Upregulation of cardioprotective SUR2A by sub-hypoxic drop in oxygen

The effects of hypoxia on gene expression have been vigorously studied, but possible effects of small changes in oxygen tension have never been addressed. SUR2A is an atypical ABC protein serving as a regulatory subunit of sarcolemmal ATP-sensitive K⁺ (K_ATP) channels. Up-regulation of SUR2A is associated with cardioprotection and improved physical endurance. Here, we have found that a 24 h-long exposure to slightly decreased ambient fractional concentration of oxygen (20% oxygen), which is an equivalent to oxygen tension at 350 m above sea level, significantly increased levels of SUR2A in the heart despite that this drop of oxygen did not affect levels of O₂, CO₂ and hematocrit in the blood or myocardial levels of ATP, lactate and NAD/NADH/NAD⁺. Hearts from mice exposed to 20% oxygen were significantly more resistant to ischaemia-reperfusion when compared to control ones. Decrease in fractional oxygen concentration of just 0.9% was associated with phosphorylation of ERK1/2, but not Akt, which was essential for up-regulation of SUR2A. These findings indicate that a small drop in oxygen tension up-regulates SUR2A in the heart by activating ERK signaling pathway. This is the first report to suggest that a minimal change in oxygen tension could have a profound signaling effect.     

Metabolic and bioprocess engineering of the yeast Candida famata for FAD production

Flavins in the form of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) play an important role in metabolism as cofactors for oxidoreductases and other enzymes. Flavin nucleotides have applications in the food industry and medicine; FAD supplements have been efficiently used for treatment of some inheritable diseases. FAD is produced biotechnologically; however, this compound is much more expensive than riboflavin. Flavinogenic yeast Candida famata synthesizes FAD from FMN and ATP in the reaction catalyzed by FAD synthetase, a product of the FAD1 gene. Expression of FAD1 from the strong constitutive promoter TEF1 resulted in 7- to 15-fold increase in FAD synthetase activity, FAD overproduction, and secretion to the culture medium. The effectiveness of FAD production under different growth conditions by one of these recombinant strains, C. famata T-FD-FM 27, was evaluated. First, the two-level Plackett–Burman design was performed to screen medium components that significantly influence FAD production. Second, central composite design was adopted to investigate the optimum value of the selected factors for achieving maximum FAD yield. FAD production varied most significantly in response to concentrations of adenine, KH₂PO₄, glycine, and (NH₄)₂SO₄. Implementation of these optimization strategies resulted in 65-fold increase in FAD production when compared to the non-optimized control conditions. Recombinant strain that has been cultivated for 40 h under optimized conditions achieved a FAD accumulation of 451 mg/l. So, for the first time yeast strains overproducing FAD were obtained, and the growth media composition for maximum production of this nucleotide was designed.     

Functional consequences of stably expressing a mutant calsequestrin (CASQ2D307H) in the CASQ2 null background

The role of calsequestrin (CASQ2) in cardiac sarcoplasmic reticulum (SR) calcium (Ca(2+)) transport has gained significant attention since point mutations in CASQ2 were reported to cause ventricular arrhythmia. In the present study, we have critically evaluated the functional consequences of expressing the CASQ2(D307H) mutant protein in the CASQ2 null mouse. We recently reported that the mutant CASQ2(D307H) protein can be stably expressed in CASQ2 null hearts, and it targets appropriately to the junctional SR (Kalyanasundaram A, Bal NC, Franzini-Armstrong C, Knollmann BC, Periasamy M. J Biol Chem 285: 3076-3083, 2010). In this study, we found that introduction of CASQ2(D307H) protein in the CASQ2 null background partially restored triadin 1 levels, which were decreased in the CASQ2 null mice. Despite twofold expression (relative to wild-type CASQ2), the mutant protein failed to increase SR Ca(2+) load. We also found that the Ca(2+) transient decays slower in the CASQ2 null and CASQ2(D307H) cells. CASQ2(D307H) myocytes, when rhythmically paced and challenged with isoproterenol, exhibit spontaneous Ca(2+) waves similar to CASQ2 null myocytes; however, the stability of Ca(2+) cycling was increased in the CASQ2(D307H) myocytes. In the presence of isoproterenol, Ca(2+)-transient amplitude in CASQ2(D307H) myocytes was significantly decreased, possibly indicating an inherent defect in Ca(2+) buffering capacity and release from the mutant CASQ2 at high Ca(2+) concentrations. We also observed polymorphic ventricular tachycardia in the CASQ2(D307H) mice, although lesser than in the CASQ2 null mice. These data suggest that CASQ2(D307H) point mutation may affect Ca(2+) buffering capacity and Ca(2+) release. We propose that poor interaction between CASQ2(D307H) and triadin 1 could affect ryanodine receptor 2 stability, thereby increasing susceptibility to delayed afterdepolarizations and triggered arrhythmic activity.     

Electrochemical screening of the indole/quinolone derivatives as potential protein kinase CK2 inhibitors

An electrochemical method based on the bioorganometallic Fc-ATP cosubstrate for kinase-catalyzed phosphorylation reactions was used for monitoring casein kinase 2 (CK2) phosphorylations in the absence and presence of five indole/quinolone-based potential inhibitors. Fc-phosphorylation of immobilized peptide RRRDDDSDDD on Au surfaces resulted in a current density at approximately 460 ± 10 mV. An electrochemical redox signal was significantly decreased in the presence of inhibitors. In addition, the electrochemical signal was concentration dependent with respect to the potential inhibitors 1 to 5, which proved to be viable CK2 drug targets with estimated IC₅₀ values in the nanomolar range.     

Early-Life Socioeconomic Status and the Prevalence of Breast Cancer in Later Life

Knowledge of mechanisms linking early-life social environment and breast cancer remains limited. We explore direct and indirect effects of early-life socioeconomic status (SES) on breast cancer prevalence in later life. Using 50-year data from the Wisconsin Longitudinal Study (N = 4,275) and structural equation modeling, we found a negative direct effect of early-life SES, indicating that women from higher-SES family background had lower breast cancer prevalence than women from lower-SES families. Additionally, early-life SES has a positive indirect effect on breast cancer via women's adult SES and age at first birth. Were it not for their higher SES in adulthood and delayed childbearing, women from higher-SES families of origin would have had lower breast cancer prevalence than women from lower-SES families. Yet, early-life SES is associated positively with adult SES and age at first birth, and women's higher adult SES and delayed childbearing are related to higher breast cancer prevalence.