RESUMEN
Although senescent cells display various morphological changes including vacuole formation, it is still unclear how these processes are regulated. We have recently identified the gene, lymphocyte antigen 6 complex, locus D (LY6D), to be upregulated specifically in senescent cells. LY6D is a glycosylphosphatidylinositol-anchored cell-surface protein whose function remains unknown. Here, we analyzed the functional relationship between LY6D and the senescence processes. We found that overexpression of LY6D induced vacuole formation and knockdown of LY6D suppressed the senescence-associated vacuole formation. The LY6D-induced vacuoles were derived from macropinocytosis, a distinct form of endocytosis. Furthermore, Src family kinases and Ras were found to be recruited to membrane lipid rafts in an LY6D-dependent manner, and inhibition of their activity impaired the LY6D-induced macropinocytosis. Finally, reduction of senescent-cell survival induced by glutamine deprivation was recovered by albumin supplementation to the culture media in an LY6D-dependent manner. Because macropinocytosis acts as an amino acid supply route, these results suggest that LY6D-mediated macropinocytosis contributes to senescent-cell survival through the incorporation of extracellular nutrients.
Asunto(s)
Moléculas de Adhesión Celular/metabolismo , Senescencia Celular , Pinocitosis , Moléculas de Adhesión Celular/genética , Línea Celular Tumoral , Supervivencia Celular , Proteínas Ligadas a GPI/genética , Proteínas Ligadas a GPI/metabolismo , Humanos , Proteínas ras/genética , Proteínas ras/metabolismo , Familia-src Quinasas/genética , Familia-src Quinasas/metabolismoRESUMEN
The purpose of this study was to discover the effects of soybean beta-conglycinin (7S-globulin) and glycinin (11S-globulin) on serum lipid levels and metabolism in the livers of normal and genetically obese mice. Male normal (ICR) and obese (KK-Ay) mice were fed ad libitum high fat diets for two weeks, followed by a 2-week restriction of diet (2 g diet/mouse/day) containing 20% casein, soybean beta-conglycinin, or soybean glycinin, and then sacrificed immediately. Serum triglyceride (TG), glucose, and insulin levels of beta-conglycinin-fed mice were lower than in casein- and glycinin-fed mice of both strains. In order to analyze the related events to these effects, enzyme activities and relative mRNA levels of lipid metabolism-related proteins were measured. The activities of two enzymes related to fatty acid beta-oxidation were higher while that of fatty acid synthase was lower in livers of beta-conglycinin-fed mice than of casein-fed both mice. Messenger RNA levels of acyl-CoA oxidase (fatty acid beta-oxidation related enzyme) were significantly higher in livers of beta-conglycinin-fed mice than of both casein-fed mice. On the contrary, mRNA levels of SREBP-1 and 2 tended to be lowered in livers of soy protein-fed mice than of both casein-fed mice. Fecal excretion of TG was higher in beta-conglycinin-fed mice than in casein-fed mice. Our results demonstrated that the soy beta-conglycinin diet reduced serum TG levels by acceleration of beta-oxidation, suppression of fatty acid synthase and/or increased TG fecal excretion, and also diminished serum glucose and insulin levels. Some of these events might be caused at the transcriptional levels, judged from the result that relative messenger RNA levels of lipid metabolism-related proteins were altered. These results suggest that soy beta-conglycinin could be a potentially useful dietary protein source for the prevention of hypertriglyceridemia, hyperinsulinemia, and hyperglycemia, which are recognized as risk factors for atherosclerosis.
Asunto(s)
Dieta , Ácido Graso Sintasas/antagonistas & inhibidores , Globulinas/farmacología , Glycine max/química , Obesidad/sangre , Proteínas de Soja/farmacología , Triglicéridos/sangre , Animales , Antígenos de Plantas , Glucemia/metabolismo , Peso Corporal , Regulación hacia Abajo/efectos de los fármacos , Ingestión de Alimentos , Ácido Graso Sintasas/genética , Heces/química , Absorción Intestinal/efectos de los fármacos , Metabolismo de los Lípidos , Lípidos/análisis , Hígado/efectos de los fármacos , Hígado/enzimología , Masculino , Ratones , Ratones Endogámicos ICR , Ratones Obesos , Obesidad/genética , Tamaño de los Órganos/fisiología , Oxidación-Reducción , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Proteínas de Almacenamiento de SemillasRESUMEN
Up to now the regulatory mechanisms, which govern the concentrations of neurosteroids in the brain, are unclear. Seasonal breeders may serve as excellent models to understand physiological changes in neurosteroid levels and their regulatory mechanisms. The present study first investigated immunohistochemically the localization of cytochrome p450 side-chain cleavage enzyme (p450scc) and 3beta-hydroxysteroid dehydrogenase/delta(5)-delta(4)-isomerase (3betaHSD) in the brain of the newt Cynops pyrrhogaster, a seasonally breeding amphibian. Both p450scc- and 3betaHSD-like immunoreactive cells were restricted to the preoptic area. Seasonal changes in neurosteroid concentrations were then examined using adult males. Pregnenolone concentrations in the brain showed marked changes during annual breeding cycle and a maximal level in August, independent of the plasma steroid levels which were all low throughout the year. Progesterone concentrations in the brain, which were lower than pregnenolone levels, also showed peaks in April and August. In contrast, the pregnenolone sulfate level was low and its change was less pronounced. To clarify environmental factors that induce seasonal changes in neurosteroid levels, adult males were further subjected to different photoperiods and ambient temperatures for 5 weeks. Both pregnenolone and progesterone concentrations in the brain were significantly higher in the long day (LD) group than in the short day (SD) group, whereas no significant effects of different ambient temperatures on neurosteroid levels were detected. These results suggest that the newt brain possesses steroidogenic enzymes p450scc and 3betaHSD and exhibits seasonal changes in the pregnenolone and progesterone concentrations. Photoperiod may be a more important environmental factor than temperature for the regulation of neurosteroid levels in the brain.