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1.
Bioorg Chem ; 97: 103703, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32143017

RESUMO

Three N-metallocenoylsphingosines with variance in the central metal (Fe, Co, Ru), the charge (neutral or cationic), and the arene ligands (Cp2, Cp*Ph) were synthesized from serine and metallocene carboxylic acids as substrate-analogous inhibitors of human acid ceramidase (AC). Their inhibitory potential was examined using the recombinant full length ASAH1 enzyme, expressed and secreted from High Five insect cells, and the fluorescent substrate Rbm14-12. All complexes inhibited AC, most strongly so ruthenium(II) complex 13a. Some antitumoral effects of the complexes, such as the interference with the microtubular and F-actin cytoskeleton of cancer cells, were correlated to their AC-inhibition, whereas others, e.g. their cytotoxicity and their induction of caspase-3/-7 activity in cancer cells, were not. All complexes accumulated preferentially in the lysosomes of cancer cells like their target AC, arrested the cells in G1 phase of the cell cycle, and displayed cytotoxicity with mostly single-digit micromolar IC50 values while inducing cancer cell apoptosis.


Assuntos
Ceramidase Ácida/antagonistas & inibidores , Antineoplásicos/química , Antineoplásicos/farmacologia , Esfingosina/análogos & derivados , Esfingosina/farmacologia , Ceramidase Ácida/metabolismo , Animais , Antineoplásicos/síntese química , Apoptose/efeitos dos fármacos , Linhagem Celular , Linhagem Celular Tumoral , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Pontos de Checagem da Fase G1 do Ciclo Celular/efeitos dos fármacos , Humanos , Neoplasias/tratamento farmacológico , Neoplasias/enzimologia , Neoplasias/metabolismo , Compostos Organometálicos/síntese química , Compostos Organometálicos/química , Compostos Organometálicos/farmacologia , Esfingosina/síntese química
2.
Proc Natl Acad Sci U S A ; 117(6): 2894-2905, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-31988137

RESUMO

The Mediator kinase module regulates eukaryotic transcription by phosphorylating transcription-related targets and by modulating the association of Mediator and RNA polymerase II. The activity of its catalytic core, cyclin-dependent kinase 8 (CDK8), is controlled by Cyclin C and regulatory subunit MED12, with its deregulation contributing to numerous malignancies. Here, we combine in vitro biochemistry, cross-linking coupled to mass spectrometry, and in vivo studies to describe the binding location of the N-terminal segment of MED12 on the CDK8/Cyclin C complex and to gain mechanistic insights into the activation of CDK8 by MED12. Our data demonstrate that the N-terminal portion of MED12 wraps around CDK8, whereby it positions an "activation helix" close to the T-loop of CDK8 for its activation. Intriguingly, mutations in the activation helix that are frequently found in cancers do not diminish the affinity of MED12 for CDK8, yet likely alter the exact positioning of the activation helix. Furthermore, we find the transcriptome-wide gene-expression changes in human cells that result from a mutation in the MED12 activation helix to correlate with deregulated genes in breast and colon cancer. Finally, functional assays in the presence of kinase inhibitors reveal that binding of MED12 remodels the active site of CDK8 and thereby precludes the inhibition of ternary CDK8 complexes by type II kinase inhibitors. Taken together, our results not only allow us to propose a revised model of how CDK8 activity is regulated by MED12, but also offer a path forward in developing small molecules that target CDK8 in its MED12-bound form.


Assuntos
Quinase 8 Dependente de Ciclina/metabolismo , Complexo Mediador/metabolismo , Domínio Catalítico , Ciclina C/genética , Ciclina C/metabolismo , Quinase 8 Dependente de Ciclina/química , Quinase 8 Dependente de Ciclina/genética , Ativação Enzimática , Humanos , Complexo Mediador/genética , Ligação Proteica , Conformação Proteica em alfa-Hélice , Domínios Proteicos
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