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Bid maintains mitochondrial cristae structure and function and protects against cardiac disease in an integrative genomics study.
Salisbury-Ruf CT, Bertram CC, Vergeade A, Lark DS, Shi Q, Heberling ML, Fortune NL, Okoye GD, Jerome WG, Wells QS, Fessel J, Moslehi J, Chen H, Roberts LJ, Boutaud O, Gamazon ER, Zinkel SS
(2018) Elife 7:
MeSH Terms: Animals, Apoptosis, BH3 Interacting Domain Death Agonist Protein, Beclin-1, Cell Respiration, Fibrosis, Gene Expression Regulation, Genome-Wide Association Study, Genomics, Heart Diseases, Heart Ventricles, Humans, Mice, Inbred C57BL, Mitochondria, Mitochondrial Proton-Translocating ATPases, Mutation, Myeloid Progenitor Cells, Myocardial Infarction, Myocytes, Cardiac, Polymorphism, Single Nucleotide, Protein Multimerization, Protein Structure, Secondary, Protein Subunits, Reactive Oxygen Species, Reproducibility of Results, Up-Regulation
Show Abstract · Added December 11, 2018
Bcl-2 family proteins reorganize mitochondrial membranes during apoptosis, to form pores and rearrange cristae. In vitro and in vivo analysis integrated with human genetics reveals a novel homeostatic mitochondrial function for Bcl-2 family protein Bid. Loss of full-length Bid results in apoptosis-independent, irregular cristae with decreased respiration. mice display stress-induced myocardial dysfunction and damage. A gene-based approach applied to a biobank, validated in two independent GWAS studies, reveals that decreased genetically determined BID expression associates with myocardial infarction (MI) susceptibility. Patients in the bottom 5% of the expression distribution exhibit >4 fold increased MI risk. Carrier status with nonsynonymous variation in Bid's membrane binding domain, Bid, associates with MI predisposition. Furthermore, Bid but not Bid associates with Mcl-1, previously implicated in cristae stability; decreased MCL-1 expression associates with MI. Our results identify a role for Bid in homeostatic mitochondrial cristae reorganization, that we link to human cardiac disease.
© 2018, Salisbury-Ruf et al.
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3 Members
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26 MeSH Terms
The unassembled flavoprotein subunits of human and bacterial complex II have impaired catalytic activity and generate only minor amounts of ROS.
Maklashina E, Rajagukguk S, Iverson TM, Cecchini G
(2018) J Biol Chem 293: 7754-7765
MeSH Terms: Bacterial Proteins, Catalysis, Crystallography, X-Ray, Electron Transport Complex II, Escherichia coli, Flavoproteins, Humans, Models, Molecular, Oxidation-Reduction, Protein Conformation, Protein Subunits, Reactive Oxygen Species
Show Abstract · Added April 1, 2019
Complex II (SdhABCD) is a membrane-bound component of mitochondrial and bacterial electron transport chains, as well as of the TCA cycle. In this capacity, it catalyzes the reversible oxidation of succinate. SdhABCD contains the SDHA protein harboring a covalently bound FAD redox center and the iron-sulfur protein SDHB, containing three distinct iron-sulfur centers. When assembly of this complex is compromised, the flavoprotein SDHA may accumulate in the mitochondrial matrix or bacterial cytoplasm. Whether the unassembled SDHA has any catalytic activity, for example in succinate oxidation, fumarate reduction, reactive oxygen species (ROS) generation, or other off-pathway reactions, is not known. Therefore, here we investigated whether unassembled SdhA flavoprotein, its homolog fumarate reductase (FrdA), and the human SDHA protein have succinate oxidase or fumarate reductase activity and can produce ROS. Using recombinant expression in , we found that the free flavoproteins from these divergent biological sources have inherently low catalytic activity and generate little ROS. These results suggest that the iron-sulfur protein SDHB in complex II is necessary for robust catalytic activity. Our findings are consistent with those reported for single-subunit flavoprotein homologs that are not associated with iron-sulfur or heme partner proteins.
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Allostery between two binding sites in the ion channel subunit TRIP8b confers binding specificity to HCN channels.
Lyman KA, Han Y, Heuermann RJ, Cheng X, Kurz JE, Lyman RE, Van Veldhoven PP, Chetkovich DM
(2017) J Biol Chem 292: 17718-17730
MeSH Terms: Allosteric Regulation, Binding Sites, HEK293 Cells, Humans, Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels, Protein Subunits, Receptors, Cytoplasmic and Nuclear
Show Abstract · Added April 2, 2019
Tetratricopeptide repeat (TPR) domains are ubiquitous structural motifs that mediate protein-protein interactions. For example, the TPR domains in the peroxisomal import receptor PEX5 enable binding to a range of type 1 peroxisomal targeting signal motifs. A homolog of PEX5, tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b), binds to and functions as an auxiliary subunit of hyperpolarization-activated cyclic nucleotide (HCN)-gated channels. Given the similarity between TRIP8b and PEX5, this difference in function raises the question of what mechanism accounts for their binding specificity. In this report, we found that the cyclic nucleotide-binding domain and the C terminus of the HCN channel are critical for conferring specificity to TRIP8b binding. We show that TRIP8b binds the HCN cyclic nucleotide-binding domain through a 37-residue domain and the HCN C terminus through the TPR domains. Using a combination of fluorescence polarization- and co-immunoprecipitation-based assays, we establish that binding at either site increases affinity at the other. Thus, allosteric coupling of the TRIP8b TPR domains both promotes binding to HCN channels and limits binding to type 1 peroxisomal targeting signal substrates. These results raise the possibility that other TPR domains may be similarly influenced by allosteric mechanisms as a general feature of protein-protein interactions.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
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1 Members
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MeSH Terms
Building collagen IV smart scaffolds on the outside of cells.
Brown KL, Cummings CF, Vanacore RM, Hudson BG
(2017) Protein Sci 26: 2151-2161
MeSH Terms: Amino Acid Motifs, Amino Acid Oxidoreductases, Animals, Antigens, Neoplasm, Basement Membrane, Collagen Type IV, Eukaryotic Cells, Extracellular Matrix, Gene Expression Regulation, Humans, Peroxidases, Protein Interaction Domains and Motifs, Protein Multimerization, Protein Structure, Secondary, Protein Subunits, Receptors, Interleukin-1
Show Abstract · Added November 2, 2017
Collagen IV scaffolds assemble through an intricate pathway that begins intracellularly and is completed extracellularly. Multiple intracellular enzymes act in concert to assemble collagen IV protomers, the building blocks of collagen IV scaffolds. After being secreted from cells, protomers are activated to initiate oligomerization, forming insoluble networks that are structurally reinforced with covalent crosslinks. Within these networks, embedded binding sites along the length of the protomer lead to the "decoration" of collagen IV triple helix with numerous functional molecules. We refer to these networks as "smart" scaffolds, which as a component of the basement membrane enable the development and function of multicellular tissues in all animal phyla. In this review, we present key molecular mechanisms that drive the assembly of collagen IV smart scaffolds.
© 2017 The Protein Society.
1 Communities
1 Members
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16 MeSH Terms
Structural and biochemical analyses reveal insights into covalent flavinylation of the Complex II homolog quinol:fumarate reductase.
Starbird CA, Maklashina E, Sharma P, Qualls-Histed S, Cecchini G, Iverson TM
(2017) J Biol Chem 292: 12921-12933
MeSH Terms: Amino Acid Substitution, Biocatalysis, Crystallography, X-Ray, Enzyme Stability, Escherichia coli, Escherichia coli Proteins, Flavin-Adenine Dinucleotide, Gene Deletion, Glutamic Acid, Hot Temperature, Models, Molecular, Molecular Docking Simulation, Mutagenesis, Site-Directed, Mutation, Oxidoreductases, Protein Conformation, Protein Denaturation, Protein Interaction Domains and Motifs, Protein Multimerization, Protein Processing, Post-Translational, Protein Subunits, Recombinant Proteins, Structural Homology, Protein, Succinate Dehydrogenase
Show Abstract · Added April 1, 2019
The Complex II homolog quinol:fumarate reductase (QFR, FrdABCD) catalyzes the interconversion of fumarate and succinate at a covalently attached FAD within the FrdA subunit. The SdhE assembly factor enhances covalent flavinylation of Complex II homologs, but the mechanisms underlying the covalent attachment of FAD remain to be fully elucidated. Here, we explored the mechanisms of covalent flavinylation of the QFR FrdA subunit. Using a Δ strain, we show that the requirement for the assembly factor depends on the cellular redox environment. We next identified residues important for the covalent attachment and selected the FrdA residue, which contributes to proton shuttling during fumarate reduction, for detailed biophysical and structural characterization. We found that QFR complexes containing FrdA have a structure similar to that of the WT flavoprotein, but lack detectable substrate binding and turnover. In the context of the isolated FrdA subunit, the anticipated assembly intermediate during covalent flavinylation, FrdA variants had stability similar to that of WT FrdA, contained noncovalent FAD, and displayed a reduced capacity to interact with SdhE. However, small-angle X-ray scattering (SAXS) analysis of WT FrdA cross-linked to SdhE suggested that the FrdA residue is unlikely to contribute directly to the FrdA-SdhE protein-protein interface. We also found that no auxiliary factor is absolutely required for flavinylation, indicating that the covalent flavinylation is autocatalytic. We propose that multiple factors, including the SdhE assembly factor and bound dicarboxylates, stimulate covalent flavinylation by preorganizing the active site to stabilize the quinone-methide intermediate.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
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Overexpressing wild-type γ2 subunits rescued the seizure phenotype in Gabrg2 Dravet syndrome mice.
Huang X, Zhou C, Tian M, Kang JQ, Shen W, Verdier K, Pimenta A, MacDonald RL
(2017) Epilepsia 58: 1451-1461
MeSH Terms: Action Potentials, Animals, Convulsants, Electric Stimulation, Epilepsies, Myoclonic, Humans, In Vitro Techniques, Inhibitory Postsynaptic Potentials, Male, Mice, Mice, Inbred C57BL, Mice, Transgenic, Mutation, Neural Pathways, Patch-Clamp Techniques, Pentylenetetrazole, Protein Subunits, Pyramidal Cells, Receptors, GABA-A, Somatosensory Cortex, Thalamus
Show Abstract · Added June 21, 2017
OBJECTIVE - The mutant γ-aminobutyric acid type A (GABA ) receptor γ2(Q390X) subunit (Q351X in the mature peptide) has been associated with the epileptic encephalopathy, Dravet syndrome, and the epilepsy syndrome genetic epilepsy with febrile seizures plus (GEFS+). The mutation generates a premature stop codon that results in translation of a stable truncated and misfolded γ2 subunit that accumulates in neurons, forms intracellular aggregates, disrupts incorporation of γ2 subunits into GABA receptors, and affects trafficking of partnering α and β subunits. Heterozygous Gabrg2 knock-in (KI) mice had reduced cortical inhibition, spike wave discharges on electroencephalography (EEG), a lower seizure threshold to the convulsant drug pentylenetetrazol (PTZ), and spontaneous generalized tonic-clonic seizures. In this proof-of-principal study, we attempted to rescue these deficits in KI mice using a γ2 subunit gene (GABRG2) replacement therapy.
METHODS - We introduced the GABRG2 allele by crossing Gabrg2 KI mice with bacterial artificial chromosome (BAC) transgenic mice overexpressing HA (hemagglutinin)-tagged human γ2 subunits, and compared GABA receptor subunit expression by Western blot and immunohistochemical staining, seizure threshold by monitoring mouse behavior after PTZ-injection, and thalamocortical inhibition and network oscillation by slice recording.
RESULTS - Compared to KI mice, adult mice carrying both mutant allele and transgene had increased wild-type γ2 and partnering α1 and β2/3 subunits, increased miniature inhibitory postsynaptic current (mIPSC) amplitudes recorded from layer VI cortical neurons, reduced thalamocortical network oscillations, and higher PTZ seizure threshold.
SIGNIFICANCE - Based on these results we suggest that seizures in a genetic epilepsy syndrome caused by epilepsy mutant γ2(Q390X) subunits with dominant negative effects could be rescued potentially by overexpression of wild-type γ2 subunits.
Wiley Periodicals, Inc. © 2017 International League Against Epilepsy.
1 Communities
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21 MeSH Terms
Reduced ethanol drinking following selective cortical interneuron deletion of the GluN2B NMDA receptors subunit.
Radke AK, Jury NJ, Delpire E, Nakazawa K, Holmes A
(2017) Alcohol 58: 47-51
MeSH Terms: Alcohol Drinking, Animals, Cerebral Cortex, Choice Behavior, Ethanol, Female, Gene Deletion, Interneurons, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Mice, Transgenic, Protein Subunits, Receptors, N-Methyl-D-Aspartate
Show Abstract · Added May 3, 2017
N-Methyl-d-aspartate receptors (NMDAR) are involved in the regulation of alcohol drinking, but the contribution of NMDAR subunits located on specific neuronal populations remains incompletely understood. The current study examined the role of GluN2B-containing NMDARs expressed on cortical principal neurons and cortical interneurons in mouse ethanol drinking. Consumption of escalating concentrations of ethanol was measured in mice with GluN2B gene deletion in either cortical principal neurons (GluN2B) or interneurons (GluN2B), using a two-bottle choice paradigm. Results showed that GluN2B, but not GluN2B, mice consumed significantly less ethanol, at relatively high concentrations, than non-mutant controls. In a second paradigm in which mice were offered a 15% ethanol concentration, without escalation, GluN2B mice were again no different from controls. These findings provide novel evidence for a contribution of interneuronal GluN2B-containing NMDARs in the regulation of ethanol drinking.
Copyright © 2016 Elsevier Inc. All rights reserved.
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1 Members
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15 MeSH Terms
LRRC8A channels support TNFα-induced superoxide production by Nox1 which is required for receptor endocytosis.
Choi H, Ettinger N, Rohrbough J, Dikalova A, Nguyen HN, Lamb FS
(2016) Free Radic Biol Med 101: 413-423
MeSH Terms: Cell Line, Cyclopentanes, Endocytosis, Gene Expression Regulation, HEK293 Cells, Humans, Indans, JNK Mitogen-Activated Protein Kinases, Membrane Proteins, Myocytes, Smooth Muscle, NADPH Oxidase 1, NF-kappa B, Phosphorylation, Protein Subunits, RNA, Small Interfering, Receptors, Tumor Necrosis Factor, Type I, Signal Transduction, Superoxide Dismutase, Superoxides, Tumor Necrosis Factor-alpha, Vascular Cell Adhesion Molecule-1
Show Abstract · Added March 26, 2019
Leucine Rich Repeat Containing 8A (LRRC8A) is a required component of volume-regulated anion channels (VRACs). In vascular smooth muscle cells, tumor necrosis factor-α (TNFα) activates VRAC via type 1 TNFα receptors (TNFR1), and this requires superoxide (O) production by NADPH oxidase 1 (Nox1). VRAC inhibitors suppress the inflammatory response to TNFα by an unknown mechanism. We hypothesized that LRRC8A directly supports Nox1 activity, providing a link between VRAC current and inflammatory signaling. VRAC inhibition by 4-(2-butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxobutyric acid (DCPIB) impaired NF-κB activation by TNFα. LRRC8A siRNA reduced the magnitude of VRAC and inhibited TNFα-induced NF-κB activation, iNOS and VCAM expression, and proliferation of VSMCs. Signaling steps disrupted by both siLRRC8A and DCPIB included; extracellular O production by Nox1, c-Jun N-terminal kinase (JNK) phosphorylation and endocytosis of TNFR1. Extracellular superoxide dismutase, but not catalase, selectively inhibited TNFR1 endocytosis and JNK phosphorylation. Thus, O is the critical extracellular oxidant for TNFR signal transduction. Reducing JNK expression (siJNK) increased extracellular O suggesting that JNK provides important negative feedback regulation to Nox1 at the plasma membrane. LRRC8A co-localized by immunostaining, and co-immunoprecipitated with, both Nox1 and its p22phox subunit. LRRC8A is a component of the Nox1 signaling complex. It is required for extracellular O production, which is in turn essential for TNFR1 endocytosis. These data are the first to provide a molecular mechanism for the potent anti-proliferative and anti-inflammatory effects of VRAC inhibition.
Copyright © 2016 Elsevier Inc. All rights reserved.
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Comparison of γ-Aminobutyric Acid, Type A (GABAA), Receptor αβγ and αβδ Expression Using Flow Cytometry and Electrophysiology: EVIDENCE FOR ALTERNATIVE SUBUNIT STOICHIOMETRIES AND ARRANGEMENTS.
Botzolakis EJ, Gurba KN, Lagrange AH, Feng HJ, Stanic AK, Hu N, Macdonald RL
(2016) J Biol Chem 291: 20440-61
MeSH Terms: Epilepsy, Flow Cytometry, Gene Expression Regulation, HEK293 Cells, Humans, Membrane Potentials, Protein Subunits, Receptors, GABA
Show Abstract · Added March 14, 2018
The subunit stoichiometry and arrangement of synaptic αβγ GABAA receptors are generally accepted as 2α:2β:1γ with a β-α-γ-β-α counterclockwise configuration, respectively. Whether extrasynaptic αβδ receptors adopt the analogous β-α-δ-β-α subunit configuration remains controversial. Using flow cytometry, we evaluated expression levels of human recombinant γ2 and δ subunits when co-transfected with α1 and/or β2 subunits in HEK293T cells. Nearly identical patterns of γ2 and δ subunit expression were observed as follows: both required co-transfection with α1 and β2 subunits for maximal expression; both were incorporated into receptors primarily at the expense of β2 subunits; and both yielded similar FRET profiles when probed for subunit adjacency, suggesting similar underlying subunit arrangements. However, because of a slower rate of δ subunit degradation, 10-fold less δ subunit cDNA was required to recapitulate γ2 subunit expression patterns and to eliminate the functional signature of α1β2 receptors. Interestingly, titrating γ2 or δ subunit cDNA levels progressively altered GABA-evoked currents, revealing more than one kinetic profile for both αβγ and αβδ receptors. This raised the possibility of alternative receptor isoforms, a hypothesis confirmed using concatameric constructs for αβγ receptors. Taken together, our results suggest a limited cohort of alternative subunit arrangements in addition to canonical β-α-γ/δ-β-α receptors, including β-α-γ/δ-α-α receptors at lower levels of γ2/δ expression and β-α-γ/δ-α-γ/δ receptors at higher levels of expression. These findings provide important insight into the role of GABAA receptor subunit under- or overexpression in disease states such as genetic epilepsies.
© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
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8 MeSH Terms
Extracellular chloride signals collagen IV network assembly during basement membrane formation.
Cummings CF, Pedchenko V, Brown KL, Colon S, Rafi M, Jones-Paris C, Pokydeshava E, Liu M, Pastor-Pareja JC, Stothers C, Ero-Tolliver IA, McCall AS, Vanacore R, Bhave G, Santoro S, Blackwell TS, Zent R, Pozzi A, Hudson BG
(2016) J Cell Biol 213: 479-94
MeSH Terms: Amino Acid Sequence, Animals, Basement Membrane, Cattle, Cell Line, Tumor, Chlorides, Collagen Type IV, Humans, Phylogeny, Protein Conformation, Protein Structure, Tertiary, Protein Subunits
Show Abstract · Added June 14, 2016
Basement membranes are defining features of the cellular microenvironment; however, little is known regarding their assembly outside cells. We report that extracellular Cl(-) ions signal the assembly of collagen IV networks outside cells by triggering a conformational switch within collagen IV noncollagenous 1 (NC1) domains. Depletion of Cl(-) in cell culture perturbed collagen IV networks, disrupted matrix architecture, and repositioned basement membrane proteins. Phylogenetic evidence indicates this conformational switch is a fundamental mechanism of collagen IV network assembly throughout Metazoa. Using recombinant triple helical protomers, we prove that NC1 domains direct both protomer and network assembly and show in Drosophila that NC1 architecture is critical for incorporation into basement membranes. These discoveries provide an atomic-level understanding of the dynamic interactions between extracellular Cl(-) and collagen IV assembly outside cells, a critical step in the assembly and organization of basement membranes that enable tissue architecture and function. Moreover, this provides a mechanistic framework for understanding the molecular pathobiology of NC1 domains.
© 2016 Cummings et al.
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12 MeSH Terms