The Phytophthora mating hormone α2 is an antagonist of the counterhormone α1

The crop destroyer Phytophthora uses mating hormones α1 and α2 to commence its sexual reproduction. The α1-induced sexual reproduction of the A2 mating type was unexpectedly found to be interfered with by the counterhormone α2 that the A2 type itself produces to induce the sexual reproduction of the A1 type. A plausible mechanism is proposed based on structure–activity relationships.     

Structure-activity relationship of clovamide and its related compounds for the inhibition of amyloid β aggregation

Alzheimer’s disease (AD), a neurodegenerative disorder, is characterized by aggregation of amyloid β-protein (Aβ). Aβ aggregates through β-sheet formation and induces cytotoxicity against neuronal cells. Inhibition of Aβ aggregation by naturally occurring compounds is thus a promising strategy for the treatment of AD. We have already reported that caffeoylquinic acids and phenylethanoid glycosides, which possess two or more catechol moieties, strongly inhibited Aβ aggregation. Clovamide (1) containing two catechol moieties, isolated from cacao beans (Theobroma cacao L.), is believed to exhibit preventive effects on Aβ aggregation. To investigate the structure-activity relationship of clovamide (1) for the inhibition of Aβ aggregation, we synthesized 1 and related compounds 2–11 through reaction between l-DOPA, d-DOPA, l-tyrosine, or l-phenylalanine and caffeic acid, p-coumaric acid, or cinnamic acid, and compounds 12 and 13 were derived from 1. Among tested compounds 1–13, those containing one or two catechol moieties exhibited potent anti-aggregation activity, whereas the non-catechol-type related compounds showed little or no activity. This suggests that at least one catechol moiety is essential for inhibition of Aβ42 aggregation, and this activity increases depending on the number of catechol moieties. Consequently, clovamide (1) and its related compounds may be a promising therapeutic option for inhibiting Aβ-mediated pathology in AD.     

Structure–activity relationship of crustacean peptide hormones

In crustaceans, various physiological events, such as molting, vitellogenesis, and sex differentiation, are regulated by peptide hormones. To understanding the functional sites of these hormones, many structure–activity relationship (SAR) studies have been published. In this review, the author focuses the SAR of crustacean hyperglycemic hormone-family peptides and androgenic gland hormone and describes the detailed results of our and other research groups. The future perspectives will be also discussed.     

Structure-activity relationship of the 7-hydroxy benzimidazole analogs as glycogen synthase kinase 3β inhibitor

Design, synthesis and the GSK3β inhibitory activities of the 7-hydroxy benzimidazole analogs are described. The solid-phase synthetic route was also developed for preparation of the analogs consisting of the novel ATP competitive scaffold. In addition, the structure-activity relationship of the 7-hydroxy benzimidazole analogs and their biological activities are reported.     

Characterization of the Fourth α Isoform of the Na,K-ATPase

The Na,K-ATPase is a major ion transport protein found in higher eukaryotic cells. The enzyme is composed of two subunits, α and β, and tissue-specific isoforms exist for each of these, α1, α2 and α3 and β1, β2 and β3. We have proposed that an additional α isoform, α4, exists based on genomic and cDNA cloning. The mRNA for this gene is expressed in rats and humans, exclusively in the testis, however the expression of a corresponding protein has not been demonstrated. In the current study, the putative α4 isoform has been functionally characterized as a novel isoform of the Na,K-ATPase in both rat testis and in α4 isoform cDNA transfected 3T3 cells. Using an α4 isoform-specific polyclonal antibody, the protein for this novel isoform is detected for the first time in both rat testis and in transfected cell lines. Ouabain binding competition assays reveal the presence of high affinity ouabain receptors in both rat testis and in transfected cell lines that have identical K _D values. Further studies of this high affinity ouabain receptor show that it also has high affinities for both Na⁺ and K⁺. The results from these experiments definitively demonstrate the presence of a novel isoform of the Na,K-ATPase in testis. Received: 4 December 1998/Revised: 1 February 1999     

Isolation and amino acid sequence of a mating pheromone produced by mating type α cells of Saccharomyces exiguus

A peptide, termed α^se pheromone, was isolated as a mating pheromone from culture filtrate of mating type a cells of Saccharomyces exiguus. The peptide showed both agglutinability-inducing activity to a cells of S. cerevisiae and shmoo-inducing action to a cells of S. cerevisiae, S. kluyveri and S. exiguus. The amino acid sequence of α^se pheromone was determined as H-Trp-His-Trp-Leu-Arg-Leu-Ser-Tyr-Gly-Gln-Pro-Ile-Tyr-OH by mass spectrometry, sequence analysis and enzymatic digestion.     

Structure-activity relationship in the antitumor activity of 6-, 8- or 6,8-substituted 3-benzylamino-β-carboline derivatives

We synthesized 47 kinds of 3-amino- or 3-benzylamino-β-carboline derivatives with a substituent on the 6-, 8-, or 6,8-carbon atoms and evaluated their antitumor activities for Hela S-3 and Sarcoma 180 cell lines using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Consequently, we succeeded to develop 3-benzylamino-8-methylamino-β-carboline (17a) and 8-methylamino-3-(3-phenoxybenzyl)amino-β-carboline (17c) with antitumor activity with IC(50) values of 0.046, 0.032 μM, respectively, against HeLa S-3 cell line, which are higher than that of previously reported 3-(3-phenoxybenzyl)amino-β-carboline (10e) of 0.074 μM. Furthermore, effects of Cl group at 6-carbon atom on the type of cell death was evaluated using 3-benzylamino-6-chloro-β-carboline (10b), 3-benzylamino-β-carboline (10d), N-(3-benzylamino)-6-chloro-9H-β-carbolin-8-yl)benzamide (14g), and N-(3-benzylamino-9H-β-carbolin-8-yl)benzamide (17b) to show no effect. Hoechst 33342 staining and DNA fragmentation assay suggested that these compounds induced cell death by apoptosis. In addition, using flow cytometry analysis, we established that the cell death pathway was through the arrest of the cell cycle in the G(2)/M phase.     

Structure-activity relationship studies of sphingosine-1-phosphate receptor agonists with N-cinnamyl-β-alanine moiety

Structure-activity relationship of sphingosine-1-phosphate receptor agonist was examined. In terms of reducing the flexibility of molecule, hit compound 1 was modified to improve S1P₁ agonistic activity as well as selectivity over S1P₃ agonistic activity. Novel S1P agonists with cinnamyl scaffold or 1,2,5,6-tetrahydropyridine scaffold were identified.     

Na,K-ATPase and the role of α isoforms in behavior

The Na,K-ATPase is composed of multiple isoforms and the isoform distribution varies with the tissue and during development. The α1 isoform for example, is the major isoform in the kidney and many other tissues, while the α2 isoform is the predominate one in skeletal muscle. All three isoforms are found in the brain although in adult rodent brain, the α3 isoform is located essentially in neurons while the α2 isoform is found in astrocytes and some limited neuronal populations. Interestingly the α4 isoform is found exclusively in the mid region of the sperm tail. The distribution of the isoforms of the Na,K-ATPase has been extensively studied in many tissues and during development. The examples cited above provide some indication to the diversity of Na,K-ATPase isoform expression. In order to understand the significance of this distribution, we have developed animals which lack the α1, α2, and α3 isoforms. It is anticipated that these studies will provide insight into the role that these isoforms play in driving various biological processes in specific tissues. Here we describe some of our studies which deal with the behavioral aspects of the α1, α2, and α3 deficient mice, particularly those that are haploinsufficient in one isoform i.e. lacking one functional gene for the α1, α2, or α3 isoforms. Such studies are important as two human diseases are associated with deficiency in the α2 and α3 isoforms. These are Familial Hemiplegic Migraine type 2 and Rapid-Onset Dystonia Parkinsonism, these diseases result from α2 and α3 isoform haploinsufficiency, respectively. We find that the haploinsufficiency of both α2 and α3 isoforms result in behavioral defects.     

Structure-activity relationship studies of Bz amide-containing α-GalCer derivatives as natural killer T cell modulators

Abstract

CD1d is a non-polymorphic antigen-presenting glycoprotein that recognizes glycolipids as ligands. Ligands bind to the hydrophobic grooves of CD1d, and the resulting ligand-CD1d complexes activate natural killer T (NKT) cells by means of T cell receptor recognition, leading to the secretion of various cytokines. However, details of the ligand recognition mechanism of a large hydrophobic ligand binding pocket and the relationship between cytokine induction and ligand structure are unclear. We report the synthesis of α-GalCer derivatives containing a Bz amide group having various substituting groups in the ceramide moiety, and the analysis of the structure-activity relationships. The assays reveal that the Bz amide-containing CD1d ligands function as NKT cell modulators displaying Th2 cytokine biasing responses. Furthermore, molecular dynamics simulation studies suggest that the phenyl groups can interact with the aromatic amino acid residues in the lipid binding pocket of CD1d.     

Structure-activity relationship (SAR) of the α-amino acid residue of potent tetrahydroisoquinoline (THIQ)-derived LFA-1/ICAM-1 antagonists

This letter describes the structure-activity relationship (SAR) of the ‘right-wing’ α-amino acid residue of potent tetrahydroisoquinoline (THIQ)-derived LFA-1/ICAM-1 antagonists. Novel (S)-substituted heteroaryl-bearing α-amino acids have been identified as replacements of the ‘right-wing’ (S)-2,3-diaminopropanoic acid (DAP) moiety. Improvement of potency in the Hut-78 assay in the presence of 10% human serum has also been achieved.     

S-Glutathionylation of the Na,K-ATPase Catalytic α Subunit Is a Determinant of the Enzyme Redox Sensitivity

Na,K-ATPase is highly sensitive to changes in the redox state, and yet the mechanisms of its redox sensitivity remain unclear. We have explored the possible involvement of S-glutathionylation of the catalytic α subunit in redox-induced responses. For the first time, the presence of S-glutathionylated cysteine residues was shown in the α subunit in duck salt glands, rabbit kidneys, and rat myocardium. Exposure of the Na,K-ATPase to oxidized glutathione (GSSG) resulted in an increase in the number of S-glutathionylated cysteine residues. Increase in S-glutathionylation was associated with dose- and time-dependent suppression of the enzyme function up to its complete inhibition. The enzyme inhibition concurred with S-glutathionylation of the Cys-454, -458, -459, and -244. Upon binding of glutathione to these cysteines, the enzyme was unable to interact with adenine nucleotides. Inhibition of the Na,K-ATPase by GSSG did not occur in the presence of ATP at concentrations above 0.5 mm. Deglutathionylation of the α subunit catalyzed by glutaredoxin or dithiothreitol resulted in restoration of the Na,K-ATPase activity. Oxidation of regulatory cysteines made them inaccessible for glutathionylation but had no profound effect on the enzyme activity. Regulatory S-glutathionylation of the α subunit was induced in rat myocardium in response to hypoxia and was associated with oxidative stress and ATP depletion. S-Glutathionylation was followed by suppression of the Na,K-ATPase activity. The rat α2 isoform was more sensitive to GSSG than the α1 isoform. Our findings imply that regulatory S-glutathionylation of the catalytic subunit plays a key role in the redox-induced regulation of Na,K-ATPase activity.     

Structure-activity relationship study of a series of caspase inhibitors containing γ-amino acid moiety for treatment of cholestatic liver disease

A series of caspase inhibitors containing γ-amino acid moiety have been synthesized. A systemic study on their structure-activity relationship of anti-apoptotic cellular activity is presented. These efforts led to the discovery of compound 20o as a potent caspase inhibitor, which demonstrated preclinical ameliorating total bilirubin efficacy with a significantly improved pharmacokinetic profile.     

Structure-activity relationship of a series of non peptidic RGD integrin antagonists targeting α5β1: part 2

Potent antagonists of the integrin α(5)β(1), which are RGD mimetics built from tyrosine are described. This paper describes the optimization of in vitro potency obtained by variation of two parts of the molecule, the central aromatic core and the amide moiety.     

Evolution of the Metazoan-Specific Importin α Gene Family

Importin αs are import receptors for nuclear localization signal-containing proteins. Most animal importin αs assort into α1, α2, and α3 groups. Studies in Drosophila melanogaster, Caenorhabditis elegans, and mouse suggest that the animal importin α gene family evolved from ancestral plant-like genes to serve paralog-specific roles in gametogenesis. To explore this hypothesis we extended the phylogenetic analysis of the importin α gene family to nonbilateral animals and investigated whether animal-like genes occur in premetazoan taxa. Maximum likelihood analysis suggests that animal-like importin α genes occur in the Choanoflaggelate Monosiga brevicollis and the amoebozoan Dictyostelium; however, both of these results are caused by long-branch attraction effects. The absence of animal-like α genes in premetazoan taxa is consistent with the hypothesis that they duplicated and then specialized to function in animal gametogenesis. The gene structures of the importin αs provide insight into how the animal importin α gene family may have evolved from the most likely ancestral gene. Interestingly, animal α1s are more similar to plant and fungal α1-like sequences than they are to animal α2s or α3s. We show that animal α1 genes share most of their introns with plant α1-like genes, and α2s and α3s share many more intron positions with each other than with the α1s. Together, phylogenetics and gene structure analysis suggests a parsimonious path for the evolution of the mammalian importin α gene family from an ancestral α1-like progenitor. Finally, these results establish a rational basis for a unified nomenclature of the importin α gene family.     

Structure-activity relationship of a series of non peptidic RGD integrin antagonists targeting α5β1: part 1

Potent antagonists of the integrin α(5)β(1), which are RGD mimetics built from tyrosine are described. This letter describes the optimization of in vitro potency obtained by variation of two parts of the molecule, the basic group and the linker between the basic group and the phenyl central core.     

Expression of the α-subunit of glycoprotein hormones in the pars tuberalis-specific glandular cells in rat,mouse and guinea-pig

The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone -subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the -subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light-and electron-microscopic immunocytochemistry demonstrated -subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the -subunit of luteinizing hormone, an antibody that labelled scattered gonadotrops. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.     

Insights into the diversity of φRSM phages infecting strains of the phytopathogen Ralstonia solanacearum complex: regulation and evolution

The filamentous φRSM phages (φRSM1 and φRSM3) have integration/excision capabilities in the phytopathogenic bacterium Ralstonia solanacearum. In the present study, we further investigated φRSM-like sequences present in the genomes of R. solanacearum strains belonging to the four major evolutionary lineages (phylotypes I–IV). Based on bioinformatics and comparative genomic analyses, we found that φRSM homologs are highly diverse in R. solanacearum complex strains. We detected an open reading frame (ORF)15 located upstream of the gene for φRSM integrase, which exhibited amino acid sequence similarity to phage repressor proteins. ORF15-encoded protein (a putative repressor) was found to encode a 104-residue polypeptide containing a DNA-binding (helix-turn-helix) domain and was expressed in R. solanacearum lysogenic strains. This suggested that φRSM3-ORF15 might be involved in the establishment and maintenance of a lysogenic state, as well as in phage immunity. Comparison of the putative repressor proteins and their binding sites within φRSM-related prophages provides insights into how these regulatory systems of filamentous phages have evolved and diverged in the R. solanacearum complex. In conclusion, φRSM phages represent a unique group of filamentous phages that are equipped with innate integration/excision (ORF14) and regulatory systems (ORF15).