Progress in the association between protein subcellular localization and tumor progression / 肿瘤

The change of subcellular localization of tumor-related proteins affects the protein structure and biological function, which is closely related to tumorigenesis, tumor progression and prognosis. Aberrant phosphorylation, acetylation and ubiquitination lead to the subcellular localization change of tumor-related proteins, subsequently disrupt the down-stream target gene expression and the related cell signal pathways, which is an important factor for tumorigenesis. The anti-cancer drugs targeting post-Translational protein modification can reverse the abnormal subcellular localization of tumor-related proteins, so as to suppress the migration of tumor cells, and induce the apoptosis of tumor cells. This paper reviews the recent studies regarding the effects of phosphorylation, acetylation and ubiquitination on subcellular localization of tumor-related proteins such as p53, p27 and forkhead box protein O1 (FOXO1), and summarizes the molecular mechanisms of subcellular localization change induced by anti-cancer drugs, furthermore discusses the great significance of protein subcellular localization in clinical tumor diagnosis and the pridiction of prognosis and the drug effect.

Dynamic Regulation of APE1/Ref-1 as a Therapeutic Target Protein / 전남의대학술지

Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multifunctional protein that plays a central role in the cellular response to DNA damage and redox regulation against oxidative stress. APE1/Ref-1 functions in the DNA base excision repair pathway, the redox regulation of several transcription factors, and the control of intracellular redox status through the inhibition of reactive oxygen species (ROS) production. APE1/Ref-1 is predominantly localized in the nucleus; however, its subcellular localization is dynamically regulated and it may be found in the mitochondria or elsewhere in the cytoplasm. Studies have identified a nuclear localization signal and a mitochondrial target sequence in APE1/Ref-1, as well as the involvement of the nuclear export system, as determinants of APE1/Ref-1 subcellular distribution. Recently, it was shown that APE1/Ref-1 is secreted in response to hyperacetylation at specific lysine residues. Additionally, post-translational modifications such as phosphorylation, S-nitrosation, and ubiquitination appear to play a role in fine-tuning the activities and subcellular localization of APE1/Ref-1. In this review, we will introduce the multifunctional role of APE1/Ref-1 and its potential usefulness as a therapeutic target in cancer and cardiovascular disease.

Rescue of Heart Failure by Mitochondrial Recovery / 대한배뇨장애요실금학회지

Heart failure (HF) is a multifactorial disease brought about by numerous, and oftentimes complex, etiological mechanisms. Although well studied, HF continues to affect millions of people worldwide and current treatments can only prevent further progression of HF. Mitochondria undoubtedly play an important role in the progression of HF, and numerous studies have highlighted mitochondrial components that contribute to HF. This review presents an overview of the role of mitochondrial biogenesis, mitochondrial oxidative stress, and mitochondrial permeability transition pore in HF, discusses ongoing studies that attempt to address the disease through mitochondrial targeting, and provides an insight on how these studies can affect future research on HF treatment.

Dynamic Regulation of APE1/Ref-1 as a Therapeutic Target Protein / 전남의대학술지

Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multifunctional protein that plays a central role in the cellular response to DNA damage and redox regulation against oxidative stress. APE1/Ref-1 functions in the DNA base excision repair pathway, the redox regulation of several transcription factors, and the control of intracellular redox status through the inhibition of reactive oxygen species (ROS) production. APE1/Ref-1 is predominantly localized in the nucleus; however, its subcellular localization is dynamically regulated and it may be found in the mitochondria or elsewhere in the cytoplasm. Studies have identified a nuclear localization signal and a mitochondrial target sequence in APE1/Ref-1, as well as the involvement of the nuclear export system, as determinants of APE1/Ref-1 subcellular distribution. Recently, it was shown that APE1/Ref-1 is secreted in response to hyperacetylation at specific lysine residues. Additionally, post-translational modifications such as phosphorylation, S-nitrosation, and ubiquitination appear to play a role in fine-tuning the activities and subcellular localization of APE1/Ref-1. In this review, we will introduce the multifunctional role of APE1/Ref-1 and its potential usefulness as a therapeutic target in cancer and cardiovascular disease.

Regulation and Role of EZH2 in Cancer / Journal of the Korean Cancer Association, 대한암학회지

Polycomb repressive complex 2 (PRC2) is the epigenetic regulator that induces histone H3 lysine 27 methylation (H3K27me3) and silences specific gene transcription. Enhancer of zeste homolog 2 (EZH2) is an enzymatic subunit of PRC2, and evidence shows that EZH2 plays an essential role in cancer initiation, development, progression, metastasis, and drug resistance. EZH2 expression is indeed regulated by various oncogenic transcription factors, tumor suppressor miRNAs, and cancer-associated non-coding RNA. EZH2 activity is also controlled by post-translational modifications, which are deregulated in cancer. The canonical role of EZH2 is gene silencing through H3K27me3, but accumulating evidence shows that EZH2 methlyates substrates other than histone and has methylase-independent functions. These non-canonical functions of EZH2 are shown to play a role in cancer progression. In this review, we summarize current information on the regulation and roles of EZH2 in cancer. We also discuss various therapeutic approaches to targeting EZH2.

Targeting the Peroxisome Proliferator-Activated Receptor-gamma to Counter the Inflammatory Milieu in Obesity

Adipose tissue, which was once viewed as a simple organ for storage of triglycerides, is now considered an important endocrine organ. Abnormal adipose tissue mass is associated with defects in endocrine and metabolic functions which are the underlying causes of the metabolic syndrome. Many adipokines, hormones secreted by adipose tissue, regulate cells from the immune system. Interestingly, most of these adipokines are proinflammatory mediators, which increase dramatically in the obese state and are believed to be involved in the pathogenesis of insulin resistance. Drugs that target peroxisome proliferator-activated receptor-gamma have been shown to possess anti-inflammatory effects in animal models of diabetes. These findings, and the link between inflammation and the metabolic syndrome, will be reviewed here.

The role of O-GlcNAc modification in glutamine-induced myocardial heat shock protein 70 expression in a rat model of endotoxic shock / 中华麻醉学杂志

Objective To investigate the role of O-linked N-acetylglutamine (O-GlcNAc) modification in glutamine-induced myocardial heat shock protein (HSP70) expression in a rat model of endotoxic shock. Methods Thirty-two 8 weeks old male SD rats weighing 250-300 g were randomly divided into 4 groups (n = 8 each):group Ⅰ control (group C); group Ⅱ LPS; group Ⅲ G+ LPS and group glutamine + LPS (group A + G + LPS). Endotoxic shock was induced by iv administration of LPS 10 mg/kg in group Ⅱ , Ⅲ and Ⅳ.Glutamine 0.75 g/kg was administered iv at 1 h before iv LPS in group Ⅲ and Ⅳ . Alloxan (an inhibitor ofO-linked N-acetylglucosamine transferase) 50 mg/kg was administered iv together with glutamine at 1 h before LPS in group Ⅳ. The animals were sacrificed at 6 h after iv LPS administration. Their hearts were removed for determination of the expression of O-GlcNAc and HSP70 in myocardium. Results Intravenous LPS significantly up-regulated the expression of O-GlcNAc and HSP70. Glutamine pretreatment further increased the expression of O-GlcNAc and HSP70. The glutamine pretreatment induced increase in O-GlcNAc and HSP70 expression was abolished by concomitant administration of alloxan. Conclusion O-GlcNAc modification may be involved in glutamine-induced myocardial HSP70 expression in endotoxic shock.

Effects of O-GIcNAc modification on glutamine-induced heat shock protein 70 expression in LPS-treated rat cardiomyocytes / 中华麻醉学杂志

Objective To investigate the effects of O-GlcNAc modification on gintamine (Glu)-induced heat shock protein 70 (HSP70) expression in LPS-treated rat cardiomyocytes.Methods Primary cultures of neonatal rat cardiomyocytes were randomly divided into 6 groups:group Ⅰ control(group C);group Ⅱ Glu;group Ⅲ LPS;group Ⅳ Glu+LPS;group Ⅴ Glu+LPS+Alloxan and group Ⅵ Gln+LPS+PUGNAc.In group C double distilled water 25 μl was added.In group Ⅱ-Ⅵ the cells were exposed to the sanle concentrations of Glu (5 mmol/L)and LPS(4 μg/ml) except Alloxan (an inhibiter of O-linked β-N-acetyl glucosamine transferase/OGT) (1 mmol/L) and PUGNAc (an inhibitor of O-linked β-N-acetyl glucosaminidase/OGA)(100μmol/L).After being incubated for 6 h,cardiomyocyte viability,O-GlcNAc modification level and HSP70 expression level were measured.Results There was no significant difference in cell viability among the six groups.The levels of O-GlcNAc modification and HSP70 expression were significantly higher in group Ⅱ-Ⅵ than in group Ⅰ,were significantly higher in group Ⅳ and group Ⅵ than in group Ⅲ,were significantly lower in group Ⅴ and higher in group Ⅵ than in group Ⅳ.Conclusion O-GlcNAc modification may be involved in Glu-induced HSPT0 expression in LPS-treated cardiomyocytes.

Cytokeratin 8 and cancer / 国际肿瘤学杂志

Cytokeratin 8 ( CK8 ) belongs to the keratin family of intermediate filament cytoskeletal proteins. A lot of researches have demonstrated that abnormal expression or post-translational modifications of CK8 may affect its activity and consequently affect the development and progression of tumors. Therefore, investigating the role of CK8 in tumorigenesis may contribute to the prevention and treatment of tumors.

Stathmin: a potential tumor biomarker / 肿瘤

Stathmin, a ubiquitously expressed cytosolic protein(Mr=19×10~3), is also called oncogene protein 18 (Op18). Stathmin is involved in the assembly of microtubule (MT) and spindle by binding the tubulin protein. It plays a key role in cell proliferation, differentiation, regeneration, and migration and has regulatory effects on the signal transduction. Recently, it is reported that stathmin is overexpressed in a variety of human malignancies. It induces tumor cell migration and invasion by regulating MT depolymeri-zation. Its post-translational modification influences the interaction with p53 protein and is involved in the initiation and progression of malignant tumor. Stathmin alone or in combination with chemotherapeutics has been used for tumor therapy. The internal association of stathmin with cancer etiology is still unknown. So, further studies are needed to determine the role of stathmin as potential tumor biomarker and a drug target in tumor therapy.

Overexpression of nicotinamide N-methyltransferase in gastric cancer tissues and its potential post-translational modification

Gastric cancer is one of the most common cancers worldwide. The purpose of this study was to find out potential markers for gastric cancer. Tumor and normal tissues from 152 gastric cancer cases were analyzed by two-dimensional gel electrophoresis (2-DE). The images of silver stained gels were analyzed and statistical analysis of spot intensities revealed that spot 4262 showed higher expression (5.7-fold increase) in cancer tissues than in normal tissues (P< 0.001). It was identified by peptide mass fingerprinting as nicotinamide N-methyltransferase (NNMT). A monoclonal antibody with a detection limit down to 10 ng was produced against NNMT in mouse. Using the prepared monoclonal antibody, western blot analysis of NNMT was performed for gastric tissues from 15 gastric cancer patients and two gastric ulcer patients. The results corroborated those of 2-DE experiments. A single spot was detected in gastric ulcer tissues while four to five spots were detected in gastric cancer tissues. In cancer tissues, two additional spots of acidic and basic form were mainly detected on 2-DE gels. This suggests that NNMT receives a post-translational modification in cancer- specific manner.

Regulation of Wnt signaling by protein-protein interaction and post-translational modifications

The Wnt signaling pathway is conserved in various species from worms to mammals, and plays important roles in cellular proliferation, differentiation, and migration. Wnt stabilizes cytoplasmic beta-catenin and then the accumulated beta-catenin is translocated into the nucleus, where it activates the transcriptional factor T-cell factor (Tcf)/lymphoid enhancer factor (Lef), and thereby stimulates the expression of genes including c-myc, c-jun, fra-1, and cyclin D1. Tight regulation of this response involves post-translational modifications of the components of the Wnt signaling pathway. Phosphorylation, ubiquitination, and sumoylation have been shown to affect the half-life of beta-catenin and the transcriptional activity of Tcf/Lef. The precise spatio-temporal patterns of these multiple modifications determine the driving force of various cellular responses.

Conjugation and deconjugation of ubiquitin regulating the destiny of proteins

The homeostasis for a number of cellular proteins is regulated by not only phosphorylation and dephosphorylation, but also ubiquitination and deubiquitination. A number of proteins involved in the degradation of polypeptides have been isolated in various eukaryotic organisms from Saccharomyces cerevisiae to human. Recently, several deubiquitinating enzymes, classified into either the Ub C-terminal hydrolase (UCH) or the Ub-specific processing protease (UBP), have been reported. It has been shown that they contain conserved domains including Cys, His, and Asp residues throughout the enzyme. These proteins have been demonstrated that Cys and His domains are critical for deubiquitinating enzymatic activity. Recently, we have shown that the Asp domain localized between Cys and His domains is also essential for cleaving the ubiquitin from protein substrates. Mouse deubiquitinating enzymes including DUB-1, DUB-2, and DUB-2A have been isolated and they showed the expression specificity. Of these, DUB- 1 and DUB-2 are expressed in lymphocytes depending on the presence of cytokines (interleukin-3 in B-lymphocytes and interleukin-2 in T- lymphocytes, respectively), indicating that they are involved in cytokine signaling pathways. Isolation of all putative DUBs will help to identify their substrates and to regulate the homeostasis of cellular proteins, especially in proliferative cells.

Protein kinase CK2 phosphorylates and interacts with deoxyhypusine synthase in HeLa cells

Deoxyhypusine is a modified lysine and formed posttranslationally to be the eukaryotic initiation factor eIF5A by deoxyhypusine synthase, employing spermidine as butylamine donor. Subsequent hydroxylation of this deoxyhypusine-containing intermediate completes the maturation of eIF5A. The previous report showed that deoxyhypusine synthase was phosphorylated by PKC in vivo and the association of deoxyhypusine synthase with PKC in CHO cells was PMA-, and Ca(2+)/phospholipid-dependent. We have extended study on the phosphorylation of deoxyhypusine synthase by protein kinase CK2 in order to define its role on the regulation of eIF5A in the cell. The results showed that deoxyhypusine synthase was phosphorylated by CK2 in vivo as well as in vitro. Endogenous CK2 in HeLa cells and the cell lysate was able to phosphorylate deoxyhypusine synthase and this modification is enhanced or decreased by the addition of CK2 effectors such as polylysine, heparin, and poly(Glu, Tyr) 4:1. Phosphoamino acid analysis of this enzyme revealed that deoxyhypusine synthase is mainly phosphorylated on threonine residue and less intensely on serine. These results suggest that phosphorylation of deoxyhypusine synthase is CK2-dependent cellular event as well as PKC-mediated effect. However, there were no observable changes in enzyme activity between the phosphorylated and unphosphorylated forms of deoxyhypusine synthase. Taken together, besides its established function in hypusine modification involving eIF5A substrate, deoxyhypusine synthase and its phosphorylation modification may have other independent cellular functions because of versatile roles of deoxyhypusine synthase.

Murine pro-tumor necrosis factor expressed in Saccharomyces cerevisiae HF7c localizes to membrane/particulate

Tumor necrosis factor (TNF) is a cytokine that is produced by immune cells in response to bacterial and viral stimuli and plays important roles in various inflammatory diseases. TNF is produced as a membrane-bound precursor, which is then cleaved to release soluble mature protein. We expressed murine pro-TNF in Saccharomyces cerevisiae and examined processing and cellular localization of the recombinant protein. Yeast cells were transformed with an expression construct carrying the pro-TNF gene under the control of alcohol dehydrogenase promoter. Immunoblotting analysis of cell homogenate revealed expression of 26 kD pro-TNF in transformed cells. Upon centrifugation, pro-TNF transformed cells fractionated into the membrane/particulate. In a clone that expresses a high level of pro-TNF, mature 17 kD TNF was detected in the culture medium, although the amount was far smaller than that of cell-associated pro-TNF. Flow cytometric analysis of yeast spheroplasts demonstrated the presence of TNF on the cell surface. Our results show that pro-TNF expressed in yeast mainly resides in the cellular membrane with an orientation similar to that of pro-TNF produced in mammalian cells. Our data suggest that the transformed yeast cells can be used for the genetic analysis of pro-TNF processing machinery in immune cells.

Structure of heavy and light chains of blood coagulation factor VIII (FVIII) involved in the activation of FVIII

Structure of human blood coagulation factor VIII (FVIII) in relation to its activation process was investigated. FVIII was purified from a commercial FVIII concentrate by immunoaffinity chromatography and its dissociated subunits, heavy and light chains were isolated. The light chain (FVIII-L) was treated with thrombin or factor Xa (FXa) in order to cleave the peptide at Aug(1689) or Arg(1721), respectively, Reassociation of FVIII-H with either of FVIII-L derivatives, FVIII-L-72 (72 kDa) and FVIII-L-65 (65 kDa) brought about the formation of heterodimers which have similar cofactor activity. The association constant of FVIII-H with FVIII-L-72 was about two-fold faster than that with FVIII-L-65, Cleavage of major FVIII-H with thrombin generated two peptides with molecular weights of 50 kDa (A(1)) and 40 kDa (A(2)) Formation of heterotrimer by reassociation of A(1), A(2) and FVIII-L-72-generated FVIII cofactor activity, while the dimers formed from A(1) or A(2) with FVIII-L-72 had no activity, suggesting that both A(1) and A(2) are required for FVIII activity, Heterotrimers formed from A(1) and A(2) with either of FVIII-L-72 or FVIII-L-65 in the presence of CaCl2 (10 mM) revealed cofactor activity, and they were dissociated into subunits with the loss of activity when EDTA (10 mM) was added, indicating that the formation of heterotrimer, the functional unit of FVIII, from A1, A(2) and FVIII-L is calcium dependent and that the cleavage of FVIII-L by FXa does not inactivate FVIII.

Effects of alcoholic extracts of seven traditional Chinese medicines and psoralen on tyrosinase in human YUGEN8 melanoma cell / 中华皮肤科杂志

Objective To explore the effects of alcoholic extracts of traditional Chinese medicines on the post-translational processing and trafficking of tyrosinase.Methods Human YUGEN8 amelanotic melanoma cells were grown in vitro;the cells were incubated with one of the seven traditional Chinese medicines,including Rhizoma Chuanxiong and psoralen.Protein analysis with Western blot,enzymolysis with endoglycosidase H (Endo H),and subcellular localization with laser confocal microscopy were per- formed.The expression,maturity and export from endoplasmic reticulum (ER) of tyrosinase in the treated cells were compared with those in the untreated controls.Results Compared with controls,an approximate- ly 80-kDa,Endo H-resistant tyrosinase doublet,which represented mature glycoform of tyrosinase,was in- creased in melanocytes treated with Semen Cuscutae,and in those treated with Semen Persicae.Within those cells,tyrosinase was distributed outside ER resident protein calnexin.Conclusion Both Semen Cus- cutae and Semen Persicae could induce tyrosinase maturation,stability and export from ER to distal site.