Pur‐alpha regulates RhoA developmental expression and downstream signaling

Pur‐alpha is an essential protein for postnatal brain development which localizes specifically to dendrites where it plays a role in the translation of neuronal RNA. Mice lacking Pur‐alpha display decreased neuronogenesis and impaired neuronal differentiation. Here we examined two Rho GTPases, Rac1 and RhoA, which play opposing roles in neurite outgrowth and are critical for dendritic maturation during mouse brain development in the presence and absence of Pur‐alpha. Pur‐alpha is developmentally regulated in the mouse brain with expression beginning shortly after birth and rapidly increasing to peak during the third week of postnatal development. RhoA levels analyzed by Western blotting rapidly fluctuated in the wild‐type mouse brain, however, in the absence of Pur‐alpha, a decrease in RhoA levels shortly after birth and a delay in the cycling of RhoA regulation was observed leading to reduced basal levels of RhoA after day 10 postnatal. Immunohistochemistry of brain tissues displayed reduced RhoA levels in the cortex and cerebellum and loss of perinuclear cytoplasmic labeling of RhoA within the cortex in the knockout mouse brain. While Rac1 levels remained relatively stable at all time points during development and were similar in both wild‐type and Pur‐alpha knockout mice, changes in subcellular localization of Rac1 were seen in the absence of Pur‐alpha. These findings suggest that Pur‐alpha can regulate RhoA at multiple levels including basal protein levels, subcellular compartmentalization, as well as turnover of active RhoA in order to promote dendritic maturation. J. Cell. Physiol. 228: 65–72, 2013. © 2012 Wiley Periodicals, Inc.     

5α‐Androst‐16‐en‐3α‐ol β‐D‐Glucuronide,Precursor of 5α‐Androst‐16‐en‐3α‐ol in Human Sweat

5α‐Androst‐16‐en‐3α‐ol (α‐androstenol) is an important contributor to human axilla sweat odor. It is assumed that α‐andostenol is excreted from the apocrine glands via a H₂O‐soluble conjugate, and this precursor was formally characterized in this study for the first time in human sweat. The possible H₂O‐soluble precursors, sulfate and glucuronide derivatives, were synthesized as analytical standards, i.e., α‐androstenol, β‐androstenol sulfates, 5α‐androsta‐5,16‐dien‐3β‐ol (β‐androstadienol) sulfate, α‐androstenol β‐glucuronide, α‐androstenol α‐glucuronide, β‐androstadienol β‐glucuronide, and α‐androstenol β‐glucuronide furanose. The occurrence of α‐androstenol β‐glucuronide was established by ultra performance liquid chromatography (UPLC)/MS (heated electrospray ionization (HESI)) in negative‐ion mode in pooled human sweat, containing eccrine and apocrine secretions and collected from 25 female and 24 male underarms. Its concentration was of 79 ng/ml in female secretions and 241 ng/ml in male secretions. The release of α‐androstenol was observed after incubation of the sterile human sweat or α‐androstenol β‐glucuronide with a commercial glucuronidase enzyme, the urine‐isolated bacteria Streptococcus agalactiae, and the skin bacteria Staphylococcus warneri DSM 20316, Staphylococcus haemolyticus DSM 20263, and Propionibacterium acnes ATCC 6919, reported to have β‐glucuronidase activities. We demonstrated that if α‐ and β‐androstenols and androstadienol sulfates were present in human sweat, their concentrations would be too low to be considered as potential precursors of malodors; therefore, the H₂O‐soluble precursor of α‐androstenol in apocrine secretion should be a β‐glucuronide.     

IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis

Inflammatory cytokines are closely related to pigmentary changes. In this study, the effects of IFN‐γ on melanogenesis were investigated. IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis in B16 melanoma cells and normal human melanocytes. MITF mRNA and protein expressions were significantly inhibited in response to IFN‐γ. IFN‐γ inhibited CREB binding to the MITF promoter but did not affect CREB phosphorylation. Instead, IFN‐γ inhibited the association of CBP and CREB through the increased association between CREB binding protein (CBP) and STAT1. These findings suggest that IFN‐γ inhibits both basal and α‐MSH‐induced melanogenesis by inhibiting MITF expression. The inhibitory action of IFN‐γ in α‐MSH‐induced melanogenesis is likely to be associated with the sequestration of CBP via the association between CBP and STAT1. These data suggest that IFN‐γ plays a role in controlling inflammation‐ or UV‐induced pigmentary changes.     

Novel renin inhibitors containing derivatives of N‐alkylleucyl‐β‐hydroxy‐γ‐amino acids

In search for new drugs lowering arterial blood pressure, which could be applied in anti‐hypertensive therapy, research concerning agents blocking of renin‐angiotensin‐aldosteron system has been conducted. Despite many years of research conducted at many research centers around the world, aliskiren is the only one renin inhibitor, which is used up to now. Four novel potential renin inhibitors, having structure based on the peptide fragment 8–13 of human angiotensinogen, a natural substrate for renin, were designed and synthesized. All these inhibitors contain unnatural moieties that are derivatives of N‐methylleucyl‐β‐hydroxy‐γ‐amino acids at the P₂‐P₁' position: 4‐[N‐(N‐methylleucyl)‐amino]‐3‐hydroxy‐7‐(3‐nitroguanidino)‐heptanoic acid (AHGHA), 4‐[N‐(N‐methylleucyl)‐amino]‐3‐hydroxy‐5‐phenyl‐pentanoic acid (AHPPA) or 4‐[N‐(N‐methylleucyl)‐amino]‐8‐benzyloxycarbonylamino‐3‐hydroxyoctanoic acid (AAHOA). The previously listed synthetic β‐hydroxy‐γ‐amino acids constitute pseudodipeptidic units that correspond to the P₁‐P₁' position of the inhibitor molecule. An unnatural amino acid, 4‐methoxyphenylalanin (Phe(4‐OMe)), was introduced at the P₃ position of the obtained compounds. Three of these compounds contain isoamylamide of 6‐aminohexanoic acid (ε‐Ahx‐Iaa) at the P₂'‐P₃' position. The proposed modifications of the selected human angiotensinogen fragment are intended to increase bioactivity, bioavailability, and stability of the inhibitor molecule in body fluids and tissues. The inhibitor Boc‐Phe(4‐OMe)‐MeLeu‐AHGHA‐OEt was obtained in the form of an ethyl ester. The hydrophobicity coefficient, expressed as log P varied between 3.95 and 8.17. In vitro renin inhibitory activity of all obtained compounds was contained within the range 10^?6‐10^?9 M. The compound Boc‐Phe(4‐OMe)‐MeLeu‐AHPPA‐Ahx‐Iaa proved to be the most active (IC₅₀ = 1.05 × 10^?9 M). The compounds Boc‐Phe(4‐OMe)‐MeLeu‐AHGHA‐Ahx‐Iaa and Boc‐Phe(4‐OMe)‐MeLeu‐AHPPA‐Ahx‐Iaa are resistant to chymotrypsin. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Syntheses and anti‐tubercular activity of β‐substituted and α,β‐disubstituted peptidyl β‐aminoboronates and boronic acids

Tuberculosis is still affecting millions of people worldwide, and new resistant strains of Mycobacterium tuberculosis are being found. It is therefore necessary to find new compounds for treatment. In this paper, we report the synthesis and in vitro testing of peptidyl β‐aminoboronic acids and β‐aminoboronates with anti‐tubercular activity. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Human α‐amino‐β‐carboxymuconate‐ε‐semialdehyde decarboxylase (ACMSD): A structural and mechanistic unveiling

Human α‐amino‐β‐carboxymuconate‐ε‐semialdehyde decarboxylase determines the fate of tryptophan metabolites in the kynurenine pathway by controlling the quinolinate levels for de novo nicotinamide adenine dinucleotide biosynthesis. The unstable nature of its substrate has made gaining insight into its reaction mechanism difficult. Our electron paramagnetic resonance (EPR) spectroscopic study on the Cu‐substituted human enzyme suggests that the native substrate does not directly ligate to the metal ion. Substrate binding did not result in a change of either the hyperfine structure or the super‐hyperfine structure of the EPR spectrum. We also determined the crystal structure of the human enzyme in its native catalytically active state (at 1.99 Å resolution), a substrate analogue‐bound form (2.50 Å resolution), and a selected active site mutant form with one of the putative substrate binding residues altered (2.32 Å resolution). These structures illustrate that each asymmetric unit contains three pairs of dimers. Consistent with the EPR findings, the ligand‐bound complex structure shows that the substrate analogue does not directly coordinate to the metal ion but is bound to the active site by two arginine residues through noncovalent interactions. Proteins 2015; 83:178–187. © 2014 Wiley Periodicals, Inc.     

Kappa opioids promote the proliferation of astrocytes via Gβγ and β‐arrestin 2‐dependent MAPK‐mediated pathways

GTP binding regulatory protein (G protein)‐coupled receptors can activate MAPK pathways via G protein‐dependent and ‐independent mechanisms. However, the physiological outcomes correlated with the cellular signaling events are not as well characterized. In this study, we examine the involvement of G protein and β‐arrestin 2 pathways in kappa opioid receptor‐induced, extracellular signal‐regulated kinase 1/2 (ERK1/2)‐mediated proliferation of both immortalized and primary astrocyte cultures. As different agonists induce different cellular signaling pathways, we tested the prototypic kappa agonist, U69593 as well as the structurally distinct, non‐nitrogenous agonist, C(2)‐methoxymethyl salvinorin B (MOM‐Sal‐B). In immortalized astrocytes, U69593, activated ERK1/2 by a rapid (min) initial stimulation that was sustained over 2 h and increased proliferation. Sequestration of activated Gβγ subunits attenuated U69593 stimulation of ERK1/2 and suppressed proliferation in these cells. Furthermore, small interfering RNA silencing of β‐arrestin 2 diminished sustained ERK activation induced by U69593. In contrast, MOM‐Sal‐B induced only the early phase of ERK1/2 phosphorylation and did not affect proliferation of immortalized astrocytes. In primary astrocytes, U69593 produced the same effects as seen in immortalized astrocytes. MOM‐Sal‐B elicited sustained ERK1/2 activation which was correlated with increased primary astrocyte proliferation. Proliferative actions of both agonists were abolished by either inhibition of ERK1/2, Gβγ subunits or β‐arrestin 2, suggesting that both G protein‐dependent and ‐independent ERK pathways are required for this outcome.     

Asymmetric Allylation of α‐Ketoester‐Derived N‐Benzoylhydrazones Promoted by Chiral Sulfoxides/N‐Oxides Lewis Bases: Highly Enantioselective Synthesis of Quaternary α‐Substituted α‐Allyl‐α‐Amino Acids

Chiral sulfoxides/N‐oxides (R)‐ 1 and (R,R)‐ 2 are effective chiral promoters in the enantioselective allylation of α‐keto ester N‐benzoylhydrazone derivatives 3a , 3b , 3c , 3d , 3e , 3f , 3g to generate the corresponding N‐benzoylhydrazine derivatives 4a , 4b , 4c , 4d , 4e , 4f , 4g , with enantiomeric excesses as high as 98%. Representative hydrazine derivatives 4a , 4b were subsequently treated with SmI₂, and the resulting amino esters 5a , 5b with LiOH to obtain quaternary α‐substituted α‐allyl α‐amino acids 6a , 6b , whose absolute configuration was assigned as (S), with fundament on chemical correlation and electronic circular dichroism (ECD) data. Chirality 25:529–540, 2013. © 2013 Wiley Periodicals, Inc.     

Solution properties of γ‐crystallins: Hydration of fish and mammal γ‐crystallins

Lens γ crystallins are found at the highest protein concentration of any tissue, ranging from 300 mg/mL in some mammals to over 1000 mg/mL in fish. Such high concentrations are necessary for the refraction of light, but impose extreme requirements for protein stability and solubility. γ‐crystallins, small stable monomeric proteins, are particularly associated with the lowest hydration regions of the lens. Here, we examine the solvation of selected γ‐crystallins from mammals (human γD and mouse γS) and fish (zebrafish γM2b and γM7). The thermodynamic water binding coefficient B₁ could be probed by sucrose expulsion, and the hydrodynamic hydration shell of tightly bound water was probed by translational diffusion and structure‐based hydrodynamic boundary element modeling. While the amount of tightly bound water of human γD was consistent with that of average proteins, the water binding of mouse γS was found to be relatively low. γM2b and γM7 crystallins were found to exhibit extremely low degrees hydration, consistent with their role in the fish lens. γM crystallins have a very high methionine content, in some species up to 15%. Structure‐based modeling of hydration in γM7 crystallin suggests low hydration is associated with the large number of surface methionine residues, likely in adaptation to the extremely high concentration and low hydration environment in fish lenses. Overall, the degree of hydration appears to balance stability and tissue density requirements required to produce and maintain the optical properties of the lens in different vertebrate species.     

Cholesterol‐β1AR interaction versus cholesterol‐β2AR interaction

Two 8‐µs all‐atom molecular dynamics simulations have been performed on the two highly homologous G protein‐coupled receptor (GPCR) subtypes, β₁‐ and β₂‐adrenergic receptors, which were embedded in a lipid bilayer with randomly dispersed cholesterol molecules. During the simulations, cholesterol molecules accumulate to different surface regions of the two receptors, suggesting the subtype specificity of cholesterol–β‐adrenergic receptor interaction and providing some clues to the physiological difference of the two subtypes. Meanwhile, comparison between the two receptors in interacting with cholesterols shed some new light on general determinants of cholesterol binding to GPCRs. Our results indicate that although the concave surface, charged residues and aromatic residues are important, neither of these stabilizing factors is indispensable for a cholesterol interaction site. Different combinations of these factors lead to the diversified binding modes of cholesterol binding to the receptors. Our long‐time simulations, for the first time, revealed the pathway of a cholesterol molecule entering the consensus cholesterol motif (CCM) site, and the binding process of cholesterol to CCM is accompanied by a side chain flipping of the conserved Trp4.50. Moreover, the simulation results suggest that the I‐/V‐/L‐rich region on the extracellular parts of helix 6 might be an alternatively conserved cholesterol‐binding site for the class‐A GPCRs. Proteins 2014; 82:760–770. © 2013 Wiley Periodicals, Inc.     

N‐terminal truncated pyroglutamyl β amyloid peptide Aβpy3‐42 shows a faster aggregation kinetics than the full‐length Aβ1‐42

We tested directly the differences in the aggregation kinetics of three important β amyloid peptides, the full‐length Aβ1‐42, and the two N‐terminal truncated and pyroglutamil modified Aβpy3‐42 and Aβpy11‐42 found in different relative concentrations in the brains in normal aging and in Alzheimer disease. By following the circular dichroism signal and the ThT fluorescence of the solution in phosphate buffer, we found substantially faster aggregation kinetics for Aβpy3‐42. This behavior is due to the particular sequence of this peptide, which is also responsible for the specific oligomeric aggregation states, found by TEM, during the fibrillization process, which are very different from those of Aβ1‐42, more prone to fibril formation. In addition, Aβpy3‐42 is found here to have an inhibitory effect on Aβ1‐42 fibrillogenesis, coherently with its known greater infective power. This is an indication of the important role of this peptide in the aggregation process of β‐peptides in Alzheimer disease. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 861–873, 2009. This article was originally published online as an accepted preprint. The “Published Online“ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Dehalogenation Activity of Selected Fungi Toward δ‐Iodo‐γ‐Lactone Derived from trans,trans‐Farnesol

Time‐course of biotransformation of racemic trans‐4‐((E)‐4′,8′‐dimethylnona‐3′,7′‐dien‐1‐yl)‐5‐iodomethyl‐4‐methyldihydrofuran‐2‐one ( 1 ) in fungal and yeast cultures was investigated. In these conditions, the substrate 1 was enantioselectively dehalogenated yielding 4‐((E)‐4′,8′‐dimethylnona‐3′,7′‐dien‐1‐yl)‐4‐methyl‐5‐methylenedihydrofuran‐2‐one ( 2 ) and its structure was established based on the spectroscopic data. The most effective biocatalyst used was Didymosphaeria igniaria, which catalyzed the process with highest rate and enantioselectivity (ee of product = 76%). The antiproliferative activity of δ‐iodo‐γ‐lactone 1 , product of its biotransformation 2 , and starting substrate (farnesol) were evaluated toward two cancer cell lines: A549 (human lung adenocarcinoma) and HL‐60 (human promyelocytic leukemia).     

Integrin αvβ3 enhances the suppressive effect of interferon‐γ on hematopoietic stem cells

Hematopoietic homeostasis depends on the maintenance of hematopoietic stem cells (HSCs), which are regulated within a specialized bone marrow (BM) niche. When HSC sense external stimuli, their adhesion status may be critical for determining HSC cell fate. The cell surface molecule, integrin αvβ3, is activated through HSC adhesion to extracellular matrix and niche cells. Integrin β3 signaling maintains HSCs within the niche. Here, we showed the synergistic negative regulation of the pro‐inflammatory cytokine interferon‐γ (IFNγ) and β3 integrin signaling in murine HSC function by a novel definitive phenotyping of HSCs. Integrin αvβ3 suppressed HSC function in the presence of IFNγ and impaired integrin β3 signaling mitigated IFNγ‐dependent negative action on HSCs. During IFNγ stimulation, integrin β3 signaling enhanced STAT1‐mediated gene expression via serine phosphorylation. These findings show that integrin β3 signaling intensifies the suppressive effect of IFNγ on HSCs, which indicates that cell adhesion via integrin αvβ3 within the BM niche acts as a context‐dependent signal modulator to regulate the HSC function under both steady‐state and inflammatory conditions.