RESUMO
The most frequent ERK2 (MAPK1) mutation in cancers, E322K, lies in the common docking (CD) site, which binds short motifs made up of basic and hydrophobic residues present in the activators MEK1 (MAP2K1) and MEK2 (MAP2K2), in dual specificity phosphatases (DUSPs) that inactivate the kinases, and in many of their substrates. Also, part of the CD site, but mutated less often in cancers, is the preceding aspartate (D321N). These mutants were categorized as gain of function in a sensitized melanoma system. In Drosophila developmental assays, we found that the aspartate but not the glutamate mutant caused gain-of-function phenotypes. Here, we catalogued additional properties of these mutants to accrue greater insight into their functions. A modest increase in nuclear retention of E322K was noted. Binding of ERK2 E322K and D321N to a small group of substrates and regulatory proteins was similar, in spite of differences in CD site integrity. Interactions with a second docking site, the F site, which should be more accessible in E322K, were modestly reduced rather than increased. The crystal structure of ERK2 E322K also indicated a disturbed dimer interface, and reduced dimerization was detected by a two-hybrid test; yet, it was detected in dimers in EGF-treated cells, although to a lesser extent than D321N or wt ERK2. These findings indicate a range of small differences in behaviors that may contribute to increased function of E322K in certain cancers.
Assuntos
Ácido Aspártico , Proteínas de Drosophila , Sistema de Sinalização das MAP Quinases , Proteína Quinase 1 Ativada por Mitógeno , Animais , Drosophila , Sistema de Sinalização das MAP Quinases/fisiologia , Mutação , Fosforilação , Proteína Quinase 1 Ativada por Mitógeno/genética , Proteínas de Drosophila/genética , Multimerização ProteicaRESUMO
Functional differentiation of the two isoforms of the protein-serine/threonine kinase, glycogen synthase kinase-3 (GSK-3), is an unsettled area of research. The isoforms are highly similar in structure and are largely redundant, though there is also evidence for specific roles. Identification of isoform-specific protein interactors may elucidate the differences in function and provide insight into isoform-selective regulation. We therefore sought to identify novel GSK-3 interaction partners and to examine differences in the interactomes of the two isoforms using both affinity purification and proximity-dependent biotinylation (BioID) mass spectrometry methods. While the interactomes of the two isomers are highly similar in HEK293 cells, BioID in HeLa cells yielded a variety of preys that are preferentially associated with one of the two isoforms. DCP1B, which favored GSK-3α, and MISP, which favored GSK-3ß, were evaluated for reciprocal interactions. The differences in interactions between isoforms may help in understanding the distinct functions and regulation of the two isoforms as well as offer avenues for the development of isoform-specific strategies.
Assuntos
Quinase 3 da Glicogênio Sintase , Humanos , Células HeLa , Glicogênio Sintase Quinase 3 beta , Células HEK293 , Isoformas de Proteínas/genéticaRESUMO
The most frequent extracellular signal-regulated kinase 2 (ERK2) mutation occurring in cancers is E322K (E-K). ERK2 E-K reverses a buried charge in the ERK2 common docking (CD) site, a region that binds activators, inhibitors, and substrates. Little is known about the cellular consequences associated with this mutation, other than apparent increases in tumor resistance to pathway inhibitors. ERK2 E-K, like the mutation of the preceding aspartate (ERK2 D321N [D-N]) known as the sevenmaker mutation, causes increased activity in cells and evades inactivation by dual-specificity phosphatases. As opposed to findings in cancer cells, in developmental assays in Drosophila, only ERK2 D-N displays a significant gain of function, revealing mutation-specific phenotypes. The crystal structure of ERK2 D-N is indistinguishable from that of wild-type protein, yet this mutant displays increased thermal stability. In contrast, the crystal structure of ERK2 E-K reveals profound structural changes, including disorder in the CD site and exposure of the activation loop phosphorylation sites, which likely account for the decreased thermal stability of the protein. These contiguous mutations in the CD site of ERK2 are both required for docking interactions but lead to unpredictably different functional outcomes. Our results suggest that the CD site is in an energetically strained configuration, and this helps drive conformational changes at distal sites on ERK2 during docking interactions.
Assuntos
Proteínas de Drosophila/genética , Drosophila melanogaster/enzimologia , Drosophila melanogaster/genética , MAP Quinases Reguladas por Sinal Extracelular/genética , Mutação/genética , Animais , Animais Geneticamente Modificados , Cristalografia por Raios X , Proteínas de Drosophila/química , Proteínas de Drosophila/metabolismo , Ativação Enzimática , Estabilidade Enzimática , MAP Quinases Reguladas por Sinal Extracelular/química , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Humanos , Modelos Moleculares , Proteínas Mutantes/metabolismoRESUMO
The pyrrole-imidazole alkaloids have fascinated chemists for decades because of their unique structures. The high nitrogen and halogen contents and the densely functionalized skeletons make their laboratory synthesis challenging. We describe herein an oxidative method for accessing the core skeletons of two classes of pyrrole-imidazole dimers. This synthetic strategy was inspired by the putative biosynthesis pathways and its development was facilitated by computational studies. Using this method, we have successfully prepared ageliferin, bromoageliferin, and dibromoageliferin in their natural enantiomeric form.
Assuntos
Alcaloides/síntese química , Materiais Biomiméticos/química , Imidazóis/síntese química , Pirróis/síntese química , Alcaloides/química , Ciclização , Dimerização , Imidazóis/química , Estrutura Molecular , Pirróis/química , Teoria QuânticaRESUMO
Previous work in our group on the cation binding of substituted cyclopentadienyl anions (Cp) showed the curious result that Cp traceless electric quadrupole moments (Θ(zz)) are almost all positive. Probing this issue further here we show that substituted Cp Θ(zz) values are always significantly more positive than the analogous substituted benzenes. Given the nature of aromatic Θ(zz) values, this is the opposite of what would be predicted. Furthermore, we show that the quadrupole moments of Cp anions do not behave as one would expect based on Cp substitutions. Unlike the quadrupole moments of substituted benzenes, which generally become more negative with the addition of electron-donating groups and more positive with the addition of electron-withdrawing groups, Cp quadrupole moments become more positive when any substituent is added, regardless of the electron-donating/withdrawing nature of the substituent. To explain these results we propose a model where the anionic Cp π-electron density repels the substituent electron density toward the molecular periphery and AIM calculations support this view.
Assuntos
Ciclopentanos/química , Ânions/química , Conformação Molecular , Teoria Quântica , EstereoisomerismoRESUMO
The cation binding of dipolar aromatics was investigated employing computational techniques. In most cases, cation binding at the pi region of the aromatic (the cation-pi interaction), which can be thought of as a cation-quadrupole interaction, is preferred over cation binding at the negative end of the dipole moment. Surprisingly, in some cases, the cation-dipole complex is not even a minimum on the potential energy surface.
Assuntos
Hidrocarbonetos Aromáticos/química , Sódio/química , Fluorbenzenos/química , Modelos Moleculares , Conformação Molecular , Especificidade por Substrato , TermodinâmicaRESUMO
Glycogen synthase kinase-3 (GSK-3) is a ubiquitously expressed protein kinase that sits at the nexus of multiple signaling pathways. Its deep integration into cellular control circuits is consummate to its implication in diseases ranging from mood disorders to diabetes to neurodegenerative diseases and cancers. The selectivity and insulation of such a promiscuous kinase from unwanted crosstalk between pathways, while orchestrating a multifaceted response to cellular stimuli, offer key insights into more general mechanisms of cell regulation. Here, we review recent advances that have contributed to the understanding of GSK-3 and its role in driving appreciation of intracellular signal coordination.
RESUMO
Vanadium complexes have been used extensively to catalyze olefin and alcohol oxidation. However, their application in C-H oxidation has not been well-studied. We report herein that commercially available Cp(2)VCl(2) catalyzes benzylic C-H oxidation selectively and effectively, giving no aromatic oxidation products.