Integration of Sugar Metabolism and Proteoglycan Synthesis by UDP-glucose Dehydrogenase

Regulation of proteoglycan and glycosaminoglycan synthesis is critical throughout development, and to maintain normal adult functions in wound healing and the immune system, among others. It has become increasingly clear that these processes are also under tight metabolic control and that availability of carbohydrate and amino acid metabolite precursors has a role in the control of proteoglycan and glycosaminoglycan turnover. The enzyme uridine diphosphate (UDP)-glucose dehydrogenase (UGDH) produces UDP-glucuronate, an essential precursor for new glycosaminoglycan synthesis that is tightly controlled at multiple levels. Here, we review the cellular mechanisms that regulate UGDH expression, discuss the structural features of the enzyme, and use the structures to provide a context for recent studies that link post-translational modifications and allosteric modulators of UGDH to its function in downstream pathways:     

Trichostatin A Improved Epigenetic Modifications of Transfected Cells but did not Improve Subsequent Cloned Embryo Development

Reprogramming impairment of DNA methylation may be partly responsible for the low efficiency in somatic cell nuclear transfer. In this study, bovine fibroblast cells were transfected with enhancer green fluorescence protein (eGFP), and then treated with a histone-deacetylase inhibitor, trichostatin A (TSA). The results showed that the effect of TSA on transfected cells was dose dependent. When the TSA concentration was over 5 ng/ml, cell proliferation was significantly inhibited. The majority of the cells died when TSA reached 100 ng/ml (P < 0.01). The number of cells in the S phase was significantly decreased in the 5- to 50-ng/ml TSA-treated groups, while the majority of the cells were at the G0/G1 phases. The number of eGFP-expressed cells were approximately twofold higher in 25-ng/ml (30.5%) and 50-ng/ml (29.5%) TSA groups than the control (15.0%). Reduced DNA methylation and improved histone acetylation were observed when the cells were treated with 10 to 50 ng/ml of TSA. Transfer of the TSA-treated cells to enucleated recipient oocytes resulted in similar cleavage rates among the experimental groups and the control. Cells treated with 50 ng/ml of TSA resulted in significantly lower blastocyst development (9.9%) than the other experimental and the control groups (around 20%). Analysis of the putative blastocysts showed that 86.7% of the embryos derived from TSA-treated cells were eGFP positive, which was higher than that from untreated cells (68.8%). In conclusion, treatment of transfected cells with TSA decreased the genome DNA methylation level, increased histone acetylation, and eGFP gene expression was activated. Donor cells with reduced DNA methylation did not improve subsequent cloned embryo development; however, transgene expression was improved in cloned embryos.     

Molecular Mechanisms of DNA Damage and Repair: Progress in Plants

Dedicated to Prof. Jan H. J. Hoeijmakers.

Referee: Dr. Nawin C. Mishra, Professor of Genetics, University of South Carolina, Department of Biological Sciences, Columbia, SC 29208

Despite stable genomes of all living organisms, they are subject to damage by chemical and physical agents in the environment (e.g., UV and ionizing radiations, chemical mutagens, fungal and bacterial toxins, etc.) and by free radicals or alkylating agents endogenously generated in metabolism. DNA is also damaged because of errors during its replication. The DNA lesions produced by these damaging agents could be altered base, missing base, mismatch base, deletion or insertion, linked pyrimidines, strand breaks, intra- and inter-strand cross-links.     

Increasing discordant antioxidant protein levels and enzymatic activities contribute to increasing redox imbalance observed during human prostate cancer progression

A metabolomics study demonstrated a decrease in glutathione and an increase in cysteine (Cys) levels in human prostate cancer (PCa) tissues as Gleason scores increased, indicating redox imbalance with PCa progression. These results were extended in the present study by analyzing the redox state of the protein thioredoxin 1 (Trx1) and sulfinylation (SO₃) of peroxiredoxins (Prxs) (PrxSO₃) in PCa tissues and cell lines. Lysates of paired human PCa tissues with varying degrees of aggressiveness and adjacent benign (BN) tissues were used for analysis. Redox Western blot analysis of Trx1 demonstrated low levels of reduced and high levels of oxidized Trx1 (functional and nonfunctional, respectively) in high-grade PCa (Gleason scores 4+4 to 4+5) in comparison to intermediate-grade PCa (Gleason scores 3+3 to 3+4) or BN tissues. PrxSO₃ were increased in high-grade PCa. Oxidized Trx1 and PrxSO₃ are indicators of oxidative stress. To study whether redox imbalance may potentially affect enzyme activities of antioxidant proteins (APs), we determined the levels of selected APs in PCa tissues by Western blot analysis and found that mitochondrial manganese superoxide dismutase (MnSOD), Prx3, and Trx1 were increased in high-grade PCa tissues compared with BN tissues. Enzyme activities of MnSOD in high-grade PCa tissues were significantly increased but at a lower magnitude compared with the levels of MnSOD protein (0.5-fold vs 2-fold increase). Trx1 activity was not changed in high-grade PCa tissues despite a large increase in Trx1 protein expression. Further studies demonstrated a significant increase in posttranslational modifications of tyrosine and lysine residues in MnSOD protein and oxidation of Cys at the active site (Cys32 and Cys35) and the regulatory site (Cys62 and Cys69) of Trx1 in high-grade PCa compared to BN tissues. These discordant changes between protein levels and enzyme activities are consistent with protein inactivation by redox imbalance and/or posttranslational modifications. In contrast, the protein level and activity of extracellular superoxide dismutase were significantly decreased in high-grade PCa compared with adjacent BN tissues. Results from cell lines mirror those from PCa tissues. Knowledge of redox-state profiles in specific cancers may help to predict the behavior and response of each cancer to chemotherapeutic drugs and radiation.