phosphothreonine and Lung-Neoplasms

Eukaryotic elongation factor-2 kinase (eEF2K) is a Ca 2+ /calmodulin (CaM)-dependent protein kinase that inhibits protein synthesis. However, the role of eEF2K in cancer development was reported paradoxically and remains to be elucidated.. Herein, A549 cells with eEF2K depletion or overexpression by stably transfected lentivirus plasmids were used in vitro and in vivo study. MTT and colony assays were used to detect cell proliferation and growth. Extracellular glucose and lactate concentration were measured using test kit. Immunoblot and co-immunoprecipitation assays were used to examine the molecular biology changes and molecular interaction in these cells. LC-MS/MS analysis and [γ- 32 P] ATP kinase assay were used to identify combining protein and phosphorylation site. Nude mice was utilized to study the correlation of eEF2K and tumor growth in vivo.. We demonstrated that eEF2K inhibited lung cancer cells proliferation and affected the inhibitory effects of EGFR inhibitor gefitinib. Mechanistically, we showed that eEF2K formed a complex with PKM2 and STAT3, thereby phosphorylated PKM2 at T129, leading to reduced dimerization of PKM2. Subsequently, PKM2 impeded STAT3 phosphorylation and STAT3-dependent c-Myc expression. eEF2K depletion promoted the nuclear translocation of PKM2 and increased aerobic glycolysis reflected by increased lactate secretion and glucose.. Our findings define a novel mechanism underlying the regulation of cancer cell proliferation by eEF2K independent of its role in protein synthesis, disclosing the diverse roles of eEF2K in cell biology, which lays foundation for the development of new anticancer therapeutic strategies.

Topics: Animals; Carrier Proteins; Cell Line, Tumor; Cell Proliferation; Elongation Factor 2 Kinase; Gefitinib; HEK293 Cells; Humans; Lung Neoplasms; Membrane Proteins; Mice, Nude; Phosphorylation; Phosphothreonine; Protein Multimerization; Proto-Oncogene Proteins c-myc; STAT3 Transcription Factor; Thyroid Hormone-Binding Proteins; Thyroid Hormones; Tumor Burden

Tumor initiating cells (TIC) of lung cancer are mainly induced by stress-related plasticity. Calcium/Calmodulin dependent protein kinase II alpha (CAMK2A) is a key calcium signaling molecule activated by exogenous and endogenous stimuli with effects on multiple cell functions but little is known about its role on TIC. In human lung adenocarcinomas (AD), CAMK2A was aberrantly activated in a proportion of cases and was an independent risk factor predicting shorter survivals. Functionally, CAMK2A enhanced TIC phenotypes in vitro and in vivo. CAMK2A regulated SOX2 expression by reducing H3K27me3 and EZH2 occupancy at SOX2 regulatory regions, leading to its epigenetic de-repression with functional consequences. Further, CAMK2A caused kinase-dependent phosphorylation of EZH2 at T487 with suppression of EZH2 activity. Together, the data demonstrated the CAMK2A-EZH2-SOX2 axis on TIC regulation. This study provided phenotypic and mechanistic evidence for the TIC supportive role of CAMK2A, implicating a novel predictive and therapeutic target for lung cancer.

Topics: Adenocarcinoma of Lung; Animals; Apoptosis; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Carcinogenesis; Cell Line, Tumor; Cell Self Renewal; Enhancer of Zeste Homolog 2 Protein; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; Mice, SCID; Molecular Targeted Therapy; Neoplastic Stem Cells; Phosphorylation; Phosphothreonine; Regulatory Sequences, Nucleic Acid; SOXB1 Transcription Factors; Survival Analysis; Up-Regulation

Hypoxic non-small cell lung cancer (NSCLC) is dependent on Notch-1 signaling for survival. Targeting Notch-1 by means of γ-secretase inhibitors (GSI) proved effective in killing hypoxic NSCLC. Post-mortem analysis of GSI-treated, NSCLC-burdened mice suggested enhanced phosphorylation of 4E-BP1 at threonines 37/46 in hypoxic tumor tissues. In vitro dissection of this phenomenon revealed that Amyloid Precursor Protein (APP) inhibition was responsible for a non-canonical 4E-BP1 phosphorylation pattern rearrangement-a process, in part, mediated by APP regulation of the pseudophosphatase Styx. Upon APP depletion we observed modifications of eIF-4F composition indicating increased recruitment of eIF-4A to the mRNA cap. This phenomenon was supported by the observation that cells with depleted APP were partially resistant to silvestrol, an antibiotic that interferes with eIF-4A assembly into eIF-4F complexes. APP downregulation in dividing human cells increased the rate of global protein synthesis, both cap- and IRES-dependent. Such an increase seemed independent of mTOR inhibition. After administration of Torin-1, APP downregulation and Mechanistic Target of Rapamycin Complex 1 (mTORC-1) inhibition affected 4E-BP1 phosphorylation and global protein synthesis in opposite fashions. Additional investigations indicated that APP operates independently of mTORC-1. Key phenomena described in this study were reversed by overexpression of the APP C-terminal domain. The presented data suggest that APP may be a novel regulator of protein synthesis in dividing human cells, both cancerous and primary. Furthermore, APP appears to affect translation initiation using mechanisms seemingly dissimilar to mTORC-1 regulation of cap-dependent protein synthesis.

Topics: Adaptor Proteins, Signal Transducing; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Carcinoma, Non-Small-Cell Lung; Cell Cycle Proteins; Cell Division; Cell Hypoxia; Cell Line, Tumor; Down-Regulation; Eukaryotic Initiation Factor-4A; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation, Neoplastic; Humans; Intracellular Signaling Peptides and Proteins; Lung Neoplasms; Mechanistic Target of Rapamycin Complex 1; Mice; Models, Biological; Multiprotein Complexes; Nuclear Proteins; Phosphoproteins; Phosphorylation; Phosphothreonine; Protein Biosynthesis; RNA Caps; RNA, Messenger; Substrate Specificity; TOR Serine-Threonine Kinases

LCRMP-1, a novel isoform of CRMP-1, can promote cancer cell migration, invasion and associate with poor clinical outcome in patients with non-small-cell lung cancer (NSCLC). However, the underlying regulatory mechanisms of LCRMP-1 in cancer cell invasiveness still remain obscure. Here, we report that GSK3β can phosphorylate LCRMP-1 at Thr-628 in consensus sequences and this phosphorylation is crucial for function of LCRMP-1 to promote filopodia formation, migration and invasion in cancer cells. Impediment of Thr-628 phosphorylation attenuates the stimulatory effects of LCRMP-1 on filopodia forming, migration and invasion abilities in cancer cells; simultaneously, kinase-dead GSK3β diminishes regulation of LCRMP-1 on cancer cell invasion. Furthermore, we also found that patients with low-level Ser-9-phosphorylated GSK3β expression and high-level LCRMP-1 expression have worse overall survival than those with high-level inactive GSK3β expressions and low-level LCRMP-1 expressions (P<0.0001). Collectively, these results demonstrate that GSK3β-dependent phosphorylation of LCRMP-1 provides an important mechanism for regulation of LCRMP-1 on cancer cell invasiveness and clinical outcome.

Topics: Amino Acid Sequence; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Cell Movement; Enzyme Activation; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Humans; Kaplan-Meier Estimate; Lung Neoplasms; Male; Middle Aged; Molecular Sequence Data; Neoplasm Invasiveness; Nerve Tissue Proteins; Phosphorylation; Phosphothreonine; Proportional Hazards Models; Protein Isoforms; Pseudopodia; Substrate Specificity

Lung cancer has a strong etiologic association with cigarette smoking. Nicotine, a major component in tobacco smoke, functions as a survival agonist that inhibits apoptosis following various stresses. However, the mechanism of action remains elusive. Mcl-1, a major antiapoptotic protein of the Bcl2 family, is extensively expressed in both small cell and non-small cell lung cancer cells, suggesting that Mcl-1 may be a therapeutic target of patients with lung cancer. Here, we found that nicotine induces Mcl-1 phosphorylation through activation of extracellular signal-regulated kinase 1/2 in association with increased chemoresistance of human lung cancer cells. Since nicotine stimulates Mcl-1 phosphorylation and survival in cells expressing wild-type but has no such effects in cells expressing T163A Mcl-1 mutant, this indicates that nicotine induces Mcl-1 phosphorylation exclusively at the T163 site and that phosphorylation of Mcl-1 at T163 is required for nicotine-induced survival. Mechanistically, nicotine-induced Mcl-1 phosphorylation significantly enhances the half-life of Mcl-1, which renders Mcl-1 a long-term survival activity. Specific depletion of Mcl-1 by RNA interference blocks nicotine-stimulated survival and enhances apoptotic cell death. Thus, nicotine-enhanced survival of lung cancer cells may occur through activation of Mcl-1 by phosphorylation at T163 site, which may contribute to development of human lung cancer and/or chemoresistance.

Topics: Apoptosis; Cell Line, Tumor; Cell Survival; Drug Resistance, Neoplasm; Enzyme Activation; Flavonoids; Half-Life; Humans; Lung Neoplasms; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Myeloid Cell Leukemia Sequence 1 Protein; Nicotine; Phosphorylation; Phosphothreonine; Propranolol; Proto-Oncogene Proteins c-bcl-2; Receptors, Adrenergic, beta

Interferon alpha (IFNalpha) induces both apoptosis and a counteracting epidermal growth factor Erk-dependent survival response in cancer cells. In this report, IFNalpha increased eukaryotic elongation factor 1A (eEF-1A) protein expression by inhibition of eEF-1A degradation via a proteasome-dependent pathway. The reduction of the expression level of eEF-1A by RNA interference enhanced the apoptosis induced by IFNalpha on the same cells. Moreover, IFNalpha induced the phosphorylation of both serine and threonine in eEF-1A. These effects were paralleled by an increased co-immunoprecipitation and colocalization of eEF-1A with C-Raf. The suppression of C-Raf kinase activity with the inhibitor BAY 43-9006 completely antagonized the increase of both eEF-1A phosphorylation and expression and of C-Raf/eEF-1A colocalization induced by IFNalpha and enhanced apoptosis and eEF-1A ubiquitination. Cell transfection with the mutated K48R ubiquitin increased EF-1A expression and desensitized tumor cells to the modulating effects of IFNalpha. The dynamic simulation of 3Dstructure of eEF-1A identified putative serine and threonine phosphorylation sites. In conclusion, the interaction between eEF-1A and C-Raf increases eEF-1A stability and induces a survival activity.

Topics: Apoptosis; Cell Line, Tumor; Humans; Immunoprecipitation; Interferon-alpha; Lung Neoplasms; Oncogene Proteins; Peptide Elongation Factor 1; Phosphorylation; Phosphoserine; Phosphothreonine; Proteasome Endopeptidase Complex; Protein Binding; Protein Processing, Post-Translational; Protein Transport; Proto-Oncogene Proteins c-raf; RNA, Small Interfering; Ubiquitin

Several non-small cell lung carcinomas (squamous cell carcinomas and adenocarcinomas) were analyzed for protein kinase activity. Soluble protein extracts derived from these tumors and from the lung parenchyma adjacent to the tumors were resolved by Mono Q anion exchange chromatography, and the fractions were assayed for phosphotransferase activity towards in vitro substrates. Myelin basic protein, casein, and a ribosomal S6-1 COOH-terminus peptide were efficient substrates for protein kinases that exhibited elevated phosphotransferase activity in the tumor extracts when compared to extracts derived from the adjacent nonneoplastic lung or from the lung parenchyma from patients with nonneoplastic lung disorders. Casein phosphotransferase activity was resolved into two peaks that eluted at 0.44 M NaCl and 0.56 M NaCl. The second peak was identified as casein kinase 2, based upon immunoreactivity to casein kinase 2-specific antipeptide antibodies and its sensitivity to inhibition by heparin sulfate. Myelin basic protein phosphotransferase activity eluted at 0.44 M NaCl, but Western blot analysis revealed that this could not be ascribed to mitogen-activated protein (MAP) kinases. This tumor associated protein kinase, designated p40TAK, exhibited a molecular mass of approximately 40 kDa upon gel filtration. In addition to myelin basic protein, it phosphorylated S6 peptide analogues and histone H1 on seryl residues. Like casein kinase 2, p40TAK exhibited elevated basal phosphotransferase activity in squamous cell carcinomas and adenocarcinomas of the lung when compared to the nonneoplastic lung parenchyma adjacent to the tumor.

Topics: Adenocarcinoma; Amino Acid Sequence; Antibodies; Blotting, Western; Carcinoma, Non-Small-Cell Lung; Carcinoma, Squamous Cell; Casein Kinases; Caseins; Chromatography, Ion Exchange; Electrophoresis, Polyacrylamide Gel; Enzyme Activation; Humans; Kinetics; Lung; Lung Neoplasms; Molecular Sequence Data; Myelin Basic Protein; Peptides; Phosphoserine; Phosphothreonine; Phosphotyrosine; Protein Kinases; Protein Serine-Threonine Kinases; Ribosomal Protein S6; Ribosomal Proteins; Substrate Specificity; Tyrosine

Slices of human lung cancer tissue were incubated with [32P]-orthophosphoric acid, and the radiolabeled beta-glucuronidase was isolated by a procedure including immunoaffinity chromatography on anti-human liver beta-glucuronidase IgG Sepharose. Following removal of endo-beta-N-acetyl-glucosaminidase H-releasable carbohydrate portions of the enzyme, the protein moiety was acid-hydrolyzed. Two-dimensional separation of the hydrolysate identified phosphoserine and phosphothreonine. This is the first demonstration of protein phosphorylation in lysosomal beta-glucuronidase.

Topics: Adenocarcinoma; Chemical Phenomena; Chemistry; Electrophoresis, Polyacrylamide Gel; Glucuronidase; Humans; Hydrolysis; Immunodiffusion; Liver; Lung; Lung Neoplasms; Phosphorylation; Phosphoserine; Phosphothreonine; Serine; Threonine