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Endothelial cells play an important role in the metabolism of adipose tissue (AT). This study aimed to analyze the changes that adipose tissue in AT endothelial cells undergo during the development of obesity, using single-nucleus RNA sequence (snRNA-seq). Mouse paraepididymal AT cells were subjected to snRNA-seq with the 10X Genomics platform. The cell types were then clustered using t-distributed stochastic neighbor embedding and unbiased computational informatics analyses. Protein-protein interactions network was established using the STRING database and visualized using Cytoscape. The dataset was subjected to differential gene enrichment analysis. In total, 21,333 cells acquired from 24 mouse paraepididymal AT samples were analyzed using snRNA-seq. This study identified 18 distinct clusters and annotated macrophages, fibroblasts, epithelial cells, T cells, endothelial cells, stem cells, neutrophil cells, and neutrophil cell types based on representative markers. Cluster 12 was defined as endothelial cells. The proportion of endothelial cells decreased with the development of obesity. Inflammatory factors, such as Vegfa and Prdm16 were upregulated in the medium obesity group but downregulated in the obesity group. Genes, such as Prox1, Erg, Flt4, Kdr, Flt1, and Pecam1 promoted the proliferation of AT endothelial cells and maintained the internal environment of AT. This study established a reference model and general framework for studying the mechanisms, biomarkers, and therapeutic targets of endothelial cell dysfunction-related diseases at the single-cell level., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Lipid droplet tethering with mitochondria for fatty acid oxidation is critical for tumor cells to counteract energy stress. However, the underlying mechanism remains unclear. Here, we demonstrate that glucose deprivation induces phosphorylation of the glycolytic enzyme phosphofructokinase, liver type (PFKL), reducing its activity and favoring its interaction with perilipin 2 (PLIN2). On lipid droplets, PFKL acts as a protein kinase and phosphorylates PLIN2 to promote the binding of PLIN2 to carnitine palmitoyltransferase 1A (CPT1A). This results in the tethering of lipid droplets and mitochondria and the recruitment of adipose triglyceride lipase to the lipid droplet-mitochondria tethering regions to engage lipid mobilization. Interfering with this cascade inhibits tumor cell proliferation, promotes apoptosis and blunts liver tumor growth in male mice. These results reveal that energy stress confers a moonlight function to PFKL as a protein kinase to tether lipid droplets with mitochondria and highlight the crucial role of PFKL in the integrated regulation of glycolysis, lipid metabolism and mitochondrial oxidation., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Dysregulation in lipid metabolism is among the most prominent metabolic alterations in cancer. Cancer cells harness lipid metabolism to obtain energy, components for biological membranes, and signaling molecules needed for proliferation, survival, invasion, metastasis, and response to the tumor microenvironment impact and cancer therapy. Here, we summarize and discuss current knowledge about the advances made in understanding the regulation of lipid metabolism in cancer cells and introduce different approaches that have been clinically used to disrupt lipid metabolism in cancer therapy., Competing Interests: Disclosures: The authors declare no competing interests exist., (© 2020 Bian et al.)

ATF5 has been shown to be a critical regulator of cell proliferation and survival; however, the underlying mechanism remains largely unknown. We demonstrate here that ATF5 interacts with the transcriptional coactivator p300, which acetylates ATF5 at lysine-29 (K29), which in turn enhances the interaction between ATF5 and p300 and binding of the ATF5/p300 complex to the ATF5 response element (ARE) region of the Egr-1 promoter. ARE-bound ATF5/p300 acetylates lysine-14 (K14) of nucleosomal histone H3 at both the ARE and serum response element (SRE) of the Egr-1 promoter, which facilitates binding of extracellular signal-regulated kinase (ERK)-phosphorylated Elk-1 to the SRE, activating the Egr-1 promoter. Interference of p300-dependent acetylation of ATF5 or nucleosomal histone H3 or blockade of ERK-dependent Elk-1 phosphorylation abrogates ATF5-dependent Egr-1 activation and cell proliferation and survival. These findings assign a central role for the ATF5/p300 complex in ATF5 function and suggest that coordinated actions by ATF5, p300, Elk-1, and ERK/mitogen-activated protein kinase (MAPK) are essential for ATF5-dependent Egr-1 activation and cell proliferation and survival.

Patients with glioblastomas, the most common primary tumors of the central nervous system, have poor prognoses because of uncontrolled tumor cell invasion and proliferation. β-Catenin plays an important role in tumor development. However, whether α-catenin expression contributes to β-catenin transactivation in glioma cells is largely unknown. We report here that α-catenin expression abrogates epidermal growth factor receptor (EGFR)-activation-induced β-catenin nuclear translocation in human glioblastoma cells, thereby attenuating β-catenin transactivation and the expression of its downstream genes CCND1 and c-myc. In addition, ectopic expression of α-catenin or depletion of β-catenin suppresses EGF-promoted glioblastoma cell migration, invasion, and proliferation. In contrast, α-catenin depletion promotes β-catenin nuclear translocation and transactivation, and tumor cell motility and growth. These findings reveal the importance of β-catenin regulation by α-catenin in cellular activities of glioblastoma cells.

A recent report published in Nature Metabolism identified that glutamine synthetase (GS), the only enzyme in mammals to produce glutamine from glutamate, can directly control cancer cell mitosis by governing the APC/C complex via a metabolism-independent mechanism. It reported that GS can directly interact with the nuclear pore protein NUP88 to abolish its binging with CDC20, therefore licensing the activation of APC/CCDC20 to permit proper metaphase to anaphase transition of mitosis. These findings illustrated a dual-function mode of action of GS in cancer cells, in which GS's metabolic and non-metabolic functions coordinate with the concentration change of glutamine in the tumor microenvironment (TME) to ensure cell survival or proliferation, respectively. These findings revealed the multi-faceted roles of glutamine synthetase in tumor development and underscored the potential to target non-canonical functions of glutamine synthetase for cancer treatment. [ABSTRACT FROM AUTHOR]

The senescence of mesenchymal stem cells (MSCs) plays a crucial role in the development and progression of systemic lupus erythematosus (SLE). Exosomes, small spherical bilayer proteolipid vesicles, contribute to the communication between various cells and their microenvironment by transferring information via their cargo, including the proteins, lipids, and RNAs. While exosomal miRNAs participate in various biological activities, correlations of circulating exosomes with senescent signs of BM-MSCs remain unclear. In our study, we aimed at exploring the roles of circulating exosomal miRNAs in the senescence of MSCs. We found that exosomes derived from SLE serum could increase the proportions of SA-β-gal positive cells, disorganize cytoskeletons, and reduce growth rates. Moreover, the expression of miR-146a declined significantly in serum exosomes of SLE patients compared with healthy controls. miR-146a could be internalized into MSCs via exosomes and participate in MSCs senescence through targeting TRAF6/NF-κB signaling. These results clarified the novel mechanism of MSCs senescence in SLE patients. [ABSTRACT FROM AUTHOR]

Increasing evidence shows miR-155 plays an important role in regulating inflammatory processes in systemic lupus erythematosus (SLE), especially in lupus nephritis (LN). Because the chemokine CXCL13 is implicated in the pathogenesis of LN, here we examined whether miR-155 can modulate the activity of CXCL13 or its receptor CXCR5. We determined the expression of CXCL13 in normal and MRL/lpr mice and found elevated levels of CXCL13 in the kidneys of MRL/lpr mice compared with normal kidneys. Besides, CXCL13 expression was mainly detected in the glomerulus, specifically to mesangial areas. We then transfected a miR-155 mimic in human renal mesangial cells (HRMCs) to overexpress miR-155 and detected decreased protein levels of CXCR5 by western blot analysis. Transfection of the miR-155 mimic into CXCL13-treated HRMCs resulted in a significantly reduced proliferation rate of HRMCs as measured by the cell-counting assay and flow cytometry. Moreover, increased intracellular miR-155 also led to decreased phosphorylation of ERK and TGF-β1 production. Together, these results revealed that miR-155 may play a role in the pathogenesis of LN. [ABSTRACT FROM AUTHOR]

The embryonic pyruvate kinase M2 (PKM2) isoform is highly expressed in human cancer. In contrast to the established role of PKM2 in aerobic glycolysis or the Warburg effect, its non-metabolic functions remain elusive. Here we demonstrate, in human cancer cells, that epidermal growth factor receptor (EGFR) activation induces translocation of PKM2, but not PKM1, into the nucleus, where K433 of PKM2 binds to c-Src-phosphorylated Y333 of ?-catenin. This interaction is required for both proteins to be recruited to the CCND1 promoter, leading to HDAC3 removal from the promoter, histone H3 acetylation and cyclin D1 expression. PKM2-dependent ?-catenin transactivation is instrumental in EGFR-promoted tumour cell proliferation and brain tumour development. In addition, positive correlations have been identified between c-Src activity, ?-catenin Y333 phosphorylation and PKM2 nuclear accumulation in human glioblastoma specimens. Furthermore, levels of ?-catenin phosphorylation and nuclear PKM2 have been correlated with grades of glioma malignancy and prognosis. These findings reveal that EGF induces ?-catenin transactivation via a mechanism distinct from that induced by Wnt/Wingless and highlight the essential non-metabolic functions of PKM2 in EGFR-promoted ?-catenin transactivation, cell proliferation and tumorigenesis. [ABSTRACT FROM AUTHOR]

Frequently occurring histone lysine succinylation is a newly identified histone modification that can be regulated by KAT2A histone succinyltransferase, which is also a histone acetyltransferase. KAT2A histone succinyltransferase activity is important for tumorigenesis; however, the mechanism underlying this tumor-promoting effect remains elusive. Here we demonstrate that KAT2A is highly expressed in human pancreatic ductal adenocarcinoma (PDAC) specimens and positively correlated with advanced stages of PDAC and short patients' survival. In addition, KAT2A expression in PDAC specimens is correlated with 14-3-3ζ expression, and KAT2A regulates H3K79 succinylation in the promoter region of YWHAZ (encoding for 14-3-3ζ) to promote YWHAZ mRNA and 14-3-3ζ expression, thereby preventing β-catenin degradation. Expression of succinyltransferase activity-defective KAT2A Y645A reduces H3K79 succinylation and 14-3-3ζ expression, leading to decreased β-catenin stability and subsequently decreased expression of cyclin D1, c-Myc, GLUT1, and LDHA. KAT2A-mediated 14-3-3ζ and β-catenin expression promotes glycolysis, cell proliferation, and migration and invasion of PDAC cells with epithelial-to-mesenchymal transition. These findings reveal a novel and instrumental role of KAT2A-mediated histone succinylation in regulation of gene expression and β-catenin stability to promote tumor cell proliferation and invasion. [ABSTRACT FROM AUTHOR]

Cancer cells prefer to utilizing aerobic glycolysis to generate energy and anabolic metabolic intermediates for cell growth. However, whether the activities of glycolytic enzymes can be regulated by specific posttranslational modifications, such as SUMOylation, in response to oncogenic signallings, thereby promoting the Warburg effect, remain largely unclear. Here, we demonstrate that phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key glycolytic enzyme, interacts with SUMO-conjugating enzyme UBC9 and is SUMOylated at K302 in glioblastoma cells. Expression of UBC9, which competitively prevents the binding of ubiquitin E3 ligase APC/C to PFKFB3 and subsequent PFKFB3 polyubiquitination, increases PFKFB3 stability and expression. Importantly, EGFR activation increases the interaction between UBC9 and PFKFB3, leading to increased SUMOylation and expression of PFKFB3. This increase is blocked by inhibition of EGFR-induced AKT activation whereas expression of activate AKT by itself was sufficient to recapitulate EGF-induced effect. Knockout of PFKFB3 expression decreases EGF-enhanced lactate production and GBM cell proliferation and this decrease was fully rescued by reconstituted expression of WT PFKFB3 whereas PFKFB3 K302R mutant expression abrogates EGF- and UBC9-regulated lactate production and GBM cell proliferation. These findings reveal a previously unknown mechanism underlying the regulation of the Warburg effect through the EGFR activation-induced and UBC9-mediated SUMOylation and stabilization of PFKFB3. [ABSTRACT FROM AUTHOR]

Summary DNA replication is initiated by assembly of the kinase cell division cycle 7 (CDC7) with its regulatory activation subunit, activator of S-phase kinase (ASK), to activate DNA helicase. However, the mechanism underlying regulation of CDC7-ASK complex is unclear. Here, we show that ADP generated from CDC7-mediated MCM phosphorylation binds to an allosteric region of CDC7, disrupts CDC7-ASK interaction, and inhibits CDC7-ASK activity in a feedback way. EGFR- and ERK-activated casein kinase 2α (CK2α) phosphorylates nuclear phosphoglycerate kinase (PGK) 1 at S256, resulting in interaction of PGK1 with CDC7. CDC7-bound PGK1 converts ADP to ATP, thereby abrogating the inhibitory effect of ADP on CDC7-ASK activity, promoting the recruitment of DNA helicase to replication origins, DNA replication, cell proliferation, and brain tumorigenesis. These findings reveal an instrumental self-regulatory mechanism of CDC7-ASK activity by its kinase reaction product ADP and a nonglycolytic role for PGK1 in abrogating this negative feedback in promoting tumor development. Graphical Abstract Highlights • ADP generated from CDC7-mediated phosphorylation inhibits CDC7-ASK activity • EGFR- and ERK1/2-dependent activation of CK2α phosphorylates PGK1 at S256 • Phosphorylated PGK1 binds to CDC7 and converts ADP to ATP • PGK1 releases ADP's inhibition on CDC7 to promote DNA replication and tumorigenesis Li et al. demonstrate that ADP generated from CDC7-mediated MCM phosphorylation binds to an allosteric region of CDC7, disrupts CDC7-ASK interaction, and inhibits CDC7-ASK activity in a feedback way. CDC7-bound PGK1 under EGFR activation condition converts ADP to ATP, thereby abrogating ADP's inhibition on CDC7-ASK activity and promoting DNA replication. [ABSTRACT FROM AUTHOR]