Circulating KCNH2 current-activating factor in patients with heart failure and ventricular tachyarrhythmia

Background

It is estimated that approximately half of the deaths in patients with HF are sudden and that the most likely causes of sudden death are lethal ventricular tachyarrhythmias such as ventricular tachycardia (VT) or fibrillation (VF). However, the precise mechanism of ventricular tachyarrhythmias remains unknown. The KCNH2 channel conducting the delayed rectifier K⁺ current (I_Kr) is recognized as the most susceptible channel in acquired long QT syndrome. Recent findings have revealed that not only suppression but also enhancement of I_Kr increase vulnerability to major arrhythmic events, as seen in short QT syndrome. Therefore, we investigated the existence of a circulating KCNH2 current-modifying factor in patients with HF.

Methodology/Principal Findings

We examined the effects of serum of HF patients on recombinant I_Kr recorded from HEK 293 cells stably expressing KCNH2 by using the whole-cell patch-clamp technique. Study subjects were 14 patients with non-ischemic HF and 6 normal controls. Seven patients had a history of documented ventricular tachyarrhythmias (VT: 7 and VF: 1). Overnight treatment with 2% serum obtained from HF patients with ventricular arrhythmia resulted in a significant enhancement in the peaks of I_Kr tail currents compared to the serum from normal controls and HF patients without ventricular arrhythmia.

Conclusions/Significance

Here we provide the first evidence for the presence of a circulating KCNH2 channel activator in patients with HF and ventricular tachyarrhythmias. This factor may be responsible for arhythmogenesis in patients with HF.     

Deletion analysis of regions at the C-terminal part of cycloisomaltooligosaccharide glucanotransferase from Bacillus circulans T-3040

Cycloisomaltooligosaccharide glucanotransferase (CITase) belongs to glycoside hydrolase family 66. According to the sequence alignment of enzymes in the same family, we divided the structure of CITase into five regions from the N terminus to the C terminus: an N-terminal conserved region (Ser1-Gly403), an insertion region (R1; Tyr404-Tyr492), two conserved regions (R2; Glu493-Ser596 and R3; Gly597-Met700), and a C-terminal variable region (R4; Lys701-Ser934). CITase catalyzes the synthesis of cycloisomaltooligosaccharides (CIs) with 7-17 glucose units (CI-7 to CI-17) from dextran. In order to clarify the functions of these C-terminal regions (R1-R4), we constructed 15 deletion mutant enzymes. M123Δ (R4-deleted), MΔ234 (R1-deleted), and MΔ23Δ (R1/R4-deleted) catalyzed CI synthesis, but other mutants were inactive. M123Δ, MΔ234, and MΔ23Δ increased their K(m) values against dextran 40. The wild-type enzyme and M123Δ produced CI-8 predominantly, but MΔ234 and MΔ23Δ lost CI-8 production specificity. The k(cat) values of MΔ234 and MΔ23Δ decreased, and these mutants showed narrowed temperature and pH stability ranges. Our deletion analysis suggests that (i) R2 and R3 are crucial for CITase to generate an active form; (ii) both R1 and R4 contribute to substrate binding; and (iii) R1 also contributes to preference of CI-8 production and enzyme stability.     

Imaging mass spectrometry for lipidomics

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool that enables the simultaneous detection and identification of biomolecules in analytes. MALDI-imaging mass spectrometry (MALDI-IMS) is a two-dimensional MALDI-MS technique used to visualize the spatial distribution of biomolecules without extraction, purification, separation, or labeling of biological samples. This technique can reveal the distribution of hundreds of ion signals in a single measurement and also helps in understanding the cellular profile of the biological system. MALDI-IMS has already revealed the characteristic distribution of several kinds of lipids in various tissues. The versatility of MALDI-IMS has opened a new frontier in several fields, especially in lipidomics. In this review, we describe the methodology and applications of MALDI-IMS to biological samples.     

Peptidyl-prolyl cis-trans isomerase xFKBP1B induces ectopic secondary axis and is involved in eye formation during Xenopus embryogenesis

Although Xenopus FKBP1A (xFKBP1A) induces an ectopic dorsal axis in Xenopus embryos, involvement of xFKBP1B, a vertebrate paralogue of FKBP1A, in embryogenesis remains undetermined. Here, we demonstrate that xFKBP1B induces ectopic dorsal axis and involves in eye formation of Xenopus embryos. Injection of the xFKBP1B mRNA in ventral blastomeres of 4-cell stage Xenopus embryos induced a secondary axis and showed multiplier effect to that of xFKBP1A on this when xFKBP1A was co-injected. In addition, BMP4 and Smad1 mRNAs did not affect the ability of xFKBP1B to induce the ectopic secondary axis when either was co-injected with xFKBP1B in ventral blastomeres, whereas they downed out that of xFKBP1A, suggesting that xFKBP1A and xFKBP1B induce the ectopic secondary axis through affecting different pathways from each other. On the other hand, the injection of the FKBP1B mRNA in dorsal blastomeres showed eye malformation, and suppressed almost completely the expression of Rx1, Mitf, and Vax2 mRNAs. xFKBP1B was expressed in the dorsal side of the embryo including the eye during embryogenesis at least until stage 46. Injection of morpholino of the xFKBP1B mRNA in dorsal blastomeres induced additional retina or failed to close tapetum nigrum in the ventral side within the optic cap, whereas it did not affect the dorsal organ development. The injection of the morpholino reduced the expression of Xotx2 and Rx1 mRNAs in the eye. These observations suggest that xFKBP1B is a key factor that regulates the expression levels of the genes involved in eye formation during Xenopus embryogenesis.     

Discovery, synthesis, and biological evaluation of novel pyrrole derivatives as highly selective potassium-competitive acid blockers

To discover a gastric antisecretory agent more potent than existing proton pump inhibitors, novel pyrrole derivatives were synthesized, and their H(+),K(+)-ATPase inhibitory activities and inhibitory action on histamine-stimulated gastric acid secretion in rats were evaluated. Among the compounds synthesized, compound 17a exhibited selective and potent H(+),K(+)-ATPase inhibitory activity through reversible and K(+)-competitive ionic binding; furthermore, compound 17c exhibited potent inhibitory action on histamine-stimulated gastric acid secretion in rats and Heidenhain pouch dogs.     

Knockdown of the Drosophila fused in sarcoma (FUS) homologue causes deficient locomotive behavior and shortening of motoneuron terminal branches

Mutations in the fused in sarcoma/translated in liposarcoma gene (FUS/TLS, FUS) have been identified in sporadic and familial forms of amyotrophic lateral sclerosis (ALS). FUS is an RNA-binding protein that is normally localized in the nucleus, but is mislocalized to the cytoplasm in ALS, and comprises cytoplasmic inclusions in ALS-affected areas. However, it is still unknown whether the neurodegeneration that occurs in ALS is caused by the loss of FUS nuclear function, or by the gain of toxic function due to cytoplasmic FUS aggregation. Cabeza (Caz) is a Drosophila orthologue of human FUS. Here, we generated Drosophila models with Caz knockdown, and investigated their phenotypes. In wild-type Drosophila, Caz was strongly expressed in the central nervous system of larvae and adults. Caz did not colocalize with a presynaptic marker, suggesting that Caz physiologically functions in neuronal cell bodies and/or their axons. Fly models with neuron-specific Caz knockdown exhibited reduced climbing ability in adulthood and anatomical defects in presynaptic terminals of motoneurons in third instar larvae. Our results demonstrated that decreased expression of Drosophila Caz is sufficient to cause degeneration of motoneurons and locomotive disability in the absence of abnormal cytoplasmic Caz aggregates, suggesting that the pathogenic mechanism underlying FUS-related ALS should be ascribed more to the loss of physiological FUS functions in the nucleus than to the toxicity of cytoplasmic FUS aggregates. Since the Caz-knockdown Drosophila model we presented recapitulates key features of human ALS, it would be a suitable animal model for the screening of genes and chemicals that might modify the pathogenic processes that lead to the degeneration of motoneurons in ALS.     

Parameterization of chlorophyll a-specific absorption coefficients and effects of their variations in a highly eutrophic lake: a case study at Lake Kasumigaura, Japan

The chlorophyll a-specific absorption coefficient ( a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) ) in a highly eutrophic lake can show characteristics distinct from that in the ocean due to the differences in the structure and composition of phytoplankton. In this study, investigated the variation of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in Lake Kasumigaura, a highly eutrophic lake in Japan, in association with the package effect and the effect of accessory pigments, and carried out the parameterization of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) . Although a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) did not vary spatially, it did show significant temporal variation, with a particularly high value after spring-bloom. This high a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in spring was attributed to a lower package effect and a higher proportion of carotenoid than the other samples. Although the value of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) was correlated with the concentration of chlorophyll-a (Chl-a), the correlation coefficient was lower than those reported in the ocean. Some lake-water samples showed variations of the package effect and the effect of accessory pigments that were independent of the concentration of Chl-a, and these independent variations resulted in the weak correlation between a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) and the concentration of Chl-a. Together, these results suggest that the factors controlling a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in highly eutrophic lakes are distinct from that in ocean samples.