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1.
Neuron ; 109(17): 2707-2716.e6, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34473954

RESUMO

The strychnine-sensitive pentameric glycine receptor (GlyR) mediates fast inhibitory neurotransmission in the mammalian nervous system. Only heteromeric GlyRs mediate synaptic transmission, as they contain the ß subunit that permits clustering at the synapse through its interaction with scaffolding proteins. Here, we show that α2 and ß subunits assemble with an unexpected 4:1 stoichiometry to produce GlyR with native electrophysiological properties. We determined structures in multiple functional states at 3.6-3.8 Å resolutions and show how 4:1 stoichiometry is consistent with the structural features of α2ß GlyR. Furthermore, we show that one single ß subunit in each GlyR gives rise to the characteristic electrophysiological properties of heteromeric GlyR, while more ß subunits render GlyR non-conductive. A single ß subunit ensures a univalent GlyR-scaffold linkage, which means the scaffold alone regulates the cluster properties.


Assuntos
Simulação de Dinâmica Molecular , Multimerização Proteica , Receptores de Glicina/química , Potenciais de Ação , Animais , Células HEK293 , Humanos , Bicamadas Lipídicas/metabolismo , Subunidades Proteicas , Receptores de Glicina/metabolismo , Células Sf9 , Spodoptera
2.
Mol Syst Biol ; 17(9): e10079, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34519429

RESUMO

We modeled 3D structures of all SARS-CoV-2 proteins, generating 2,060 models that span 69% of the viral proteome and provide details not available elsewhere. We found that ˜6% of the proteome mimicked human proteins, while ˜7% was implicated in hijacking mechanisms that reverse post-translational modifications, block host translation, and disable host defenses; a further ˜29% self-assembled into heteromeric states that provided insight into how the viral replication and translation complex forms. To make these 3D models more accessible, we devised a structural coverage map, a novel visualization method to show what is-and is not-known about the 3D structure of the viral proteome. We integrated the coverage map into an accompanying online resource (https://aquaria.ws/covid) that can be used to find and explore models corresponding to the 79 structural states identified in this work. The resulting Aquaria-COVID resource helps scientists use emerging structural data to understand the mechanisms underlying coronavirus infection and draws attention to the 31% of the viral proteome that remains structurally unknown or dark.


Assuntos
Enzima de Conversão de Angiotensina 2/metabolismo , Interações Hospedeiro-Patógeno/genética , Processamento de Proteína Pós-Traducional , SARS-CoV-2/metabolismo , Glicoproteína da Espícula de Coronavírus/metabolismo , Sistemas de Transporte de Aminoácidos Neutros/química , Sistemas de Transporte de Aminoácidos Neutros/genética , Sistemas de Transporte de Aminoácidos Neutros/metabolismo , Enzima de Conversão de Angiotensina 2/química , Enzima de Conversão de Angiotensina 2/genética , Sítios de Ligação , COVID-19/genética , COVID-19/metabolismo , COVID-19/virologia , Biologia Computacional/métodos , Proteínas do Envelope de Coronavírus/química , Proteínas do Envelope de Coronavírus/genética , Proteínas do Envelope de Coronavírus/metabolismo , Proteínas do Nucleocapsídeo de Coronavírus/química , Proteínas do Nucleocapsídeo de Coronavírus/genética , Proteínas do Nucleocapsídeo de Coronavírus/metabolismo , Humanos , Proteínas de Transporte da Membrana Mitocondrial/química , Proteínas de Transporte da Membrana Mitocondrial/genética , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Modelos Moleculares , Mimetismo Molecular , Neuropilina-1/química , Neuropilina-1/genética , Neuropilina-1/metabolismo , Fosfoproteínas/química , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Mapeamento de Interação de Proteínas/métodos , Multimerização Proteica , SARS-CoV-2/química , SARS-CoV-2/genética , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/genética , Proteínas da Matriz Viral/química , Proteínas da Matriz Viral/genética , Proteínas da Matriz Viral/metabolismo , Proteínas Viroporinas/química , Proteínas Viroporinas/genética , Proteínas Viroporinas/metabolismo , Replicação Viral
3.
Nat Commun ; 12(1): 4932, 2021 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-34389733

RESUMO

BAX is a pro-apoptotic member of the BCL-2 family, which regulates the balance between cellular life and death. During homeostasis, BAX predominantly resides in the cytosol as a latent monomer but, in response to stress, transforms into an oligomeric protein that permeabilizes the mitochondria, leading to apoptosis. Because renegade BAX activation poses a grave risk to the cell, the architecture of BAX must ensure monomeric stability yet enable conformational change upon stress signaling. The specific structural features that afford both stability and dynamic flexibility remain ill-defined and represent a critical control point of BAX regulation. We identify a nexus of interactions involving four residues of the BAX core α5 helix that are individually essential to maintaining the structure and latency of monomeric BAX and are collectively required for dimeric assembly. The dual yet distinct roles of these residues reveals the intricacy of BAX conformational regulation and opportunities for therapeutic modulation.


Assuntos
Aminoácidos/genética , Apoptose/genética , Mutação , Transdução de Sinais/genética , Proteína X Associada a bcl-2/genética , Aminoácidos/química , Aminoácidos/metabolismo , Animais , Sítios de Ligação/genética , Células Cultivadas , Citosol/metabolismo , Humanos , Camundongos Knockout , Mitocôndrias/metabolismo , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Multimerização Proteica , Proteína X Associada a bcl-2/química , Proteína X Associada a bcl-2/metabolismo
4.
J Phys Chem Lett ; 12(34): 8164-8169, 2021 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-34410720

RESUMO

GPCR oligomerization plays a critical role in cellular signaling, yet the stoichiometry of the interactions between oligomers and binding ligands in living cells remains a longstanding challenge. Here, by developing a dual-color simultaneous tracking system based on a total internal reflection fluorescence microscope (TIRFM), the CCR5-CCL5 interactions are visualized and quantitatively assessed in real time. Results show that each oligomeric state of CCR5 could bind with CCL5 but with different binding affinities; CCR5 dimers have a 3.5-fold higher binding affinity than the monomers. The dimerization may cause an asymmetric conformational change which makes the first binding pocket have a 3.5-fold higher binding affinity and the second have only a half compared with the monomeric CCR5. This study is the first example to directly scrutinize the CCR5-CCL5 interactions at the single-molecule level on living cell membranes and will offer great potential for the interaction stoichiometry study of diverse surface proteins.


Assuntos
Membrana Celular/metabolismo , Multimerização Proteica , Receptores Acoplados a Proteínas G/química , Receptores Acoplados a Proteínas G/metabolismo , Linhagem Celular , Cor , Ligantes , Ligação Proteica , Estrutura Quaternária de Proteína
5.
Nat Commun ; 12(1): 4709, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34354080

RESUMO

Allostery represents a fundamental mechanism of biological regulation that involves long-range communication between distant protein sites. It also provides a powerful framework for novel therapeutics. NMDA receptors (NMDARs), glutamate-gated ionotropic receptors that play central roles in synapse maturation and plasticity, are prototypical allosteric machines harboring large extracellular N-terminal domains (NTDs) that provide allosteric control of key receptor properties with impact on cognition and behavior. It is commonly thought that GluN2A and GluN2B receptors, the two predominant NMDAR subtypes in the adult brain, share similar allosteric transitions. Here, combining functional and structural interrogation, we reveal that GluN2A and GluN2B receptors utilize different long-distance allosteric mechanisms involving distinct subunit-subunit interfaces and molecular rearrangements. NMDARs have thus evolved multiple levels of subunit-specific allosteric control over their transmembrane ion channel pore. Our results uncover an unsuspected diversity in NMDAR molecular mechanisms with important implications for receptor physiology and precision drug development.


Assuntos
Receptores de N-Metil-D-Aspartato/metabolismo , Regulação Alostérica , Animais , Feminino , Células HEK293 , Humanos , Técnicas In Vitro , Camundongos , Modelos Moleculares , Mutagênese Sítio-Dirigida , Oócitos/metabolismo , Fotoquímica , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , Subunidades Proteicas , Ratos , Receptores de N-Metil-D-Aspartato/química , Receptores de N-Metil-D-Aspartato/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Xenopus laevis
6.
Nat Commun ; 12(1): 4718, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34354069

RESUMO

Phospholipid synthesis and fat storage as triglycerides are regulated by lipin phosphatidic acid phosphatases (PAPs), whose enzymatic PAP function requires association with cellular membranes. Using hydrogen deuterium exchange mass spectrometry, we find mouse lipin 1 binds membranes through an N-terminal amphipathic helix, the Ig-like domain and HAD phosphatase catalytic core, and a middle lipin (M-Lip) domain that is conserved in mammalian and mammalian-like lipins. Crystal structures of the M-Lip domain reveal a previously unrecognized protein fold that dimerizes. The isolated M-Lip domain binds membranes both in vitro and in cells through conserved basic and hydrophobic residues. Deletion of the M-Lip domain in lipin 1 reduces PAP activity, membrane association, and oligomerization, alters subcellular localization, diminishes acceleration of adipocyte differentiation, but does not affect transcriptional co-activation. This establishes the M-Lip domain as a dimeric protein fold that binds membranes and is critical for full functionality of mammalian lipins.


Assuntos
Fosfatidato Fosfatase/química , Células 3T3-L1 , Adipogenia , Sequência de Aminoácidos , Animais , Membrana Celular/metabolismo , Sequência Conservada , Cristalografia por Raios X , Células HEK293 , Humanos , Espectrometria de Massa com Troca Hidrogênio-Deutério , Proteínas de Membrana/química , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Modelos Moleculares , Simulação de Dinâmica Molecular , Fosfatidato Fosfatase/genética , Fosfatidato Fosfatase/metabolismo , Ligação Proteica , Domínios Proteicos , Dobramento de Proteína , Multimerização Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Deleção de Sequência , Homologia de Sequência de Aminoácidos , Transcrição Genética
7.
Nat Commun ; 12(1): 4849, 2021 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-34381032

RESUMO

Although various artificial protein nanoarchitectures have been constructed, controlling the transformation between different protein assemblies has largely been unexplored. Here, we describe an approach to realize the self-assembly transformation of dimeric building blocks by adjusting their geometric arrangement. Thermotoga maritima ferritin (TmFtn) naturally occurs as a dimer; twelve of these dimers interact with each other in a head-to-side manner to generate 24-meric hollow protein nanocage in the presence of Ca2+ or PEG. By tuning two contiguous dimeric proteins to interact in a fully or partially side-by-side fashion through protein interface redesign, we can render the self-assembly transformation of such dimeric building blocks from the protein nanocage to filament, nanorod and nanoribbon in response to multiple external stimuli. We show similar dimeric protein building blocks can generate three kinds of protein materials in a manner that highly resembles natural pentamer building blocks from viral capsids that form different protein assemblies.


Assuntos
Nanoestruturas/química , Proteínas/química , Cálcio/química , Ferritinas/química , Nanoestruturas/ultraestrutura , Nanotecnologia , Polietilenoglicóis/química , Multimerização Proteica , Thermotoga maritima
8.
Int J Mol Sci ; 22(16)2021 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-34445230

RESUMO

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is one of the best studied enzymes. It is crucial for photosynthesis, and thus for all of biosphere's productivity. There are four isoforms of this enzyme, differing by amino acid sequence composition and quaternary structure. However, there is still a group of organisms, dinoflagellates, single-cell eukaryotes, that are confirmed to possess Rubisco, but no successful purification of the enzyme of such origin, and hence a generation of a crystal structure was reported to date. Here, we are using in silico tools to generate the possible structure of Rubisco from a dinoflagellate representative, Symbiodinium sp. We selected two templates: Rubisco from Rhodospirillum rubrum and Rhodopseudomonas palustris. Both enzymes are the so-called form II Rubiscos, but the first is exclusively a homodimer, while the second one forms homo-hexamers. Obtained models show no differences in amino acids crucial for Rubisco activity. The variation was found at two closely located inserts in the C-terminal domain, of which one extends a helix and the other forms a loop. These inserts most probably do not play a direct role in the enzyme's activity, but may be responsible for interaction with an unknown protein partner, possibly a regulator or a chaperone. Analysis of the possible oligomerization interface indicated that Symbiodinium sp. Rubisco most likely forms a trimer of homodimers, not just a homodimer. This hypothesis was empowered by calculation of binding energies. Additionally, we found that the protein of study is significantly richer in cysteine residues, which may be the cause for its activity loss shortly after cell lysis. Furthermore, we evaluated the influence of the loop insert, identified exclusively in the Symbiodinium sp. protein, on the functionality of the recombinantly expressed R. rubrum Rubisco. All these findings shed new light onto dinoflagellate Rubisco and may help in future obtainment of a native, active enzyme.


Assuntos
Multimerização Proteica , Rhodospirillum rubrum/enzimologia , Ribulose-Bifosfato Carboxilase/química , Domínios Proteicos , Rhodospirillum rubrum/genética , Ribulose-Bifosfato Carboxilase/genética
9.
Viruses ; 13(7)2021 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-34372582

RESUMO

Ebolavirus (EBOV) is a negative-sense RNA virus that causes severe hemorrhagic fever in humans. The matrix protein VP40 facilitates viral budding by binding to lipids in the host cell plasma membrane and driving the formation of filamentous, pleomorphic virus particles. The C-terminal domain of VP40 contains two highly-conserved cysteine residues at positions 311 and 314, but their role in the viral life cycle is unknown. We therefore investigated the properties of VP40 mutants in which the conserved cysteine residues were replaced with alanine. The C311A mutation significantly increased the affinity of VP40 for membranes containing phosphatidylserine (PS), resulting in the assembly of longer virus-like particles (VLPs) compared to wild-type VP40. The C314A mutation also increased the affinity of VP40 for membranes containing PS, albeit to a lesser degree than C311A. The double mutant behaved in a similar manner to the individual mutants. Computer modeling revealed that both cysteine residues restrain a loop segment containing lysine residues that interact with the plasma membrane, but Cys311 has the dominant role. Accordingly, the C311A mutation increases the flexibility of this membrane-binding loop, changes the profile of hydrogen bonding within VP40 and therefore binds to PS with greater affinity. This is the first evidence that mutations in VP40 can increase its affinity for biological membranes and modify the length of Ebola VLPs. The Cys311 and Cys314 residues therefore play an important role in dynamic interactions at the plasma membrane by modulating the ability of VP40 to bind PS.


Assuntos
Ebolavirus/genética , Proteínas da Matriz Viral/genética , Animais , Células COS , Membrana Celular/metabolismo , Chlorocebus aethiops , Cisteína/genética , Ebolavirus/metabolismo , Humanos , Lipídeos/fisiologia , Simulação de Dinâmica Molecular , Fosfatidilserinas/metabolismo , Polimorfismo de Nucleotídeo Único/genética , Ligação Proteica , Multimerização Proteica , Proteínas da Matriz Viral/metabolismo , Proteínas da Matriz Viral/ultraestrutura , Vírion/metabolismo , Montagem de Vírus/genética , Liberação de Vírus/genética
10.
Int J Mol Sci ; 22(16)2021 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-34445785

RESUMO

Protein homo-oligomerization is a very common phenomenon, and approximately half of proteins form homo-oligomeric assemblies composed of identical subunits. The vast majority of such assemblies possess internal symmetry which can be either exploited to help or poses challenges during structure determination. Moreover, aspects of symmetry are critical in the modeling of protein homo-oligomers either by docking or by homology-based approaches. Here, we first provide a brief overview of the nature of protein homo-oligomerization. Next, we describe how the symmetry of homo-oligomers is addressed by crystallographic and non-crystallographic symmetry operations, and how biologically relevant intermolecular interactions can be deciphered from the ordered array of molecules within protein crystals. Additionally, we describe the most important aspects of protein homo-oligomerization in structure determination by NMR. Finally, we give an overview of approaches aimed at modeling homo-oligomers using computational methods that specifically address their internal symmetry and allow the incorporation of other experimental data as spatial restraints to achieve higher model reliability.


Assuntos
Multimerização Proteica/fisiologia , Proteínas/química , Algoritmos , Humanos , Modelos Moleculares , Simulação de Acoplamento Molecular/métodos , Conformação Proteica , Reprodutibilidade dos Testes
11.
Int J Mol Sci ; 22(15)2021 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-34360683

RESUMO

Despite the known importance of the transmembrane domain (TMD) of syndecan receptors in cell adhesion and signaling, the molecular basis for syndecan TMD function remains unknown. Using in vivo invertebrate models, we found that mammalian syndecan-2 rescued both the guidance defects in C. elegans hermaphrodite-specific neurons and the impaired development of the midline axons of Drosophila caused by the loss of endogenous syndecan. These compensatory effects, however, were reduced significantly when syndecan-2 dimerization-defective TMD mutants were introduced. To further investigate the role of the TMD, we generated a chimera, 2eTPC, comprising the TMD of syndecan-2 linked to the cytoplasmic domain of platelet-derived growth factor receptor (PDGFR). This chimera exhibited SDS-resistant dimer formation that was lost in the corresponding dimerization-defective syndecan-2 TMD mutant, 2eT(GL)PC. Moreover, 2eTPC specifically enhanced Tyr 579 and Tyr 857 phosphorylation in the PDGFR cytoplasmic domain, while the TMD mutant failed to support such phosphorylation. Finally, 2eTPC, but not 2eT(GL)PC, induced phosphorylation of Src and PI3 kinase (known downstream effectors of Tyr 579 phosphorylation) and promoted Src-mediated migration of NIH3T3 cells. Taken together, these data suggest that the TMD of a syndecan-2 specifically regulates receptor cytoplasmic domain function and subsequent downstream signaling events controlling cell behavior.


Assuntos
Adesão Celular , Domínios Proteicos , Transdução de Sinais , Sindecana-2/metabolismo , Animais , Células HEK293 , Humanos , Camundongos , Células NIH 3T3 , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação , Multimerização Proteica , Processamento de Proteína Pós-Traducional , Sindecana-2/fisiologia , Quinases da Família src/metabolismo
12.
J Chem Phys ; 155(7): 075101, 2021 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-34418942

RESUMO

Intercellular fluids in living organisms contain high concentrations of macromolecules such as nucleic acid and protein. Over the past few decades, several studies have examined membraneless organelles in terms of liquid-liquid phase separation. These studies have investigated aggregation/attraction among a rich variety of biomolecules. Here, we studied the association between the polymerization/depolymerization of actin, interconversion between monomeric (G-actin) and filamentous states (F-actin), and water/water phase separation in a binary polymer solution using polyethylene glycol (PEG) and dextran (DEX). We found that actin, which is a representative cytoskeleton, changes its distribution in a PEG/DEX binary solution depending on its polymerization state: monomeric G-actin is distributed homogeneously throughout the solution, whereas polymerized F-actin is localized only within the DEX-rich phase. We extended our study by using fragmin, which is a representative actin-severing and -depolymerizing factor. It took hours to restore a homogeneous actin distribution from localization within the DEX-rich phase, even with the addition of fragmin in an amount that causes complete depolymerization. In contrast, when actin that had been depolymerized by fragmin in advance was added to a solution with microphase-separation, F-actin was found in DEX-rich phase droplets. The micro-droplets tended to deform into a non-spherical morphology under conditions where they contained F-actin. These findings suggest that microphase-separation is associated with the dynamics of polymerization and localization of the actin cytoskeleton. We discuss our observations by taking into consideration the polymer depletion effect.


Assuntos
Actinas/química , Multimerização Proteica , Dextranos/química , Modelos Moleculares , Polietilenoglicóis/química , Estrutura Quaternária de Proteína , Soluções , Água/química
13.
Nat Commun ; 12(1): 5083, 2021 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-34426577

RESUMO

AMPA receptor (AMPAR) abundance and positioning at excitatory synapses regulates the strength of transmission. Changes in AMPAR localisation can enact synaptic plasticity, allowing long-term information storage, and is therefore tightly controlled. Multiple mechanisms regulating AMPAR synaptic anchoring have been described, but with limited coherence or comparison between reports, our understanding of this process is unclear. Here, combining synaptic recordings from mouse hippocampal slices and super-resolution imaging in dissociated cultures, we compare the contributions of three AMPAR interaction domains controlling transmission at hippocampal CA1 synapses. We show that the AMPAR C-termini play only a modulatory role, whereas the extracellular N-terminal domain (NTD) and PDZ interactions of the auxiliary subunit TARP γ8 are both crucial, and each is sufficient to maintain transmission. Our data support a model in which γ8 accumulates AMPARs at the postsynaptic density, where the NTD further tunes their positioning. This interplay between cytosolic (TARP γ8) and synaptic cleft (NTD) interactions provides versatility to regulate synaptic transmission and plasticity.


Assuntos
Região CA1 Hipocampal/metabolismo , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Receptores de AMPA/metabolismo , Sinapses/metabolismo , Sequência de Aminoácidos , Animais , Corantes Fluorescentes/metabolismo , Imageamento Tridimensional , Camundongos Endogâmicos C57BL , Modelos Neurológicos , Mutação/genética , Plasticidade Neuronal , Neurônios/metabolismo , Ligação Proteica , Domínios Proteicos , Multimerização Proteica , Receptores de AMPA/química , Transmissão Sináptica
14.
Mol Cell ; 81(16): 3246-3261.e11, 2021 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-34352208

RESUMO

The Wnt/ß-catenin pathway is a highly conserved, frequently mutated developmental and cancer pathway. Its output is defined mainly by ß-catenin's phosphorylation- and ubiquitylation-dependent proteasomal degradation, initiated by the multi-protein ß-catenin destruction complex. The precise mechanisms underlying destruction complex function have remained unknown, largely because of the lack of suitable in vitro systems. Here we describe the in vitro reconstitution of an active human ß-catenin destruction complex from purified components, recapitulating complex assembly, ß-catenin modification, and degradation. We reveal that AXIN1 polymerization and APC promote ß-catenin capture, phosphorylation, and ubiquitylation. APC facilitates ß-catenin's flux through the complex by limiting ubiquitylation processivity and directly interacts with the SCFß-TrCP E3 ligase complex in a ß-TrCP-dependent manner. Oncogenic APC truncation variants, although part of the complex, are functionally impaired. Nonetheless, even the most severely truncated APC variant promotes ß-catenin recruitment. These findings exemplify the power of biochemical reconstitution to interrogate the molecular mechanisms of Wnt/ß-catenin signaling.


Assuntos
Proteína da Polipose Adenomatosa do Colo/genética , Proteína Axina/genética , beta Catenina/genética , Proteína da Polipose Adenomatosa do Colo/ultraestrutura , Proteína Axina/química , Proteína Axina/ultraestrutura , Humanos , Complexos Multiproteicos/genética , Complexos Multiproteicos/ultraestrutura , Fosforilação/genética , Multimerização Proteica/genética , Proteólise , Ubiquitinação/genética , Via de Sinalização Wnt
15.
Int J Mol Sci ; 22(16)2021 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-34445435

RESUMO

Retinal guanylate cyclases (RetGCs) promote the Ca2+-dependent synthesis of cGMP that coordinates the recovery phase of visual phototransduction in retinal rods and cones. The Ca2+-sensitive activation of RetGCs is controlled by a family of photoreceptor Ca2+ binding proteins known as guanylate cyclase activator proteins (GCAPs). The Mg2+-bound/Ca2+-free GCAPs bind to RetGCs and activate cGMP synthesis (cyclase activity) at low cytosolic Ca2+ levels in light-activated photoreceptors. By contrast, Ca2+-bound GCAPs bind to RetGCs and inactivate cyclase activity at high cytosolic Ca2+ levels found in dark-adapted photoreceptors. Mutations in both RetGCs and GCAPs that disrupt the Ca2+-dependent cyclase activity are genetically linked to various retinal diseases known as cone-rod dystrophies. In this review, I will provide an overview of the known atomic-level structures of various GCAP proteins to understand how protein dimerization and Ca2+-dependent conformational changes in GCAPs control the cyclase activity of RetGCs. This review will also summarize recent structural studies on a GCAP homolog from zebrafish (GCAP5) that binds to Fe2+ and may serve as a Fe2+ sensor in photoreceptors. The GCAP structures reveal an exposed hydrophobic surface that controls both GCAP1 dimerization and RetGC binding. This exposed site could be targeted by therapeutics designed to inhibit the GCAP1 disease mutants, which may serve to mitigate the onset of retinal cone-rod dystrophies.


Assuntos
Cálcio/metabolismo , Proteínas Ativadoras de Guanilato Ciclase/química , Ferro/metabolismo , Proteínas de Peixe-Zebra/química , Peixe-Zebra/metabolismo , Animais , Proteínas Ativadoras de Guanilato Ciclase/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Transdução de Sinal Luminoso , Modelos Moleculares , Conformação Proteica , Multimerização Proteica , Proteínas de Peixe-Zebra/metabolismo
16.
Int J Mol Sci ; 22(16)2021 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-34445158

RESUMO

α-Synuclein oligomers are thought to play an important role in the pathogenesis of dementia with Lewy bodies (DLB). There is no effective cure for DLB at present. Previously, we demonstrated that in APP- and tau-transgenic mice, oral or intranasal rifampicin reduced brain Aß and tau oligomers and improved mouse cognition. In the present study, we expanded our research to DLB. Rifampicin was intranasally administered to 6-month-old A53T-mutant α-synuclein-transgenic mice at 0.1 mg/day for 1 month. The mice displayed memory impairment but no motor deficit at this age, indicating a suitable model of DLB. α-Synuclein pathologies were examined by the immunohistochemical/biochemical analyses of brain tissues. Cognitive function was evaluated by the Morris water maze test. Intranasal rifampicin significantly reduced the levels of [pSer129] α-synuclein in the hippocampus and α-synuclein oligomers in the visual cortex and hippocampus. The level of the presynaptic marker synaptophysin in the hippocampus was recovered to the level in non-transgenic littermates. In the Morris water maze, a significant improvement in spatial reference memory was observed in rifampicin-treated mice. Taken together with our previous findings, these results suggest that intranasal rifampicin is a promising remedy for the prevention of neurodegenerative dementia, including Alzheimer's disease, frontotemporal dementia, and DLB.


Assuntos
Cognição/efeitos dos fármacos , Demência/tratamento farmacológico , Doença por Corpos de Lewy/tratamento farmacológico , Rifampina/uso terapêutico , alfa-Sinucleína/metabolismo , Administração Intranasal , Animais , Demência/metabolismo , Demência/patologia , Modelos Animais de Doenças , Feminino , Corpos de Lewy/efeitos dos fármacos , Corpos de Lewy/metabolismo , Corpos de Lewy/patologia , Doença por Corpos de Lewy/metabolismo , Doença por Corpos de Lewy/patologia , Masculino , Camundongos Transgênicos , Multimerização Proteica/efeitos dos fármacos , Rifampina/administração & dosagem , alfa-Sinucleína/análise
17.
Int J Mol Sci ; 22(15)2021 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-34360542

RESUMO

In this study, a reliable and simple method of untagged recombinant human HspB7 preparation was developed. Recombinant HspB7 is presented in two oligomeric forms with an apparent molecular weight of 36 kDa (probably dimers) and oligomers with an apparent molecular weight of more than 600 kDa. By using hydrophobic and size-exclusion chromatography, we succeeded in preparation of HspB7 dimers. Mild oxidation promoted the formation of large oligomers, whereas the modification of Cys 126 by iodoacetamide prevented it. The deletion of the first 13 residues or deletion of the polySer motif (residues 17-29) also prevented the formation of large oligomers of HspB7. Cys-mutants of HspB6 and HspB8 containing a single-Cys residue in the central part of the ß7 strand in a position homologous to that of Cys137 in HspB1 can be crosslinked to the wild-type HspB7 through a disulfide bond. Immobilized on monoclonal antibodies, the wild-type HspB6 interacted with the wild-type HspB7. We suppose that formation of heterodimers of HspB7 with HspB6 and HspB8 may be important for the functional activity of these small heat shock proteins.


Assuntos
Proteínas de Choque Térmico HSP27/química , Multimerização Proteica , Proteínas Recombinantes/química , Humanos , Domínios Proteicos , Estrutura Quaternária de Proteína
18.
mBio ; 12(4): e0209421, 2021 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-34399606

RESUMO

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent for coronavirus disease 2019 (COVID-19), encodes two proteases required for replication. The main protease (Mpro), encoded as part of two polyproteins, pp1a and pp1ab, is responsible for 11 different cleavages of these viral polyproteins to produce mature proteins required for viral replication. Mpro is therefore an attractive target for therapeutic interventions. Certain proteins in cells under oxidative stress undergo modification of reactive cysteines. We show Mpro is susceptible to glutathionylation, leading to inhibition of dimerization and activity. Activity of glutathionylated Mpro could be restored with reducing agents or glutaredoxin. Analytical studies demonstrated that glutathionylated Mpro primarily exists as a monomer and that modification of a single cysteine with glutathione is sufficient to block dimerization and inhibit its activity. Gel filtration studies as well as analytical ultracentrifugation confirmed that glutathionylated Mpro exists as a monomer. Tryptic and chymotryptic digestions of Mpro as well as experiments using a C300S Mpro mutant revealed that Cys300, which is located at the dimer interface, is a primary target of glutathionylation. Moreover, Cys300 is required for inhibition of activity upon Mpro glutathionylation. These findings indicate that Mpro dimerization and activity can be regulated through reversible glutathionylation of a non-active site cysteine, Cys300, which itself is not required for Mpro activity, and provides a novel target for the development of agents to block Mpro dimerization and activity. This feature of Mpro may have relevance to the pathophysiology of SARS-CoV-2 and related bat coronaviruses. IMPORTANCE SARS-CoV-2 is responsible for the devastating COVID-19 pandemic. Therefore, it is imperative that we learn as much as we can about the biochemistry of the coronavirus proteins to inform development of therapy. One attractive target is the main protease (Mpro), a dimeric enzyme necessary for viral replication. Most work thus far developing Mpro inhibitors has focused on the active site. Our work has revealed a regulatory mechanism for Mpro activity through glutathionylation of a cysteine (Cys300) at the dimer interface, which can occur in cells under oxidative stress. Cys300 glutathionylation inhibits Mpro activity by blocking its dimerization. This provides a novel accessible and reactive target for drug development. Moreover, this process may have implications for disease pathophysiology in humans and bats. It may be a mechanism by which SARS-CoV-2 has evolved to limit replication and avoid killing host bats when they are under oxidative stress during flight.


Assuntos
Proteases 3C de Coronavírus/metabolismo , Cisteína/química , Glutationa/química , Multimerização Proteica , SARS-CoV-2/metabolismo , Animais , COVID-19/patologia , Quirópteros/virologia , Proteases 3C de Coronavírus/antagonistas & inibidores , Dimerização , Glutarredoxinas/metabolismo , Humanos , SARS-CoV-2/enzimologia
20.
J Phys Chem Lett ; 12(32): 7878-7884, 2021 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-34382809

RESUMO

The histone-like nucleoid structuring (H-NS) protein controls the expression of hundreds of genes in Gram-positive bacteria through its capability to coat and condense DNA. This mechanism requires the formation of superhelical H-NS protein filaments that are sensitive to temperature and salinity, allowing H-NS to act as an environment sensor. We use multiscale modeling and simulations to obtain detailed insights into the mechanism of H-NS filament's sensitivity to environmental changes. Through the simulations of the superhelical H-NS filament, we reveal how different environments induce heterogeneity of H-NS monomers. Further, we observe that transient self-association within the H-NS filament creates temperature-inducible strain and might mildly oppose DNA binding. We also probe different H-NS-DNA complex architectures and show that complexation enhances the stability of both DNA and H-NS superhelices. Overall, our results provide unprecedented molecular insights into the environmental sensing and DNA interactions of a prototypical nucleoid-structuring bacterial protein filament.


Assuntos
Proteínas de Bactérias/química , Proteínas de Ligação a DNA/química , Sequência de Aminoácidos , Proteínas de Bactérias/metabolismo , DNA/química , DNA/metabolismo , Proteínas de Ligação a DNA/metabolismo , Simulação de Dinâmica Molecular , Ligação Proteica , Domínios Proteicos , Multimerização Proteica , Salinidade , Salmonella typhimurium/química , Temperatura
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