RESUMEN
Mitochondrial uncoupling protein 1 (UCP1) is responsible for nonshivering thermogenesis in brown adipose tissue (BAT). UCP1 increases the conductance of the inner mitochondrial membrane (IMM) for protons to make BAT mitochondria generate heat rather than ATP. HDAC6 is a cytosolic deacetylase for non-histone substrates to regulate various cellular processes, including mitochondrial quality control and dynamics. Here, we showed that the body temperature of HDAC6 knockout mice is slightly decreased in normal hosing condition. Interestingly, UCP1 was downregulated in BAT of HDAC6 knockout mice, which extensively linked mitochondrial thermogenesis. Mechanistically, we showed that cAMP-PKA signaling plays a key role in HDAC6-dependent UCP1 expression. Notably, the size of brown adipocytes and lipid droplets in HDAC6 knockout BAT is increased. Taken together, our findings suggested that HDAC6 contributes to mitochondrial thermogenesis in BAT by increasing UCP1 expression through cAMP-PKA signaling pathway.
Asunto(s)
Adipocitos Marrones/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Activación Enzimática , Histona Desacetilasa 6/metabolismo , Termogénesis , Proteína Desacopladora 1/genética , Tejido Adiposo Pardo/fisiología , Animales , Células Cultivadas , Regulación de la Expresión Génica , Histona Desacetilasa 6/genética , Metabolismo de los Lípidos , Masculino , Ratones , Ratones Noqueados , Mitocondrias/genética , Mitocondrias/metabolismo , Transducción de Señal , Proteína Desacopladora 1/metabolismoRESUMEN
Lipids in microalgae are energy-rich compounds and considered as an attractive feedstock for biodiesel production. To redirect carbon flux from competing pathways to the fatty acid synthesis pathway of Tetraselmis sp., we used three types of chemical inhibitors that can block the starch synthesis pathway or photorespiration, under nitrogen-sufficient and nitrogen-deficient conditions. The starch synthesis pathway in chloroplasts and the cytosol can be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 1,2-cyclohexane diamine tetraacetic acid (CDTA), respectively. Degradation of glycine into ammonia during photorespiration was blocked by aminooxyacetate (AOA) to maintain biomass concentration. Inhibition of starch synthesis pathways in the cytosol by CDTA increased fatty acid productivity by 27% under nitrogen deficiency, whereas the blocking of photorespiration in mitochondria by AOA was increased by 35% under nitrogen-sufficient conditions. The results of this study indicate that blocking starch or photorespiration pathways may redirect the carbon flux to fatty acid synthesis.
Asunto(s)
Ciclo del Carbono/efectos de la radiación , Chlorophyta/metabolismo , Ácidos Grasos/biosíntesis , Microalgas/efectos de los fármacos , Microalgas/metabolismo , Ácido Aminooxiacético/antagonistas & inhibidores , Ácido Aminooxiacético/metabolismo , Amoníaco/metabolismo , Biodegradación Ambiental , Biocombustibles , Biomasa , Carbohidratos/análisis , Carbohidratos/biosíntesis , Cloroplastos/efectos de los fármacos , Citosol/efectos de los fármacos , Diurona/antagonistas & inhibidores , Ácido Edético/análogos & derivados , Ácido Edético/antagonistas & inhibidores , Ácidos Grasos/análisis , Glicina/metabolismo , Nitrógeno/metabolismo , Almidón/biosíntesis , InaniciónRESUMEN
The acetylation of p53 is critical in modulating its pro-apoptotic roles. However, its regulatory mechanism and physiological significance are unclear. Here, we show HDAC6 negatively regulates pro-apoptotic acetylation of p53 at lysine residue 120 (K120) in mesenchymal stem cells (MSCs). The loss of HDAC6 expression in MSCs increases K120 acetylation of p53, which is successfully reversed by the wild-type but not by catalytically dead HDAC6. Deletion of HDAC6 induces caspase-dependent apoptosis by promoting transactivation of Bax and suppression of Bcl-2. Moreover, HDAC6 deficiency leads to mitochondrial dysfunction characterized by aberrant reactive oxygen species production and defective oxidative phosphorylation, which is reversed by ectopic expression of wild-type or acetylation mimetic p53. This study demonstrates that HDAC6 is a critical regulator of a pro-apoptotic p53 K120 acetylation and mitochondrial function in MSCs, suggesting that the modulation of HDAC6 activity could be a novel approach to improve MSC- based therapies.
Asunto(s)
Apoptosis/fisiología , Histona Desacetilasas/deficiencia , Células Madre Mesenquimatosas/citología , Células Madre Mesenquimatosas/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Acetilación , Animales , Apoptosis/genética , Histona Desacetilasa 6 , Histona Desacetilasas/genética , Histona Desacetilasas/metabolismo , Lisina/química , Lisina/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Proteína p53 Supresora de Tumor/químicaRESUMEN
RAP80, a member of the BRCA1-A complex, is a well-known crucial regulator of cell cycle checkpoint and DNA damage repair in the nucleus. However, it is still unclear whether Rap80 localizes to another region outside the nucleus and plays different roles with its partners. Here, we found mitochondrial p32 as a novel binding partner of RAP80 by using yeast two-hybrid screening. RAP80 directly binds the internal region of p32 through its arginine rich C-terminal domain. Based on the interaction, we showed that a subset of RAP80 localizes to mitochondria where p32 exists. Loss of function study revealed that RAP80 deficiency reduces the protein level of p32 and p32 dependent mitochondrial translating proteins such as Rieske and COX1. As a result, mitochondrial membrane potential and oxygen consumption are reduced in RAP80 knockdown cells, indicating mitochondrial dysfunction. Our study identifies a novel interaction between RAP80 and p32, which is important for preserving intact mitochondrial function.
Asunto(s)
Proteínas Portadoras/metabolismo , Mitocondrias/metabolismo , Proteínas Mitocondriales/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Portadoras/genética , Células Cultivadas , Proteínas de Unión al ADN , Chaperonas de Histonas , Humanos , Proteínas Mitocondriales/genética , Mutación , Proteínas Nucleares/deficiencia , Proteínas Nucleares/genéticaRESUMEN
Temperature is a critical environmental factor that affects microalgal growth. However, microalgal coping mechanisms for temperature variations are unclear. Here, we determined changes in transcriptome, total carbohydrate, total fatty acid methyl ester, and fatty acid composition of Tetraselmis sp. KCTC12432BP, a strain with a broad temperature tolerance range, to elucidate the tolerance mechanisms in response to large temperature variations. Owing to unavailability of genome sequence information, de novo transcriptome assembly coupled with BLAST analysis was performed using strand specific RNA-seq data. This resulted in 26,245 protein-coding transcripts, of which 83.7% could be annotated to putative functions. We identified more than 681 genes differentially expressed, suggesting an organelle-specific response to temperature variation. Among these, the genes related to the photosynthetic electron transfer chain, which are localized in the plastid thylakoid membrane, were upregulated at low temperature. However, the transcripts related to the electron transport chain and biosynthesis of phosphatidylethanolamine localized in mitochondria were upregulated at high temperature. These results show that the low energy uptake by repressed photosynthesis under low and high temperature conditions is compensated by different mechanisms, including photosystem I and mitochondrial oxidative phosphorylation, respectively. This study illustrates that microalgae tolerate different temperature conditions through organelle specific mechanisms.