Synthesis and conformational characterization of the epidermal growth factor-like domain of blood coagulation factor IX carrying xylosyl-glucose

Solid-phase synthesis of glycopeptide generally requires the protection of both peptide side chains and hydroxyl groups of the carbohydrate portion. However, if the mild coupling conditions are used, the protection of the carbohydrate portion can be omitted. In this paper, we demonstrated it by the synthesis of Fmoc-serine carrying unmasked xylosyl glucose followed by the solid-phase synthesis of epidermal growth factor (EGF)-like domain of factor IX (45-87) using the unit. The product was well characterized by enzymatic digestion, amino acid analysis and mass spectrometry. The secondary structure of the product as well as glucosylated and non-glycosylated EGF-like domain was characterized by circular dichroism (CD) spectroscopy.     

A recombinant molt-inhibiting hormone of the kuruma prawn has a similar secondary structure to a native hormone: determination of disulfide bond arrangement and measurements of circular dichroism spectra

In crustaceans, molt-inhibiting hormone (MIH) is presumed to regulate molting through suppressing synthesis and/or secretion of ecdysteroids by the Y-organ. Recently, a recombinant MIH of the kuruma prawn Penaeus japonicus was produced in E. coli. To approximate the secondary structure of native and recombinant MIH of P. japonicus containing six cysteine residues, the arrangements of disulfide bridges in both MIHs were determined by characterizing their enzymatic digests, and their circular dichroism spectra were measured. The arrangements of disulfide bonds in both MIHs were determined to be identical, and they were linked between Cys7 and Cys44, Cys24 and Cys40, and Cys27 and Cys53. The circular dichroism spectra of both MIHs were very close, and demonstrated that they were rich in a-helix. a-Helix contents in native and recombinant MIHs were calculated to be 49.3% and 46.0%, respectively. All these results strongly suggested that the recombinant MIH was folded in the same manner as the native MIH.     

Exogenous expression of mouse Dnmt3 induces apoptosis in Xenopus early embryos

Mouse DNA (cytosine-5) methyltransferases Dnmt3a and Dnmt3b are expected to be de novo-type DNA methyltransferases. In the present study, we found that exogenously expressed mouse Dnmt3a or Dnmt3b induced abnormal cell clusters at the gastrulation stage in Xenopus embryos. The abnormal cells were judged to be apoptotic from the positive staining with the TdT dUTP nucleotide end-labeling method and the rescue by hBcl-x(L), a Bcl-2 homologue. On the other hand, neither bacterial DNA (cytosine-5) methyltransferase nor Dnmt3b3, one of the three isoforms of Dnmt3b that has no DNA methylation activity, induced apoptosis. In addition, mutant Dnmt3a and the other two Dnmt3b isoforms, Dnmt3b1 and Dnmt3b2, which have no DNA methylation activity due to a change of the cysteine residue in the catalytic center to an alanine residue, retained the ability to induce apoptosis. This indicates that the apoptosis was not induced by DNA methylation activity. The domain of Dnmt3b1 (3b2) responsible for the apoptosis is the catalytic domain in the carboxyl-terminal half.     

Long-term treatment with glibenclamide increases susceptibility of streptozotocin-induced diabetic rat heart to reperfusion-induced ventricular tachycardia

This study investigated the effects of long-term treatment with glibenclamide (GLIB) on the susceptibility of streptozotocin (STZ)-induced diabetic heart to ischemia/reperfusion insults. Starting 4 weeks after the injection of STZ, rats were treated with GLIB (0.1 mg/kg, ip, three times a week, STZ-GLIB group) or vehicle (STZ-VEH group) for 8 weeks. The recovery of cardiac performance, released creatine kinase (CK), and incidence of ventricular arrhythmias were studied during the reperfusion period in isolated hearts from rats in STZ-GLIB (n = 14) and in STZ-VEH groups (n = 13) and from age-matched control rats (CNT group, n = 14). Each heart was subjected to 5 min of global low-flow ischemia followed by 25 min of no-flow ischemia, with a subsequent 30 min of reperfusion. Plasma glucose level was not significantly different between the STZ-GLIB and STZ-VEH groups. The recovery of cardiac performance and the released CK during reperfusion period were significantly lower in both STZ-VEH and STZ-GLIB groups than in the CNT group (P < 0.01 and P < 0.05, respectively). Reperfusion resulted in an incidence of ventricular fibrillation in 23% and 21% in STZ-VEH and STZ-GLIB groups, respectively (P = ns). These values were significantly lower than that of the CNT group (100%, P < 0.001 for both). More importantly, the incidence of ventricular tachycardia in the STZ-GLIB group was significantly higher than that in the STZ-VEH group (93% vs 54%, P < 0.05) and was not significantly different from that in the CNT group (93% vs 100%, P = ns). The results suggest that STZ-induced protection against reperfusion-induced ventricular arrhythmias in diabetic heart may be partially abrogated by long-term treatment with GLIB.     

Synthesis of an unnatural N-glycan-linked dolichyl pyrophosphate precursor

An unnatural alpha-D-mannopyranose-linked chitobiosyl dolichyl pyrophosphate, a stereoisomer of the N-glycan biosynthesis intermediate, was synthesized. The protected trisaccharide, alpha-D-Man-(1-->4)-beta-D-GlcNAc-(1-->4)-D-GlcNAc, carrying a 4-methylbenzoyl group was prepared for the convenience of a TLC analysis. 1-O-Phosphorylation, condensation with dolichyl phosphate, and subsequent deprotection afforded the title compound.     

Exercise ameliorates high-fat diet-induced impairment of differentiation of adipose-derived stem cells into neuron-like cells in rats

Adipose-derived stem cells (ADSCs) can differentiate into neurons under particular conditions. It remains largely unknown whether this differentiation potential is affected by physical conditions such as obesity, which modulates the functions of adipose tissue. In this study, we determined the impact of either a 9-week high-fat diet (60% fat; HFD) or 9-week exercise training on the differentiation potential of ADSCs into neuron-like cells in male Wistar rats. Rats were randomly assigned to a normal diet-fed (ND-SED) group, HFD-fed (HFD-SED) group, or exercise-trained HFD-fed group (HFD-EX). After a 9-week intervention, ADSCs from all groups differentiated into neuron-like cells. Expression of neuronal marker proteins (nestin, βIII-tubulin, and microtubule-associated protein 2 [MAP2]) and the average length of cell neurites were lower in cells from HFD-SED rats than in other groups. Instead, protein expression of COX IV and Cyt-c, the Bax/Bcl-2 and LC3-II/I ratio, and the malondialdehyde level in culture medium were higher in cells from HFD-SED rats. No significant difference between ND-SED and HFD-EX rats was observed, except for the average length of cell neurites in MAP2. Thus, HFD impaired the differentiation potential of ADSCs into neuron-like cells, which was accompanied by increases in apoptotic activity and oxidative stress. Importantly, exercise training ameliorated the HFD-induced impairment of neurogenesis in ADSCs. The adipose tissue microenvironment could influence the differentiation potential of ADSCs, a source of autologous stem cell therapy.     

Surface-bound basement membrane components accelerate amyloid-β peptide nucleation in air-free wells: An in vitro model of cerebral amyloid angiopathy

Cerebral amyloid angiopathy is caused by deposition of the amyloid β-peptide which consists of mainly 39–40 residues to the cortical and leptomeningeal vessel walls. There are no definite in vitro systems to support the hypothesis that the vascular basement membrane may act as a scaffold of amyloid β-peptide carried by perivascular drainage flow and accelerate its amyloid fibril formation in vivo. We previously reported the critical roles of interfaces and agitation on the nucleation of amyloid fibrils at low concentrations of amyloid β-peptide monomers. Here, we reproduced the perivascular drainage flow in vitro by using N-hydroxysuccinimide-Sepharose 4 Fast flow beads as an inert stirrer in air-free wells rotated at 1 rpm. We then reproduced the basement membranes in the media of cerebral arteries in vitro by conjugating Matrigel and other proteins on the surface of Sepharose beads. These beads were incubated with 5 μM amyloid β(1–40) at 37 °C without air, where amyloid β(1–40) alone does not form amyloid fibrils. Using the initiation time of fibril growth kinetics (i.e., the lag time of fibril growth during which nuclei, on-pathway oligomers and protofibrils are successively formed) as a parameter of the efficiency of biological molecules to induce amyloid fibril formation, we found that basement membrane components including Matrigel, laminin, fibronectin, collagen type IV and fibrinogen accelerate the initiation of amyloid β-peptide fibril growth in vitro. These data support the essential role of vascular basement membranes in the development of cerebral amyloid angiopathy.