GTP in the mitochondrial matrix plays a crucial role in organellar iron homoeostasis.
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ABSTRACT:
SUBMITTER: Gordon DM
PROVIDER: S-EPMC1635451 | biostudies-other | 2006 Nov
REPOSITORIES: biostudies-other
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Project description:Background The risk of cardiovascular disease is known to increase after menopause. Mitochondria, which undergo quality control via mitochondrial autophagy, play a crucial role in the regulation of cellular senescence. The aim of this study was to investigate whether the effect of estrogen-mediated protection from senescence on arteries is attributed to the induction of mitochondrial autophagy. Methods and Results We used human umbilical vein cells, vascular smooth muscle cells, and 12-week-old female C57BL/6 mice. The administration of 17β-estradiol (E2) to cells inhibited cellular senescence and mitochondrial dysfunction. Furthermore, E2 increased mitochondrial autophagy, maintaining mitochondrial function, and retarding cellular senescence. Of note, E2 did not modulate LC3 (light chain 3), and ATG7 (autophagy related 7) deficiency did not suppress mitochondrial autophagy in E2-treated cells. Conversely, E2 increased the colocalization of Rab9 with LAMP2 (lysosomal-associated membrane protein 2) signals. The E2-mediated effects on mitochondrial autophagy were abolished by the knockdown of either Ulk1 or Rab9. These results suggest that E2-mediated mitochondrial autophagy is associated with Rab9-dependent alternative autophagy. E2 upregulated SIRT1 (sirtuin 1) and activated LKB1 (liver kinase B1), AMPK (adenosine monophosphate-activated protein kinase), and Ulk1, indicating that the effect of E2 on the induction of Rab9-dependent alternative autophagy is mediated by the SIRT1/LKB1/AMPK/Ulk1 pathway. Compared with the sham-operated mice, ovariectomized mice showed reduced mitochondrial autophagy and accelerated mitochondrial dysfunction and arterial senescence; these detrimental alterations were successfully rescued by the administration of E2. Conclusions We showed that E2-induced mitochondrial autophagy plays a crucial role in the delay of vascular senescence. The Rab9-dependent alternative autophagy is behind E2-induced mitochondrial autophagy.
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Project description:Tomato mosaic virus (ToMV), like other eukaryotic positive-strand RNA viruses, replicates its genomic RNA in replication complexes formed on intracellular membranes. Previous studies showed that a host seven-pass transmembrane protein TOM1 is necessary for efficient ToMV multiplication. Here, we show that a small GTP-binding protein ARL8, along with TOM1, is co-purified with a FLAG epitope-tagged ToMV 180K replication protein from solubilized membranes of ToMV-infected tobacco (Nicotiana tabacum) cells. When solubilized membranes of ToMV-infected tobacco cells that expressed FLAG-tagged ARL8 were subjected to immunopurification with anti-FLAG antibody, ToMV 130K and 180K replication proteins and TOM1 were co-purified and the purified fraction showed RNA-dependent RNA polymerase activity that transcribed ToMV RNA. From uninfected cells, TOM1 co-purified with FLAG-tagged ARL8 less efficiently, suggesting that a complex containing ToMV replication proteins, TOM1, and ARL8 are formed on membranes in infected cells. In Arabidopsis thaliana, ARL8 consists of four family members. Simultaneous mutations in two specific ARL8 genes completely inhibited tobamovirus multiplication. In an in vitro ToMV RNA translation-replication system, the lack of either TOM1 or ARL8 proteins inhibited the production of replicative-form RNA, indicating that TOM1 and ARL8 are required for efficient negative-strand RNA synthesis. When ToMV 130K protein was co-expressed with TOM1 and ARL8 in yeast, RNA 5'-capping activity was detected in the membrane fraction. This activity was undetectable or very weak when the 130K protein was expressed alone or with either TOM1 or ARL8. Taken together, these results suggest that TOM1 and ARL8 are components of ToMV RNA replication complexes and play crucial roles in a process toward activation of the replication proteins' RNA synthesizing and capping functions.
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Project description:This SuperSeries is composed of the SubSeries listed below. Refer to individual Series
2016-07-01 | E-GEOD-70196 | biostudies-arrayexpress
Project description:Tooth enamel is generated by ameloblasts. Any failure in amelogenesis results in defects in the enamel, a condition known as amelogenesis imperfecta. Here, we report that mice with deficient autophagy in epithelial-derived tissues (K14-Cre;Atg7F/F and K14-Cre;Atg3F/F conditional knockout mice) exhibit amelogenesis imperfecta. Micro-computed tomography imaging confirmed that enamel density and thickness were significantly reduced in the teeth of these mice. At the molecular level, ameloblast differentiation was compromised through ectopic accumulation and activation of NRF2, a specific substrate of autophagy. Through bioinformatic analyses, we identified Bcl11b, Dlx3, Klk4, Ltbp3, Nectin1, and Pax9 as candidate genes related to amelogenesis imperfecta and the NRF2-mediated pathway. To investigate the effects of the ectopic NRF2 pathway activation caused by the autophagy deficiency, we analyzed target gene expression and NRF2 binding to the promoter region of candidate target genes and found suppressed gene expression of Bcl11b, Dlx3, Klk4, and Nectin1 but not of Ltbp3 and Pax9. Taken together, our findings indicate that autophagy plays a crucial role in ameloblast differentiation and that its failure results in amelogenesis imperfecta through ectopic NRF2 activation.
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Project description:We show that Glis3 is expressed in gonocytes, SSCs and SPCs, but not in differentiated spermatogonia or subsequent stages of spermatogenesis nor in Sertoli or Leydig cells. We further demonstrate that Glis3-deficiency causes a severe impairment in spermatogenesis in mice. Although the number of gonocytes was slightly diminished in Glis3KO testis, the number undifferentiated, PLZF+ spermatogonia was dramatically reduced leading to a virtual block in the progression of spermatogenesis. Gene expression profiling showed that the expression of a number of genes associated with self-renewal and differentiation of spermatogonial cells was significantly decreased in 1-week-old Glis3KO2 testis. These included a set of GDNF-dependent genes, such as Etv5, Bcl6b, Lhx1, Brachyury, Id4, and Pou3f1, and GDNF-independent genes, such as FoxO1, Oct4, and Zbtb16. Impairment of the nuclear localization of FoxO1 may be in part responsible for the reduced expression of Ret, Lhx1, and Sall4 in Glis3KO2 testis. Our study identifies Glis3 as a novel and critical regulator of early stages of spermatogenesis. Thy1+ cells were isolated from 3 WT and 3 Glis3KO2 testis at postnatal day 4, and total RNAs were purified from them. Then the samples were applied to Agilent mouse genome chip.
2016-07-01 | E-GEOD-70195 | biostudies-arrayexpress
Project description:We show that Glis3 is expressed in gonocytes, SSCs and SPCs, but not in differentiated spermatogonia or subsequent stages of spermatogenesis nor in Sertoli or Leydig cells. We further demonstrate that Glis3-deficiency causes a severe impairment in spermatogenesis in mice. Although the number of gonocytes was slightly diminished in Glis3KO testis, the number undifferentiated, PLZF+ spermatogonia was dramatically reduced leading to a virtual block in the progression of spermatogenesis. Gene expression profiling showed that the expression of a number of genes associated with self-renewal and differentiation of spermatogonial cells was significantly decreased in 1-week-old Glis3KO2 testis. These included a set of GDNF-dependent genes, such as Etv5, Bcl6b, Lhx1, Brachyury, Id4, and Pou3f1, and GDNF-independent genes, such as FoxO1, Oct4, and Zbtb16. Impairment of the nuclear localization of FoxO1 may be in part responsible for the reduced expression of Ret, Lhx1, and Sall4 in Glis3KO2 testis. Our study identifies Glis3 as a novel and critical regulator of early stages of spermatogenesis. Testis total RNAs were purified from 4 WT and 4 Glis3KO2 at 1 week old age, and 3WT and 3 Glis3KO2 at 3 week-old age. Then the samples were applied to Agilent mouse genome chip.
2016-07-01 | E-GEOD-70194 | biostudies-arrayexpress
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