Peptides binding to a Gb3 mimic selected from a phage library

Peptides binding to a Gb3 mimic were selected from 12-mer peptide library. The self-assembled monolayer (SAM) of a Gb3 mimic was formed on the gold surface, and biopanning was carried out with the phage display peptide library. After three rounds of biopanning, four individual sequences were obtained from 10 phage clones, and the selected peptides having the specific 7-mer sequence (FHENWPS) showed affinities to the Gb3 mimic as strong as to RCA120. Molecular dynamics calculations suggested that the peptides bound to the Gb3 mimic by hydrophobic interaction and hydrogen bonding formation, and the cooperative interactions played an important role in the recognition. The Stx-1 binding was inhibited by the peptides.     

Novel metabolism of 1 alpha,25-dihydroxyvitamin D3 with C24-C25 bond cleavage catalyzed by human CYP24A1

Our previous study revealed that human CYP24A1 catalyzes a remarkable metabolism consisting of both C-23 and C-24 hydroxylation pathways that used both 25(OH)D(3) and 1alpha,25(OH)(2)D(3) as substrates, while rat CYP24A1 showed extreme predominance of the C-24 over C-23 hydroxylation pathway [Sakaki, T., Sawada, N., Komai, K., Shiozawa, S., Yamada, S., Yamamoto, K., Ohyama, Y. and Inouye, K. (2000) Eur. J. Biochem. 267, 6158-6165]. In this study, by using the Escherichia coli expression system for human CYP24A1, we identified 25,26,27-trinor-23-ene-D(3) and 25,26,27-trinor-23-ene-1alpha(OH)D(3) as novel metabolites of 25(OH)D(3) and 1alpha,25(OH)(2)D(3), respectively. These metabolites appear to be closely related to the C-23 hydroxylation pathway, because human CYP24A1 produces much more of these metabolites than does rat CYP24A1. We propose that the C(24)-C(25) bond cleavage occurs by a unique reaction mechanism including radical rearrangement. Namely, after hydrogen abstraction of the C-23 position of 1alpha,25(OH)(2)D(3), part of the substrate-radical intermediate is converted into 25,26,27-trinor-23-ene-1alpha(OH)D(3), while a major part of them is converted into 1alpha,23,25(OH)(3)D(3). Because the C(24)-C(25) bond cleavage abolishes the binding affinity of 1alpha,25(OH)D(3) for the vitamin D receptor, this reaction is quite effective for inactivation of 1alpha,25(OH)D(3).     

Metabolism of A-ring diastereomers of 1alpha,25-dihydroxyvitamin D3 by CYP24A1

The metabolism of 1alpha,25(OH)(2)D(3) (1alpha,3beta) and its A-ring diastereomers, 1beta,25(OH)(2)D(3) (1beta,3beta), 1alpha,25(OH)(2)-3-epi-D(3) (1alpha,3alpha), and 1beta,25(OH)(2)-3-epi-D(3) (1beta,3alpha), was examined to compare the substrate specificity and reaction specificity of CYP24A1 between humans and rats. The ratio between C-23 and C-24 oxidation pathways in human CYP24A1-dependent metabolism of (1alpha,3alpha) and (1beta,3alpha) was 1:1, although the ratio for (1alpha,3beta) and (1beta,3beta) was 1:4. These results indicate that the orientation of the hydroxyl group at the C-3 position determines the ratio between C-23 and C-24 oxidation pathways. A remarkable increase of metabolites in the C-23 oxidation pathway was also observed in rat CYP24A1-dependent metabolism. The binding affinity of human CYP24A1 for A-ring diastereomers was (1alpha,3beta)>(1alpha,3alpha)>(1beta,3beta)>(1beta,3alpha), indicating that both hydroxyl groups at C-1 and C-3 positions significantly affect substrate-binding. The information obtained in this study is quite useful for understanding substrate recognition of CYP24A1 and designing new vitamin D analogs.     

Establishment and characterization of Roberts syndrome and SC phocomelia model medaka (Oryzias latipes)

Roberts syndrome and SC phocomelia (RBS/SC) are genetic autosomal recessive syndromes caused by establishment of cohesion 1 homolog 2 ( ESCO 2) mutation. RBS/SC appear to have a variety of clinical features, even with the same mutation of the ESCO2 gene. Here, we established and genetically characterized a medaka model of RBS/SC by reverse genetics. The RBS/SC model was screened from a mutant medaka library produced by the Targeting Induced Local Lesions in Genomes method. The medaka mutant carrying the homozygous mutation at R80S in the conserved region of ESCO2 exhibited clinical variety (i.e. developmental arrest with craniofacial and chromosomal abnormalities and embryonic lethality) as characterized in RBS/SC. Moreover, widespread apoptosis and downregulation of some gene expression, including notch1a, were detected in the R80S mutant. The R80S mutant is the animal model for RBS/SC and a valuable resource that provides the opportunity to extend knowledge of ESCO2. Downregulation of some gene expression in the R80S mutant is an important clue explaining non-correlation between genotype and phenotype in RBS/SC.     

Severe inhibition of in vitro cardiomyogenesis in mouse embryonic stem cells ectopically expressing EGAM1C homeoprotein

Embryoid bodies were prepared from mouse embryonic stem cells expressing exogenous EGAM1C to analyze their ability to differentiate toward terminally differentiated cell types. The generation of cardiomyocytes was severely suppressed in Egam1c transfectants without upregulation of Nkx2-5, a crucial gene for cardiomyogenesis. These results indicate that EGAM1C is capable of affecting terminal differentiation in mouse embryonic stem cells.     

Identification of a novel ADAMTS9/GON-1 function for protein transport from the ER to the Golgi

A disintegrin-like and metalloprotease with thrombospondin type I motif (ADAMTS9) is a member of the secreted metalloprotease family that is believed to digest extracellular matrix (ECM) proteins outside of cells. Its Caenorhabditis elegans orthologue, GON-1, is involved in ECM degradation and is required for gonad morphogenesis. ADAMTS9 and GON-1 have similar domain structures, and both have a unique C-terminal domain called the "GON domain," whose function remains unknown. Here we show that down-regulation of human ADAMTS9 and C. elegans GON-1 results in the inhibition of protein transport from the endoplasmic reticulum (ER) to the Golgi. This phenotype was rescued by the expression of the GON domain localizing in the ER in human cells and C. elegans. We propose a novel function of ADAMTS9 and GON-1 in the ER that promotes protein transport from the ER to the Golgi. This function is GON-domain dependent but protease activity independent.     

Overcoming hERG issues for brain-penetrating cathepsin S inhibitors: 2-cyanopyrimidines. Part 2

We describe here orally active and brain-penetrant cathepsin S selective inhibitors, which are virtually devoid of hERG K(+) channel affinity, yet exhibit nanomolar potency against cathepsin S and over 100-fold selectivity to cathepsin L. The new non-peptidic inhibitors are based on a 2-cyanopyrimidine scaffold bearing a spiro[3.5]non-6-yl-methyl amine at the 4-position. The brain-penetrating cathepsin S inhibitors demonstrate potential clinical utility for the treatment of multiple sclerosis and neuropathic pain.