RESUMO
Bcl-2 homologues (such as Bcl-x(L)) promote survival in part through sequestration of "activator" BH3-only proteins (such as Puma), preventing them from directly activating Bax. It is thus assumed that inhibition of interactions between activators and Bcl-x(L) is a prerequisite for small molecules to antagonize Bcl-x(L) and induce cell death. The biological properties, described here of a terphenyl-based alpha-helical peptidomimetic inhibitor of Bcl-x(L) attest that displacement of Bax from Bcl-x(L) is also critical. Terphenyl 14 triggers Bax-dependent but Puma-independent cell death, disrupting Bax/Bcl-x(L) interactions without affecting Puma/Bcl-x(L) interactions. In cell-free assays, binding of inactive Bax to Bcl-x(L), followed by its displacement from Bcl-x(L) by terphenyl 14, produces mitochondrially permeabilizing Bax molecules. Moreover, the peptidomimetic kills yeast cells that express Bax and Bcl-x(L), and it uses Bax-binding Bcl-x(L) to induce mammalian cell death. Likewise, ectopic expression of Bax in yeast and mammalian cells enhances sensitivity to another Bcl-x(L) inhibitor, ABT-737, when Bcl-x(L) is present. Thus, the interaction of Bcl-x(L) with Bax paradoxically primes Bax at the same time it keeps Bax activity in check, and displacement of Bax from Bcl-x(L) triggers an apoptotic signal by itself. This mechanism might contribute to the clinical efficiency of Bcl-x(L) inhibitors.
Assuntos
Proteína X Associada a bcl-2/metabolismo , Proteína bcl-X/metabolismo , Sequência de Aminoácidos , Animais , Proteínas Reguladoras de Apoptose/genética , Proteínas Reguladoras de Apoptose/metabolismo , Sítios de Ligação , Compostos de Bifenilo/farmacologia , Morte Celular/efeitos dos fármacos , Morte Celular/genética , Morte Celular/fisiologia , Linhagem Celular Tumoral , Sistema Livre de Células , Células Cultivadas , Técnicas de Silenciamento de Genes , Células HeLa , Humanos , Técnicas In Vitro , Camundongos , Camundongos Knockout , Mitocôndrias/metabolismo , Modelos Biológicos , Mimetismo Molecular , Dados de Sequência Molecular , Mutação , Nitrofenóis/farmacologia , Piperazinas/farmacologia , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , RNA Interferente Pequeno/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Sulfonamidas/farmacologia , Compostos de Terfenil/farmacologia , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Técnicas do Sistema de Duplo-Híbrido , Proteína X Associada a bcl-2/deficiência , Proteína X Associada a bcl-2/genética , Proteína bcl-X/deficiência , Proteína bcl-X/genéticaRESUMO
Apoptosis, a form of cell death by self-destruction, has been reported in gametes and preimplantation embryos both in vitro and in vivo. Recent evidence suggests that cell death processes, whose control deserves to be elucidated, can impact embryo developmental competence. Moreover, quality of the gametes (particularly of the oocytes) is relevant not only for their survival rates but exert an influence during the early stages of embryo development. Thus, the investigation of apoptosis-related genes and mechanisms in early embryos is crucial. BCL-2 family proteins, through balanced interactions between pro- and anti-death members, play a pivotal role in controlling cell life and death. In this article, we review the literature concerning the expression of Bcl-2 family members in gametes and early embryos. Research results indicate that the various Bcl-2 subfamilies (pro- and anti-apoptotic "multidomain" family members and "BH3-only" death factors) exhibit a dynamic expression pattern during male and female gamete differentiation and early embryo development. While pro-apoptotic Bax protein plays a critical role in germ cell and early embryo degeneration, the relative importance of the prosurvival (Bcl-2, Bcl-xL, Bcl-w, Mcl-1) and "BH3-only" (Bim, Bad, Bik) members is not clear. Although information on expression patterns of Bcl-2 family transcripts and proteins is necessary, other elements such as transcriptional control (by environmental stimuli), subcellular localization and post-translational modifications should also be taken into account. Aside from basic research, a better understanding of apoptosis-related proteins and mechanisms involved in gamete and embryo viability at the molecular level may provide new guides for diagnosis and therapeutic strategies.