RESUMO
The classical nuclear factor kappaB (NF-kappaB) signaling pathway is under the control of the IkappaB kinase (IKK) complex, which consists of IKK-1, IKK-2, and NF-kappaB essential modulator (NEMO). This complex is responsible for the regulation of cell proliferation, survival, and differentiation. Dysregulation of this pathway is associated with several human diseases, and as such, its inhibition offers an exciting opportunity for therapeutic intervention. NEMO binding domain (NBD) peptides inhibit the binding of recombinant NEMO to IKK-2 in vitro. However, direct evidence of disruption of this binding by NBD peptides in biological systems has not been provided. Using a cell system, we expanded on previous observations to show that NBD peptides inhibit inflammation-induced but not basal cytokine production. We report that these peptides cause the release of IKK-2 from an IKK complex and disrupt NEMO-IKK-2 interactions in cells. We demonstrate that by interfering with NEMO-IKK-2 interactions, NBD peptides inhibit IKK-2 phosphorylation, without affecting signaling intermediates upstream of the IKK complex of the NF-kappaB pathway. Furthermore, in a cell-free system of IKK complex activation by TRAF6 (TNF receptor-associated factor 6), we show that these peptides inhibit the ability of this complex to phosphorylate downstream substrates, such as p65 and inhibitor of kappaB alpha (IkappaB alpha). Thus, consistent with the notion that NEMO regulates IKK-2 catalytic activity by serving as a scaffold, appropriately positioning IKK-2 for activation by upstream kinase(s), our findings provide novel insights into the molecular mechanisms by which NBD peptides exert their anti-inflammatory effects in cells.
Assuntos
Anti-Inflamatórios/farmacologia , Quinase I-kappa B/metabolismo , Quinase I-kappa B/farmacologia , Complexos Multiproteicos/metabolismo , Peptídeos/farmacologia , Fator de Transcrição RelA/metabolismo , Anti-Inflamatórios/química , Anti-Inflamatórios/metabolismo , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Citocinas/metabolismo , Humanos , Quinase I-kappa B/antagonistas & inibidores , Quinase I-kappa B/química , Complexos Multiproteicos/antagonistas & inibidores , Peptídeos/química , Peptídeos/metabolismo , Fosforilação , Ligação Proteica/efeitos dos fármacos , Estrutura Terciária de Proteína , Fator 6 Associado a Receptor de TNF/metabolismo , Fator de Transcrição RelA/antagonistas & inibidoresRESUMO
The Janus kinase family consists of four members: JAK-1, -2, -3 and TYK-2. While JAK-2 and JAK-3 have been well characterized biochemically, there is little data on TYK-2. Recent work suggests that TYK-2 may play a critical role in the development of a number of inflammatory processes. We have carried out a series of biochemical studies to better understand TYK-2 enzymology and its inhibition profile, in particular how the TYK-2 phosphorylated forms differ from each other and from the other JAK family members. We have expressed and purified milligram quantities of the TYK-2 kinase domain (KD) to high purity and developed a method to separate the non-, mono- (pY(1054)) and di-phosphorylated forms of the enzyme. Kinetic studies (k(cat(app))/K(m(app))) indicated that phosphorylation of the TYK-2-KD (pY(1054)) increased the catalytic efficiency 4.4-fold compared to its non-phosphorylated form, while further phosphorylation to generate the di-phosphorylated enzyme imparted no further increase in activity. These results are in contrast to those obtained with the JAK-2-KD and JAK-3-KD, where little or no increase in activity occurred upon mono-phosphorylation, while di-phosphorylation resulted in a 5.1-fold increase in activity for the JAK-2-KD. Moreover, ATP-competitive inhibitors demonstrated 10-30-fold shifts in potency (K(i(app))) as a result of the TYK-2-KD phosphorylation state, while the shifts for JAK-3-KD were only 2-3-fold and showed little or no change for JAK-2-KD. Thus, the phosphorlyation state imparted differential effects on both activity and inhibition within the JAK family of kinases.
Assuntos
Janus Quinase 2/biossíntese , Janus Quinase 2/isolamento & purificação , Janus Quinase 3/biossíntese , Janus Quinase 3/isolamento & purificação , TYK2 Quinase/biossíntese , TYK2 Quinase/isolamento & purificação , Animais , Catálise , Humanos , Janus Quinase 2/antagonistas & inibidores , Janus Quinase 3/antagonistas & inibidores , Camundongos , Fosforilação , Estrutura Terciária de Proteína , TYK2 Quinase/antagonistas & inibidoresRESUMO
NF-kappaB signaling plays a pivotal role in a variety of pathological conditions. Because of its central role in the overall NF-kappaB regulation, IKK-2 is a viable target for drug discovery. In order to enable structure-based design of IKK-2 inhibitors, we carried out a rational generation of IKK-2 mutants based on induced-fit docking of a selective IKK-2 inhibitor, PHA-408, into the homology model of IKK-2. One mutant we have characterized is a catalytically inactive form of IKK-2, D145A IKK-2, wherein the catalytic aspartic acid, D145 was replaced with alanine. Unlike the WT enzyme, D145A IKK-2 is devoid of kinase activity despite its ability to bind ATP with high affinity and is not phosphorylated at the T loop. In addition, this mutant binds a diverse collection of inhibitors with comparable binding affinities to WT IKK-2. Another interesting mutant we have characterized is F26A IKK-2 (F26 is an aromatic residue located at the very tip of the Gly-rich loop). Pre-incubation of F26A IKK-2 with PHA-408 revealed the role of F26 in the time-dependent binding of this inhibitor. Thus, functional characterization of these mutants provides the first evidence showing the role of a Gly-rich loop residue of a kinase in binding kinetics. These two mutants along with others that we have identified could be used to validate homology models and probe the interactions of IKK-2 with a variety of inhibitors.
Assuntos
Quinase I-kappa B/metabolismo , Animais , Células Cultivadas , Simulação por Computador , Descoberta de Drogas/métodos , Humanos , Quinase I-kappa B/biossíntese , Quinase I-kappa B/química , Quinase I-kappa B/genética , Indazóis/química , Indazóis/metabolismo , Ácidos Isonicotínicos/química , Ácidos Isonicotínicos/metabolismo , Cinética , Modelos Moleculares , Mutagênese Sítio-Dirigida , Mutação , Fosforilação , Ligação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Spodoptera , Homologia Estrutural de ProteínaRESUMO
Janus-associated kinases (JAKs) play critical roles in cytokine signaling, and have emerged as viable therapeutic targets in inflammation and oncology related diseases. To date, targeting JAK proteins with highly selective inhibitor compounds have remained elusive. We have expressed the active kinase domains for both JAK2 and JAK3 and devised purification protocols to resolve the non-, mono- (Y1007) and diphosphorylated (Y1007 and Y1008) states of JAK2 and non- and monophosphorylated states of JAK3 (Y980). An optimal purified protein yield of 20, 29 and 69mg per 20L cell culture was obtained for the three JAK2 forms, respectively, and 12.2 and 2.3mg per 10L fermentation for the two JAK3 forms allowing detailed biochemical and biophysical studies. To monitor the purification process we developed a novel HPLC activity assay where a sequential order of phosphorylation was observed whereby the first tyrosine residue was completely phosphorylated prior to phosphorylation of the tandem tyrosine residue. A Caliper-based microfluidics assay was used to determine the kinetic parameters (K(m) and k(cat)) for each phosphorylated state, showing that monophosphorylated (Y1007) JAK2 enzyme activity increased 9-fold over that of the nonphosphorylated species, and increased an additional 6-fold for the diphosphorylated (Y1007/Y1008) species, while phosphorylation of JAK3 resulted in a negligible increase in activity. Moreover, crystal structures have been generated for each isolated state of JAK2 and JAK3 with resolutions better than 2.4A. The generation of these reagents has enabled kinetic and structural characterization to inform the design of potent and selective inhibitors of the JAK family.
Assuntos
Janus Quinase 2/química , Janus Quinase 2/isolamento & purificação , Janus Quinase 3/química , Janus Quinase 3/isolamento & purificação , Sequência de Aminoácidos , Biocatálise , Cromatografia Líquida de Alta Pressão , Cristalização , Eletroforese em Gel de Poliacrilamida , Fermentação , Humanos , Cinética , Dados de Sequência Molecular , Fosforilação , Estrutura Terciária de ProteínaRESUMO
The inhibition of PKC-zeta has been proposed to be a potential drug target for immune and inflammatory diseases. A series of 2-(6-phenyl-1H indazol-3-yl)-1H-benzo[d]imidazoles with initial high crossover to CDK-2 has been optimized to afford potent and selective inhibitors of protein kinase c-zeta (PKC-zeta). The determination of the crystal structures of key inhibitor:CDK-2 complexes informed the design and analysis of the series. The most selective and potent analog was identified by variation of the aryl substituent at the 6-position of the indazole template to give a 4-NH(2) derivative. The analog displays good selectivity over other PKC isoforms (alpha, betaII, gamma, delta, epsilon, mu, theta, eta and iota/lambda) and CDK-2, however it displays marginal selectivity against a panel of other kinases (37 profiled).
Assuntos
Benzimidazóis/síntese química , Química Farmacêutica/métodos , Inibidores Enzimáticos/farmacologia , Imidazóis/síntese química , Proteína Quinase C/química , Proteína Quinase C/isolamento & purificação , Benzimidazóis/farmacologia , Cristalografia por Raios X , Ciclina A/química , Quinase 2 Dependente de Ciclina/metabolismo , Desenho de Fármacos , Humanos , Imidazóis/farmacologia , Concentração Inibidora 50 , Modelos Químicos , Modelos Moleculares , Conformação Molecular , Isoformas de ProteínasRESUMO
Inducible, microsomal prostaglandin E synthase 1 (mPGES-1), the terminal enzyme in the prostaglandin (PG) biosynthetic pathway, constitutes a promising therapeutic target for the development of new anti-inflammatory drugs. To elucidate structure-function relationships and to enable structure-based design, an mPGES-1 homology model was developed using the three-dimensional structure of the closest homologue of the MAPEG family (Membrane Associated Proteins in Eicosanoid and Glutathione metabolism), mGST-1. The ensuing model of mPGES-1 is a homo-trimer, with each monomer consisting of four membrane-spanning segments. Extensive structure refinement revealed an inter-monomer salt bridge (K26-E77) as well as inter-helical interactions within each monomer, including polar hydrogen bonds (e.g. T78-R110-T129) and hydrophobic pi-stacking (F82-F103-F106), all contributing to the overall stability of the homo-trimer of mPGES-1. Catalytic co-factor glutathione (GSH) was docked into the mPGES-1 model by flexible optimization of both the ligand and the protein conformations, starting from the initial location ascertained from the mGST-1 structure. Possible binding site for the substrate, prostaglandin H(2) (PGH(2)), was identified by systematically probing the refined molecular structure of mPGES-1. A binding model was generated by induced fit docking of PGH(2) in the presence of GSH. The homology model prescribes three potential inhibitor binding sites per mPGES-1 trimer. This was further confirmed experimentally by equilibrium dialysis study which generated a binding stoichiometric ratio of approximately three inhibitor molecules to three mPGES-1 monomers. The structural model that we have derived could serve as a useful tool for structure-guided design of inhibitors for this emergently important therapeutic target.
Assuntos
Inibidores Enzimáticos/química , Oxirredutases Intramoleculares/química , Microssomos/enzimologia , Sequência de Aminoácidos , Biopolímeros , Inibidores Enzimáticos/farmacologia , Humanos , Oxirredutases Intramoleculares/antagonistas & inibidores , Oxirredutases Intramoleculares/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Prostaglandina-E Sintases , Conformação Proteica , Homologia de Sequência de AminoácidosRESUMO
The Janus kinase (JAK) family consists of four members: JAK-1, -2, -3 and tyrosine kinase 2 (TYK-2). Recent work suggests that cytokine signaling through TYK-2 may play a critical role in a number of inflammatory processes. We recently described the purification and characterization of phosphorylated isoforms of the TYK-2 kinase domain (TYK-2 KD) and its high resolution 3D structure in the presence of inhibitors. We now report the expression and a two-step purification procedure for the doubly tagged full-length construct, H6-FL-TYK-2-FLAG, and examine its properties compared to those of TYK-2 KD. In the presence of ATP and a peptide substrate, H6-FL-TYK-2-FLAG showed a marked lag in phosphopeptide product formation, while TYK-2 KD showed no such lag. This lag could be eliminated by ATP pretreatment, suggesting that the H6-FL-TYK-2-FLAG enzyme was activated by phosphorylation. The potencies of several nanomolar inhibitors were similar for TYK-2 KD and H6-FL-TYK-2-FLAG. However, these same inhibitors were about 1000 times less potent inhibiting the autophosphorylation of H6-FL-TYK-2-FLAG than they were inhibiting the phosphorylation of a peptide substrate modeled after the activation loop sequence of TYK-2. This intriguing result suggests that autophosphorylation and, thus, activation of H6-FL-TYK-2-FLAG is relatively insensitive to inhibition and that present inhibitors act to inhibit TYK-2 subsequent to activation. Inhibition of TYK-2 autophosphorylation may represent a new area of investigation for the JAK family.
Assuntos
TYK2 Quinase/antagonistas & inibidores , TYK2 Quinase/metabolismo , Trifosfato de Adenosina/química , Trifosfato de Adenosina/metabolismo , Domínio Catalítico , Eletroforese em Gel de Poliacrilamida , Histidina/química , Humanos , Cinética , Oligopeptídeos/química , Fosforilação , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Proteínas Recombinantes de Fusão/antagonistas & inibidores , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/isolamento & purificação , Proteínas Recombinantes de Fusão/metabolismo , TYK2 Quinase/química , TYK2 Quinase/isolamento & purificaçãoRESUMO
Janus kinases (JAKs) are critical regulators of cytokine pathways and attractive targets of therapeutic value in both inflammatory and myeloproliferative diseases. Although the crystal structures of active JAK1 and JAK2 kinase domains have been reported recently with the clinical compound CP-690550, the structures of both TYK2 and JAK3 with CP-690550 have remained outstanding. Here, we report the crystal structures of TYK2, a first in class structure, and JAK3 in complex with PAN-JAK inhibitors CP-690550 ((3R,4R)-3-[4-methyl-3-[N-methyl-N-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino]piperidin-1-yl]-3-oxopropionitrile) and CMP-6 (tetracyclic pyridone 2-t-butyl-9-fluoro-3,6-dihydro-7H-benz[h]-imidaz[4,5-f]isoquinoline-7-one), both of which bind in the ATP-binding cavities of both JAK isozymes in orientations similar to that observed in crystal structures of JAK1 and JAK2. Additionally, a complete thermodynamic characterization of JAK/CP-690550 complex formation was completed by isothermal titration calorimetry, indicating the critical role of the nitrile group from the CP-690550 compound. Finally, computational analysis using WaterMap further highlights the critical positioning of the CP-690550 nitrile group in the displacement of an unfavorable water molecule beneath the glycine-rich loop. Taken together, the data emphasize the outstanding properties of the kinome-selective JAK inhibitor CP-690550, as well as the challenges in obtaining JAK isozyme-selective inhibitors due to the overall structural and sequence similarities between the TYK2, JAK1, JAK2 and JAK3 isozymes. Nevertheless, subtle amino acid variations of residues lining the ligand-binding cavity of the JAK enzymes, as well as the global positioning of the glycine-rich loop, might provide the initial clues to obtaining JAK-isozyme selective inhibitors.
Assuntos
Benzimidazóis/metabolismo , Inibidores Enzimáticos/metabolismo , Janus Quinase 3/química , Piridonas/metabolismo , Pirimidinas/metabolismo , Pirróis/metabolismo , TYK2 Quinase/química , Sítios de Ligação , Calorimetria , Humanos , Janus Quinase 3/metabolismo , Cinética , Modelos Moleculares , Piperidinas , Ligação Proteica , Estrutura Terciária de Proteína , TYK2 Quinase/metabolismoRESUMO
Leukotrienes are important mediators in a number of inflammatory diseases and therefore are a target of several therapeutic approaches. The first committed step in the synthesis of leukotrienes is the conversion of arachidonic acid to leukotriene A(4) (LTA(4)) in two successive reactions catalyzed by 5-lipoxygenase (5-LOX). Assays to measure 5-LOX activity typically have been low throughput and time consuming. In this article, we describe a fluorescence assay that is amenable to high-throughput screening in a 384-well microplate format. The fluorescent signal is measured during oxidation of 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) by human 5-LOX. The assay has been found to reliably identify small molecule inhibitors of human 5-LOX. The IC(50) values of several 5-LOX inhibitors in this new assay are comparable to those determined in a standard spectrophotometric assay that measures the formation of the 5(S)-hydroperoxyeicosatetraenoic acid (5-HpETE) product. In addition, we demonstrate the use of the assay in a high-throughput screen of the Pfizer compound collection to identify inhibitors of 5-LOX.