RESUMO
Direct interactions between pro- and anti-apoptotic BCL-2 family members form the basis of cell death decision-making at the outer mitochondrial membrane (OMM). Here we report that three anti-apoptotic BCL-2 proteins (MCL-1, BCL-2 and BCL-XL) found untethered from the OMM function as transcriptional regulators of a prosurvival and growth program. Anti-apoptotic BCL-2 proteins engage a BCL-2 homology (BH) domain sequence found in SUFU (suppressor of fused), a tumour suppressor and antagonist of the GLI DNA-binding proteins. BCL-2 proteins directly promote SUFU turnover, inhibit SUFU-GLI interaction, and induce the expression of the GLI target genes BCL-2, MCL-1 and BCL-XL. Anti-apoptotic BCL-2 protein/SUFU feedforward signalling promotes cancer cell survival and growth, and can be disabled with BH3 mimetics-small molecules that target anti-apoptotic BCL-2 proteins. Our findings delineate a chemical strategy for countering drug resistance in GLI-associated tumours and reveal unanticipated functions for BCL-2 proteins as transcriptional regulators.
Assuntos
Neoplasias/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas Repressoras/metabolismo , Transcrição Gênica , Proteínas Supressoras de Tumor/metabolismo , Animais , Antineoplásicos/farmacologia , Apoptose , Sistemas CRISPR-Cas , Proliferação de Células , Sobrevivência Celular , Feminino , Regulação Neoplásica da Expressão Gênica , Genótipo , Células HEK293 , Humanos , Camundongos , Camundongos Knockout , Camundongos Nus , Mimetismo Molecular , Proteína de Sequência 1 de Leucemia de Células Mieloides/deficiência , Proteína de Sequência 1 de Leucemia de Células Mieloides/genética , Proteína de Sequência 1 de Leucemia de Células Mieloides/metabolismo , Células NIH 3T3 , Neoplasias/tratamento farmacológico , Neoplasias/genética , Neoplasias/patologia , Fragmentos de Peptídeos/metabolismo , Fenótipo , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/genética , Interferência de RNA , Proteínas Repressoras/genética , Transdução de Sinais , Fatores de Tempo , Transcrição Gênica/efeitos dos fármacos , Transfecção , Proteínas Supressoras de Tumor/genética , Proteína GLI1 em Dedos de Zinco/genética , Proteína GLI1 em Dedos de Zinco/metabolismo , Proteína bcl-X/genética , Proteína bcl-X/metabolismoRESUMO
Misactivation of the seven-transmembrane protein Smoothened (Smo) is frequently associated with basal cell carcinoma and medulloblastoma. Cellular exposure to secreted Hedgehog (Hh) protein or oncogenic mutations in Hh pathway components induces Smo accumulation in the primary cilium, an antenna-like organelle with mostly unknown cellular functions. Despite the data supporting an indispensable role of the primary cilium in Smo activation, the mechanistic underpinnings of this dependency remain unclear. Using a cell-membrane-impermeable Smo antagonist (IHR-1), we demonstrate that Smo supplied with a synthetic agonist or activated with oncogenic mutations can signal without ciliary accumulation. Similarly, cells with compromised ciliary Smo trafficking due to loss of the phosphatidylinositol-4-phosphate 3-kinase (PI3K)-C2α retain transcriptional response to an exogenously supplied Smo agonist. These observations suggest that assembly of a Smo-signaling complex in the primary cilium is not a prerequisite for Hh pathway activation driven by Smo agonists or oncogenic Smo molecules.
Assuntos
Proteínas Hedgehog/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Transdução de Sinais , Animais , Linhagem Celular , Cílios/metabolismo , Humanos , Modelos Moleculares , Estrutura Secundária de Proteína , Estrutura Terciária de ProteínaRESUMO
Isolated from the sponge Terpios hoshinota that causes coral black disease, nakiterpiosin was the first C-nor-D-homosteroid discovered from a marine source. We provide in this account an overview of the chemistry and biology of this natural product. We also include a short history of the synthesis of C-nor-D-homosteroids and the results of some unpublished biological studies of nakiterpiosin.
RESUMO
The Hedgehog (Hh) and Wnt signal transduction pathways are master regulators of embryogenesis and tissue renewal and represent anticancer therapeutic targets. Using genome-wide RNA interference screening in murine cultured cells, we established previously unknown associations between these signaling pathways and genes linked to developmental malformations, diseases of premature tissue degeneration, and cancer. We identified functions in both pathways for the multitasking kinase Stk11 (also known as Lkb1), a tumor suppressor implicated in lung and cervical cancers. We found that Stk11 loss resulted in disassembly of the primary cilium, a cellular organizing center for Hh pathway components, thus dampening Hh signaling. Loss of Stk11 also induced aberrant signaling through the Wnt pathway. Chemicals that targeted the Wnt acyltransferase Porcupine or that restored primary cilia length by inhibiting the tubulin deacetylase HDAC6 (histone deacetylase 6) countered deviant pathway activities driven by Stk11 loss. Our study demonstrates that Stk11 is a critical mediator in both the Hh and the Wnt pathways, and our approach provides a platform to support the development of targeted therapeutic strategies.
Assuntos
Cílios/metabolismo , Proteínas Hedgehog/metabolismo , Proteínas Serina-Treonina Quinases/deficiência , Transdução de Sinais/genética , Proteínas Wnt/metabolismo , Células 3T3 , Proteínas Quinases Ativadas por AMP , Aciltransferases , Animais , Western Blotting , Primers do DNA/genética , Imunofluorescência , Técnicas de Silenciamento de Genes , Genômica , Desacetilase 6 de Histona , Histona Desacetilases/metabolismo , Fatores de Transcrição Kruppel-Like/metabolismo , Proteínas de Membrana/metabolismo , Camundongos , Microscopia Eletrônica de Transmissão , Proteínas do Tecido Nervoso/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Peixe-Zebra , Proteína Gli3 com Dedos de ZincoRESUMO
Suppression of oncogenic Wnt-mediated signaling holds promise as an anti-cancer therapeutic strategy. We previously reported a novel class of small molecules (IWR-1/2, inhibitors of Wnt response) that antagonize Wnt signaling by stabilizing the Axin destruction complex. Herein, we present the results of structure-activity relationship studies of these compounds.
Assuntos
Aminoquinolinas/química , Imidas/química , Proteínas Wnt/antagonistas & inibidores , Animais , Proteína Axina , Proteínas Repressoras/metabolismo , Transdução de Sinais , Relação Estrutura-Atividade , Cauda , Proteínas Wnt/metabolismo , Peixe-Zebra/metabolismoRESUMO
The pervasive influence of secreted Wnt signaling proteins in tissue homeostasis and tumorigenesis has galvanized efforts to identify small molecules that target Wnt-mediated cellular responses. By screening a diverse synthetic chemical library, we have discovered two new classes of small molecules that disrupt Wnt pathway responses; whereas one class inhibits the activity of Porcupine, a membrane-bound acyltransferase that is essential to the production of Wnt proteins, the other abrogates destruction of Axin proteins, which are suppressors of Wnt/beta-catenin pathway activity. With these small molecules, we establish a chemical genetic approach for studying Wnt pathway responses and stem cell function in adult tissue. We achieve transient, reversible suppression of Wnt/beta-catenin pathway response in vivo, and we establish a mechanism-based approach to target cancerous cell growth. The signal transduction mechanisms shown here to be chemically tractable additionally contribute to Wnt-independent signal transduction pathways and thus could be broadly exploited for chemical genetics and therapeutic goals.