Direct interaction of endogenous Kv channels with syntaxin enhances exocytosis by neuroendocrine cells

K(+) efflux through voltage-gated K(+) (Kv) channels can attenuate the release of neurotransmitters, neuropeptides and hormones by hyperpolarizing the membrane potential and attenuating Ca(2+) influx. Notably, direct interaction between Kv2.1 channels overexpressed in PC12 cells and syntaxin has recently been shown to facilitate dense core vesicle (DCV)-mediated release. Here, we focus on endogenous Kv2.1 channels and show that disruption of their interaction with native syntaxin after ATP-dependent priming of the vesicles by Kv2.1 syntaxin-binding peptides inhibits Ca(2+) -triggered exocytosis of DCVs from cracked PC12 cells in a specific and dose-dependent manner. The inhibition cannot simply be explained by the impairment of the interaction of syntaxin with its SNARE cognates. Thus, direct association between endogenous Kv2.1 and syntaxin enhances exocytosis and in combination with the Kv2.1 inhibitory effect to hyperpolarize the membrane potential, could contribute to the known activity dependence of DCV release in neuroendocrine cells and in dendrites where Kv2.1 commonly expresses and influences release.     

Synthesis and evaluation of 2,3-dinorprostaglandins: Dinor-PGD1 and 13-epi-dinor-PGD1 are peroxisome proliferator-activated receptor α/γ dual agonists

2,3-Dinorprostaglandins (dinor-PGs) have been regarded as β-oxidation products of arachidonic-acid-derived prostaglandins, but their biological activities in mammalian cells remain unclear. On the other hand, C18 polyunsaturated fatty acids (PUFAs), such as γ-linolenic acid (GLA), have various biological activities, and dinor-PGs are speculated to be biosynthesized from GLA. Here, we synthesized dinor-PGs that may possibly be derived from GLA and examined their activities towards peroxisome proliferator-activated receptors (PPARs). Dinor-PGD₁ (1) and its epimer 13-epi-dinor-PGD₁ (epi-1) were found to be dual agonists for PPARα/γ, whereas PGD₂ derived from arachidonic acid is selective for PPARγ. Thus, GLA-derived dinor-PGs may have unique biological roles.     

Small-molecular inhibitors of Ca2+-induced mitochondrial permeability transition (MPT) derived from muscle relaxant dantrolene

A structure consisting of substituted hydantoin linked to a 5-(halophenyl)furan-2-yl group via an amide bond was identified as a promising scaffold for development of low-molecular-weight therapeutic agents to treat vascular dysfunction, including ischemia/reperfusion injury. Among the compounds synthesized, 5-(3,5-dichlorophenyl)-N-{2,4-dioxo-3-[(pyridin-3-yl)methyl]imidazolidin-1-yl}-2-furamide (17) possessed the most potent inhibitory activity against Ca²⁺-induced mitochondrial swelling. The structural development, synthesis and structure–activity relationship of these compounds are described.     

New palaeontological assemblage, sedimentological and chronological data from the Pleistocene Ma U'Oi cave (northern Vietnam)

This paper describes recent material gathered during the second fieldwork at Ma U'Oi in November 2002 by a Vietnamese–French–Japanese team. The Ma U'Oi cave, located in the province of Hoà Binh (60 km SW from Hanoi), northern Vietnam, belongs to a karstic network developed in Triassic dark-grey limestones.

The cave is filled with coarse-grained breccias containing numerous fossil remains, partially preserved at several loci inside the cave (wall, vault and ground). We describe new teeth which confirm the occurrence of mammal taxa already mentioned at Ma U'Oi (Bacon et al., 2004)[Bacon, A-M., Demeter, F., Schuster, M., Long, V.T., Thuy, N.K., Antoine, P-O., Sen, S., Nga, H.H., Huong, N.T.M., 2004. The Pleistocene Ma U'Oi cave, northern Vietnam: palaeontology, sedimentology and palaeoenvironments. Geobios 37, 305–314], while others, mainly microvertebrates, emphasize the occurrence of new species for the Pleistocene of Vietnam. We report here, for the first time, the occurrence of these microvertebrates of different groups (primates, rodents, insectivores, small reptiles and amphibians) in the faunal assemblage. Among mammal taxa, the presence of one more hominid affiliated to archaic Homo is also attested by our findings. U/Th dating carried out on 2 samples extracted from breccia speleothems confirms the biochronological estimate, with fossiliferous fillings ranging from late Middle Pleistocene to Late Pleistocene.     

Phenanthridin-6-one derivatives as the first class of non-steroidal pharmacological chaperones for Niemann-Pick disease type C1 protein

Niemann-Pick disease type C is a fatal, progressive neurodegenerative disease mostly caused by mutations in Nieamnn-Pick type C1 (NPC1), a late endosomal membrane protein that is essential for intracellular cholesterol transport. The most prevalent mutation, I1061T (Ile to Thr), interferes with the protein folding process. Consequently, mutated but intrinsically functional NPC1 proteins are prematurely degraded via proteasome, leading to loss of NPC1 function. Previously, we reported sterol derivatives as pharmacological chaperones for NPC1, and showed that these derivatives can normalize folding-defective phenotypes of I1061T NPC1 mutant by directly binding to, and stabilizing, the protein. Here, we report a series of compounds containing a phenanthridin-6-one scaffold as the first class of non-steroidal pharmacological chaperones for NPC1. We also examined their structure-activity relationships.     

Design and synthesis of dysidiolide analogs from vitamin D3: novel class of Cdc25A inhibitors

Potent dysidiolide analogs were synthesized by structural hybridization of dysidiolide and vitamin D(3). These analogs exhibited strong inhibitory activity toward dual-specificity phosphatase Cdc25A (IC(50)=0.44-0.89 microM).     

Structure-activity relationship of N-methyl-bisindolylmaleimide derivatives as cell death inhibitors

A series of N-methyl-bisindolylmaleimide derivatives was synthesized and evaluated as cell death inhibitors. N-Methyl-2-[1-(3-aminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)maleimide (21) was the most potent inhibitor of H2O2-induced necrotic death of human leukemia HL60 cells among them.     

Efficient shoot organogenesis in petioles of yam (Dioscorea spp)

Shoot organogenesis was successfully achieved in petiole explants excised from 6 to 8-week old in vitro plantlets of yam Dioscorea rotundata P. cv. Kponan fissa, Dioscorea cayenensis L. cv. Krengle IB14 and cv. Krengle IB35, and Dioscorea alata L. cv. Bete bete. Only the basipetal portion of the petiole acquired competence, and plants regenerated within 21?days on MS medium supplemented with 2?% sucrose, 100?mg/l myo-inositol, 10???M kinetin and 1.5?mM putrescine referred to as yam regeneration medium (YRM). Plant regeneration was significantly (p?<?0.01) higher (42?%) with 2?% sucrose compared to 1, 3 and 4?% sucrose which produced 4, 25 and 15?% regeneration respectively. The age of the donor yam plantlet was critical to regeneration, and the highest regeneration efficiency was obtained with explants from 8-week old plantlets. Addition of the antioxidants lipoic acid (19.4???M), and l-cysteine (28.5???M) to the culture medium stimulated axillary branching in regenerated shoots. Among the four yam cultivars tested, cv. Kponan fissa, cv. Krengle IB14 and cv. Bete bete had similar response at 10???M kinetin, while the cv. Krengle IB35 regenerated best at a lower concentration of kinetin (0.5???M).     

Crystal structural characterization reveals novel oligomeric interactions of human voltage‐dependent anion channel 1

Voltage‐dependent anion channel 1 (VDAC1), which is located in the outer mitochondrial membrane, plays important roles in various cellular processes. For example, oligomerization of VDAC1 is involved in the release of cytochrome c to the cytoplasm, leading to apoptosis. However, it is unknown how VDAC1 oligomerization occurs in the membrane. In the present study, we determined high‐resolution crystal structures of oligomeric human VDAC1 (hVDAC1) prepared by using an Escherichia coli cell‐free protein synthesis system, which avoided the need for denaturation and refolding of the protein. Broad‐range screening using a bicelle crystallization method produced crystals in space groups C222 and P22₁2₁, which diffracted to a resolution of 3.10 and 3.15 Å, respectively. Each crystal contained two hVDAC1 protomers in the asymmetric unit. Dimer within the asymmetrical unit of the crystal in space group C222 were oriented parallel, whereas those of the crystal in space group P22₁2₁ were oriented anti‐parallel. From a model of the crystal in space group C222, which we constructed by using crystal symmetry operators, a heptameric structure with eight patterns of interaction between protomers, including hydrophobic interactions with β‐strands, hydrophilic interactions with loop regions, and protein–lipid interactions, was observed. It is possible that by having multiple patterns of interaction, VDAC1 can form homo‐ or hetero‐oligomers not only with other VDAC1 protomers but also with other proteins such as VDAC2, VDAC3 and apoptosis‐regulating proteins in the Bcl‐2 family.     

Leaf n‐Alkanes as Characters Differentiating Coastal and Continental Juniperus deltoides Populations from the Balkan Peninsula

The composition of the cuticular n‐alkanes isolated from the leaves of nine populations of Juniperus deltoides R.P.Adams from continental and coastal areas of the Balkan Peninsula was characterized by GC‐FID and GC/MS analyses. In the leaf waxes, 14 n‐alkane homologues with chain‐lengths ranging from C₂₂ to C₃₅ were identified. n‐Tritriacontane (C₃₃) was dominant in the waxes of all populations, but variations between the populations in the contents of all n‐alkanes were observed. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses) were used to investigate the diversity and variability of the cuticular‐leaf‐n‐alkane patterns of the nine J. deltoides populations. This is the first report on the n‐alkane composition for this species. The multivariate statistical analyses evidenced a high correlation of the leaf‐n‐alkane pattern with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon.