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Tumors override energy stress to grow. However, how nucleotide synthesis is regulated under energy stress is unclear. We demonstrate here that glucose deprivation or hypoxia results in the AMPK-mediated phosphorylation of phosphoribosyl pyrophosphate synthetase 1 (PRPS1) S180 and PRPS2 S183, leading to conversion of PRPS hexamers to monomers and thereby inhibiting PRPS1/2 activity, nucleotide synthesis, and nicotinamide adenine dinucleotide (NAD) production. Knock-in of nonphosphorylatable PRPS1/2 mutants, which have uninhibited activity, in brain tumor cells under energy stress exhausts cellular ATP and NADPH and increases reactive oxygen species levels, thereby promoting cell apoptosis. The expression of those mutants inhibits brain tumor formation and enhances the inhibitory effect of the glycolysis inhibitor 2-deoxy-d-glucose on tumor growth. Our findings highlight the significance of recalibrating tumor cell metabolism by fine-tuning nucleotide and NAD synthesis in tumor growth. Significance: Our findings elucidate an instrumental function of AMPK in direct regulation of nucleic acid and NAD synthesis in tumor cells in response to energy stress. AMPK phosphorylates PRPS1/2, converts PRPS1/2 hexamers to monomers, and inhibits PRPS1/2 activity and subsequent nucleotide and NAD synthesis to maintain tumor cell growth and survival. Cancer Discov; 8(1); 94-107. ©2017 AACR. This article is highlighted in the In This Issue feature, p. 1 ., (©2017 American Association for Cancer Research.)

Background: Rapid tumor growth inevitably results in energy stress, including deficiency of glutamine, a critical amino acid for tumor cell proliferation. However, whether glutamine deficiency allows tumor cells to use lipid droplets as an energy resource and the mechanism underlying this potential regulation remain unclear. Methods: We purified lipid droplets from H322 and H358 human non-small-cell lung cancer (NSCLC) cells under glutamine deprivation conditions and performed immunoblotting to determine the binding of choline kinase (CHK) α2 to lipid droplets. Immunofluorescence was used to quantify lipid droplet numbers and sizes. Immunoprecipitation and immunoblotting were performed to examine AMPK activation and CHKα2 phosphorylation. Cellular fatty acid levels, mitochondrial acetyl coenzyme A and ATP production, and cell apoptosis and proliferation were measured. Immunohistochemical analyses were performed to determine the expression levels of ACC pS79 and CHKα2 pS279 in tumor specimens from NSCLC patients. The prognostic value of ACC pS79 and CHKα2 pS279 was assessed using the Kaplan-Meier method and Cox regression models. Results: Glutamine deficiency induces AMPK-mediated CHKα2 S279 phosphorylation, which promotes the binding of CHKα2 to lipid droplets, resulting in recruitment of cytosolic lipase ATGL and autophagosomes and subsequent lipolysis of lipid droplets to sustain tumor cell survival and proliferation. In addition, the levels of ACC pS79 and CHKα S279 were much higher in human NSCLC specimens than in their adjacent normal tissues and positively correlated with each other. Notably, ACC pS79 and CHKα pS279 expression levels alone were associated with poor prognosis of NSCLC patients, and combined values of both phosphorylation levels were correlated with worse prognosis of the patients. Conclusion: CHKα2 plays a critical role in lipolysis of lipid droplets in NSCLC. ACC pS79 and CHKα2 pS279 alone or in combination can be used as prognostic markers in NSCLC. [ABSTRACT FROM AUTHOR]

Metabolic enzymes can perform non-metabolic functions and play critical roles in the regulation of a variety of important cellular activities. Phosphoenolpyruvate carboxykinase 1 (PCK1), a gluconeogenesis enzyme, was recently identified as an AKT-regulated protein kinase that phosphorylates INSIG1/2 to promote nuclear SREBP1-dependent lipogenesis. However, the relationship of this regulation with the progression of non-small-cell lung carcinoma (NSCLC) is unclear. Here, we demonstrate that epidermal growth factor receptor (EGFR) activation induces AKT-dependent PCK1 pS90, PCK1-mediated INSIG1 pS207/INSIG2 pS151, and nuclear SREBP1 accumulation in NSCLC cells. In addition, the expression levels of AKT pS473, PCK1 pS90, INSIG1 pS207/INSIG2 pS151, and nuclear SREBP1 are higher in 451 analyzed human NSCLC specimens than in their adjacent normal tissues and positively correlated with each other in the tumor specimens. Furthermore, the expression levels of PCK1 pS90, INSIG1 pS207/INSIG2 pS151, and nuclear SREBP1 are associated with TNM stage and progression in NSCLC. Importantly, levels of PCK1 pS90 or INSIG1 pS207/INSIG2 pS151 are positively correlated with poor prognosis in NSCLC patients, and the combined expression value of the PCK1 and INSIG1/2 phosphorylation has a better prognostic value than that of each individual protein phosphorylation value and is an independent prognostic marker for NSCLC. These findings reveal the role of PCK1-mediated nuclear SREBP1 activation in NSCLC progression and highlight the potential to target the protein kinase activity of PCK1 for the diagnosis and treatment of human NSCLC. [ABSTRACT FROM AUTHOR]

Background: The identification of prognostic markers for non-small-cell lung carcinoma (NSCLC) is needed for clinical practice. The metabolism-reprogramming marker ketohexokinase (KHK)-A and acetyl-CoA synthetase 2 (ACSS2) phosphorylation at S659 (ACSS2 pS659) play important roles in tumorigenesis and tumor development. However, the clinical significance of KHK-A and ACSS2 pS659 in NSCLC is largely unknown. Methods: The expression levels of KHK-A and ACSS2 pS659 were assessed by immunohistochemistry analyses of surgical specimens from 303 NSCLC patients. The prognostic values of KHK-A and ACSS2 pS659 were evaluated by Kaplan–Meier methods and Cox regression models. Results: The expression levels of KHK-A and ACSS2 pS659 were significantly higher in NSCLC tissues than those in adjacent non-tumor tissues (P < 0.0001). KHK-A or ACSS2 pS659 alone and the combination of KHK-A and ACSS2 pS659 were inversely correlated with overall survival in NSCLC patients (P < 0.001). The multivariate analysis indicated that KHK-A or ACSS2 pS659 and KHK-A/ACSS2 pS659 were independent prognostic biomarkers for NSCLC (P = 0.008 for KHK-A, P < 0.001 for ACSS2 pS659, and P < 0.001 for KHK-A/ACSS2 pS659). Furthermore, the combination of KHK-A and ACSS2 pS659 can be used as a prognostic indicator for all stages of NSCLC. Conclusions: KHK-A or ACSS2 pS659 alone and the combination of KHK-A and ACSS2 pS659 can be used as prognostic markers for NSCLC. Our findings highlight the important role of metabolic reprogramming in NSCLC progression. [ABSTRACT FROM AUTHOR]

Protein kinases regulate every aspect of cellular activity, whereas metabolic enzymes are responsible for energy production and catabolic and anabolic processes. Emerging evidence demonstrates that some metabolic enzymes, such as pyruvate kinase M2 (PKM2), phosphoglycerate kinase 1 (PGK1), ketohexokinase (KHK) isoform A (KHK-A), hexokinase (HK), and nucleoside diphosphate kinase 1 and 2 (NME1/2), that phosphorylate soluble metabolites can also function as protein kinases and phosphorylate a variety of protein substrates to regulate the Warburg effect, gene expression, cell cycle progression and proliferation, apoptosis, autophagy, exosome secretion, T cell activation, iron transport, ion channel opening, and many other fundamental cellular functions. The elevated protein kinase functions of these moonlighting metabolic enzymes in tumor development make them promising therapeutic targets for cancer. [ABSTRACT FROM AUTHOR]

High expression of PD-L1 in tumor cells contributes to tumor immune evasion. However, whether PD-L1 expression in tumor cells is regulated by the availability of nutrients is unknown. Here, we show that in human glioblastoma cells, high glucose promotes hexokinase (HK) 2 dissociation from mitochondria and its subsequent binding and phosphorylation of IκBα at T291. This leads to increased interaction between IκBα and μ-calpain protease and subsequent μ-calpain-mediated IκBα degradation and NF-κB activation-dependent transcriptional upregulation of PD-L1 expression. Expression of IκBα T291A in glioblastoma cells blocked high glucose-induced PD-L1 expression and promoted CD8+ T cell activation and infiltration into the tumor tissue, reducing brain tumor growth. Combined treatment with an HK inhibitor and an anti-PD-1 antibody eliminates tumor immune evasion and remarkably enhances the anti-tumor effect of immune checkpoint blockade. These findings elucidate a novel mechanism underlying the upregulation of PD-L1 expression mediated by aerobic glycolysis and underscore the roles of HK2 as a glucose sensor and a protein kinase in regulation of tumor immune evasion. [Display omitted] • High glucose induces PD-L1 expression in human glioblastoma cells • Mitochondria-dissociated HK2 phosphorylates IκBα at T291 • μ-Calpain binds to T291-phosphorylated IκBα and degrades IκBα • IκBα pT291 increases NF-κB-dependent upregulation of PD-L1 and tumor immune evasion Guo et al. demonstrate that aberrantly upregulated aerobic glycolysis in tumor cells promotes the dissociation of HK2 from mitochondria and binds to cytosolic IκBα. Importantly, HK2 acts as a protein kinase and phosphorylates IκBα, resulting in IκBα degradation and NF-κB-activation-dependent PD-L1 expression for tumor immune evasion. [ABSTRACT FROM AUTHOR]

Histone methylation regulates DNA repair. However, the mechanisms that underlie the regulation of histone methylation during this repair remain to be further defined. Here, we show that exposure to ionizing radiation induces DNA-PK-dependent phosphorylation of nuclear fumarase at Thr 236, which leads to an interaction between fumarase and the histone variant H2A.Z at DNA double-strand break (DSB) regions. Locally generated fumarate inhibits KDM2B histone demethylase activity, resulting in enhanced dimethylation of histone H3 Lys 36; in turn, this increases the accumulation of the Ku70-containing DNA-PK at DSB regions for non-homologous end-joining DNA repair and cell survival. These findings reveal a feedback mechanism that underlies DNA-PK regulation by chromatin-associated fumarase and an instrumental function of fumarase in regulating histone H3 methylation and DNA repair. [ABSTRACT FROM AUTHOR]

Pyruvate kinase M2 (PKM2) is upregulated in multiple cancer types and contributes to the Warburg effect by unclear mechanisms. Here we demonstrate that EGFR-activated ERK2 binds directly to PKM2 Ile 429/Leu 431 through the ERK2 docking groove and phosphorylates PKM2 at Ser 37, but does not phosphorylate PKM1. Phosphorylated PKM2 Ser 37 recruits PIN1 for cis-trans isomerization of PKM2, which promotes PKM2 binding to importin ?5 and translocating to the nucleus. Nuclear PKM2 acts as a coactivator of ?-catenin to induce c-Myc expression, resulting in the upregulation of GLUT1, LDHA and, in a positive feedback loop, PTB-dependent PKM2 expression. Replacement of wild-type PKM2 with a nuclear translocation-deficient mutant (S37A) blocks the EGFR-promoted Warburg effect and brain tumour development in mice. In addition, levels of PKM2 Ser 37 phosphorylation correlate with EGFR and ERK1/2 activity in human glioblastoma specimens. Our findings highlight the importance of nuclear functions of PKM2 in the Warburg effect and tumorigenesis. [ABSTRACT FROM AUTHOR]

Glycolytic reprogramming is a typical feature of cancer. However, the cancer-specific modulation of glycolytic enzymes requires systematic elucidation. Here, we report a range of dysregulated modifications in association with a family of enzymes specifically related to the glycolysis pathway by systematic identification of delta masses at the proteomic scale in human non-small-cell lung cancer. The most significant modification is the delta mass of 79.967 Da at serine 58 (Ser58) of triosephosphate isomerase (TPI), which is confirmed to be phosphorylation. Blocking TPI Ser58 phosphorylation dramatically inhibits glycolysis, cancer growth, and metastasis. The protein kinase PRKACA directly phosphorylates TPI Ser58, thereby enhancing TPI enzymatic activity and glycolysis. The upregulation of TPI Ser58 phosphorylation is detected in various human tumor specimens and correlates with poor survival. Therefore, our study identifies a number of cancer-specific protein modifications spanned on glycolytic enzymes and unravels the significance of TPI Ser58 phosphorylation in glycolysis and lung cancer development. [Display omitted] • Widespread and diverse protein modifications map to the glycolytic enzymes • Triosephosphate isomerase (TPI) Ser58 phosphorylation is elevated in multiple tumors • TPI Ser58 phosphorylation promotes glycolysis and tumor development in lung cancer • PRKACA is responsible for the phosphorylation of TPI at Ser58 Duan et al. demonstrate extensive modifications of glycolytic enzymes in cancer and show that triosephosphate isomerase (TPI) Ser58 phosphorylation is significantly elevated in tumors. Blocking TPI Ser58 phosphorylation inhibits aerobic glycolysis, cancer cell growth, and metastasis. PRKACA directly phosphorylates TPI at Ser58, thereby enhancing glycolysis metabolism and tumor development. [ABSTRACT FROM AUTHOR]

ERK1/2 is an important subfamily of mitogen-activated protein kinases that control a broad range of cellular activities and physiological processes. ERK1/2 can be activated transiently or persistently by MEK1/2 and upstream MAP3Ks in conjunction with regulation and involvement of scaffolding proteins and phosphatases. Activation of ERK1/2 generally promotes cell survival; but under certain conditions, ERK1/2 can have pro-apoptotic functions.iubmbLife, 58: 621 – 631, 2006 [ABSTRACT FROM AUTHOR]

ERK1/2 MAP kinases are important regulators in cellular signaling, whose activity is normally reversibly regulated by threonine-tyrosine phosphorylation. In contrast, we have found that stress-induced ERK1/2 activity is downregulated by ubiquitin/proteasome-mediated degradation of ERK1/2. The PHD domain of MEKK1, a RING finger-like structure, exhibited E3 ubiquitin ligase activity toward ERK2 in vitro and in vivo. Moreover, both MEKK1 kinase activity and the docking motif on ERK1/2 were involved in ERK1/2 ubiquitination. Significantly, cells expressing ERK2 with the docking motif mutation were resistant to sorbitol-induced apoptosis. Therefore, MEKK1 functions not only as an upstream activator of the ERK and JNK through its kinase domain, but also as an E3 ligase through its PHD domain, providing a negative regulatory mechanism for decreasing ERK1/2 activity. [Copyright &y& Elsevier]

Overcoming metabolic stress is a critical step in tumorigenesis. Acetyl coenzyme A (acetyl-CoA) converted from glucose or acetate is a substrate used for histone acetylation to regulate gene expression. However, how acetyl-CoA is produced under nutritional stress conditions is unclear. Herein we report that nutritional stress induces nuclear translocation of ACSS2 (acyl-CoA synthetase short-chain family member 2). This translocation is mediated by AMP-activated protein kinase (AMPK)-dependent ACSS2 Ser659 phosphorylation and subsequent exposure of the nuclear localization signal of ACSS2 to KPNA1/importin α5 for binding. In the nucleus, ACSS2 forms a complex with TFEB (transcription factor EB) and utilizes the acetate generated from histone deacetylation to locally produce acetyl-CoA for histone acetylation in the promoter regions of TFEB target genes. Knock-in of nuclear translocation-deficient or inactive ACSS2 mutants in glioblastoma cells abrogates glucose deprivation-induced lysosomal biogenesis and autophagy, reduces cell survival, inhibits brain tumorigenesis, and enhances the inhibitory effect of the glucose metabolism inhibitor 2-deoxy-d-glucose on tumor growth. These results reveal a novel biologic role for ACSS2 in recycling of nuclear acetate for histone acetylation to promote lysosomal and autophagy-related gene expression and counteract nutritional stress, highlighting the importance of ACSS2 in maintaining autophagy and lysosome-mediated cellular energy homeostasis during tumor development. [ABSTRACT FROM PUBLISHER]

Macroautophagy/autophagy is a cellular defense response to stress conditions and is crucial for cell homeostasis maintenance. However, the precise mechanism underlying autophagy initiation, especially in response to glutamine deprivation and hypoxia, is yet to be explored. We recently discovered that PGK1 (phosphoglycerate kinase 1), a glycolytic enzyme, functions as a protein kinase, phosphorylating BECN1/Beclin 1 to initiate autophagy. Under glutamine deprivation or hypoxia stimulation, PGK1 is acetylated at K388 by NAA10/ARD1 in an MTOR-inhibition-dependent manner, leading to the interaction between PGK1 and BECN1 and the subsequent phosphorylation of BECN1 at S30 by PGK1. This phosphorylation enhances ATG14-associated PIK3C3/VPS34-BECN1-PIK3R4/VPS15 complex activity, thereby increasing phosphatidylinositol-3-phosphate (PtdIns3P) generation in the initiation stage of autophagy. Furthermore, NAA10-dependent PGK1 acetylation and PGK1-dependent BECN1 phosphorylation are required for glutamine deprivation- and hypoxia-induced autophagy and brain tumor formation. Our work reveals the important dual roles of PGK1 as a glycolytic enzyme and a protein kinase in the mutual regulation of cell metabolism and autophagy in maintaining cell homeostasis. [ABSTRACT FROM PUBLISHER]

Metabolic enzymes have non-canonical functions and play vital roles in the regulation of various cellular activities. Phosphoenolpyruvate carboxykinase 1 (PCK1), a gluconeogenic enzyme, was recently identified as an AKT-dependent protein kinase and promoted sterol regulatory element-binding protein 1 (SREBP1)–dependent lipogenesis. However, association of this protein kinase activity of PCK1 with progression of oesophageal squamous cell carcinoma (ESCC) is unclear. We examined 200 ESCC patient samples and prognosis using immunohistochemistry, multivariate Cox regression and Kaplan–Meier Plot analyses. We show that the expression levels of AKT pS473, AKT-regulated PCK1 pS90, PCK1-mediated INSIG1 pS207/INSIG2 pS151 and nuclear SREBP1 were higher in analysed 200 human ESCC specimens than in their adjacent non-tumour tissues; the expression levels of these proteins were significantly and positively correlated with each other in tumour specimens. In addition, the expression levels of PCK1 pS90, INSIG1 pS207/INSIG2 pS151 and SREBP1 were associated with the tumour, node and metastasis stage and progression in ESCC. Importantly, levels of PCK1 pS90 or INSIG1 pS207/INSIG2 pS151 or nuclear SREBP1 were positively correlated with poor prognosis in patients with ESCC, and the combined expression values of PCK1 pS90, INSIG1 pS207/INSIG2 pS151 and nuclear SREBP1 had a better prognostic value than that of each individual protein expression value and was an independent prognostic marker for ESCC. These findings reveal the role of PCK1 protein kinase activity-dependent SREBP1 activation in ESCC progression. The regulation of SREBP1 by AKT activation-dependent PCK1 protein kinase activity may provide the potential for the diagnosis and treatment of human ESCC. • AKT pS473, PCK1 pS90, INSIG1 pS207/INSIG2 pS151 and active sterol regulatory element-binding protein 1 (SREBP1) are high in oesophageal squamous cell carcinoma (ESCC). • The levels of these markers are positively correlated with each other in ESCC. • The levels of these markers are positively associated with ESCC progression. • The combined value of phosphoenolpyruvate carboxykinase 1, INSIG1/2 and SREBP1 is a prognostic marker for ESCC. [ABSTRACT FROM AUTHOR]

Summary It is unclear how the Warburg effect that exemplifies enhanced glycolysis in the cytosol is coordinated with suppressed mitochondrial pyruvate metabolism. We demonstrate here that hypoxia, EGFR activation, and expression of K-Ras G12V and B-Raf V600E induce mitochondrial translocation of phosphoglycerate kinase 1 (PGK1); this is mediated by ERK-dependent PGK1 S203 phosphorylation and subsequent PIN1-mediated cis - trans isomerization. Mitochondrial PGK1 acts as a protein kinase to phosphorylate pyruvate dehydrogenase kinase 1 (PDHK1) at T338, which activates PDHK1 to phosphorylate and inhibit the pyruvate dehydrogenase (PDH) complex. This reduces mitochondrial pyruvate utilization, suppresses reactive oxygen species production, increases lactate production, and promotes brain tumorigenesis. Furthermore, PGK1 S203 and PDHK1 T338 phosphorylation levels correlate with PDH S293 inactivating phosphorylation levels and poor prognosis in glioblastoma patients. This work highlights that PGK1 acts as a protein kinase in coordinating glycolysis and the tricarboxylic acid (TCA) cycle, which is instrumental in cancer metabolism and tumorigenesis. [ABSTRACT FROM AUTHOR]

Summary: Tumor-specific pyruvate kinase M2 (PKM2) is essential for the Warburg effect. In addition to its well-established role in aerobic glycolysis, PKM2 directly regulates gene transcription. However, the mechanism underlying this nonmetabolic function of PKM2 remains elusive. We show here that PKM2 directly binds to histone H3 and phosphorylates histone H3 at T11 upon EGF receptor activation. This phosphorylation is required for the dissociation of HDAC3 from the CCND1 and MYC promoter regions and subsequent acetylation of histone H3 at K9. PKM2-dependent histone H3 modifications are instrumental in EGF-induced expression of cyclin D1 and c-Myc, tumor cell proliferation, cell-cycle progression, and brain tumorigenesis. In addition, levels of histone H3 T11 phosphorylation correlate with nuclear PKM2 expression levels, glioma malignancy grades, and prognosis. These findings highlight the role of PKM2 as a protein kinase in its nonmetabolic functions of histone modification, which is essential for its epigenetic regulation of gene expression and tumorigenesis. [ABSTRACT FROM AUTHOR]

Summary: Increased transcriptional activity of β-catenin resulting from Wnt/Wingless-dependent or -independent signaling has been detected in many types of human cancer, but the underlying mechanism of Wnt-independent regulation remains unclear. We demonstrate here that EGFR activation results in disruption of the complex of β-catenin and α-catenin, thereby abrogating the inhibitory effect of α-catenin on β-catenin transactivation via CK2α-dependent phosphorylation of α-catenin at S641. ERK2, which is activated by EGFR signaling, directly binds to CK2α via the ERK2 docking groove and phosphorylates CK2α primarily at T360/S362, subsequently enhancing CK2α activity toward α-catenin phosphorylation. In addition, levels of α-catenin S641 phosphorylation correlate with levels of ERK1/2 activity in human glioblastoma specimens and with grades of glioma malignancy. This EGFR-ERK-CK2-mediated phosphorylation of α-catenin promotes β-catenin transactivation and tumor cell invasion. These findings highlight the importance of the crosstalk between EGFR and Wnt pathways in tumor development. [Copyright &y& Elsevier]

Summary: Activated Ras has been found in many types of cancer. However, the mechanism underlying Ras-promoted tumor metastasis remains unclear. We demonstrate here that activated Ras induces tyrosine dephosphorylation and inhibition of FAK mediated by the Ras downstream Fgd1-Cdc42-PAK1-MEK-ERK signaling cascade. ERK phosphorylates FAK S910 and recruits PIN1 and PTP-PEST, which colocalize with FAK at the lamellipodia of migrating cells. PIN1 binding and prolyl isomerization of FAK cause PTP-PEST to interact with and dephosphorylate FAK Y397. Inhibition of FAK mediated by this signal relay promotes Ras-induced cell migration, invasion, and metastasis. These findings uncover the importance of sequential modification of FAK—by serine phosphorylation, isomerization, and tyrosine dephosphorylation—in the regulation of FAK activity and, thereby, in Ras-related tumor metastasis. [Copyright &y& Elsevier]

Lipid droplets are important for cancer cell growth and survival. However, the mechanism underlying the initiation of lipid droplet lipolysis is not well understood. We demonstrate here that glucose deprivation induces the binding of choline kinase (CHK) α2 to lipid droplets, which is sequentially mediated by AMPK-dependent CHKα2 S279 phosphorylation and KAT5-dependent CHKα2 K247 acetylation. Importantly, CHKα2 with altered catalytic domain conformation functions as a protein kinase and phosphorylates PLIN2 at Y232 and PLIN3 at Y251. The phosphorylated PLIN2/3 dissociate from lipid droplets and are degraded by Hsc70-mediated autophagy, thereby promoting lipid droplet lipolysis, fatty acid oxidation, and brain tumor growth. In addition, levels of CHKα2 S279 phosphorylation, CHKα2 K247 acetylation, and PLIN2/3 phosphorylation are positively correlated with one another in human glioblastoma specimens and are associated with poor prognosis in glioblastoma patients. These findings underscore the role of CHKα2 as a protein kinase in lipolysis and glioblastoma development. [Display omitted] • CHKα2 binds to lipid droplets in an AMPK- and KAT5-dependent manner • KAT5-dependent CHKα2 acetylation converts CHKα2 from a dimer to a monomer • CHKα2 phosphorylates PLIN2/3 and promotes their disassociation from lipid droplet • CHKα2 promotes lipid droplet lipolysis, β-oxidation, and brain tumor growth Liu et al. demonstrate that glucose deprivation induces AMPK- and KAT5-dependent binding of CHKα2 to lipid droplets, where CHKα2 functions as a protein kinase and phosphorylates PLIN2/3, resulting in phosphorylation and autophagy-dependent degradation of PLIN2/3 and promotion of lipid droplet lipolysis, fatty acid oxidation, and brain tumor growth. [ABSTRACT FROM AUTHOR]

Glutaminase regulates glutaminolysis to promote cancer cell proliferation. However, the mechanism underlying glutaminase activity regulation is largely unknown. Here, we demonstrate that kidney-type glutaminase (GLS) is highly expressed in human pancreatic ductal adenocarcinoma (PDAC) specimens with correspondingly upregulated glutamine dependence for PDAC cell proliferation. Upon oxidative stress, the succinyl-coenzyme A (CoA) synthetase ADP-forming subunit β (SUCLA2) phosphorylated by p38 mitogen-activated protein kinase (MAPK) at S79 dissociates from GLS, resulting in enhanced GLS K311 succinylation, oligomerization, and activity. Activated GLS increases glutaminolysis and the production of nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione, thereby counteracting oxidative stress and promoting tumor cell survival and tumor growth in mice. In addition, the levels of SUCLA2 pS79 and GLS K311 succinylation, which were mutually correlated, were positively associated with advanced stages of PDAC and poor prognosis for patients. Our findings reveal critical regulation of GLS by SUCLA2-coupled GLS succinylation regulation and underscore the regulatory role of metabolites in glutaminolysis and PDAC development. • GLS is upregulated in human pancreatic ductal adenocarcinoma • GLS K311 succinylation enhances the oligomerization and activity of GLS • p38-phosphorylated SUCLA2 dissociates from GLS and promotes GLS K311 succinylation • GLS succinylation promotes glutaminolysis and tumor growth Tong et al. demonstrate that oxidative stress removes GLS-associated SUCLA2 to catalyze succinyl-CoA. This dissociation enhances succinyl-CoA-dependent GLS K311 succinylation and activity, leading to increased production of NADPH and GSH against oxidative-stress-induced ROS production and apoptosis and promoting tumor cell proliferation and tumor growth in mice. [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]