Identification of ciliary neurotrophic factor receptor α as a mediator of neurotoxicity induced by α‐synuclein

Accumulating evidence suggests that extracellular α‐synuclein (eSNCA) plays an important role in the pathogenesis of Parkinson's disease or related synucleinopathies by inducing neurotoxicity directly or indirectly via microglial or astroglial activation. However, the mechanisms by which this occurs remain to be characterized. To explore these mechanisms, we combined three biochemical techniques – stable isotope labeling of amino acid in cell cultures (SILAC), biotin labeling of plasma membrane proteins followed by affinity purification, and analysis of unique proteins binding to SNCA peptides on membrane arrays. The SILAC proteomic analysis identified 457 proteins, of which, 245 or 172 proteins belonged to membrane or membrane associated proteins, depending on the various bioinformatics tools used for interpretation. In dopamine neuronal cells treated with eSNCA, the levels of 86 membrane proteins were increased and 35 were decreased compared with untreated cells. In peptide array analysis, 127 proteins were identified as possibly interacting with eSNCA. Of those, seven proteins were overlapped with the membrane proteins that displayed alterations in relative abundance after eSNCA treatment. One was ciliary neurotrophic factor receptor, which appeared to modulate eSNCA‐mediated neurotoxicity via mechanisms related to JAK1/STAT3 signaling but independent of eSNCA endocytosis.     

The expression of α2β1 integrin and α smooth muscle actin in fibroblasts grown on collagen

The maturation of connective tissue involves the organization of collagen fibres by resident fibroblasts. Fibroblast attachment to collagen has been demonstrated to involve cell surface receptors, integrins of the β₁ family. Integrins are associated with cytoplasmic actin of microfilaments either directly or through focal adhesions. The major actin isoform of fibroblast microfilaments is β actin and to a lesser extent α smooth muscle (α SM) actin. Cultured human dermal fibroblasts derived from adult dermis, newborn foreskin or keloid scar were grown on either uncoated or collagen-coated surfaces. The expression and synthesis of both α₂β₁ integrin and α SM actin were followed by immunohistology and immunoprecipitation. Fibroblasts on uncoated surfaces expressed little α₂β₁ integrin on their surface, while 20 per cent of them demonstrated α SM actin within microfilaments. Fibroblasts grown on a collagen-coated surface minimally expressed α SM actin in microfilament structures and a majority of the cells were positive for α₂β₁ integrin on their membranes. Using [³⁵S]-methionine incorporation and immunoprecipitation, it was shown that fibroblasts grown in uncoated dishes synthesized more α SM actin than fibroblasts grown on collagen-coated dishes. In contrast, fibroblasts grown on collagen coated dishes synthesized more α₂β₁ integrin compared to the same cells grown on uncoated dishes. Fibroblasts maintained on a type I collagen upregulate the expression and synthesis of α₂β₁ integrin, and downregulate the expression and synthesis of α SM actin. © 1998 John Wiley & Sons, Ltd.     

The mesenchymal α11β1 integrin attenuates PDGF-BB-stimulated chemotaxis of embryonic fibroblasts on collagens

α11β1 constitutes the most recent addition to the integrin family and has been shown to display a binding preference for interstitial collagens found in mesenchymal tissues. We have previously observed that when α11β1 integrin is expressed in cells lacking endogenous collagen receptors, it can mediate PDGF-BB-dependent chemotaxis on collagen I in vitro. To determine in which cells PDGF and α11β1 might cooperate in regulating cell migration in vivo, we studied in detail the expression and distribution of α11 integrin chain in mouse embryos and tested the ability of PDGF isoforms to stimulate the α11β1-mediated cell migration of embryonic fibroblasts.Full-length mouse α11 cDNA was sequenced and antibodies were raised to deduced α11 integrin amino acid sequence. In the embryonic mouse head, α11 protein and RNA were localized to ectomesenchymally derived cells. In the periodontal ligament, α11β1 was expressed as the only detectable collagen-binding integrin, and α11β1 is thus a major receptor for cell migration and matrix organization in this cell population. In the remainder of the embryo, the α11 chain was expressed in a subset of mesenchymal cells including tendon/ligament fibroblasts, perichondrial cells, and intestinal villi fibroblasts. Most of the α11-expressing cells also expressed the α2 integrin chain, but no detectable overlap was found with the α1 integrin chain. In cells expressing multiple collagen receptors, these might function to promote a more stable cell adhesion and render the cells more resistant to chemotactic stimuli.Wild-type embryonic fibroblasts activated mainly the PDGF β receptor in response to PDGF-BB and migrated on collagens I, II, III, IV, V, and XI in response to PDGF-BB in vitro, whereas mutant fibroblasts that lacked α11β1 in their collagen receptor repertoire showed a stronger chemotactic response on collagens when stimulated with PDGF-BB. In the cellular context of embryonic fibroblasts, α11β1 is thus anti-migratory.We speculate that the PDGF BB-dependent cell migration of mesenchymal cells is tightly regulated by the collagen receptor repertoire, and disturbances of this repertoire might lead to unregulated cell migration that could affect normal embryonic development and tissue structure.     

Induction of mouse β integrin expression following transfection with human α4 chain

We report here an analysis of the expression and function of the α chain of human VLA-4 in stable mouse L cell transfectants and the requirement for the β chain in these processes. L cells were transfected with human α4 cDNA or α4 and human β1 cDNA. Unexpectedly, human α4 cDNA, when transfected alone, could induce de novo surface expression of host β7 and increased expression of host β1. Induction of mouse β7 and β1 surface expression was not due to de novo gene activation, but instead represented α4/β intracellular subunit association and transport to the cell surface. Transfection with human β1 prevented surface expression of mouse β integrins. Whereas human α4 and human β1 subunits associated very tightly in anti-α4 immunoprecipitates, human α4 and mouse β subunits were only partially associated. Furthermore, binding of human/mouse chimeric receptors to recombinant VCAM, a major ligand for α4β7 and α4β1, was very poor, whereas human α4/human β1 receptors bound strongly to VCAM. One α4 transfectant, which exhibited a tight human α4/mouse β1 association, could be induced, but only after PMA activation, to bind strongly to VCAM. These results indicate that α4 subunits have specific affinity for β7 and β1 integrins and require β subunits for surface expression as well as high affinity ligand binding activity. Our results indicate that a tight association between the α4 and β subunit appears to be critical for ligand binding, consistent with a direct as well as regulatory role for the β subunit in ligand binding. Furthermore, these studies demonstrate that expression of foreign recombinant proteins can alter host cell protein expression resulting in de novo surface protein expression. © 1996 Wiley-Liss, Inc.     

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.     

Studies on the 5α-androstane-3β, 17β-diol-6α-hydroxylase and on the 5α-androstane-3β, 17β-diol-7α-hydroxylase in anterior hypophysis of male rats.

In anterior pituitaries from male rats, it appeared that 5α-androstane-3β, 17β-diol was quickly metabolized into 5α-androstane-3β,6α-17β-triol and 5α-androstane-3β,7α, 17β-triol by action of 6α- and 7α-hydroxylases. Hydroxysteroid hydroxylases were located in endoplasmic reticulum and were dependent on NADPH⁺. Their optimum pH was 8.0, optima temperature, 37°C, and their apparent Km was 2.7 μM. Hydroxylative reactions were not reversible and not modified by gonadectomy. Hydroxylation seemed an efficient control of the pituitary level of 5α-andros-tane-3β, 17β-diol.     

DIGESTION IN ADULT FEMALES OF THE LEAF‐FOOTED BUG Leptoglossus zonatus (HEMIPTERA: COREIDAE) WITH EMPHASIS ON THE GLYCOSIDE HYDROLASES α‐AMYLASE, α‐GALACTOSIDASE,AND α‐GLUCOSIDASE

The leaffooted bug, Leptoglossus zonatus (Hemiptera: Coreidae) is an emerging pest of several crops around the World and up to now very little is known of its digestive system. In this article, glycoside hydrolase (carbohydrase) activities in the adult midgut cells and in the luminal contents of L. zonatus adult females were studied. The results showed the distribution of digestive carbohydrases in adults of this heteropteran species in the different intestinal compartments. Determination of the spatial distribution of α‐glucosidase activity in L. zonatus midgut showed only one major molecular form, which was not equally distributed between soluble and membrane‐bound isoforms, being more abundant as a membrane‐bound enzyme. The majority of digestive carbohydrases were found in the soluble fractions. Activities against starch, maltose and the synthetic substrate NPαGlu were found to show the highest levels of activity, followed by enzymes active against galactosyl oligosaccharides. Based on ion‐exchange chromatography elution profiles and banding patterns in mildly denaturing electrophoresis, both midgut α‐amylases and α‐galactosidases showed at least two isoforms. The data suggested that the majority of carbohydrases involved in initial digestion were present in the midgut lumen, whereas final digestion of starch and of galactosyl oligosaccharides takes place partially within the lumen and partially at the cell surface. The complex of carbohydrases here described was qualitatively appropriate for the digestion of free oligosaccharides and oligomaltodextrins released by α‐amylases acting on maize seed starch granules.     

Conformations of peptides containing a chiral cyclic α, α‐disubstituted α‐amino acid within the sequence of Aib residues

A single chiral cyclic α,α‐disubstituted amino acid, (3S,4S)‐1‐amino‐(3,4‐dimethoxy)cyclopentanecarboxylic acid [(S,S)‐Ac₅c^dOM], was placed at the N‐terminal or C‐terminal positions of achiral α‐aminoisobutyric acid (Aib) peptide segments. The IR and ¹H NMR spectra indicated that the dominant conformations of two peptides Cbz‐[(S,S)‐Ac₅c^dOM]‐(Aib)₄‐OEt ( 1) and Cbz‐(Aib)₄‐[(S,S)‐Ac₅c^dOM]‐OMe (2) in solution were helical structures. X‐ray crystallographic analysis of 1 and 2 revealed that a left‐handed (M) 3₁₀‐helical structure was present in 1 and that a right‐handed (P) 3₁₀‐helical structure was present in 2 in their crystalline states. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Selection and structural analysis of de novo proteins from an α3β3 genetic library

The construction of novel functional proteins has been a key area of protein engineering. However, there are few reports of functional proteins constructed from artificial scaffolds. Here, we have constructed a genetic library encoding α3β3 de novo proteins to generate novel scaffolds in smaller size using a binary combination of simplified hydrophobic and hydrophilic amino acid sets. To screen for folded de novo proteins, we used a GFP‐based screening system and successfully obtained the proteins from the colonies emitting the very bright fluorescence as a similar intensity of GFP. Proteins isolated from the very bright colonies (vTAJ) and bright colonies (wTAJ) were analyzed by circular dichroism (CD), 8‐anilino‐1‐naphthalenesulfonate (ANS) binding assay, and analytical size‐exclusion chromatography (SEC). CD studies revealed that vTAJ and wTAJ proteins had both α‐helix and β‐sheet structures with thermal stabilities. Moreover, the selected proteins demonstrated a variety of association states existing as monomer, dimer, and oligomer formation. The SEC and ANS binding assays revealed that vTAJ proteins tend to be a characteristic of the folded protein, but not in a molten‐globule state. A vTAJ protein, vTAJ13, which has a packed globular structure and exists as a monomer, was further analyzed by nuclear magnetic resonance. NOE connectivities between backbone signals of vTAJ13 suggested that the protein contains three α‐helices and three β‐strands as intended by its design. Thus, it would appear that artificially generated α3β3 de novo proteins isolated from very bright colonies using the GFP fusion system exhibit excellent properties similar to folded proteins and would be available as artificial scaffolds to generate functional proteins with catalytic and ligand binding properties.     

Engineering the serpin α1‐antitrypsin: A diversity of goals and techniques

α₁‐Antitrypsin (α₁‐AT) serves as an archetypal example for the serine proteinase inhibitor (serpin) protein family and has been used as a scaffold for protein engineering for >35 years. Techniques used to engineer α₁‐AT include targeted mutagenesis, protein fusions, phage display, glycoengineering, and consensus protein design. The goals of engineering have also been diverse, ranging from understanding serpin structure–function relationships, to the design of more potent or more specific proteinase inhibitors with potential therapeutic relevance. Here we summarize the history of these protein engineering efforts, describing the techniques applied to engineer α₁‐AT, specific mutants of interest, and providing an appended catalog of the >200 α₁‐AT mutants published to date.     

Alanine substitutions of noncysteine residues in the cysteine‐stabilized αβ motif

The protein scaffold is a peptide framework with a high tolerance of residue modifications. The cysteine‐stabilized αβ motif (CSαβ) consists of an α‐helix and an antiparallel triple‐stranded β‐sheet connected by two disulfide bridges. Proteins containing this motif share low sequence identity but high structural similarity and has been suggested as a good scaffold for protein engineering. The Vigna radiate defensin 1 (VrD1), a plant defensin, serves here as a model protein to probe the amino acid tolerance of CSαβ motif. A systematic alanine substitution is performed on the VrD1. The key residues governing the inhibitory function and structure stability are monitored. Thirty‐two of 46 residue positions of VrD1 are altered by site‐directed mutagenesis techniques. The circular dichroism spectrum, intrinsic fluorescence spectrum, and chemical denaturation are used to analyze the conformation and structural stability of proteins. The secondary structures were highly tolerant to the amino acid substitutions; however, the protein stabilities were varied for each mutant. Many mutants, although they maintained their conformations, altered their inhibitory function significantly. In this study, we reported the first alanine scan on the plant defensin containing the CSαβ motif. The information is valuable to the scaffold with the CSαβ motif and protein engineering.     

Amyloid β‐induced astrogliosis is mediated by β1‐integrin via NADPH oxidase 2 in Alzheimer's disease

Astrogliosis is a hallmark of Alzheimer′s disease (AD) and may constitute a primary pathogenic component of that disorder. Elucidation of signaling cascades inducing astrogliosis should help characterizing the function of astrocytes and identifying novel molecular targets to modulate AD progression. Here, we describe a novel mechanism by which soluble amyloid‐β modulates β1‐integrin activity and triggers NADPH oxidase (NOX)‐dependent astrogliosis in vitro and in vivo. Amyloid‐β oligomers activate a PI3K/classical PKC/Rac1/NOX pathway which is initiated by β1‐integrin in cultured astrocytes. This mechanism promotes β1‐integrin maturation, upregulation of NOX2 and of the glial fibrillary acidic protein (GFAP) in astrocytes in vitro and in hippocampal astrocytes in vivo. Notably, immunochemical analysis of the hippocampi of a triple‐transgenic AD mouse model shows increased levels of GFAP, NOX2, and β1‐integrin in reactive astrocytes which correlates with the amyloid β‐oligomer load. Finally, analysis of these proteins in postmortem frontal cortex from different stages of AD (II to V/VI) and matched controls confirmed elevated expression of NOX2 and β1‐integrin in that cortical region and specifically in reactive astrocytes, which was most prominent at advanced AD stages. Importantly, protein levels of NOX2 and β1‐integrin were significantly associated with increased amyloid‐β load in human samples. These data strongly suggest that astrogliosis in AD is caused by direct interaction of amyloid β oligomers with β1‐integrin which in turn leads to enhancing β1‐integrin and NOX2 activity via NOX‐dependent mechanisms. These observations may be relevant to AD pathophysiology.     

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.     

Enantiodifferentiation of α‐hydroxyalkanephosphonic acids in 31P NMR with application of α‐cyclodextrin as chiral discriminating agent

α‐Cyclodextrin was shown to be convenient chemical shift reagent for determination of the enantiomeric composition of α‐hydroxyphosphonic acids by means of ³¹P NMR. The developed methodology appeared to be reliable, repetitive, easy to perform and simple for interpretation. Enantiomeric discrimination in the ³¹P NMR spectra for 12 of 13 studied hydroxyphosphonates was achieved, with baseline separation of resonances obtained for eight compounds. In those cases, the chemical nonequivalence values ranged from 0.069 to 0.313 ppm. The studies showed that enantioselectivity is strongly influenced by the solution pD and the optimal condition was found at pD 2 or 10 depending on the guest structure. On the basis of the ROESY spectra the complexation modes of selected hydroxyphosphonates with α‐cyclodextrin was postulated. Chirality 2010. © 2009 Wiley‐Liss, Inc.     

Folding type-specific secondary structure propensities of amino acids,derived from α-helical, β-sheet, α/β, and α+β proteins of known structures

Folding type-specific secondary structure propensities of 20 naturally occurring amino acids have been derived from α-helical, β-sheet, α/β, and α+β proteins of known structures. These data show that each residue type of amino acids has intrinsic propensities in different regions of secondary structures for different folding types of proteins. Each of the folding types shows markedly different rank ordering, indicating folding type-specific effects on the secondary structure propensities of amino acids. Rigorous statistical tests have been made to validate the folding type-specific effects. It should be noted that α and β proteins have relatively small α-helices and β-strands forming propensities respectively compared with those of α+β and α/β proteins. This may suggest that, with more complex architectures than α and β proteins, α+β and α/β proteins require larger propensities to distinguish from interacting α-helices and β-strands. Our finding of folding type-specific secondary structure propensities suggests that sequence space accessible to each folding type may have differing features. Differing sequence space features might be constrained by topological requirement for each of the folding types. Almost all strong β-sheet forming residues are hydrophobic in character regardless of folding types, thus suggesting the hydrophobicities of side chains as a key determinant of β-sheet structures. In contrast, conformational entropy of side chains is a major determinant of the helical propensities of amino acids, although other interactions such as hydrophobicities and charged interactions cannot be neglected. These results will be helpful to protein design, class-based secondary structure prediction, and protein folding. © 1998 John Wiley & Sons, Inc. Biopoly 45: 35–49, 1998