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Interaction of α Carboxyl Terminus 1 Peptide With the Connexin 43 Carboxyl Terminus Preserves Left Ventricular Function After Ischemia-Reperfusion Injury.
Jiang J, Hoagland D, Palatinus JA, He H, Iyyathurai J, Jourdan LJ, Bultynck G, Wang Z, Zhang Z, Schey K, Poelzing S, McGowan FX, Gourdie RG
(2019) J Am Heart Assoc 8: e012385
MeSH Terms: Animals, Computer Simulation, Connexin 43, Mice, Microscopy, Confocal, Myocardial Contraction, Myocardial Reperfusion Injury, Peptide Fragments, Phosphorylation, Surface Plasmon Resonance, Tandem Mass Spectrometry, Ventricular Function, Left, Zonula Occludens-1 Protein
Show Abstract · Added March 24, 2020
Background α Carboxyl terminus 1 (αCT1) is a 25-amino acid therapeutic peptide incorporating the zonula occludens-1 (ZO-1)-binding domain of connexin 43 (Cx43) that is currently in phase 3 clinical testing on chronic wounds. In mice, we reported that αCT1 reduced arrhythmias after cardiac injury, accompanied by increases in protein kinase Cε phosphorylation of Cx43 at serine 368. Herein, we characterize detailed molecular mode of action of αCT1 in mitigating cardiac ischemia-reperfusion injury. Methods and Results To study αCT1-mediated increases in phosphorylation of Cx43 at serine 368, we undertook mass spectrometry of protein kinase Cε phosphorylation assay reactants. This indicated potential interaction between negatively charged residues in the αCT1 Asp-Asp-Leu-Glu-Iso sequence and lysines (Lys345, Lys346) in an α-helical sequence (helix 2) within the Cx43-CT. In silico modeling provided further support for this interaction, indicating that αCT1 may interact with both Cx43 and ZO-1. Using surface plasmon resonance, thermal shift, and phosphorylation assays, we characterized a series of αCT1 variants, identifying peptides that interacted with either ZO-1-postsynaptic density-95/disks large/zonula occludens-1 2 or Cx43-CT, but with limited or no ability to bind both molecules. Only peptides competent to interact with Cx43-CT, but not ZO-1-postsynaptic density-95/disks large/zonula occludens-1 2 alone, prompted increased pS368 phosphorylation. Moreover, in an ex vivo mouse model of ischemia-reperfusion injury, preischemic infusion only with those peptides competent to bind Cx43 preserved ventricular function after ischemia-reperfusion. Interestingly, a short 9-amino acid variant of αCT1 (αCT11) demonstrated potent cardioprotective effects when infused either before or after ischemic injury. Conclusions Interaction of αCT1 with the Cx43, but not ZO-1, is correlated with cardioprotection. Pharmacophores targeting Cx43-CT could provide a translational approach to preserving heart function after ischemic injury.
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13 MeSH Terms
Differential abundance of CK1α provides selectivity for pharmacological CK1α activators to target WNT-dependent tumors.
Li B, Orton D, Neitzel LR, Astudillo L, Shen C, Long J, Chen X, Kirkbride KC, Doundoulakis T, Guerra ML, Zaias J, Fei DL, Rodriguez-Blanco J, Thorne C, Wang Z, Jin K, Nguyen DM, Sands LR, Marchetti F, Abreu MT, Cobb MH, Capobianco AJ, Lee E, Robbins DJ
(2017) Sci Signal 10:
MeSH Terms: Animals, Antineoplastic Agents, Benzoates, Casein Kinase Ialpha, Enzyme Activation, Enzyme Activators, Gene Expression Regulation, Neoplastic, HCT116 Cells, Humans, Mice, Mice, Inbred BALB C, Mice, Inbred C57BL, Mice, Nude, Neoplasm Metastasis, Neoplasms, Organ Culture Techniques, Phosphorylation, Pyrvinium Compounds, Signal Transduction, Surface Plasmon Resonance, Wnt Proteins, Wnt Signaling Pathway, Xenograft Model Antitumor Assays, Xenopus laevis
Show Abstract · Added July 18, 2017
Constitutive WNT activity drives the growth of various human tumors, including nearly all colorectal cancers (CRCs). Despite this prominence in cancer, no WNT inhibitor is currently approved for use in the clinic largely due to the small number of druggable signaling components in the WNT pathway and the substantial toxicity to normal gastrointestinal tissue. We have shown that pyrvinium, which activates casein kinase 1α (CK1α), is a potent inhibitor of WNT signaling. However, its poor bioavailability limited the ability to test this first-in-class WNT inhibitor in vivo. We characterized a novel small-molecule CK1α activator called SSTC3, which has better pharmacokinetic properties than pyrvinium, and found that it inhibited the growth of CRC xenografts in mice. SSTC3 also attenuated the growth of a patient-derived metastatic CRC xenograft, for which few therapies exist. SSTC3 exhibited minimal gastrointestinal toxicity compared to other classes of WNT inhibitors. Consistent with this observation, we showed that the abundance of the SSTC3 target, CK1α, was decreased in WNT-driven tumors relative to normal gastrointestinal tissue, and knocking down CK1α increased cellular sensitivity to SSTC3. Thus, we propose that distinct CK1α abundance provides an enhanced therapeutic index for pharmacological CK1α activators to target WNT-driven tumors.
Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
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24 MeSH Terms
Rearrangement of the Extracellular Domain/Extracellular Loop 1 Interface Is Critical for Thyrotropin Receptor Activation.
Schaarschmidt J, Nagel MB, Huth S, Jaeschke H, Moretti R, Hintze V, von Bergen M, Kalkhof S, Meiler J, Paschke R
(2016) J Biol Chem 291: 14095-108
MeSH Terms: Animals, CHO Cells, Cricetinae, Cricetulus, Glycosylation, Humans, Mass Spectrometry, Models, Molecular, Mutation, Proteolysis, Receptors, Thyrotropin, Surface Plasmon Resonance
Show Abstract · Added April 8, 2017
The thyroid stimulating hormone receptor (TSHR) is a G protein-coupled receptor (GPCR) with a characteristic large extracellular domain (ECD). TSHR activation is initiated by binding of the hormone ligand TSH to the ECD. How the extracellular binding event triggers the conformational changes in the transmembrane domain (TMD) necessary for intracellular G protein activation is poorly understood. To gain insight in this process, the knowledge on the relative positioning of ECD and TMD and the conformation of the linker region at the interface of ECD and TMD are of particular importance. To generate a structural model for the TSHR we applied an integrated structural biology approach combining computational techniques with experimental data. Chemical cross-linking followed by mass spectrometry yielded 17 unique distance restraints within the ECD of the TSHR, its ligand TSH, and the hormone-receptor complex. These structural restraints generally confirm the expected binding mode of TSH to the ECD as well as the general fold of the domains and were used to guide homology modeling of the ECD. Functional characterization of TSHR mutants confirms the previously suggested close proximity of Ser-281 and Ile-486 within the TSHR. Rigidifying this contact permanently with a disulfide bridge disrupts ligand-induced receptor activation and indicates that rearrangement of the ECD/extracellular loop 1 (ECL1) interface is a critical step in receptor activation. The experimentally verified contact of Ser-281 (ECD) and Ile-486 (TMD) was subsequently utilized in docking homology models of the ECD and the TMD to create a full-length model of a glycoprotein hormone receptor.
© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
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12 MeSH Terms
The catalytic domains of Clostridium sordellii lethal toxin and related large clostridial glucosylating toxins specifically recognize the negatively charged phospholipids phosphatidylserine and phosphatidic acid.
Varela Chavez C, Hoos S, Haustant GM, Chenal A, England P, Blondel A, Pauillac S, Lacy DB, Popoff MR
(2015) Cell Microbiol 17: 1477-93
MeSH Terms: Anions, Bacterial Toxins, Binding Sites, Catalytic Domain, Cell Membrane, Enzyme-Linked Immunosorbent Assay, Phosphatidic Acids, Phosphatidylserines, Protein Binding, Surface Plasmon Resonance
Show Abstract · Added September 28, 2015
Clostridium sordellii lethal toxin (TcsL) is a potent virulence factor belonging to the large clostridial glucosylating toxin family. TcsL enters target cells via receptor-mediated endocytosis and delivers the N-terminal catalytic domain (TcsL-cat) into the cytosol upon an autoproteolytic process. TcsL-cat inactivates small GTPases including Rac and Ras by glucosylation with uridine-diphosphate (UDP)-glucose as cofactor leading to drastic changes in cytoskeleton and cell viability. TcsL-cat was found to preferentially bind to phosphatidylserine (PS)-containing membranes and to increase the glucosylation of Rac anchored to lipid membrane. We here report binding affinity measurements of TcsL-cat for brain PS-containing membranes by surface plasmon resonance and enzyme-linked immunosorbent assay (ELISA). In addition, TcsL-cat bound to phosphatidic acid (PA) and, to a lesser extent, to other anionic lipids, but not to neutral lipids, sphingolipids or sterol. We further show that the lipid unsaturation status influenced TcsL-cat binding to phospholipids, PS with unsaturated acyl chains and PA with saturated acyl chains being the preferred bindingsubstrates. Phospholipid binding site is localized at the N-terminal four helical bundle structure (1-93 domain). However, TcsL-1-93 bound to a broad range of substrates, whereas TcsL-cat, which is the active domain physiologically delivered into the cytosol, selectively bound to PS and PA. Similar findings were observed with the other large clostridial glucosylating toxins from C. difficile, C. novyi and C. perfringens.
© 2015 John Wiley & Sons Ltd.
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10 MeSH Terms
Analysis of nidogen-1/laminin γ1 interaction by cross-linking, mass spectrometry, and computational modeling reveals multiple binding modes.
Lössl P, Kölbel K, Tänzler D, Nannemann D, Ihling CH, Keller MV, Schneider M, Zaucke F, Meiler J, Sinz A
(2014) PLoS One 9: e112886
MeSH Terms: Animals, Cross-Linking Reagents, HEK293 Cells, Humans, Kinetics, Laminin, Membrane Glycoproteins, Mice, Models, Molecular, Protein Structure, Tertiary, Surface Plasmon Resonance, Tandem Mass Spectrometry
Show Abstract · Added January 24, 2015
We describe the detailed structural investigation of nidogen-1/laminin γ1 complexes using full-length nidogen-1 and a number of laminin γ1 variants. The interactions of nidogen-1 with laminin variants γ1 LEb2-4, γ1 LEb2-4 N836D, γ1 short arm, and γ1 short arm N836D were investigated by applying a combination of (photo-)chemical cross-linking, high-resolution mass spectrometry, and computational modeling. In addition, surface plasmon resonance and ELISA studies were used to determine kinetic constants of the nidogen-1/laminin γ1 interaction. Two complementary cross-linking strategies were pursued to analyze solution structures of laminin γ1 variants and nidogen-1. The majority of distance information was obtained with the homobifunctional amine-reactive cross-linker bis(sulfosuccinimidyl)glutarate. In a second approach, UV-induced cross-linking was performed after incorporation of the diazirine-containing unnatural amino acids photo-leucine and photo-methionine into laminin γ1 LEb2-4, laminin γ1 short arm, and nidogen-1. Our results indicate that Asn-836 within laminin γ1 LEb3 domain is not essential for complex formation. Cross-links between laminin γ1 short arm and nidogen-1 were found in all protein regions, evidencing several additional contact regions apart from the known interaction site. Computational modeling based on the cross-linking constraints indicates the existence of a conformational ensemble of both the individual proteins and the nidogen-1/laminin γ1 complex. This finding implies different modes of interaction resulting in several distinct protein-protein interfaces.
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12 MeSH Terms
The signaling phospholipid PIP3 creates a new interaction surface on the nuclear receptor SF-1.
Blind RD, Sablin EP, Kuchenbecker KM, Chiu HJ, Deacon AM, Das D, Fletterick RJ, Ingraham HA
(2014) Proc Natl Acad Sci U S A 111: 15054-9
MeSH Terms: Amino Acids, Animals, Biological Transport, Cell Nucleus, Chromatography, Computer Simulation, Crystallography, X-Ray, Electrons, Humans, Ligands, Lipids, Mice, Models, Molecular, Molecular Conformation, Mutation, Mutation, Missense, Peptides, Phosphatidylinositols, Signal Transduction, Solvents, Steroidogenic Factor 1, Surface Plasmon Resonance, Surface Properties, Temperature, Water
Show Abstract · Added August 18, 2015
The signaling phosphatidylinositol lipids PI(4,5)P2 (PIP2) and PI(3,4,5)P3 (PIP3) bind nuclear receptor 5A family (NR5As), but their regulatory mechanisms remain unknown. Here, the crystal structures of human NR5A1 (steroidogenic factor-1, SF-1) ligand binding domain (LBD) bound to PIP2 and PIP3 show the lipid hydrophobic tails sequestered in the hormone pocket, as predicted. However, unlike classic nuclear receptor hormones, the phosphoinositide head groups are fully solvent-exposed and complete the LBD fold by organizing the receptor architecture at the hormone pocket entrance. The highest affinity phosphoinositide ligand PIP3 stabilizes the coactivator binding groove and increases coactivator peptide recruitment. This receptor-ligand topology defines a previously unidentified regulatory protein-lipid surface on SF-1 with the phosphoinositide head group at its nexus and poised to interact with other proteins. This surface on SF-1 coincides with the predicted binding site of the corepressor DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region on chromosome X), and importantly harbors missense mutations associated with human endocrine disorders. Our data provide the structural basis for this poorly understood cluster of human SF-1 mutations and demonstrates how signaling phosphoinositides function as regulatory ligands for NR5As.
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25 MeSH Terms
Ultra-compact silicon photonic devices reconfigured by an optically induced semiconductor-to-metal transition.
Ryckman JD, Hallman KA, Marvel RE, Haglund RF, Weiss SM
(2013) Opt Express 21: 10753-63
MeSH Terms: Equipment Design, Equipment Failure Analysis, Miniaturization, Photons, Semiconductors, Silicon, Surface Plasmon Resonance
Show Abstract · Added April 27, 2017
Vanadium dioxide (VO(2)) is a promising reconfigurable optical material and has long been a focus of condensed matter research owing to its distinctive semiconductor-to-metal phase transition (SMT), a feature that has stimulated recent development of thermally reconfigurable photonic, plasmonic, and metamaterial structures. Here, we integrate VO(2) onto silicon photonic devices and demonstrate all-optical switching and reconfiguration of ultra-compact broadband Si-VO(2) absorption modulators (L < 1 μm) and ring-resonators (R ~ λ(0)). Optically inducing the SMT in a small, ~0.275 μm(2), active area of polycrystalline VO(2) enables Si-VO(2) structures to achieve record values of absorption modulation, ~4 dB μm(-1), and intracavity phase modulation, ~π/5 rad μm(-1). This in turn yields large, tunable changes to resonant wavelength,
Δλ(SMT)
~ 3 nm, approximately 60 times larger than Si-only control devices, and enables reconfigurable filtering and optical modulation in excess of 7 dB from modest Q-factor (~10(3)), high-bandwidth ring resonators (>100 GHz). All-optical integrated Si-VO(2) devices thus constitute platforms for reconfigurable photonics, bringing new opportunities to realize dynamic on-chip networks and ultrafast optical shutters and modulators.
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7 MeSH Terms
Fiber-to-chip coupler designed using an optical transformation.
Markov P, Valentine JG, Weiss SM
(2012) Opt Express 20: 14705-13
MeSH Terms: Electronics, Equipment Design, Equipment Failure Analysis, Fiber Optic Technology, Optical Devices, Silicon, Surface Plasmon Resonance, Transducers
Show Abstract · Added April 27, 2017
An integrated silicon photonics coupler for fiber to waveguide conversion was designed employing a transformation optics approach. Quasi-conformal mapping was used to obtain achievable material properties, which were realized by a distorted hexagonal lattice of air holes in silicon. The coupler, measuring only 10 μm in length and fabricated with a single-step lithography process, exhibits a peak simulated transmission efficiency of nearly 100% for in-plane mode conversion and a factor of 5 improvement over butt coupling for fiber to waveguide mode conversion in experimental testing.
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8 MeSH Terms
Mutation in cyclophilin B that causes hyperelastosis cutis in American Quarter Horse does not affect peptidylprolyl cis-trans isomerase activity but shows altered cyclophilin B-protein interactions and affects collagen folding.
Ishikawa Y, Vranka JA, Boudko SP, Pokidysheva E, Mizuno K, Zientek K, Keene DR, Rashmir-Raven AM, Nagata K, Winand NJ, Bächinger HP
(2012) J Biol Chem 287: 22253-65
MeSH Terms: Animals, Asthenia, Circular Dichroism, Collagen, Cyclophilins, Endoplasmic Reticulum, Rough, Horses, Kinetics, Mice, Mice, Transgenic, Molecular Chaperones, Mutation, Peptidylprolyl Isomerase, Protein Binding, Protein Folding, Protein Structure, Tertiary, Skin Diseases, Surface Plasmon Resonance, cis-trans-Isomerases
Show Abstract · Added November 2, 2017
The rate-limiting step of folding of the collagen triple helix is catalyzed by cyclophilin B (CypB). The G6R mutation in cyclophilin B found in the American Quarter Horse leads to autosomal recessive hyperelastosis cutis, also known as hereditary equine regional dermal asthenia. The mutant protein shows small structural changes in the region of the mutation at the side opposite the catalytic domain of CypB. The peptidylprolyl cis-trans isomerase activity of the mutant CypB is normal when analyzed in vitro. However, the biosynthesis of type I collagen in affected horse fibroblasts shows a delay in folding and secretion and a decrease in hydroxylysine and glucosyl-galactosyl hydroxylysine. This leads to changes in the structure of collagen fibrils in tendon, similar to those observed in P3H1 null mice. In contrast to cyclophilin B null mice, where little 3-hydroxylation was found in type I collagen, 3-hydroxylation of type I collagen in affected horses is normal. The mutation disrupts the interaction of cyclophilin B with the P-domain of calreticulin, with lysyl hydroxylase 1, and probably other proteins, such as the formation of the P3H1·CypB·cartilage-associated protein complex, resulting in less effective catalysis of the rate-limiting step in collagen folding in the rough endoplasmic reticulum.
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19 MeSH Terms
Structural basis of thrombin-mediated factor V activation: the Glu666-Glu672 sequence is critical for processing at the heavy chain-B domain junction.
Corral-Rodríguez MÁ, Bock PE, Hernández-Carvajal E, Gutiérrez-Gallego R, Fuentes-Prior P
(2011) Blood 117: 7164-73
MeSH Terms: Amino Acid Chloromethyl Ketones, Amino Acid Sequence, Antithrombins, Benzamidines, Biocatalysis, Catalytic Domain, Crystallography, X-Ray, Enzyme Activation, Enzymes, Immobilized, Factor V, Factor Va, Humans, Kinetics, Models, Molecular, Peptide Fragments, Protein Conformation, Protein Interaction Domains and Motifs, Recombinant Proteins, Spectrometry, Fluorescence, Surface Plasmon Resonance, Surface Properties, Thrombin
Show Abstract · Added January 20, 2015
Thrombin-catalyzed activation of coagulation factor V (FV) is an essential positive feedback reaction within the blood clotting system. Efficient processing at the N- (Arg(709)-Ser(710)) and C-terminal activation cleavage sites (Arg(1545)-Ser(1546)) requires initial substrate interactions with 2 clusters of positively charged residues on the proteinase surface, exosites I and II. We addressed the mechanism of activation of human factor V (FV) using peptides that cover the entire acidic regions preceding these cleavage sites, FV (657-709)/ (FVa2) and FV(1481-1545)/(FVa3). FVa2 appears to interact mostly with exosite I, while both exosites are involved in interactions with the C-terminal linker. The 1.7-Å crystal structure of irreversibly inhibited thrombin bound to FVa2 unambiguously reveals docking of FV residues Glu(666)-Glu(672) to exosite I. These findings were confirmed in a second, medium-resolution structure of FVa2 bound to the benzamidine-inhibited proteinase. Our results suggest that the acidic A2-B domain linker is involved in major interactions with thrombin during cofactor activation, with its more N-terminal hirudin-like sequence playing a critical role. Modeling experiments indicate that FVa2, and likely also FVa3, wrap around thrombin in productive thrombin·FV complexes that cover a large surface of the activator to engage the active site.
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22 MeSH Terms