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1.
J Immunother Cancer ; 9(1)2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33408094

RESUMO

BACKGROUND: Hematopoietic progenitor kinase 1 (HPK1 or MAP4K1) has been demonstrated as a negative intracellular immune checkpoint in mediating antitumor immunity in studies with HPK1 knockout and kinase dead mice. Pharmacological inhibition of HPK1 is desirable to investigate the role of HPK1 in human immune cells with therapeutic implications. However, a significant challenge remains to identify a small molecule inhibitor of HPK1 with sufficient potency, selectivity, and other drug-like properties suitable for proof-of-concept studies. In this report, we identified a novel, potent, and selective HPK1 small molecule kinase inhibitor, compound K (CompK). A series of studies were conducted to investigate the mechanism of action of CompK, aiming to understand its potential application in cancer immunotherapy. METHODS: Human primary T cells and dendritic cells (DCs) were investigated with CompK treatment under conditions relevant to tumor microenvironment (TME). Syngeneic tumor models were used to assess the in vivo pharmacology of CompK followed by human tumor interrogation ex vivo. RESULTS: CompK treatment demonstrated markedly enhanced human T-cell immune responses under immunosuppressive conditions relevant to the TME and an increased avidity of the T-cell receptor (TCR) to recognize viral and tumor-associated antigens (TAAs) in significant synergy with anti-PD1. Animal model studies, including 1956 sarcoma and MC38 syngeneic models, revealed improved immune responses and superb antitumor efficacy in combination of CompK with anti-PD-1. An elevated immune response induced by CompK was observed with fresh tumor samples from multiple patients with colorectal carcinoma, suggesting a mechanistic translation from mouse model to human disease. CONCLUSION: CompK treatment significantly improved human T-cell functions, with enhanced TCR avidity to recognize TAAs and tumor cytolytic activity by CD8+ T cells. Additional benefits include DC maturation and priming facilitation in tumor draining lymph node. CompK represents a novel pharmacological agent to address cancer treatment resistance.

2.
Drug Discov Today ; 2021 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-33497831

RESUMO

Kinases, accounting for 20% of the human genome, have been the focus of pharmaceutical drug discovery efforts for over three decades. Despite concerns surrounding the tractability of kinases as drug targets, it is evident that kinase drug discovery offers great potential, underscored by the US Food and Drug Administration (FDA) approval of 48 small-molecule kinase inhibitors. Despite these successes, it is challenging to identify novel kinome selective inhibitors with good pharmacokinetic/pharmacodynamic (PK/PD) properties, and resistance to kinase inhibitor treatment frequently arises. A new era of kinase drug discovery predicates the need for diverse and powerful tools to discover the next generation of kinase inhibitors. Here, we outline key tenets of the Bristol Meyers Squibb (BMS) kinase platform, to enable efficient generation of highly optimized kinase inhibitors.

3.
J Med Chem ; 64(1): 677-694, 2021 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-33370104

RESUMO

A search for structurally diversified Tyk2 JH2 ligands from 6 (BMS-986165), a pyridazine carboxamide-derived Tyk2 JH2 ligand as a clinical Tyk2 inhibitor currently in late development for the treatment of psoriasis, began with a survey of six-membered heteroaryl groups in place of the N-methyl triazolyl moiety in 6. The X-ray co-crystal structure of an early lead (12) revealed a potential new binding pocket. Exploration of the new pocket resulted in two frontrunners for a clinical candidate. The potential hydrogen bonding interaction with Thr599 in the pocket was achieved with a tertiary amide moiety, confirmed by the X-ray co-crystal structure of 29. When the diversity search was extended to nicotinamides, a single fluorine atom addition was found to significantly enhance the permeability, which directly led to the discovery of 7 (BMS-986202) as a clinical Tyk2 inhibitor that binds to Tyk2 JH2. The preclinical studies of 7, including efficacy studies in mouse models of IL-23-driven acanthosis, anti-CD40-induced colitis, and spontaneous lupus, will also be presented.


Assuntos
Ciclopropanos/farmacologia , Descoberta de Drogas , Oxazóis/farmacologia , Inibidores de Proteínas Quinases/farmacologia , TYK2 Quinase/antagonistas & inibidores , Animais , Catálise , Cristalografia por Raios X , Ciclopropanos/química , Humanos , Camundongos , Oxazóis/química , Ligação Proteica , Inibidores de Proteínas Quinases/química , Psoríase/tratamento farmacológico , Relação Estrutura-Atividade , TYK2 Quinase/metabolismo
4.
ACS Med Chem Lett ; 11(3): 266-271, 2020 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-32184955

RESUMO

Necroptosis has been implicated in a variety of disease states, and RIPK3 is one of the kinases identified to play a critical role in this signaling pathway. In an effort to identify RIPK3 kinase inhibitors with a novel profile, mechanistic studies were incorporated at the hit triage stage. Utilization of these assays enabled identification of a Type II DFG-out inhibitor for RIPK3, which was confirmed by protein crystallography. Structure-based drug design on the inhibitors targeting this previously unreported conformation enabled an enhancement in selectivity against key off-target kinases.

5.
Sci Transl Med ; 11(502)2019 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-31341059

RESUMO

TYK2 is a nonreceptor tyrosine kinase involved in adaptive and innate immune responses. A deactivating coding variant has previously been shown to prevent receptor-stimulated activation of this kinase and provides high protection from several common autoimmune diseases but without immunodeficiency. An agent that recapitulates the phenotype of this deactivating coding variant may therefore represent an important advancement in the treatment of autoimmunity. BMS-986165 is a potent oral agent that similarly blocks receptor-stimulated activation of TYK2 allosterically and with high selectivity and potency afforded through optimized binding to a regulatory domain of the protein. Signaling and functional responses in human TH17, TH1, B cells, and myeloid cells integral to autoimmunity were blocked by BMS-986165, both in vitro and in vivo in a phase 1 clinical trial. BMS-986165 demonstrated robust efficacy, consistent with blockade of multiple autoimmune pathways, in murine models of lupus nephritis and inflammatory bowel disease, supporting its therapeutic potential for multiple immune-mediated diseases.


Assuntos
Autoimunidade/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , TYK2 Quinase/química , Animais , Feminino , Voluntários Saudáveis , Compostos Heterocíclicos/farmacologia , Humanos , Interferon alfa-2/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos SCID , Inibidores de Proteínas Quinases/farmacologia , TYK2 Quinase/antagonistas & inibidores
6.
J Med Chem ; 62(20): 8973-8995, 2019 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-31318208

RESUMO

Small molecule JAK inhibitors have emerged as a major therapeutic advancement in treating autoimmune diseases. The discovery of isoform selective JAK inhibitors that traditionally target the catalytically active site of this kinase family has been a formidable challenge. Our strategy to achieve high selectivity for TYK2 relies on targeting the TYK2 pseudokinase (JH2) domain. Herein we report the late stage optimization efforts including a structure-guided design and water displacement strategy that led to the discovery of BMS-986165 (11) as a high affinity JH2 ligand and potent allosteric inhibitor of TYK2. In addition to unprecedented JAK isoform and kinome selectivity, 11 shows excellent pharmacokinetic properties with minimal profiling liabilities and is efficacious in several murine models of autoimmune disease. On the basis of these findings, 11 appears differentiated from all other reported JAK inhibitors and has been advanced as the first pseudokinase-directed therapeutic in clinical development as an oral treatment for autoimmune diseases.


Assuntos
Doenças Autoimunes/tratamento farmacológico , Descoberta de Drogas , Compostos Heterocíclicos/farmacologia , Inibidores de Proteínas Quinases/farmacologia , TYK2 Quinase/antagonistas & inibidores , Regulação Alostérica/efeitos dos fármacos , Animais , Cristalografia por Raios X , Compostos Heterocíclicos/química , Compostos Heterocíclicos/farmacocinética , Compostos Heterocíclicos/uso terapêutico , Humanos , Camundongos , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacocinética , Inibidores de Proteínas Quinases/uso terapêutico
7.
J Med Chem ; 62(20): 8953-8972, 2019 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-31314518

RESUMO

As a member of the Janus (JAK) family of nonreceptor tyrosine kinases, TYK2 plays an important role in mediating the signaling of pro-inflammatory cytokines including IL-12, IL-23, and type 1 interferons. The nicotinamide 4, identified by a SPA-based high-throughput screen targeting the TYK2 pseudokinase domain, potently inhibits IL-23 and IFNα signaling in cellular assays. The described work details the optimization of this poorly selective hit (4) to potent and selective molecules such as 47 and 48. The discoveries described herein were critical to the eventual identification of the clinical TYK2 JH2 inhibitor (see following report in this issue). Compound 48 provided robust inhibition in a mouse IL-12-induced IFNγ pharmacodynamic model as well as efficacy in an IL-23 and IL-12-dependent mouse colitis model. These results demonstrate the ability of TYK2 JH2 domain binders to provide a highly selective alternative to conventional TYK2 orthosteric inhibitors.


Assuntos
Niacinamida/análogos & derivados , Ácidos Nicotínicos/farmacologia , Inibidores de Proteínas Quinases/farmacologia , TYK2 Quinase/antagonistas & inibidores , Regulação Alostérica , Animais , Humanos , Ligantes , Camundongos , Niacinamida/metabolismo , Niacinamida/farmacologia , Ácidos Nicotínicos/metabolismo , Inibidores de Proteínas Quinases/metabolismo , Relação Estrutura-Atividade
8.
ACS Med Chem Lett ; 10(3): 383-388, 2019 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-30891145

RESUMO

In sharp contrast to a previously reported series of 6-anilino imidazopyridazine based Tyk2 JH2 ligands, 6-((2-oxo-N1-substituted-1,2-dihydropyridin-3-yl)amino)imidazo[1,2-b]pyridazine analogs were found to display dramatically improved metabolic stability. The N1-substituent on 2-oxo-1,2-dihydropyridine ring can be a variety of alkyl, aryl, and heteroaryl groups, but among them, 2-pyridyl provided much enhanced Caco-2 permeability, attributed to its ability to form intramolecular hydrogen bonds. Further structure-activity relationship studies at the C3 position led to the identification of highly potent and selective Tyk2 JH2 inhibitor 6, which proved to be highly effective in inhibiting IFNγ production in a rat pharmacodynamics model and fully efficacious in a rat adjuvant arthritis model.

9.
J Med Chem ; 62(7): 3228-3250, 2019 04 11.
Artigo em Inglês | MEDLINE | ID: mdl-30893553

RESUMO

Bruton's tyrosine kinase (BTK), a non-receptor tyrosine kinase, is a member of the Tec family of kinases and is essential for B cell receptor (BCR) mediated signaling. BTK also plays a critical role in the downstream signaling pathways for the Fcγ receptor in monocytes, the Fcε receptor in granulocytes, and the RANK receptor in osteoclasts. As a result, pharmacological inhibition of BTK is anticipated to provide an effective strategy for the clinical treatment of autoimmune diseases such as rheumatoid arthritis and lupus. This article will outline the evolution of our strategy to identify a covalent, irreversible inhibitor of BTK that has the intrinsic potency, selectivity, and pharmacokinetic properties necessary to provide a rapid rate of inactivation systemically following a very low dose. With excellent in vivo efficacy and a very desirable tolerability profile, 5a (branebrutinib, BMS-986195) has advanced into clinical studies.


Assuntos
Tirosina Quinase da Agamaglobulinemia/antagonistas & inibidores , Descoberta de Drogas , Indóis/farmacologia , Piperidinas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Animais , Artrite Reumatoide/tratamento farmacológico , Relação Dose-Resposta a Droga , Humanos , Indóis/farmacocinética , Indóis/uso terapêutico , Concentração Inibidora 50 , Lúpus Eritematoso Sistêmico/tratamento farmacológico , Macaca fascicularis , Camundongos , Piperidinas/farmacocinética , Piperidinas/uso terapêutico , Inibidores de Proteínas Quinases/farmacocinética , Inibidores de Proteínas Quinases/uso terapêutico
10.
Bioorg Med Chem Lett ; 28(18): 3080-3084, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30097367

RESUMO

Incorporation of a suitably-placed electrophilic group transformed a series of reversible BTK inhibitors based on carbazole-1-carboxamide and tetrahydrocarbazole-1-carboxamide into potent, irreversible inhibitors. Removal of one ring from the core of these compounds provided a potent irreversible series of 2,3-dimethylindole-7-carboxamides having excellent potency and improved selectivity, with the additional advantages of reduced lipophilicity and molecular weight.


Assuntos
Tirosina Quinase da Agamaglobulinemia/antagonistas & inibidores , Carbazóis/farmacologia , Indóis/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Tirosina Quinase da Agamaglobulinemia/metabolismo , Carbazóis/síntese química , Carbazóis/química , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Humanos , Indóis/síntese química , Indóis/química , Modelos Moleculares , Estrutura Molecular , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/química , Relação Estrutura-Atividade
12.
Anal Biochem ; 497: 8-17, 2016 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-26743718

RESUMO

XIAP (X-chromosome-linked inhibitor of apoptosis protein) is a central apoptosis regulator that blocks cell death by inhibiting caspase-3, caspase-7, and caspase-9 via binding interactions with the XIAP BIR2 and BIR3 domains (where BIR is baculovirus IAP repeat). Smac protein, in its dimeric form, effectively antagonizes XIAP by concurrently targeting both its BIR2 and BIR3 domains. Here we describe the development of highly sensitive homogeneous time-resolved fluorescence resonance energy transfer (HTRF) assays to measure binding affinities of potent bivalent peptidomimetic inhibitors of XIAP. Our results indicate that these assays can differentiate Smac-mimetic inhibitors with a wide range of binding affinities down to the picomolar range. Furthermore, we demonstrate the utility of these fluorescent tools for characterization of inhibitor off-rates, which as a crucial determinant of target engagement and cellular potency is another important parameter to guide optimization in a structure-based drug discovery effort. Our study also explores how increased inhibitor valency can lead to enhanced potency at multimeric proteins such as IAP.


Assuntos
Transferência Ressonante de Energia de Fluorescência/métodos , Peptidomiméticos/farmacologia , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/antagonistas & inibidores , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/metabolismo , Animais , Caspase 3/metabolismo , Linhagem Celular , Humanos , Camundongos Endogâmicos BALB C , Peptidomiméticos/química , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/química
13.
Bioanalysis ; 8(4): 265-74, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26807991

RESUMO

BACKGROUND: A target protein-based affinity extraction LC-MS/MS method was developed to enable plasma level determination following ultralow dosing (0.1-3 µg/kg) of an inhibitor of apoptosis proteins molecule. Methodology & results: Affinity extraction (AE) utilizing immobilized target protein BIR2/BIR3 was used to selectively capture the inhibitor of apoptosis proteins molecule from dog plasma and enable removal of background matrix components. Pretreatment of plasma samples using protein precipitation was found to provide an additional sensitivity gain. A LLOQ of 7.8 pM was achieved by combining protein precipitation with AE. The method was used to support an ultralow dose dog toxicity study. CONCLUSION: AE-LC-MS/MS, utilizing target protein, is a highly sensitive methodology for small molecule quantification with potential for broader applicability.


Assuntos
Análise Química do Sangue/métodos , Fracionamento Químico/métodos , Cromatografia Líquida/métodos , Proteínas Inibidoras de Apoptose/antagonistas & inibidores , Isoquinolinas/análise , Limite de Detecção , Oligopeptídeos/análise , Bibliotecas de Moléculas Pequenas/análise , Espectrometria de Massas em Tandem/métodos , Animais , Cães , Feminino , Humanos , Proteínas Imobilizadas/antagonistas & inibidores , Proteínas Imobilizadas/química , Proteínas Inibidoras de Apoptose/química , Isoquinolinas/química , Isoquinolinas/farmacologia , Masculino , Oligopeptídeos/química , Oligopeptídeos/farmacologia , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/farmacologia
14.
Exp Cell Res ; 338(2): 251-60, 2015 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-26302264

RESUMO

Cellular levels of inhibitor of apoptosis (IAP) proteins are elevated in multiple human cancers and their activities often play a part in promoting cancer cell survival by blocking apoptotic pathways, controlling signal transduction pathways and contributing to resistance. These proteins function through interactions of their BIR (baculoviral IAP repeat) protein domains with pathway components and these interactions are endogenously antagonized by Smac/Diablo (second mitochondrial activator of caspases/direct IAP binding protein with low isoelectric point). This report describes development of synthetic smac mimetics (SM) and compares their binding, antiproliferative and anti-tumor activities. All dimeric antagonists inhibit in vitro smac tetrapeptide binding to recombinant IAP proteins, rescue IAP-bound caspase-3 activity and show anti-proliferative activity against human A875 melanoma cells. One heterodimeric SM, SM3, binds tightly to IAP proteins in vitro and slowly dissociates (greater than two hours) from these protein complexes compared to the other antagonists. In addition, in vitro SM anti-proliferation potency is influenced by ABCB1 transporter (ATP-binding cassette, sub-family B; MDR1, P-gp) activities and one antagonist, SM5, does not appear to be an ABCB1 efflux pump substrate. All dimeric smac mimetics inhibit the growth of human melanoma A875 tumors implanted in athymic mice at well-tolerated doses. One antagonist, SM4, shows broad spectrum in vivo anti-tumor activity and modulates known pharmacodynamic markers of IAP antagonism. These data taken together demonstrate the range of diverse dimeric IAP antagonist activities and supports their potential as anticancer agents.


Assuntos
Antineoplásicos/farmacologia , Transporte Biológico/efeitos dos fármacos , Caspase 3/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/antagonistas & inibidores , Proteínas Mitocondriais/antagonistas & inibidores , Subfamília B de Transportador de Cassetes de Ligação de ATP/metabolismo , Animais , Apoptose/efeitos dos fármacos , Proteínas Reguladoras de Apoptose , Biomimética/métodos , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Feminino , Células HCT116 , Humanos , Proteínas Inibidoras de Apoptose/antagonistas & inibidores , Melanoma/tratamento farmacológico , Melanoma/metabolismo , Camundongos Endogâmicos BALB C , Camundongos Nus , Ligação Proteica/efeitos dos fármacos , Estrutura Terciária de Proteína/efeitos dos fármacos
15.
ACS Med Chem Lett ; 6(7): 770-5, 2015 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-26191364

RESUMO

A series of dimeric macrocyclic compounds were prepared and evaluated as antagonists for inhibitor of apoptosis proteins. The most potent analogue 11, which binds to XIAP and c-IAP proteins with high affinity and induces caspase-3 activation and ultimately cell apoptosis, inhibits growth of human melanoma and colorectal cell lines at low nanomolar concentrations. Furthermore, compound 11 demonstrated significant antitumor activity in the A875 human melanoma xenograft model at doses as low as 2 mg/kg on a q3d schedule.

16.
J Med Chem ; 58(3): 1556-62, 2015 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-25584393

RESUMO

The prominent role of IAPs in controlling cell death and their overexpression in a variety of cancers has prompted the development of IAP antagonists as potential antitumor therapies. We describe the identification of a series of heterodimeric antagonists with highly potent antiproliferative activities in cIAP- and XIAP-dependent cell lines. Compounds 15 and 17 further demonstrate curative efficacy in human melanoma and lung cancer xenograft models and are promising candidates for advanced studies.


Assuntos
Antineoplásicos/farmacologia , Descoberta de Drogas , Proteínas Inibidoras de Apoptose/antagonistas & inibidores , Neoplasias Experimentais/tratamento farmacológico , Prolina/farmacologia , Animais , Antineoplásicos/síntese química , Antineoplásicos/química , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Camundongos , Estrutura Molecular , Neoplasias Experimentais/patologia , Prolina/síntese química , Prolina/química , Relação Estrutura-Atividade
17.
Bioorg Med Chem Lett ; 24(21): 5022-9, 2014 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-25278234

RESUMO

Bivalent heterodimeric IAP antagonists that incorporate (R)-tetrahydroisoquinoline in the P3' subunit show high affinity for the BIR2 domain and demonstrated potent IAP inhibitory activities in biochemical and cellular assays. Potent in vivo efficacy was observed in a variety of human tumor xenograft models. The bivalent heterodimeric molecule 3 with a P3-P3' benzamide linker induced pharmacodynamic markers of apoptosis and was efficacious when administered intravenously at a dose of 1mg/kg to mice harboring A875 human melanoma tumors. Analog 5, with a polyamine group incorporated at the P2' thiovaline side chain exhibited antiproliferative activity against the P-gp expressing HCT116/VM46 cell line.


Assuntos
Antineoplásicos/farmacologia , Descoberta de Drogas , Proteínas Inibidoras de Apoptose/antagonistas & inibidores , Melanoma/tratamento farmacológico , Neoplasias Pancreáticas/tratamento farmacológico , Tetra-Hidroisoquinolinas/química , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Animais , Antineoplásicos/química , Apoptose/efeitos dos fármacos , Sítios de Ligação , Feminino , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Modelos Moleculares , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de Xenoenxerto
18.
J Neurosci ; 31(30): 10749-51, 2011 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-21795526
19.
Macromol Biosci ; 10(7): 736-45, 2010 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-20480511

RESUMO

Sedimentation velocity (SV) analytical ultracentrifugation has re-emerged as an important tool in the characterization of biological macromolecules and nanoparticles. The computational analysis of the evolution of the macromolecular concentration profile allows the characterization of many hydrodynamic and thermodynamic properties of the macromolecules and their interactions. The Rayleigh interference optical system is often the detection method of choice, for its usually superior data quality and the wide applicability of refractive index sensitive detection. However, the interference optical system is also sensitive to the redistribution of co-solvent molecules, which are not of primary experimental interest. In principle, their contribution can be eliminated by an exact geometric and compositional match of the sample solution and the reference solution, achieving the complete optical subtraction of unwanted buffer signals. Unfortunately, in practice, this can often not be perfectly achieved for various reasons, leading to signal offsets arising from unmatched sedimentation of solvent components. If unrecognized, this can lead to significant misfit, accompanied by significant errors in the macromolecular sedimentation parameters. In the present work, we describe an approach of computationally accounting for signals from sedimenting buffer components through explicitly modeling their redistribution with Lamm equation solutions, implemented in the software SEDFIT. We demonstrate how this can restore the SV analysis to yield a high quality fit of the data and to provide correct macromolecular sedimentation parameters.


Assuntos
Fracionamento Químico/métodos , Interferometria/métodos , Solventes/química , Ultracentrifugação/métodos , Animais , Tampões (Química) , Bovinos , Modelos Químicos , Soroalbumina Bovina/análise , Cloreto de Sódio/análise
20.
Proc Natl Acad Sci U S A ; 106(30): 12329-34, 2009 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-19617541

RESUMO

The activity of many ligand-gated ion channels and cell surface receptors is modulated by small molecules and ions, but an understanding of the underlying molecular mechanisms is scarce. For kainate, but not AMPA subtype glutamate receptors, the binding of Na(+) and Cl(-) ions to discrete, electrostatically coupled sites in the extracellular ligand binding domain (LBD) dimer assembly regulates the rate of entry into the desensitized state, which occurs when the dimer interface ruptures and the channel closes. Studies on glutamate receptors have defined the LBD dimer assembly as a key functional unit that controls activation and desensitization. Here we use analytical ultracentrifugation to probe the energetic effects of allosteric ions on kainate receptor dimer stability in solution, using a GluR6 mutant that desensitizes slowly. Our results show that sodium and chloride ions modulate kainate receptor dimer affinity as much as 50-fold, and that removal of either Cl(-) or Na(+) disrupts the dimer. The applicability of a similar allosteric mechanism for modulation of delta2 glutamate receptors by Ca(2+) was also tested. Our results indicate that ions can contribute substantial free energy to active state stabilization in both these receptors, and provide quantitative measurements of the energetic consequences of allosteric ion binding to a ligand-gated ion channel.


Assuntos
Cloretos/química , Estrutura Terciária de Proteína , Receptores de Ácido Caínico/química , Sódio/química , Regulação Alostérica , Sequência de Aminoácidos , Sítios de Ligação/genética , Cálcio/química , Cálcio/metabolismo , Linhagem Celular , Cloretos/metabolismo , Transferência de Energia , Cinética , Ligantes , Modelos Moleculares , Dados de Sequência Molecular , Mutação , Multimerização Proteica , Receptores de Ácido Caínico/genética , Receptores de Ácido Caínico/metabolismo , Sódio/metabolismo , Ultracentrifugação
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