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61.
62.
Teng YK Verburg RJ Verpoort KN Diepenhorst GM Bajema IM van Tol MJ Jol-van der Zijde EC Toes RE Huizinga TW van Laar JM 《Arthritis research & therapy》2007,9(5):R106
In order to identify pathogenic correlates of refractory rheumatoid arthritis (RA), antibodies against anti-cyclic citrullinated
protein (ACPAs) were investigated in RA patients in whom the dysregulated immune system had been ablated by high-dose chemotherapy
(HDC) and autologous haematopoietic stem cell transplantation (HSCT). Six patients with refractory RA were extensively characterized
in terms of levels of total immunoglobulins, RA-specific autoantibodies (ACPAs and rheumatoid factor) and antibodies against
rubella, tetanus toxoid (TT) and phosphorylcholine before and after HDC plus HSCT. Additionally, the avidity of ACPAs was
measured before and after treatment and compared with the avidity of TT antibodies following repeated immunizations. Synovial
biopsies were obtained by arthroscopy before HDC plus HSCT, and analyzed by immunohistochemistry. In the three patients with
clinically long-lasting responses to HDC plus HSCT (median 423 days), significant reductions in ACPA-IgG levels after therapy
were observed (median level dropped from 215 to 34 arbitrary units/ml; P = 0.05). In contrast, stable ACPA-IgG levels were observed in three patients who relapsed shortly after HDC plus HSCT (median
of 67 days). Clinical responders had ACPA-IgG of lower avidity (r = 0.75; P = 0.08) and higher degree of inflammation histologically (r = 0.73; P = 0.09). Relapse (after 38 to 530 days) in all patients was preceded by rising levels of low avidity ACPA-IgG (after 30 to
388 days), in contrast to the stable titres of high avidity TT antibodies. In conclusion, humoral autoimmune responses were
differentially modulated by immunoablative therapy in patients with synovial inflammation and low avidity ACPA-IgG autoantibodies
as compared with patients with high levels of high avidity ACPA-IgG. The distinct clinical disease course after immunoablative
therapy based on levels and avidity of ACPA-IgG indicates that refractory RA is not a single disease entity. 相似文献
63.
Mikio Kato Robert Blanton Guang-Rong Wang Timothy J. Judson Yuich Abe Masafumi Myoishi Richard H. Karas Michael E. Mendelsohn 《The Journal of biological chemistry》2012,287(49):41342-41351
Vascular smooth muscle cell (VSMC) tone is regulated by the state of myosin light chain (MLC) phosphorylation, which is in turn regulated by the balance between MLC kinase and MLC phosphatase (MLCP) activities. RhoA activates Rho kinase, which phosphorylates the regulatory subunit of MLC phosphatase, thereby inhibiting MLC phosphatase activity and increasing contraction and vascular tone. Nitric oxide is an important mediator of VSMC relaxation and vasodilation, which acts by increasing cyclic GMP (cGMP) levels in VSMC, thereby activating cGMP-dependent protein kinase Iα (PKGIα). PKGI is known to phosphorylate Rho kinase, preventing Rho-mediated inhibition of MLC phosphatase, promoting vasorelaxation, although the molecular mechanisms that mediate this are unclear. Here we identify RhoA as a target of activated PKGIα and show further that PKGIα binds directly to RhoA, inhibiting its activation and translocation. In protein pulldown and immunoprecipitation experiments, binding of RhoA and PKGIα was demonstrated via a direct interaction between the amino terminus of RhoA (residues 1–44), containing the switch I domain of RhoA, and the amino terminus of PKGIα (residues 1–59), which includes a leucine zipper heptad repeat motif. Affinity assays using cGMP-immobilized agarose showed that only activated PKGIα binds RhoA, and a leucine zipper mutant PKGIα was unable to bind RhoA even if activated. Furthermore, a catalytically inactive mutant of PKGIα bound RhoA but did not prevent RhoA activation and translocation. Collectively, these results support that RhoA is a PKGIα target and that direct binding of activated PKGIα to RhoA is central to cGMP-mediated inhibition of the VSMC Rho kinase contractile pathway. 相似文献
64.
Lapinsky DJ Aggarwal S Nolan TL Surratt CK Lever JR Acharya R Vaughan RA Pandhare A Blanton MP 《Bioorganic & medicinal chemistry letters》2012,22(1):523-526
Towards addressing the knowledge gap of how bupropion interacts with the dopamine transporter (DAT) and nicotinic acetylcholine receptors (nAChRs), a ligand was synthesized in which the chlorine of bupropion was isosterically replaced with an iodine and a photoreactive azide was added to the 4'-position of the aromatic ring. Analog (±)-3 (SADU-3-72) demonstrated modest DAT and α4β2 nAChR affinity. A radioiodinated version was shown to bind covalently to hDAT expressed in cultured cells and affinity-purified, lipid-reincorporated human α4β2 neuronal nAChRs. Co-incubation of (±)-[(125)I]-3 with non-radioactive (±)-bupropion or (-)-cocaine blocked labeling of these proteins. Compound (±)-[(125)I]-3 represents the first successful example of a DAT and nAChR photoaffinity ligand based on the bupropion scaffold. Such ligands are expected to assist in mapping bupropion-binding pockets within plasma membrane monoamine transporters and ligand-gated nAChR ion channels. 相似文献
65.
Shouryadeep Srivastava Ayman K. Hamouda Akash Pandhare Phaneendra K. Duddempudi Mitesh Sanghvi Jonathan B. Cohen Michael P. Blanton 《The Journal of biological chemistry》2009,284(37):24939-24947
Nicotinic acetylcholine receptor (nAChR) agonists, such as epibatidine and its molecular derivatives, are potential therapeutic agents for a variety of neurological disorders. In order to identify determinants for subtype-selective agonist binding, it is important to determine whether an agonist binds in a common orientation in different nAChR subtypes. To compare the mode of binding of epibatidine in a muscle and a neuronal nAChR, we photolabeled Torpedo α2βγδ and expressed human α4β2 nAChRs with [3H]epibatidine and identified by Edman degradation the photolabeled amino acids. Irradiation at 254 nm resulted in photolabeling of αTyr198 in agonist binding site Segment C of the principal (+) face in both α subunits and of γLeu109 and γTyr117 in Segment E of the complementary (−) face, with no labeling detected in the δ subunit. For affinity-purified α4β2 nAChRs, [3H]epibatidine photolabeled α4Tyr195 (equivalent to Torpedo αTyr190) in Segment C as well as β2Val111 and β2Ser113 in Segment E (equivalent to Torpedo γLeu109 and γTyr111, respectively). Consideration of the location of the photolabeled amino acids in homology models of the nAChRs based upon the acetylcholine-binding protein structure and the results of ligand docking simulations suggests that epibatidine binds in a single preferred orientation within the α-γ transmitter binding site, whereas it binds in two distinct orientations in the α4β2 nAChR.Nicotinic acetylcholine receptors (nAChRs)3 are prototypical members of the Cys loop superfamily of neurotransmitter-gated ion channels that mediate the actions of the neurotransmitter acetylcholine (1). nAChRs from vertebrate skeletal muscle and the electric organs of Torpedo rays are heteropentamers of homologous subunits with a stoichiometry of 2α:β:γ(ϵ):δ that are arranged pseudosymmetrically around central cation-selective ion channels (1, 2). There are 12 mammalian neuronal nAChR subunit genes: nine neuronal α subunits (α2–α10) and three neuronal β subunits (β2–β4). The α4β2 nAChR is the most abundant and widely distributed nAChR subtype expressed in the brain and is a major target for potential therapeutic agents for neurological diseases and conditions, including nicotine dependence and Alzheimer and Parkinson diseases (3, 4). Although the ratio of α4 to β2 subunit in vivo is uncertain, expressed receptors containing either three α4 or three β2 subunits have distinct pharmacological properties (5, 6).The agonist binding sites (ABS) of nAChRs are located within the amino-terminal extracellular domain at the interface of adjacent subunits (α-γ and α-δ in the Torpedo nAChR), and different nAChR subunit combinations form ABS with distinct physical and pharmacological properties (3, 7). Affinity labeling studies with Torpedo nAChR and site-directed mutational analyses of muscle and neuronal nAChRs identified key amino acids delineating the ABS from three noncontiguous stretches of the α subunit (Segments A-C, the principal component (+ face)) and three noncontiguous regions of the non-α subunit (Segments D–F, the complementary component (− face)) (8, 9). The three-dimensional structure of the ABS in the absence and presence of nAChR agonists or competitive antagonists has been determined for snail acetylcholine-binding proteins (AChBPs) that are soluble homopentamers homologous to the extracellular (amino-terminal) domain of a nAChR (10–12). In the AChBP, four aromatic amino acids from Segments A–C that are conserved within α subunits, along with a conserved Trp in Segment D, form a core aromatic “pocket” with a dimension optimal for accommodation of a trimethylammonium group. The other amino acids in the non-α subunits closest to the aromatic pocket, which are generally not conserved among γ, δ, or neuronal β subunits, are on three antiparallel β strands. The AChBP structure was used to refine the structure of the Torpedo nAChR in the absence of agonist to 4 Å resolution (13). In this structure, there is a reorientation of Segments A–C, resulting in the absence of a well defined core aromatic binding pocket.Analysis of agonist interactions with mutant nAChRs containing fluorine-substituted core aromatic residues provides evidence that cation-π interactions, particularly with αTrp149 in Segment B, are important determinants of agonist binding affinity (14) and for the higher affinity binding of nicotine to α4β2 nAChRs compared with α2βγδ nAChRs (15). Mutational analyses and molecular docking calculations have also provided evidence that two molecules of very similar structure may actually bind to a single receptor in very different orientations, as seen for two high affinity antagonists, d-tubocurarine and its quaternary ammonium analog metocurine, binding to the AChBP and to the muscle nAChR (16, 17).Photoaffinity labeling provides an alternative means to identify amino acids contributing to a drug binding site (18, 19) and has been used to determine the orientation of drugs bound in the ABS of Torpedo nAChR (20). Epibatidine binds with very high affinity (∼10 pm) to heteromeric neuronal nAChRs (e.g. α4β2) and with nanomolar affinity to α7 and muscle-type/Torpedo nAChRs (3). Utilizing a photoreactive analogue of epibatidine (azidoepibatidine; Fig. 1) and mass spectrometry, Tomizawa et al. (21) identified photolabeled amino acids in the Aplysia AChBP (Tyr195 in Segment C and Met116 in Segment E), establishing an orientation for bound azidoepibatidine consistent with the orientation of epibatidine in an AChBP crystal structure (12).Open in a separate windowFIGURE 1.Structure of [3H]epibatidine (top) and azidoepibatidine (bottom).In this report, we use [3H]epibatidine as a photoaffinity reagent to identify the amino acids photolabeled in an expressed α4β2 nAChR and in the Torpedo α2βγδ nAChR. Comparisons of the labeled amino acids seen in the Torpedo nAChR α-γ binding site and in the α4β2 nAChR, in conjunction with the results of docking calculations for epibatidine binding to homology models of the α2βγδ and α4β2 nAChRs, suggests that epibatidine binds in a single orientation in the α-γ site but in two orientations in the α4β2 ABS. 相似文献
66.
Blanton S. Tolbert Yasuyuki Miyazaki Shawn Barton Benyam Kinde Patrice Starck Rashmi Singh Ad Bax David A. Case Michael F. Summers 《Journal of biomolecular NMR》2010,47(3):205-219
Ribonucleic acid structure determination by NMR spectroscopy relies primarily on local structural restraints provided by 1H–
1H NOEs and J-couplings. When employed loosely, these restraints are broadly compatible with A- and B-like helical geometries
and give rise to calculated structures that are highly sensitive to the force fields employed during refinement. A survey
of recently reported NMR structures reveals significant variations in helical parameters, particularly the major groove width.
Although helical parameters observed in high-resolution X-ray crystal structures of isolated A-form RNA helices are sensitive
to crystal packing effects, variations among the published X-ray structures are significantly smaller than those observed
in NMR structures. Here we show that restraints derived from aromatic 1H–
13C residual dipolar couplings (RDCs) and residual chemical shift anisotropies (RCSAs) can overcome NMR restraint and force
field deficiencies and afford structures with helical properties similar to those observed in high-resolution X-ray structures. 相似文献
67.
Arun Kumar Maheswara R. Duvvari Venkatesh C. Prabhakaran Jyoti S. Shetty Gowri J. Murthy Susan H. Blanton 《Human genetics》2010,128(4):365-371
Microspherophakia is an autosomal-recessive congenital disorder characterized by small spherical lens. It may be isolated
or occur as part of a hereditary systemic disorder, such as Marfan syndrome, autosomal dominant and recessive forms of Weill-Marchesani
syndrome, autosomal dominant glaucoma–lens ectopia–microspherophakia–stiffness–shortness syndrome, autosomal dominant microspherophakia
with hernia, and microspherophakia-metaphyseal dysplasia. The purpose of this study was to map and identify the gene for isolated
microspherophakia in two consanguineous Indian families. Using a whole-genome linkage scan in one family, we identified a
likely locus for microspherophakia (MSP1) on chromosome 14q24.1–q32.12 between markers D14S588 and D14S1050 in a physical
distance of 22.76 Mb. The maximum multi-point lod score was 2.91 between markers D14S1020 and D14S606. The MSP1 candidate
region harbors 110 reference genes. DNA sequence analysis of one of the genes, LTBP2, detected a homozygous duplication (insertion) mutation, c.5446dupC, in the last exon (exon 36) in affected family members.
This homozygous mutation is predicted to elongate the LTBP2 protein by replacing the last 6 amino acids with 27 novel amino
acids. Microspherophakia in the second family did not map to this locus, suggesting genetic heterogeneity. The present study
suggests a role for LTBP2 in the structural stability of ciliary zonules, and growth and development of lens. 相似文献
68.
Polarized light based scheme to monitor column performance in a continuous foam fractionation column
Background
A polarized light scattering technique was used to monitor the performance of a continuously operated foam fractionation process. The S 11 and S 12 parameters, elements of the light scattering matrix, combined together (S 11 +S 12) have been correlated with the bubble size and liquid content for the case of a freely draining foam. The performance of a foam fractionation column is known to have a strong dependence on the bubble size distribution and liquid hold up in foam. In this study the enrichment is used as a metric, representative of foam properties and column performance, and correlated to the S 11 +S 12 parameter. 相似文献69.
We used a series of adamantane derivatives to probe the structure of the phencyclidine locus in either the resting or desensitized state of the nicotinic acetylcholine receptor (AChR). Competitive radioligand binding and photolabeling experiments using well-characterized noncompetitive antagonists such as the phencyclidine analogue [piperidyl-3,4-(3)H(N)]-N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine ([(3)H]TCP), [(3)H]ethidium, [(3)H]tetracaine, [(14)C]amobarbital, and 3-(trifluoromethyl)-3-(m-[(125)I]iodophenyl)diazirine ([(125)I]TID) were performed. Thermodynamic and structure-function relationship analyses yielded the following results. (1) There is a good structure-function relationship for adamantane amino derivatives inhibiting [(3)H]TCP or [(3)H]tetracaine binding to the resting AChR. (2) Since the same derivatives inhibit neither [(14)C]amobarbital binding nor [(125)I]TID photoincorporation, we conclude that these positively charged molecules preferably bind to the TCP locus, perhaps interacting with alphaGlu(262) residues at position M2-20. (3) The opposite is true for the neutral molecule adamantane, which prefers the TID (or barbiturate) locus instead of the TCP site. (4) The TID site is smaller and more hydrophobic (it accommodates neutral molecules with a maximal volume of 333 +/- 45 A(3)) than the TCP locus, which has room for positively charged molecules with volumes as large as 461 A(3) (e.g., crystal violet). This supports the concept that the resting ion channel is tapering from the extracellular mouth to the middle portion. (5) Finally, although both the hydrophobic environment and the size of the TCP site are practically the same in both states, there is a more obvious cutoff in the desensitized state than in the resting state, suggesting that the desensitization process constrains the TCP locus. A plausible location of neutral and charged adamantane derivatives is shown in a model of the resting ion channel. 相似文献
70.
Anita L. DeStefano L. Adrienne Cupples Kathleen S. Arnos J. H. Jr. Asher Clinton T. Baldwin Susan Blanton Melisa L. Carey Elias O. da Silva T. B. Friedman Jacquie Greenberg Anil K. Lalwani Aubrey Milunsky Walter E. Nance Arti Pandya Rajkumar S. Ramesar Andrew P. Read May Tassabejhi Edward R. Wilcox L. A. Farrer 《Human genetics》1998,102(5):499-506
Waardenburg syndrome (WS) type 1 is an autosomal dominant disorder characterized by sensorineural hearing loss, pigmentary
abnormalities of the eye, hair, and skin, and dystopia canthorum. The phenotype is variable and affected individuals may exhibit
only one or a combination of several of the associated features. To assess the relationship between phenotype and gene defect,
clinical and genotype data on 48 families (271 WS individuals) collected by members of the Waardenburg Consortium were pooled.
Forty-two unique mutations in the PAX3 gene, previously identified in these families, were grouped in five mutation categories: amino acid (AA) substitution in
the paired domain, AA substitution in the homeodomain, deletion of the Ser-Thr-Pro-rich region, deletion of the homeodomain
and the Ser-Thr-Pro-rich region, and deletion of the entire gene. These mutation classes are based on the structure of the
PAX3 gene and were chosen to group mutations predicted to have similar defects in the gene product. Association between mutation
class and the presence of hearing loss, eye pigment abnormality, skin hypopigmentation, or white forelock was evaluated using
generalized estimating equations, which allowed for incorporation of a correlation structure that accounts for potential similarity
among members of the same family. Odds for the presence of eye pigment abnormality, white forelock, and skin hypopigmentation
were 2, 8, and 5 times greater, respectively, for individuals with deletions of the homeodomain and the Pro-Ser-Thr-rich region
compared to individuals with an AA substitution in the homeodomain. Odds ratios that differ significantly from 1.0 for these
traits may indicate that the gene products resulting from different classes of mutations act differently in the expression
of WS. Although a suggestive association was detected for hearing loss with an odds ratio of 2.6 for AA substitution in the
paired domain compared with AA substitution in the homeodomain, this odds ratio did not differ significantly from 1.0.
Received: 27 July 1997 / Accepted: 9 December 1997 相似文献