosis. The in silico studies validated that 12d binds to the activator binding site on pyruvate kinase M2 (PKM2) overexpressed in OC while the lactate dehydrogenase (LDH)-coupled enzyme assay established 12d as a potent PKM2 activator with an AC50 of 0.6 nM. Hence, this study provides fruitful evidence for the designed compounds as anticancer agents against OC.

microRNA-1 Regulates Metabolic Flexibility in Skeletal Muscle via Pyruvate Metabolism

MicroRNA-1 (miR-1) is the most abundant miRNA in adult skeletal muscle. To determine the function of miR-1 in adult skeletal muscle, we generated an inducible, skeletal muscle-specific miR-1 knockout (KO) mouse. Integration of RNA-sequencing (RNA-seq) data from miR-1 KO muscle with Argonaute 2 enhanced crosslinking and immunoprecipitation sequencing (AGO2 eCLIP-seq) from human skeletal muscle identified miR-1 target genes involved with glycolysis and pyruvate metabolism. The loss of miR-1 in skeletal muscle induced cancer-like metabolic reprogramming, as shown by higher pyruvate kinase muscle isozyme M2 (PKM2) protein levels, which promoted glycolysis. Comprehensive bioenergetic and metabolic phenotyping combined with skeletal muscle proteomics and metabolomics further demonstrated that miR-1 KO induced metabolic inflexibility as a result of pyruvate oxidation resistance. While the genetic loss of miR-1 reduced endurance exercise performance in mice and in C. elegans, the physiological down-regulation of miR-1 expression in response to a hypertrophic stimulus in both humans and mice causes a similar metabolic reprogramming that supports muscle cell growth. Taken together, these data identify a novel post-translational mechanism of adult skeletal muscle metabolism regulation mediated by miR-1.

The Role of PKM2 in Multiple Signaling Pathways Related to Neurological Diseases

Pyruvate kinase M2 (PKM2) is a key rate-limiting enzyme in glycolysis. It is well known that PKM2 plays a vital role in the proliferation of tumor cells. However, PKM2 can also exert its biological functions by mediating multiple signaling pathways in neurological diseases, such as Alzheimer's disease (AD), cognitive dysfunction, ischemic stroke, post-stroke depression, cerebral small-vessel disease, hypoxic-ischemic encephalopathy, traumatic brain injury, spinal cord injury, Parkinson's disease (PD), epilepsy, neuropathic pain, and autoimmune diseases. In these diseases, PKM2 can exert various biological functions, including regulation of glycolysis, inflammatory responses, apoptosis, proliferation of cells, oxidative stress, mitochondrial dysfunction, or pathological autoimmune responses. Moreover, the complexity of PKM2's biological characteristics determines the diversity of its biological functions. However, the role of PKM2 is not entirely the same in different diseases or cells, which is related to its oligomerization, subcellular localization, and post-translational modifications. This article will focus on the biological characteristics of PKM2, the regulation of PKM2 expression, and the biological role of PKM2 in neurological diseases. With this review, we hope to have a better understanding of the molecular mechanisms of PKM2, which may help researchers develop therapeutic strategies in clinic.

Lysine lactylation in the regulation of tumor biology

Lysine lactylation (Kla), a newly discovered post-translational modification (PTM) of lysine residues, is progressively revealing its crucial role in tumor biology. A growing body of evidence supports its capacity of transcriptional regulation through histone modification and modulation of non-histone protein function. It intricately participates in a myriad of events in the tumor microenvironment (TME) by orchestrating the transitions of immune states and augmenting tumor malignancy. Its preferential modification of metabolic proteins underscores its specific regulatory influence on metabolism. This review focuses on the effect and the probable mechanisms of Kla-mediated regulation of tumor metabolism, the upstream factors that determine Kla intensity, and its potential implications for the clinical diagnosis and treatment of tumors.

Protein tyrosine phosphatase 1B (PTP1B) function, structure, and inhibition strategies to develop antidiabetic drugs

Tyrosine protein phosphatase non-receptor type 1 (PTP1B; also known as protein tyrosine phosphatase 1B) is a member of the protein tyrosine phosphatase (PTP) family and is a soluble enzyme that plays an essential role in different physiological processes, including the regulation of metabolism, specifically in insulin and leptin sensitivity. PTP1B is crucial in the pathogenesis of type 2 diabetes mellitus and obesity. These biological functions have made PTP1B validated as an antidiabetic and anti-obesity, and potentially anticancer, molecular target. Four main approaches aim to inhibit PTP1B: orthosteric, allosteric, bidentate inhibition, and PTPN1 gene silencing. Developing a potent and selective PTP1B inhibitor is still challenging due to the enzyme's ubiquitous expression, subcellular location, and structural properties. This article reviews the main advances in the study of PTP1B since it was first isolated in 1988, as well as recent contextual information related to the PTP family to which this protein belongs. Furthermore, we offer an overview of the role of PTP1B in diabetes and obesity, and the challenges to developing selective, effective, potent, bioavailable, and cell-permeable compounds that can inhibit the enzyme.

Understanding lactate in the development of Hepatitis B virus-related hepatocellular carcinoma

Hepatitis B Virus (HBV) is a hepatotropic virus that can establish a persistent and chronic infection in humans. Chronic hepatitis B (CHB) infection is associated with an increased risk of hepatic decompensation, cirrhosis, and hepatocellular carcinoma (HCC). Lactate level, as the end product of glycolysis, plays a substantial role in metabolism beyond energy production. Emerging studies indicate that lactate is linked to patient mortality rates, and HBV increases overall glucose consumption and lactate production in hepatocytes. Excessive lactate plays a role in regulating the tumor microenvironment (TME), immune cell function, autophagy, and epigenetic reprogramming. The purpose of this review is to gather and summarize the existing knowledge of the lactate's functions in the dysregulation of the immune system, which can play a crucial role in the development of HBV-related HCC. Therefore, it is reasonable to hypothesize that lactate with intriguing functions can be considered an immunomodulatory metabolite in immunotherapy.

Pyruvate Kinase M2: A Potential Regulator of Cardiac Injury Through Glycolytic and Non-glycolytic Pathways

ABSTRACT

Adult animals are unable to regenerate heart cells due to postnatal cardiomyocyte cycle arrest, leading to higher mortality rates in cardiomyopathy. However, reprogramming of energy metabolism in cardiomyocytes provides a new perspective on the contribution of glycolysis to repair, regeneration, and fibrosis after cardiac injury. Pyruvate kinase (PK) is a key enzyme in the glycolysis process. This review focuses on the glycolysis function of PKM2, although PKM1 and PKM2 both play significant roles in the process after cardiac injury. PKM2 exists in both low-activity dimer and high-activity tetramer forms. PKM2 dimers promote aerobic glycolysis but have low catalytic activity, leading to the accumulation of glycolytic intermediates. These intermediates enter the pentose phosphate pathway to promote cardiomyocyte proliferation and heart regeneration. Additionally, they activate adenosine triphosphate (ATP)-sensitive K + (K ATP ) channels, protecting the heart against ischemic damage. PKM2 tetramers function similar to PKM1 in glycolysis, promoting pyruvate oxidation and subsequently ATP generation to protect the heart from ischemic damage. They also activate KDM5 through the accumulation of αKG, thereby promoting cardiomyocyte proliferation and cardiac regeneration. Apart from glycolysis, PKM2 interacts with transcription factors like Jmjd4, RAC1, β-catenin, and hypoxia-inducible factor (HIF)-1α, playing various roles in homeostasis maintenance, remodeling, survival regulation, and neovascularization promotion. However, PKM2 has also been implicated in promoting cardiac fibrosis through mechanisms like sirtuin (SIRT) 3 deletion, TG2 expression enhancement, and activation of transforming growth factor-β1 (TGF-β1)/Smad2/3 and Jak2/Stat3 signals. Overall, PKM2 shows promising potential as a therapeutic target for promoting cardiomyocyte proliferation and cardiac regeneration and addressing cardiac fibrosis after injury.

Importance of Michaelis Constants for Cancer Cell Redox Balance and Lactate Secretion-Revisiting the Warburg Effect

Cancer cells metabolize a large fraction of glucose to lactate, even under a sufficient oxygen supply. This phenomenon-the "Warburg Effect"-is often regarded as not yet understood. Cancer cells change gene expression to increase the uptake and utilization of glucose for biosynthesis pathways and glycolysis, but they do not adequately up-regulate the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS). Thereby, an increased glycolytic flux causes an increased production of cytosolic NADH. However, since the corresponding gene expression changes are not neatly fine-tuned in the cancer cells, cytosolic NAD+ must often be regenerated by loading excess electrons onto pyruvate and secreting the resulting lactate, even under sufficient oxygen supply. Interestingly, the Michaelis constants (KM values) of the enzymes at the pyruvate junction are sufficient to explain the priorities for pyruvate utilization in cancer cells: 1. mitochondrial OXPHOS for efficient ATP production, 2. electrons that exceed OXPHOS capacity need to be disposed of and secreted as lactate, and 3. biosynthesis reactions for cancer cell growth. In other words, a number of cytosolic electrons need to take the "emergency exit" from the cell by lactate secretion to maintain the cytosolic redox balance.

Pyruvate kinase M2 sustains cardiac mitochondrial quality surveillance in septic cardiomyopathy by regulating prohibitin 2 abundance via S91 phosphorylation

The endogenous mitochondrial quality control (MQC) system serves to protect mitochondria against cellular stressors. Although mitochondrial dysfunction contributes to cardiac damage during many pathological conditions, the regulatory signals influencing MQC disruption during septic cardiomyopathy (SC) remain unclear. This study aimed to investigate the involvement of pyruvate kinase M2 (PKM2) and prohibitin 2 (PHB2) interaction followed by MQC impairment in the pathogenesis of SC. We utilized LPS-induced SC models in PKM2 transgenic (PKM2TG) mice, PHB2S91D-knockin mice, and PKM2-overexpressing HL-1 cardiomyocytes. After LPS-induced SC, cardiac PKM2 expression was significantly downregulated in wild-type mice, whereas PKM2 overexpression in vivo sustained heart function, suppressed myocardial inflammation, and attenuated cardiomyocyte death. PKM2 overexpression relieved sepsis-related mitochondrial damage via MQC normalization, evidenced by balanced mitochondrial fission/fusion, activated mitophagy, restored mitochondrial biogenesis, and inhibited mitochondrial unfolded protein response. Docking simulations, co-IP, and domain deletion mutant protein transfection experiments showed that PKM2 phosphorylates PHB2 at Ser91, preventing LPS-mediated PHB2 degradation. Additionally, the A domain of PKM2 and the PHB domain of PHB2 are required for PKM2-PHB2 binding and PHB2 phosphorylation. After LPS exposure, expression of a phosphorylation-defective PHB2S91A mutant negated the protective effects of PKM2 overexpression. Moreover, knockin mice expressing a phosphorylation-mimetic PHB2S91D mutant showed improved heart function, reduced inflammation, and preserved mitochondrial function following sepsis induction. Abundant PKM2 expression is a prerequisite to sustain PKM2-PHB2 interaction which is a key element for preservation of PHB2 phosphorylation and MQC, presenting novel interventive targets for the treatment of septic cardiomyopathy.

Targeting pyruvate kinase M2 for the treatment of kidney disease

Pyruvate kinase M2 (PKM2), a rate limiting enzyme in glycolysis, is a cellular regulator that has received extensive attention and regards as a metabolic regulator of cellular metabolism and energy. Kidney is a highly metabolically active organ, and glycolysis is the important energy resource for kidney. The accumulated evidences indicates that the enzymatic activity of PKM2 is disturbed in kidney disease progression and treatment, especially diabetic kidney disease and acute kidney injury. Modulating PKM2 post-translational modification determines its enzymatic activity and nuclear translocation that serves as an important interventional approach to regulate PKM2. Emerging evidences show that PKM2 and its post-translational modification participate in kidney disease progression and treatment through modulating metabolism regulation, podocyte injury, fibroblast activation and proliferation, macrophage polarization, and T cell regulation. Interestingly, PKM2 activators (TEPP-46, DASA-58, mitapivat, and TP-1454) and PKM2 inhibitors (shikonin, alkannin, compound 3k and compound 3h) have exhibited potential therapeutic property in kidney disease, which indicates the pleiotropic effects of PKM2 in kidney. In the future, the deep investigation of PKM2 pleiotropic effects in kidney is urgently needed to determine the therapeutic effect of PKM2 activator/inhibitor to benefit patients. The information in this review highlights that PKM2 functions as a potential biomarker and therapeutic target for kidney diseases.

Small-molecule targeting PKM2 provides a molecular basis of lactylation-dependent fibroblast-like synoviocytes proliferation inhibition against rheumatoid arthritis

Fibroblast-like synoviocytes (FLS) play an important role in rheumatoid arthritis (RA)-related swelling and bone damage. Therefore, novel targets for RA therapy in FLS are urgently discovered for improving pathologic phenomenon, especially joint damage and dyskinesia. Here, we suggested that pyruvate kinase M2 (PKM2) in FLS represented a pharmacological target for RA treatment by antimalarial drug artemisinin (ART). We demonstrated that ART selectively inhibited human RA-FLS and rat collagen-induced arthritis (CIA)-FLS proliferation and migration without observed toxic effects. In particular, the identification of targets revealed that PKM2 played a crucial role as a primary regulator of the cell cycle, leading to the heightened proliferation of RA-FLS. ART exhibited a direct interaction with PKM2, resulting in an allosteric modulation that enhances the lactylation modification of PKM2. This interaction further promoted the binding of p300, ultimately preventing the nuclear translocation of PKM2 and inducing cell cycle arrest at the S phase. In vivo, ART obviously suppressed RA-mediated synovial hyperplasia, bone damage and inflammatory response to further improve motor behavior in CIA-rats. Taken together, these findings indicate that directing interventions towards PKM2 in FLS could offer a hopeful avenue for pharmaceutical treatments of RA through the regulation of cell cycle via PKM2 lactylation.

Fibrotic pathways and fibroblast-like synoviocyte phenotypes in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis, characterized by osteophyte formation, cartilage degradation, and structural and cellular alterations of the synovial membrane. Activated fibroblast-like synoviocytes (FLS) of the synovial membrane have been identified as key drivers, secreting humoral mediators that maintain inflammatory processes, proteases that cause cartilage and bone destruction, and factors that drive fibrotic processes. In normal tissue repair, fibrotic processes are terminated after the damage has been repaired. In fibrosis, tissue remodeling and wound healing are exaggerated and prolonged. Various stressors, including aging, joint instability, and inflammation, lead to structural damage of the joint and micro lesions within the synovial tissue. One result is the reduced production of synovial fluid (lubricants), which reduces the lubricity of the cartilage areas, leading to cartilage damage. In the synovial tissue, a wound-healing cascade is initiated by activating macrophages, Th2 cells, and FLS. The latter can be divided into two major populations. The destructive thymocyte differentiation antigen (THY)1─ phenotype is restricted to the synovial lining layer. In contrast, the THY1+ phenotype of the sublining layer is classified as an invasive one with immune effector function driving synovitis. The exact mechanisms involved in the transition of fibroblasts into a myofibroblast-like phenotype that drives fibrosis remain unclear. The review provides an overview of the phenotypes and spatial distribution of FLS in the synovial membrane of OA, describes the mechanisms of fibroblast into myofibroblast activation, and the metabolic alterations of myofibroblast-like cells.