Band 401, Heft 11

The mitochondrial ATP synthase is a multi-subunit enzyme complex located in the inner mitochondrial membrane which is essential for oxidative phosphorylation under physiological conditions. In this review, we analyse the enzyme functions involved in cancer progression by dissecting specific conditions in which ATP synthase contributes to cancer development or metastasis. Moreover, we propose the role of ATP synthase in the formation of the permeability transition pore (PTP) as an additional mechanism which controls tumour cell death. We further describe transcriptional and translational modifications of the enzyme subunits and of the inhibitor protein IF1 that may promote adaptations leading to cancer metabolism. Finally, we outline ATP synthase gene mutations and epigenetic modifications associated with cancer development or drug resistance, with the aim of highlighting this enzyme complex as a potential novel target for future anti-cancer therapy.

Thioredoxin interacting protein (TXNIP) is an important physiological inhibitor of the thioredoxin (TXN) redox system in cells. Regulation of TXNIP expression and/or activity not only plays an important role in redox regulation but also exerts redox-independent physiological effects that exhibit direct pathophysiological consequences including elevated inflammatory response, aberrant glucose metabolism, cellular senescence and apoptosis, cellular immunity, and tumorigenesis. This review provides a brief overview of the current knowledge concerning the redox-dependent and independent roles of TXNIP and its relevance to various disease states. The implications for the therapeutic targeting of TXNIP will also be discussed.

Chaperones of the 70 kDa heat shock protein (Hsp70) superfamily are key components of the cellular proteostasis system. Together with its co-chaperones, Hsp70 forms proteostasis subsystems that antagonize protein damage during physiological and stress conditions. This function stems from highly regulated binding and release cycles of protein substrates, which results in a flow of unfolded, partially folded and misfolded species through the Hsp70 subsystem. Specific factors control how Hsp70 makes decisions regarding folding and degradation fates of the substrate proteins. In this review, we summarize how the flow of Hsp70 substrates is controlled in the cell with special emphasis on recent advances regarding substrate release mechanisms.

Cytochrome P450s are an important group of enzymes catalyzing hydroxylation, and epoxidations reactions. In this work we describe the characterization of the CinA–CinC fusion enzyme system of a previously reported P450 using genetically fused heme (CinA) and FMN (CinC) enzyme domains from Citrobacter braaki . We observed that mixing individually inactivated heme (-) with FMN (-) domain in the CinA-10aa linker - CinC fusion constructs results in recovered activity and the formation of (2S)-2β-hydroxy,1,8-cineole (174 µM), a similar amount when compared to the fully functional fusion protein (176 µM). We also studied the effect of the fusion linker length in the activity complementation assay. Our results suggests an intermolecular interaction between heme and FMN parts from different CinA–CinC fusion protein similar to proposed mechanisms for P450 BM3 on the other hand, linker length plays a crucial influence on the activity of the fusion constructs. However, complementation assays show that inactive constructs with shorter linker lengths have functional subunits, and that the lack of activity might be due to incorrect interaction between fused enzymes.

Myocardial zinc dyshomeostasis is associated with caspase-3 activation, ErbB2 degradation and apoptosis during hypoxia/reoxygenation. Zinc pyrithione replenishes intracellular zinc, suppresses caspase-3, augments ErbB2 levels and improves cell survival. We hypothesize that zinc is capable of modulating redox and endoplasmic reticulum (ER) stress in the setting of cardiomyocyte hypoxia-reoxygenation. Hypoxia/reoxygenation lowered intracellular zinc, increased ER as well as oxidative stress in H9c2 cells, both of which were effectively attenuated by zinc supplementation. Silencing of gp91phox attenuated oxidative and ER stress, decreased caspase-3 activation and improved cell survival. Mimicking the oxidative insult using 50 μM H 2 O 2 increased the caspase-3 activity that correlated with decreased ErbB2 levels, concomitant with augmented ER stress. N -acetyl cysteine (NAC) administration completely suppressed ER stress as well as caspase-3 activity. Zinc depletion using TPEN also resulted in lowered ErbB2 and increased apoptosis, along with NOX2 mRNA upregulation, increased oxidative and ER stress. Repletion with zinc suppressed NOX2 mRNA, lowered oxidative as well as ER stress and decreased cell death. These results suggest that zinc dyshomeostasis, along with oxidative stress contribute to the unfolded protein response during myocardial H/R and that zinc replenishment corrects zinc homeostasis, alleviates associated stress and improves cardiomyocyte survival.

Histone deacetylases (HDACs) can regulate the progression of various cancers, while their roles in oral cancer cells are not well known. Our present study found that the HDAC1 was over expressed in oral squamous cell carcinoma (OSCC) cells and tissues. Targeted inhibition of HDAC1 via its specific inhibitor PCI24781 or siRNA can inhibit the proliferation of OSCC cells and increase their sensitivity to the chemo-sensitivity such as doxorubicin treatment. HDAC1 can regulate the expression of proliferating cell nuclear antigen (PCNA) via decreasing its mRNA stability. While over expression of PCNA can attenuate HDAC1 inhibition induced suppression of cell proliferation. We checked the expression of various miRNAs which can target the 3′UTR of PCNA. Results showed that HDAC1 can negative regulate the expression of miR-154-5p, inhibitor of miR-154-5p can attenuate PCI24781 treatment decreased PCNA expression and cell proliferation. Collectively, our present study suggested that HDAC1 can promote the growth and progression of OSCC via regulation of miR-154-5p/PCNA signals.

We aimed to investigate the impact of oxytocin on serum thiol/disulphide and malonylyldialdehyde (MDA)/glutathione balance under acute stress (AS) and chronic stress (CS) exposure in rats. Animals were allocated into control (C), AS and CS groups, then the groups subdivided as intranasal oxytocin or saline applied groups, randomly. Animals in the AS or CS groups were exposed to combined cold-immobilisation stress. Salivary corticosterone levels and elevated plus maze (EPM) scores were used to assess stress response. MDA, glutathione, thiol-disulphide levels were measured in the serum samples. Oxytocin treatment attenuated stress response regardless of the stress duration verified by lower corticosterone level and favorable profile in EPM parameters measured. Furthermore, oxytocin modulated oxidant profile suggesting lowered oxidant stress with decreased serum MDA/glutathione and disulfide/native thiol ratios. Oxytocin improves the response of organism to stress via both its anxiolytic and antioxidant effects. That’s why it can be considered as a protective measure to employ methods to increase endogenous oxytocin and/or to apply exogenous oxytocin to prevent stress-induced increase in oxidant stress, which plays a pivotal role in the pathogenesis of various stress-related diseases.

The incretin hormone glucose-dependent insulinotropic polypeptide (GIP), released postprandially from K-cells, has established actions on adipocytes and lipid metabolism. In addition, xenin, a related peptide hormone also secreted from K-cells after a meal, has postulated effects on energy regulation and lipid turnover. The current study has probed direct individual and combined effects of GIP and xenin on adipocyte function in 3T3-L1 adipocytes, using enzyme-resistant peptide analogues, ( d -Ala 2 )GIP and xenin-25-Gln, and knockdown (KD) of receptors for both peptides. ( d -Ala 2 )GIP stimulated adipocyte differentiation and lipid accumulation in 3T3-L1 adipocytes over 96 h, with xenin-25-Gln evoking similar effects. Combined treatment significantly countered these individual adipogenic effects. Individual receptor KD impaired lipid accumulation and adipocyte differentiation, with combined receptor KD preventing differentiation. ( d -Ala 2 )GIP and xenin-25-Gln increased glycerol release from 3T3-L1 adipocytes, but this lipolytic effect was significantly less apparent with combined treatment. Key adipogenic and lipolytic genes were upregulated by ( d -Ala 2 )GIP or xenin-25-Gln, but not by dual peptide culture. Similarly, both ( d -Ala 2 )GIP and xenin-25-Gln stimulated insulin-induced glucose uptake in 3T3-L1 adipocytes, but this effect was annulled by dual treatment. In conclusion, GIP and xenin possess direct, comparable, lipogenic and lipolytic actions in 3T3-L1 adipocytes. However, effects on lipid metabolism are significantly diminished by combined administration.