Electrophysiological characterization of the Cyclophilin D-deleted mitochondrial permeability transition pore

Mitochondria isolated from engineered mice lacking Cyclophilin D (CypD), a component of the Permeability Transition Pore (PTP) complex, can still undergo a Ca^2?+?-dependent but Cyclosporin A-insensitive permeabilization of the inner membrane. Higher Ca^2?+? concentrations are required than for wild-type controls. The characteristics of the pore formed in this system were not known, and it has been proposed that they might differ substantially from those of the normal PTP. To test this hypothesis, we have characterized the PTP of isogenic wild-type and CypD^? mouse liver mitochondria in patch clamp experiments, which allow biophysical characterization. The pores observed in the two cases, very similar to those of rat liver mitochondria, are indistinguishable according to a number of criteria. The only clear difference is in their sensitivity to Cyclosporin A. CypD is thus shown to be an auxiliary, modulatory component of the “standard” PTP, which forms and has essentially the same properties even in its absence. The observations suggest that Ca^2?+?, CypD, and presumably other inducers and inhibitors act at the level of an activation or assembly process. Activation is separate and upstream of the gating observable on a short or medium-term time scale. Once the pore is activated, its molecular dynamics and biophysical properties may thus be predicted not to depend on the details of the induction process.     

Direct force measurement of single DNA–peptide interactions using atomic force microscopy

The selective interactions between DNA and miniature (39 residues) engineered peptide were directly measured at the single‐molecule level by using atomic force microscopy. This peptide (p007) contains an α‐helical recognition site similar to leucine zipper GCN4 and specifically recognizes the ATGAC sequence in the DNA with nanomolar affinity. The average rupture force was 42.1 pN, which is similar to the unbinding forces of the digoxigenin–antidigoxigenin complex, one of the strongest interactions in biological systems. The single linear fit of the rupture forces versus the logarithm of pulling rates showed a single energy barrier with a transition state located at 0.74 nm from the bound state. The smaller k_off compared with that of other similar systems was presumably due to the increased stability of the helical structure by putative folding residues in p007. This strong sequence‐specific DNA–peptide interaction has a potential to be utilized to prepare well‐defined mechanically stable DNA–protein hybrid nanostructures. Copyright © 2013 John Wiley & Sons, Ltd.     

Isolation and Structure of a New Victoxinine Derivative Produced by Helminthosporium victoriae

The structures of alkyl radicals generated in several methyl esters of fatty acids by irradiation with UV light were studied by the spin trapping technique. A spin trap, deuterated nitrosodurene, traps alkyl radicals in both saturated and unsaturated esters at the ambient temperature. The trapped radicals and their hyperfine splitting constants from several esters were as follows: pentadienyl radicals (a_N= 13.8 ~ 14.0 G, a_H = 5.9 ~ 6.0 G) from methyl linoleate, linolenate and docosahexaenoate; allyl radicals (a_N = 13.9 G, a_H = 6.8 G) and α-carbon radicals (a_N = 13.3 G, a_H = 10.0 G) from methyl oleate and elaidate; α-carbon radicals (a_N = 13.3 ~ 13.4 G, a_H = 9.6 ~ 10.0 G) and secondary alkyl radicals (a_N = 13.9 G, a_H = 6.8 ~ 7.2 G) from saturated esters.     

Down-regulated miR-15a mediates the epithelial–mesenchymal transition in renal tubular epithelial cells promoted by high glucose

High glucose (HG) has been reported to be associated with renal dysfunction. And one potential mechanism underlining the dysfunction is the epithelial–mesenchymal transition (EMT) of renal tubular epithelial cells. Present study showed that EMT was induced in the HG-treated renal tubular epithelial cells by promoting the expression of mesenchymal phenotype molecules, such as α-SMA and collagen I, and down-regulating the expression of epithelial phenotype molecule E-cadherin. Moreover, we have identified the down-regulation of miR-15a which was accompanied with the HG-induced EMT. And the miR-15a overexpression inhibited the α-SMA, collagen I expression, and the promotion of E-cadherin expression by targeting and down-regulating AP4 which was also significantly promoted by the HG in the renal tubular epithelial cells. Thus, this study revealed that the weakening regulation on the AP4 expression by miR-15a might contribute to the HG-induced EMT in the renal tubular epithelial cells.     

Mitotic catastrophe triggered in human cancer cells by the viral protein apoptin

Mitotic catastrophe is an oncosuppressive mechanism that senses mitotic failure leading to cell death or senescence. As such, it protects against aneuploidy and genetic instability, and its induction in cancer cells by exogenous agents is currently seen as a promising therapeutic end point. Apoptin, a small protein from Chicken Anemia Virus (CAV), is known for its ability to selectively induce cell death in human tumor cells. Here, we show that apoptin triggers p53-independent abnormal spindle formation in osteosarcoma cells. Approximately 50% of apoptin-positive cells displayed non-bipolar spindles, a 10-fold increase as compared to control cells. Besides, tumor cells expressing apoptin are greatly limited in their progress through anaphase and telophase, and a significant drop in mitotic cells past the meta-to-anaphase transition is observed. Time-lapse microscopy showed that mitotic osteosarcoma cells expressing apoptin displayed aberrant mitotic figures and/or had a prolonged cycling time during mitosis. Importantly, all dividing cells expressing apoptin eventually underwent cell death either during mitosis or during the following interphase. We infer that apoptin can efficiently trigger cell death in dividing human tumor cells through induction of mitotic catastrophe. However, the killing activity of apoptin is not only confined to dividing cells, as the CAV-derived protein is also able to trigger caspase-3 activation and apoptosis in non-mitotic cancer cells.     

Cenozoic climate change and diversification on the continental shelf and slope: evolution of gastropod diversity in the family Solariellidae (Trochoidea)

Recent expeditions have revealed high levels of biodiversity in the tropical deep‐sea, yet little is known about the age or origin of this biodiversity, and large‐scale molecular studies are still few in number. In this study, we had access to the largest number of solariellid gastropods ever collected for molecular studies, including many rare and unusual taxa. We used a Bayesian chronogram of these deep‐sea gastropods (1) to test the hypothesis that deep‐water communities arose onshore, (2) to determine whether Antarctica acted as a source of diversity for deep‐water communities elsewhere and (3) to determine how factors like global climate change have affected evolution on the continental slope. We show that although fossil data suggest that solariellid gastropods likely arose in a shallow, tropical environment, interpretation of the molecular data is equivocal with respect to the origin of the group. On the other hand, the molecular data clearly show that Antarctic species sampled represent a recent invasion, rather than a relictual ancestral lineage. We also show that an abrupt period of global warming during the Palaeocene Eocene Thermal Maximum (PETM) leaves no molecular record of change in diversification rate in solariellids and that the group radiated before the PETM. Conversely, there is a substantial, although not significant increase in the rate of diversification of a major clade approximately 33.7 Mya, coinciding with a period of global cooling at the Eocene–Oligocene transition. Increased nutrients made available by contemporaneous changes to erosion, ocean circulation, tectonic events and upwelling may explain increased diversification, suggesting that food availability may have been a factor limiting exploitation of deep‐sea habitats. Tectonic events that shaped diversification in reef‐associated taxa and deep‐water squat lobsters in central Indo‐West Pacific were also probably important in the evolution of solariellids during the Oligo‐Miocene.     

High TMPRSS4 expression is a predictor of poor prognosis in cervical squamous cell carcinoma

Objective The aim of this study was to clarify the clinical role of TMPRSS4 expression in cervical squamous cell carcinoma (CSCC) and to investigate the role of TMPRSS4 in predicting outcomes of patients with CSCC. Methods The retrospective study enrolled 87 patients diagnosed with CSCC between 2004 and 2006. TMPRSS4 expression in CSCC was assessed by immunohistochemistry, and data on clinical variables were collected by retrospective chart review. The impact of TMPRSS4 expression on 5-year disease-free survival (DFS) and 5-year overall survival (OS) was assessed by Kaplan–Meier analysis and Cox proportional hazards modeling. Results The high expression of TMPRSS4 was 63.2% in 87 patients with CSCC, and 17.5% in 40 patients with benign cervical disease (P < 0.001). High TMPRSS4 expression was significantly associated with tumor grade (P = 0.005), lymph node metastasis (P = 0.004), and deep cervical stromal invasion (P = 0.025). Patients with high expression of TMPRSS4 had shorter OS and DFS than those with low expression (P = 0.0205 and P = 0.0318, respectively). In multivariate Cox regression analysis, high expression of TMPRSS4 was a potential prognostic indicator for OS (P = 0.041) and DFS (P = 0.015). Conclusion Our findings suggest that TMPRSS4 might play an important role in the progression of CSCC. TMPRSS4 could be a potential prognostic marker of CSCC.     

Cellular processes underlying cerebral cavernous malformations: Autophagy as another point of view

A growing amount of evidence indicates that autophagy plays a pivotal role in a plethora of human pathological conditions. We have recently broadened the list of the so-called autophagy-related diseases, describing the involvement of defective autophagy in the pathogenesis of cerebral cavernous malformations.