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Proteomic Analysis of S-Palmitoylated Proteins in Ocular Lens Reveals Palmitoylation of AQP5 and MP20.
Wang Z, Schey KL
(2018) Invest Ophthalmol Vis Sci 59: 5648-5658
MeSH Terms: Animals, Aquaporin 5, Blotting, Western, Cattle, Chromatography, Liquid, Electrophoresis, Polyacrylamide Gel, Eye Proteins, Immunoblotting, Lens, Crystalline, Lipoylation, Membrane Proteins, Palmitates, Proteomics, Tandem Mass Spectrometry
Show Abstract · Added April 4, 2019
Purpose - The purpose of this study was to characterize the palmitoyl-proteome in lens fiber cells. S-palmitoylation is the most common form of protein S-acylation and the reversible nature of this modification functions as a molecular switch to regulate many biological processes. This modification could play important roles in regulating protein functions and protein-protein interactions in the lens.
Methods - The palmitoyl-proteome of bovine lens fiber cells was investigated by combining acyl-biotin exchange (ABE) chemistry and mass-spectrometry analysis. Due to the possibility of false-positive results from ABE experiment, a method was also developed for direct detection of palmitoylated peptides by mass spectrometry for validating palmitoylation of lens proteins MP20 and AQP5. Palmitoylation levels on AQP5 in different regions of the lens were quantified after iodoacetamide (IAA)-palmitate exchange.
Results - The ABE experiment identified 174 potential palmitoylated proteins. These proteins include 39 well-characterized palmitoylated proteins, 92 previously reported palmitoylated proteins in other tissues, and 43 newly identified potential palmitoylated proteins including two important transmembrane proteins in the lens, AQP5 and MP20. Further analysis by direct detection of palmitoylated peptides confirmed palmitoylation of AQP5 on C6 and palmitoylation of MP20 on C159. Palmitoylation of AQP5 was found to only occur in a narrow region of the inner lens cortex and does not occur in the lens epithelium, in the lens outer cortex, or in the lens nucleus.
Conclusions - AQP5 and MP20 are among 174 palmitoylated proteins found in bovine lens fiber cells. This modification to AQP5 and MP20 may play a role in their translocation from the cytoplasm to cell membranes during fiber cell differentiation.
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14 MeSH Terms
Substrate stiffness heterogeneities disrupt endothelial barrier integrity in a micropillar model of heterogeneous vascular stiffening.
VanderBurgh JA, Hotchkiss H, Potharazu A, Taufalele PV, Reinhart-King CA
(2018) Integr Biol (Camb) 10: 734-746
MeSH Terms: Adherens Junctions, Animals, Aorta, Atherosclerosis, Cattle, Cell Adhesion, Cell Communication, Cell Movement, Dimethylpolysiloxanes, Endothelial Cells, Endothelium, Vascular, Focal Adhesions, Human Umbilical Vein Endothelial Cells, Humans, Leukocytes, Materials Testing, Neutrophils, Phenotype, Tunica Intima, Vascular Stiffness, Vinculin
Show Abstract · Added April 10, 2019
Intimal stiffening has been linked with increased vascular permeability and leukocyte transmigration, hallmarks of atherosclerosis. However, recent evidence indicates age-related intimal stiffening is not uniform but rather characterized by increased point-to-point heterogeneity in subendothelial matrix stiffness, the impact of which is much less understood. To investigate the impact of spatially heterogeneous matrix rigidity on endothelial monolayer integrity, we develop a micropillar model to introduce closely-spaced, step-changes in substrate rigidity and compare endothelial monolayer phenotype to rigidity-matched, uniformly stiff and compliant substrates. We found equivalent disruption of adherens junctions within monolayers on step-rigidity and uniformly stiff substrates relative to uniformly compliant substrates. Similarly, monolayers cultured on step-rigidity substrates exhibited equivalent percentages of leukocyte transmigration to monolayers on rigidity-matched, uniformly stiff substrates. Adherens junction tension and focal adhesion density, but not size, increased within monolayers on step-rigidity and uniformly stiff substrates compared to more compliant substrates suggesting that elevated tension is disrupting adherens junction integrity. Leukocyte transmigration frequency and time, focal adhesion size, and focal adhesion density did not differ between stiff and compliant sub-regions of step-rigidity substrates. Overall, our results suggest that endothelial monolayers exposed to mechanically heterogeneous substrates adopt the phenotype associated with the stiffer matrix, indicating that spatial heterogeneities in intimal stiffness observed with age could disrupt endothelial barrier integrity and contribute to atherogenesis.
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21 MeSH Terms
Eigenstrain as a mechanical set-point of cells.
Lin S, Lampi MC, Reinhart-King CA, Tsui G, Wang J, Nelson CA, Gu L
(2018) Biomech Model Mechanobiol 17: 951-959
MeSH Terms: Animals, Aorta, Biomechanical Phenomena, Cattle, Cells, Cultured, Endothelial Cells, Models, Biological, Stress, Mechanical
Show Abstract · Added April 10, 2019
Cell contraction regulates how cells sense their mechanical environment. We sought to identify the set-point of cell contraction, also referred to as tensional homeostasis. In this work, bovine aortic endothelial cells (BAECs), cultured on substrates with different stiffness, were characterized using traction force microscopy (TFM). Numerical models were developed to provide insights into the mechanics of cell-substrate interactions. Cell contraction was modeled as eigenstrain which could induce isometric cell contraction without external forces. The predicted traction stresses matched well with TFM measurements. Furthermore, our numerical model provided cell stress and displacement maps for inspecting the fundamental regulating mechanism of cell mechanosensing. We showed that cell spread area, traction force on a substrate, as well as the average stress of a cell were increased in response to a stiffer substrate. However, the cell average strain, which is cell type-specific, was kept at the same level regardless of the substrate stiffness. This indicated that the cell average strain is the tensional homeostasis that each type of cell tries to maintain. Furthermore, cell contraction in terms of eigenstrain was found to be the same for both BAECs and fibroblast cells in different mechanical environments. This implied a potential mechanical set-point across different cell types. Our results suggest that additional measurements of contractility might be useful for monitoring cell mechanosensing as well as dynamic remodeling of the extracellular matrix (ECM). This work could help to advance the understanding of the cell-ECM relationship, leading to better regenerative strategies.
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MeSH Terms
Structural basis of arrestin-3 activation and signaling.
Chen Q, Perry NA, Vishnivetskiy SA, Berndt S, Gilbert NC, Zhuo Y, Singh PK, Tholen J, Ohi MD, Gurevich EV, Brautigam CA, Klug CS, Gurevich VV, Iverson TM
(2017) Nat Commun 8: 1427
MeSH Terms: Amino Acid Sequence, Animals, Arrestins, Binding Sites, Cattle, Crystallography, X-Ray, Humans, Mitogen-Activated Protein Kinase 10, Models, Molecular, Phytic Acid, Protein Conformation, Protein Structure, Quaternary, Recombinant Proteins, Signal Transduction
Show Abstract · Added March 14, 2018
A unique aspect of arrestin-3 is its ability to support both receptor-dependent and receptor-independent signaling. Here, we show that inositol hexakisphosphate (IP) is a non-receptor activator of arrestin-3 and report the structure of IP-activated arrestin-3 at 2.4-Å resolution. IP-activated arrestin-3 exhibits an inter-domain twist and a displaced C-tail, hallmarks of active arrestin. IP binds to the arrestin phosphate sensor, and is stabilized by trimerization. Analysis of the trimerization surface, which is also the receptor-binding surface, suggests a feature called the finger loop as a key region of the activation sensor. We show that finger loop helicity and flexibility may underlie coupling to hundreds of diverse receptors and also promote arrestin-3 activation by IP. Importantly, we show that effector-binding sites on arrestins have distinct conformations in the basal and activated states, acting as switch regions. These switch regions may work with the inter-domain twist to initiate and direct arrestin-mediated signaling.
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14 MeSH Terms
Using two-site binding models to analyze microscale thermophoresis data.
Tso SC, Chen Q, Vishnivetskiy SA, Gurevich VV, Iverson TM, Brautigam CA
(2018) Anal Biochem 540-541: 64-75
MeSH Terms: Adenosine Monophosphate, Algorithms, Animals, Aptamers, Nucleotide, Binding Sites, Cattle, Kinetics, Models, Molecular, Monte Carlo Method, Mutagenesis, Site-Directed, Phytic Acid, Protein Binding, Recombinant Proteins, beta-Arrestin 2
Show Abstract · Added March 14, 2018
The emergence of microscale thermophoresis (MST) as a technique for determining the dissociation constants for bimolecular interactions has enabled these quantities to be measured in systems that were previously difficult or impracticable. However, most models for analyses of these data featured the assumption of a simple 1:1 binding interaction. The only model widely used for multiple binding sites was the Hill equation. Here, we describe two new MST analytic models that assume a 1:2 binding scheme: the first features two microscopic binding constants (K(1) and K(2)), while the other assumes symmetry in the bivalent molecule, culminating in a model with a single macroscopic dissociation constant (K) and a single factor (α) that accounts for apparent cooperativity in the binding. We also discuss the general applicability of the Hill equation for MST data. The performances of the algorithms on both real and simulated data are assessed, and implementation of the algorithms in the MST analysis program PALMIST is discussed.
Copyright © 2017 Elsevier Inc. All rights reserved.
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14 MeSH Terms
Gene Regulatory Enhancers with Evolutionarily Conserved Activity Are More Pleiotropic than Those with Species-Specific Activity.
Fish A, Chen L, Capra JA
(2017) Genome Biol Evol 9: 2615-2625
MeSH Terms: Animals, Callithrix, Cats, Cattle, Conserved Sequence, Databases, Genetic, Dogs, Enhancer Elements, Genetic, Evolution, Molecular, Genetic Pleiotropy, Histones, Humans, Macaca mulatta, Mice, Rabbits, Rats, Swine
Show Abstract · Added March 14, 2018
Studies of regulatory activity and gene expression have revealed an intriguing dichotomy: There is substantial turnover in the regulatory activity of orthologous sequences between species; however, the expression level of orthologous genes is largely conserved. Understanding how distal regulatory elements, for example, enhancers, evolve and function is critical, as alterations in gene expression levels can drive the development of both complex disease and functional divergence between species. In this study, we investigated determinants of the conservation of regulatory enhancer activity for orthologous sequences across mammalian evolution. Using liver enhancers identified from genome-wide histone modification profiles in ten diverse mammalian species, we compared orthologous sequences that exhibited regulatory activity in all species (conserved-activity enhancers) to shared sequences active only in a single species (species-specific-activity enhancers). Conserved-activity enhancers have greater regulatory potential than species-specific-activity enhancers, as quantified by both the density and diversity of transcription factor binding motifs. Consistent with their greater regulatory potential, conserved-activity enhancers have greater regulatory activity in humans than species-specific-activity enhancers: They are active across more cellular contexts, and they regulate more genes than species-specific-activity enhancers. Furthermore, the genes regulated by conserved-activity enhancers are expressed in more tissues and are less tolerant of loss-of-function mutations than those targeted by species-specific-activity enhancers. These consistent results across various stages of gene regulation demonstrate that conserved-activity enhancers are more pleiotropic than their species-specific-activity counterparts. This suggests that pleiotropy is associated with the conservation of regulatory across mammalian evolution.
© The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
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17 MeSH Terms
Sigma-1 receptor ligands inhibit catecholamine secretion from adrenal chromaffin cells due to block of nicotinic acetylcholine receptors.
Brindley RL, Bauer MB, Hartley ND, Horning KJ, Currie KPM
(2017) J Neurochem 143: 171-182
MeSH Terms: Adrenal Medulla, Animals, Anisoles, Catecholamines, Cattle, Cells, Cultured, Chromaffin Cells, Dose-Response Relationship, Drug, Ligands, Male, Mice, Mice, Inbred C57BL, Nicotinic Antagonists, Propylamines, Receptors, Nicotinic, Receptors, sigma
Show Abstract · Added September 28, 2017
Adrenal chromaffin cells (ACCs) are the neuroendocrine arm of the sympathetic nervous system and key mediators of the physiological stress response. Acetylcholine (ACh) released from preganglionic splanchnic nerves activates nicotinic acetylcholine receptors (nAChRs) on chromaffin cells causing membrane depolarization, opening voltage-gated Ca channels (VGCC), and exocytosis of catecholamines and neuropeptides. The serotonin transporter is expressed in ACCs and interacts with 5-HT receptors to control secretion. In addition to blocking the serotonin transporter, some selective serotonin reuptake inhibitors (SSRIs) are also agonists at sigma-1 receptors which function as intracellular chaperone proteins and can translocate to the plasma membrane to modulate ion channels. Therefore, we investigated whether SSRIs and other sigma-1 receptor ligands can modulate stimulus-secretion coupling in ACCs. Escitalopram and fluvoxamine (100 nM to 1 μM) reversibly inhibited nAChR currents. The sigma-1 receptor antagonists NE-100 and BD-1047 also blocked nAChR currents (≈ 50% block at 100 nM) as did PRE-084, a sigma-1 receptor agonist. Block of nAChR currents by fluvoxamine and NE-100 was not additive suggesting a common site of action. VGCC currents were unaffected by the drugs. Neither the increase in cytosolic [Ca ] nor the resulting catecholamine secretion evoked by direct membrane depolarization to bypass nAChRs was altered by fluvoxamine or NE-100. However, both Ca entry and catecholamine secretion evoked by the cholinergic agonist carbachol were significantly reduced by fluvoxamine or NE-100. Together, our data suggest that sigma-1 receptors do not acutely regulate catecholamine secretion. Rather, SSRIs and other sigma-1 receptor ligands inhibit secretion evoked by cholinergic stimulation because of direct block of Ca entry via nAChRs.
© 2017 International Society for Neurochemistry.
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16 MeSH Terms
Gβγ directly modulates vesicle fusion by competing with synaptotagmin for binding to neuronal SNARE proteins embedded in membranes.
Zurawski Z, Page B, Chicka MC, Brindley RL, Wells CA, Preininger AM, Hyde K, Gilbert JA, Cruz-Rodriguez O, Currie KPM, Chapman ER, Alford S, Hamm HE
(2017) J Biol Chem 292: 12165-12177
MeSH Terms: Animals, Binding, Competitive, Calcium Signaling, Cattle, Cell Line, GTP-Binding Protein beta Subunits, GTP-Binding Protein gamma Subunits, Humans, Lipid Bilayers, Liposomes, Membrane Fusion, Models, Molecular, Mutation, Nerve Tissue Proteins, Peptide Fragments, Protein Conformation, Protein Interaction Domains and Motifs, Protein Multimerization, Rats, Recombinant Fusion Proteins, Recombinant Proteins, Synaptosomal-Associated Protein 25, Synaptotagmin I, Syntaxin 1
Show Abstract · Added July 12, 2017
G-coupled G protein-coupled receptors can inhibit neurotransmitter release at synapses via multiple mechanisms. In addition to Gβγ-mediated modulation of voltage-gated calcium channels (VGCC), inhibition can also be mediated through the direct interaction of Gβγ subunits with the soluble -ethylmaleimide attachment protein receptor (SNARE) complex of the vesicle fusion apparatus. Binding studies with soluble SNARE complexes have shown that Gβγ binds to both ternary SNARE complexes, t-SNARE heterodimers, and monomeric SNAREs, competing with synaptotagmin 1(syt1) for binding sites on t-SNARE. However, in secretory cells, Gβγ, SNAREs, and synaptotagmin interact in the lipid environment of a vesicle at the plasma membrane. To approximate this environment, we show that fluorescently labeled Gβγ interacts specifically with lipid-embedded t-SNAREs consisting of full-length syntaxin 1 and SNAP-25B at the membrane, as measured by fluorescence polarization. Fluorescently labeled syt1 undergoes competition with Gβγ for SNARE-binding sites in lipid environments. Mutant Gβγ subunits that were previously shown to be more efficacious at inhibiting Ca-triggered exocytotic release than wild-type Gβγ were also shown to bind SNAREs at a higher affinity than wild type in a lipid environment. These mutant Gβγ subunits were unable to inhibit VGCC currents. Specific peptides corresponding to regions on Gβ and Gγ shown to be important for the interaction disrupt the interaction in a concentration-dependent manner. In fusion assays using full-length t- and v-SNAREs embedded in liposomes, Gβγ inhibited Ca/synaptotagmin-dependent fusion. Together, these studies demonstrate the importance of these regions for the Gβγ-SNARE interaction and show that the target of Gβγ, downstream of VGCC, is the membrane-embedded SNARE complex.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
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24 MeSH Terms
Differential manipulation of arrestin-3 binding to basal and agonist-activated G protein-coupled receptors.
Prokop S, Perry NA, Vishnivetskiy SA, Toth AD, Inoue A, Milligan G, Iverson TM, Hunyady L, Gurevich VV
(2017) Cell Signal 36: 98-107
MeSH Terms: Amino Acid Sequence, Animals, Arrestins, COS Cells, Cattle, Cercopithecus aethiops, Conserved Sequence, HEK293 Cells, Humans, Lysine, Mutant Proteins, Mutation, Protein Binding, Protein Structure, Secondary, Receptors, G-Protein-Coupled, Rhodopsin
Show Abstract · Added March 14, 2018
Non-visual arrestins interact with hundreds of different G protein-coupled receptors (GPCRs). Here we show that by introducing mutations into elements that directly bind receptors, the specificity of arrestin-3 can be altered. Several mutations in the two parts of the central "crest" of the arrestin molecule, middle-loop and C-loop, enhanced or reduced arrestin-3 interactions with several GPCRs in receptor subtype and functional state-specific manner. For example, the Lys139Ile substitution in the middle-loop dramatically enhanced the binding to inactive M muscarinic receptor, so that agonist activation of the M did not further increase arrestin-3 binding. Thus, the Lys139Ile mutation made arrestin-3 essentially an activation-independent binding partner of M, whereas its interactions with other receptors, including the β-adrenergic receptor and the D and D dopamine receptors, retained normal activation dependence. In contrast, the Ala248Val mutation enhanced agonist-induced arrestin-3 binding to the β-adrenergic and D dopamine receptors, while reducing its interaction with the D dopamine receptor. These mutations represent the first example of altering arrestin specificity via enhancement of the arrestin-receptor interactions rather than selective reduction of the binding to certain subtypes.
Copyright © 2017. Published by Elsevier Inc.
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16 MeSH Terms
Formation of S-[2-(N-Deoxyadenosinyl)ethyl]glutathione in DNA and Replication Past the Adduct by Translesion DNA Polymerases.
Sedgeman CA, Su Y, Guengerich FP
(2017) Chem Res Toxicol 30: 1188-1196
MeSH Terms: Animals, Cattle, Chromatography, Liquid, DNA Adducts, DNA Replication, DNA-Directed DNA Polymerase, Ethylene Dibromide, Glutathione, Tandem Mass Spectrometry
Show Abstract · Added March 14, 2018
1,2-Dibromoethane (DBE, ethylene dibromide) is a potent carcinogen due at least in part to its DNA cross-linking effects. DBE cross-links glutathione (GSH) to DNA, notably to sites on 2'-deoxyadenosine and 2'-deoxyguanosine ( Cmarik , J. L. , et al. ( 1991 ) J. Biol. Chem. 267 , 6672 - 6679 ). Adduction at the N6 position of 2'-deoxyadenosine (dA) had not been detected, but this is a site for the linkage of O-alkylguanine DNA alkyltransferase ( Chowdhury , G. , et al. ( 2013 ) Angew. Chem. Int. Ed. 52 , 12879 - 12882 ). We identified and quantified a new adduct, S-[2-(N-deoxyadenosinyl)ethyl]GSH, in calf thymus DNA using LC-MS/MS. Replication studies were performed in duplex oligonucleotides containing this adduct with human DNA polymerases (hPols) η, ι, and κ, as well as with Sulfolobus solfataricus Dpo4, Escherichia coli polymerase I Klenow fragment, and bacteriophage T7 polymerase. hPols η and ι, Dpo4, and Klenow fragment were able to bypass the adduct with only slight impedance; hPol η and ι showed increased misincorporation opposite the adduct compared to that of unmodified 2'-deoxyadenosine. LC-MS/MS analysis of full-length primer extension products by hPol η confirmed the incorporation of dC opposite S-[2-(N-deoxyadenosinyl)ethyl]GSH and also showed the production of a -1 frameshift. These results reveal the significance of N-dA GSH-DBE adducts in blocking replication, as well as producing mutations, by human translesion synthesis DNA polymerases.
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9 MeSH Terms