RESUMO
The sterol regulatory element-binding proteins (SREBP) are key transcriptional regulators of lipid metabolism and cellular growth. It has been proposed that SREBP signaling regulates cellular growth through its ability to drive lipid biosynthesis. Unexpectedly, we find that loss of SREBP activity inhibits cancer cell growth and viability by uncoupling fatty acid synthesis from desaturation. Integrated lipid profiling and metabolic flux analysis revealed that cancer cells with attenuated SREBP activity maintain long-chain saturated fatty acid synthesis, while losing fatty acid desaturation capacity. We traced this defect to the uncoupling of fatty acid synthase activity from stearoyl-CoA desaturase 1 (SCD1)-mediated desaturation. This deficiency in desaturation drives an imbalance between the saturated and monounsaturated fatty acid pools resulting in severe lipotoxicity. Importantly, replenishing the monounsaturated fatty acid pool restored growth to SREBP-inhibited cells. These studies highlight the importance of fatty acid desaturation in cancer growth and provide a novel mechanistic explanation for the role of SREBPs in cancer metabolism.
Assuntos
Regulação Neoplásica da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/metabolismo , Neoplasias/metabolismo , Animais , Ciclo Celular , Linhagem Celular Tumoral , Proliferação de Células , Ácido Graxo Sintases/metabolismo , Perfilação da Expressão Gênica , Humanos , Camundongos , Camundongos Endogâmicos NOD , Modelos Estatísticos , Transplante de Neoplasias , Transdução de Sinais , Estearoil-CoA Dessaturase/metabolismo , Esteróis/metabolismoRESUMO
Detection and quantification of fatty acid fluxes in animal model systems following physiological, pathological, or pharmacological challenges is key to our understanding of complex metabolic networks as these macronutrients also activate transcription factors and modulate signaling cascades including insulin sensitivity. To enable noninvasive, real-time, spatiotemporal quantitative imaging of fatty acid fluxes in animals, we created a bioactivatable molecular imaging probe based on long-chain fatty acids conjugated to a reporter molecule (luciferin). We show that this probe faithfully recapitulates cellular fatty acid uptake and can be used in animal systems as a valuable tool to localize and quantitate in real time lipid fluxes such as intestinal fatty acid absorption and brown adipose tissue activation. This imaging approach should further our understanding of basic metabolic processes and pathological alterations in multiple disease models.