Design,synthesis, and evaluation of imidazo[1,2-b]pyridazine derivatives having a benzamide unit as novel VEGFR2 kinase inhibitors

The vascular endothelial growth factor (VEGF) signaling pathway has been implicated in tumor angiogenesis, and inhibition of the VEGF pathway is considered an efficacious method for treating cancer. Herein, we describe synthetic studies of imidazo[1,2-b]pyridazine derivatives as VEGF receptor 2 (VEGFR2) kinase inhibitors. The imidazo[1,2-b]pyridazine scaffold was designed and synthesized as a hinge binder according to the previously reported crystal structure of pyrrolo[3,2-d]pyrimidine 1 with VEGFR2. Structure–activity relationship studies revealed that meta-substituted 6-phenoxy-imidazo[1,2-b]pyridazine derivatives had potent affinity for VEGFR2. In particular, N-[3-(imidazo[1,2-b]pyridazin-6-yloxy)phenyl]-3-(trifluoromethyl)benzamide (6b) exhibited strong inhibitory activity against VEGFR2 with an IC₅₀ value of 7.1 nM, and it inhibited platelet-derived growth factor receptor β kinase with an IC₅₀ value of 15 nM.     

MultiBac: expanding the research toolbox for multiprotein complexes

Protein complexes composed of many subunits carry out most essential processes in cells and, therefore, have become the focus of intense research. However, deciphering the structure and function of these multiprotein assemblies imposes the challenging task of producing them in sufficient quality and quantity. To overcome this bottleneck, powerful recombinant expression technologies are being developed. In this review, we describe the use of one of these technologies, MultiBac, a baculovirus expression vector system that is particularly tailored for the production of eukaryotic multiprotein complexes. Among other applications, MultiBac has been used to produce many important proteins and their complexes for their structural characterization, revealing fundamental cellular mechanisms.     

MafT, a new member of the small Maf protein family in zebrafish

Small Maf proteins play critical roles on morphogenesis and homeostasis through associating with CNC proteins. To date, three small Maf proteins, MafF, MafG, and MafK, have been reported in vertebrates, which share redundant functions. In this study, we tried to identify and characterize small Maf proteins in zebrafish to elucidate their conservation and diversity in the fish kingdom. We identified homolog genes of MafG and MafK but not MafF in zebrafish, indicating the former two are conserved among vertebrates. In addition, a novel type of small Maf protein MafT was identified. MafT protein bound MARE sequence as a homodimer or heterodimers with zebrafish Nrf2 or p45 Nfe2. Co-overexpression of MafT and Nrf2 synergistically activated MARE-mediated gene expression in zebrafish embryos. These results indicated that MafT is a new member of small Maf proteins and involved in the Nrf2-dependent gene regulation in cellular defense system.     

Folding units in calcium vector protein of amphioxus: Structural and functional properties of its amino- and carboxy-terminal halves

Muscle of amphioxus contains large amounts of a four EF-hand Ca2+-binding protein, CaVP, and its target, CaVPT. To study the domain structure of CaVP and assess the structurally important determinants for its interaction with CaVPT, we expressed CaVP and its amino (N-CaVP) and carboxy-terminal halves (C-CaVP). The interactive properties of recombinant and wild-type CaVP are very similar, despite three post-translational modifications in the wild-type protein. N-CaVP does not bind Ca2+, shows a well-formed hydrophobic core, and melts at 44 degrees C. C-CaVP binds two Ca2+ with intrinsic dissociation constants of 0.22 and 140 microM (i.e., very similar to the entire CaVP). The metal-free domain in CaVP and C-CaVP shows no distinct melting transition, whereas its 1Ca2+ and 2Ca2+) forms melt in the 111 degrees -123 degrees C range, suggesting that C-CaVP and the carboxy- domain of CaVP are natively unfolded in the metal-free state and progressively gain structure upon binding of 1Ca2+ and 2Ca2+. Thermal denaturation studies provide evidence for interdomain interaction: the apo, 1Ca2+ and 2Ca2+ states of the carboxy-domain destabilize to different degrees the amino-domain. Only C-CaVP forms a Ca2+-dependent 1:1 complex with CaVPT. Our results suggest that the carboxy-terminal domain of CaVP interacts with CaVPT and that the amino-terminal lobe modulates this interaction.     

Light-affected ca fluxes in protoplasts from vallisneria mesophyll cells

In Vallisneria gigantea Graebner mesophyll cells, red light irradiation induces cytoplasmic streaming by decreasing the Ca²⁺ concentration in the cytoplasm, while far-red light irradiation inhibits it by increasing the concentration (S Takagi, R Nagai 1985 Plant Cell Physiol 26: 941-951). To examine the effects of light irradiation on Ca²⁺ fluxes across the cell membrane, protoplasts are isolated from the mesophyll cells. Changes in Ca²⁺ concentration in a solution bathing the protoplasts are monitored by spectrophotometry, using the Ca²⁺ -sensitive dye murexide. Red light irradiation induces an increase in Ca²⁺ concentration, which means an efflux of Ca²⁺ from the protoplasts. Subsequent far-red light irradiation produces a rapid decrease in Ca²⁺ concentration down to the dark control level; however, this is not observed in the presence of the Ca²⁺ -channel blocker nifedipine. Vanadate inhibits both the streaming and the Ca²⁺ efflux induced by red light irradiation. The results suggest that red light and far-red light control Ca²⁺ movements across the cell membrane, which in turn regulate the streaming.     

Coexpression of the receptor-associated protein gephyrin changes the ligand binding affinities of alpha 2 glycine receptors.

The inhibitory glycine receptor (GlyR) is a ligand-gated chloride channel protein, whose ligand binding alpha subunit occurs in several isoforms in the mammalian central nervous system. Here we show that coexpression of the GlyR-associated protein gephyrin changes the agonist and antagonist binding affinities of GlyRs generated by alpha 2 subunit expression in 293 kidney cells. Thus, a receptor-associated protein modifies the functional properties of a neurotransmitter receptor. This may contribute to an optimization of the postsynaptic neurotransmitter response.     

Amino acid sequence studies on cyanogen bromide peptides of chicken caldesmon which bind to calmodulin

Three major calmodulin-binding cyanogen bromide peptides (fragments A, B, and D) were isolated from chicken gizzard muscle caldesmon and their amino acid sequences were determined. The molecular masses of fragments A, B, and D were estimated to 16, 12, and 9 kDa, respectively, by SDS-urea polyacrylamide gel electrophoresis. Fragment A was composed of 102 amino acid residues and contained homoserine at the C terminus. The amino acid sequence from the 37th residue of fragment A corresponds to the N-terminal sequence of the 15 kDa peptide which was obtained by thrombin digestion [Mornet, D., Audemard, E., & Derancourt, J. (1988) Biochem. Biophys. Res. Commun. 154, 564-571]. Thrombin 15 kDa peptide binds to F-actin but does not bind to calmodulin. Thus the N-terminal 36 residues and the C-terminal part from the 37th residue of fragment A are supposed to bind to calmodulin and F-actin, respectively. The sequences of fragments B and D were identical, but fragment D was composed of 64 amino acid residues and ended with tryptophan, whereas fragment B was of 98 or 99 amino acid residues and ended with proline. Both fragments B and D are supposed to be the C-terminal peptides of chicken caldesmon. Fragment B had heterogeneous sequences at the C-terminal region. These results can explain the reported heterogeneity of chicken caldesmon in charge and molecular mass.     

Time Interval from Symptom Onset to Hospital Care in Patients with Acute Heart Failure: A Report from the Tokyo Cardiac Care Unit Network Emergency Medical Service Database

Aims

There seems to be two distinct patterns in the presentation of acute heart failure (AHF) patients; early- vs. gradual-onset. However, whether time-dependent relationship exists in outcomes of patients with AHF remains unclear.

Methods

The Tokyo Cardiac Care Unit Network Database prospectively collects information of emergency admissions via EMS service to acute cardiac care facilities from 67 participating hospitals in the Tokyo metropolitan area. Between 2009 and 2011, a total of 3811 AHF patients were registered. The documentation of symptom onset time was mandated by the on-site ambulance team. We divided the patients into two groups according to the median onset-to-hospitalization (OH) time for those patients (2h); early- (presenting ≤2h after symptom onset) vs. gradual-onset (late) group (>2h). The primary outcome was in-hospital mortality.

Results

The early OH group had more urgent presentation, as demonstrated by a higher systolic blood pressure (SBP), respiratory rate, and higher incidence of pulmonary congestion (48.6% vs. 41.6%; P<0.001); whereas medical comorbidities such as stroke (10.8% vs. 7.9%; P<0.001) and atrial fibrillation (30.0% vs. 26.0%; P<0.001) were more frequently seen in the late OH group. Overall, 242 (6.5%) patients died during hospitalization. Notably, a shorter OH time was associated with a better in-hospital mortality rate (odds ratio, 0.71; 95% confidence interval, 0.51−0.99; P = 0.043).

Conclusions

Early-onset patients had rather typical AHF presentations (e.g., higher SBP or pulmonary congestion) but had a better in-hospital outcome compared to gradual-onset patients.