scholarly journals Transmission of cell stress from endoplasmic reticulum to mitochondria

2002 ◽  
Vol 157 (7) ◽  
pp. 1151-1160 ◽  
Author(s):  
Osamu Hori ◽  
Fusae Ichinoda ◽  
Takashi Tamatani ◽  
Atsushi Yamaguchi ◽  
Naoya Sato ◽  
...  
Keyword(s):  
Er Stress ◽  
Nuclear Gene ◽  
Brefeldin A ◽  
Wild Type ◽  
Nuclear Gene Expression ◽  
Cultured Astrocytes ◽  
Associated Proteins ◽  
Steady State Levels

The rat homologue of a mitochondrial ATP-dependent protease Lon was cloned from cultured astrocytes exposed to hypoxia. Expression of Lon was enhanced in vitro by hypoxia or ER stress, and in vivo by brain ischemia. These observations suggested that changes in nuclear gene expression (Lon) triggered by ER stress had the potential to impact important mitochondrial processes such as assembly and/or degradation of cytochrome c oxidase (COX). In fact, steady-state levels of nuclear-encoded COX IV and V were reduced, and mitochondrial-encoded subunit II was rapidly degraded under ER stress. Treatment of cells with cycloheximide caused a similar imbalance in the accumulation of COX subunits, and enhanced mRNA for Lon and Yme1, the latter another mitochondrial ATP-dependent protease. Furthermore, induction of Lon or GRP75/mtHSP70 by ER stress was inhibited in PERK (−/−) cells. Transfection studies revealed that overexpression of wild-type or proteolytically inactive Lon promoted assembly of COX II into a COX I–containing complex, and partially prevented mitochondrial dysfunction caused by brefeldin A or hypoxia. These observations demonstrated that suppression of protein synthesis due to ER stress has a complex effect on the synthesis of mitochondrial-associated proteins, both COX subunits and ATP-dependent proteases and/or chaperones contributing to assembly of the COX complex.

scholarly journals Expression of a dominant allele of human ARF1 inhibits membrane traffic in vivo

1994 ◽  
Vol 124 (3) ◽  
pp. 289-300 ◽  
Author(s):  
CJ Zhang ◽  
AG Rosenwald ◽  
MC Willingham ◽  
S Skuntz ◽  
J Clark ◽  
...  
Keyword(s):  
Golgi Apparatus ◽  
Rat Kidney ◽  
Brefeldin A ◽  
Membrane Traffic ◽  
Immunoblot Analysis ◽  
In Vitro Assays ◽  
Wild Type ◽  
Discernible Effect

ADP-ribosylation factor (ARF) proteins and inhibitory peptides derived from ARFs have demonstrated activities in a number of in vitro assays that measure ER-to-Golgi and intra-Golgi transport and endosome fusion. To better understand the roles of ARF proteins in vivo, stable cell lines were obtained from normal rat kidney (NRK) cells transfected with either wild-type or a dominant activating allele ([Q71L]) of the human ARF1 gene under the control of the interferon-inducible mouse Mx1 promoter. Upon addition of interferon, expression of ARF1 proteins increased with a half-time of 7-8 h, as determined by immunoblot analysis. Induction of mutant ARF1, but not wild-type ARF1, led to an inhibition of protein secretion with kinetics similar to that observed for induction of protein expression. Examination of the Golgi apparatus and the ER by indirect immunofluorescence or transmission electron microscopy revealed that expression of low levels of mutant ARF1 protein correlated with a dramatic increase in vesiculation of the Golgi apparatus and expansion of the ER lumen, while expression of substantially higher levels of wild-type ARF1 had no discernible effect. Endocytosis was also inhibited by expression of mutant ARF1, but not by the wild-type protein. Finally, the expression of [Q71L]ARF1, but not wild-type ARF1, antagonized the actions of brefeldin A, as determined by the delayed loss of ARF and beta-COP from Golgi membranes and disruption of the Golgi apparatus. General models for the actions of ARF1 in membrane traffic events are discussed.

scholarly journals G-CSF improves murine G6PC3-deficient neutrophil function by modulating apoptosis and energy homeostasis

Blood ◽  
2011 ◽  
Vol 117 (14) ◽  
pp. 3881-3892 ◽  
Author(s):  
Hyun Sik Jun ◽  
Young Mok Lee ◽  
Ki Duk Song ◽  
Brian C. Mansfield ◽  
Janice Y. Chou
Keyword(s):  
Er Stress ◽  
Energy Homeostasis ◽  
Neutrophil Function ◽  
Mitochondrial Pathway ◽  
Neutrophil Apoptosis ◽  
Wild Type ◽  
Similar Survival ◽  
Neutrophil Survival

Abstract G6PC3 (or glucose-6-phosphatase-β) deficiency underlies a congenital neutropenia syndrome in which neutrophils exhibit enhanced endoplasmic reticulum (ER) stress, increased apoptosis, impaired energy homeostasis, and impaired functionality. Here we show that murine G6pc3−/− neutrophils undergoing ER stress activate protein kinase-like ER kinase and phosphatidylinositol 3,4,5-trisphosphate/Akt signaling pathways, and that neutrophil apoptosis is mediated in part by the intrinsic mitochondrial pathway. In G6PC3-deficient patients, granulocyte colony-stimulating factor (G-CSF) improves neutropenia, but its impact on neutrophil apoptosis and dysfunction is unknown. We now show that G-CSF delays neutrophil apoptosis in vitro by modulating apoptotic mediators. However, G6pc3−/− neutrophils in culture exhibit accelerated apoptosis compared with wild-type neutrophils both in the presence or absence of G-CSF. Limiting glucose (0.6mM) accelerates apoptosis but is more pronounced for wild-type neutrophils, leading to similar survival profiles for both neutrophil populations. In vivo G-CSF therapy completely corrects neutropenia and normalizes levels of p-Akt, phosphatidylinositol 3,4,5-trisphosphate, and active caspase-3. Neutrophils from in vivo G-CSF–treated G6pc3−/− mice exhibit increased glucose uptake and elevated intracellular levels of G6P, lactate, and adenosine-5′-triphosphate, leading to improved functionality. Together, the results strongly suggest that G-CSF improves G6pc3−/− neutrophil survival by modulating apoptotic mediators and rectifies function by enhancing energy homeostasis.

scholarly journals Changes in the Mitochondria-Related Nuclear Gene Expression Profile during Human Oocyte Maturation by the IVM Technique

Cells ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 297
Author(s):  
Zhi-Yong Yang ◽  
Min Ye ◽  
Ya-Xin Xing ◽  
Qi-Gui Xie ◽  
Jian-Hong Zhou ◽  
...  
Keyword(s):  
Oocyte Maturation ◽  
Single Cell Analysis ◽  
Nuclear Gene ◽  
Mature Stage ◽  
Human Oocyte ◽  
Acid Oxidation ◽  
Developmental Needs ◽  
Nuclear Gene Expression

To address which mitochondria-related nuclear differentially expressed genes (DEGs) and related pathways are altered during human oocyte maturation, single-cell analysis was performed in three oocyte states: in vivo matured (M-IVO), in vitro matured (M-IVT), and failed to mature in vitro (IM-IVT). There were 691 DEGs and 16 mitochondria-related DEGs in the comparison of M-IVT vs. IM-IVT oocytes, and 2281 DEGs and 160 mitochondria-related DEGs in the comparison of M-IVT vs. M-IVO oocytes, respectively. The GO and KEGG analyses showed that most of them were involved in pathways such as oxidative phosphorylation, pyruvate metabolism, peroxisome, and amino acid metabolism, i.e., valine, leucine, isoleucine, glycine, serine, and threonine metabolism or degradation. During the progress of oocyte maturation, the metabolic pathway, which derives the main source of ATP, shifted from glucose metabolism to pyruvate and fatty acid oxidation in order to maintain a low level of damaging reactive oxygen species (ROS) production. Although the immature oocytes could be cultured to a mature stage by an in vitro technique (IVM), there were still some differences in mitochondria-related regulations, which showed that the mitochondria were regulated by nuclear genes to compensate for their developmental needs. Meanwhile, the results indicated that the current IVM culture medium should be optimized to compensate for the special need for further development according to this disclosure, as it was a latent strategy to improve the effectiveness of the IVM procedure.

scholarly journals Global Proteotoxicity Caused by Human β2 Microglobulin Variants Impairs the Unfolded Protein Response in C. elegans

2021 ◽  
Vol 22 (19) ◽  
pp. 10752
Author(s):  
Sarah C. Good ◽  
Katherine M. Dewison ◽  
Sheena E. Radford ◽  
Patricija van Oosten-Hawle
Keyword(s):  
Er Stress ◽  
Molecular Mechanisms ◽  
Amyloid Fibrils ◽  
Signal Sequence ◽  
Systemic Amyloidosis ◽  
Wild Type ◽  
Β2 Microglobulin ◽  
C Elegans

Aggregation of β2 microglobulin (β2m) into amyloid fibrils is associated with systemic amyloidosis, caused by the deposition of amyloid fibrils containing the wild-type protein and its truncated variant, ΔN6 β2m, in haemo-dialysed patients. A second form of familial systemic amyloidosis caused by the β2m variant, D76N, results in amyloid deposits in the viscera, without renal dysfunction. Although the folding and misfolding mechanisms of β2 microglobulin have been widely studied in vitro and in vivo, we lack a comparable understanding of the molecular mechanisms underlying toxicity in a cellular and organismal environment. Here, we established transgenic C. elegans lines expressing wild-type (WT) human β2m, or the two highly amyloidogenic naturally occurring variants, D76N β2m and ΔN6 β2m, in the C. elegans bodywall muscle. Nematodes expressing the D76N β2m and ΔN6 β2m variants exhibit increased age-dependent and cell nonautonomous proteotoxicity associated with reduced motility, delayed development and shortened lifespan. Both β2m variants cause widespread endogenous protein aggregation contributing to the increased toxicity in aged animals. We show that expression of β2m reduces the capacity of C. elegans to cope with heat and endoplasmic reticulum (ER) stress, correlating with a deficiency to upregulate BiP/hsp-4 transcripts in response to ER stress in young adult animals. Interestingly, protein secretion in all β2m variants is reduced, despite the presence of the natural signal sequence, suggesting a possible link between organismal β2m toxicity and a disrupted ER secretory metabolism.

scholarly journals Regulation of cytoplasmic dynein function in vivo by the Drosophila Glued complex.

1995 ◽  
Vol 131 (2) ◽  
pp. 411-425 ◽  
Author(s):  
M McGrail ◽  
J Gepner ◽  
A Silvanovich ◽  
S Ludmann ◽  
M Serr ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Cytoplasmic Dynein ◽  
Chain Gene ◽  
Gene Products ◽  
Wild Type ◽  
Microtubule Associated Proteins ◽  
Dynein Motor ◽  
Associated Proteins

The Drosophila Glued gene product shares sequence homology with the p150 component of vertebrate dynactin. Dynactin is a multiprotein complex that stimulates cytoplasmic dynein-mediated vesicle motility in vitro. In this report, we present biochemical, cytological, and genetic evidence that demonstrates a functional similarity between the Drosophila Glued complex and vertebrate dynactin. We show that, similar to the vertebrate homologues in dynactin, the Glued polypeptides are components of a 20S complex. Our biochemical studies further reveal differential expression of the Glued polypeptides, all of which copurify as microtubule-associated proteins. In our analysis of the Glued polypeptides encoded by the dominant mutation, Glued, we identify a truncated polypeptide that fails to assemble into the wild-type 20S complex, but retains the ability to copurify with microtubules. The spatial and temporal distribution of the Glued complex during oogenesis is shown by immunocytochemistry methods to be identical to the pattern previously described for cytoplasmic dynein. Significantly, the pattern of Glued distribution in oogenesis is dependent on dynein function, as well as several other gene products known to be required for proper dynein localization. In genetic complementation studies, we find that certain mutations in the cytoplasmic dynein heavy chain gene Dhc64C act as dominant suppressors or enhancers of the rough eye phenotype of the dominant Glued mutation. Furthermore, we show that a mutation that was previously isolated as a suppressor of the Glued mutation is an allele of Dhc64C. Together with the observed dependency of Glued localization on dynein function, these genetic interactions demonstrate a functional association between the Drosophila dynein motor and Glued complexes.

scholarly journals The Golgi-Associated Hook3 Protein Is a Member of a Novel Family of Microtubule-Binding Proteins

2001 ◽  
Vol 152 (5) ◽  
pp. 923-934 ◽  
Author(s):  
Jason H. Walenta ◽  
Aaron J. Didier ◽  
Xinran Liu ◽  
Helmut Krämer
Keyword(s):  
Golgi Complex ◽  
Membrane Trafficking ◽  
Spatial Organization ◽  
Large Fraction ◽  
Coiled Coil ◽  
Brefeldin A ◽  
Associated Proteins ◽  
Terminal Domains

Microtubules are central to the spatial organization of diverse membrane-trafficking systems. Here, we report that Hook proteins constitute a novel family of cytosolic coiled coil proteins that bind to organelles and to microtubules. The conserved NH2-terminal domains of Hook proteins mediate attachment to microtubules, whereas the more divergent COOH-terminal domains mediate the binding to organelles. Human Hook3 bound to Golgi membranes in vitro and was enriched in the cis-Golgi in vivo. Unlike other cis-Golgi–associated proteins, however, a large fraction of Hook3 maintained its juxtanuclear localization after Brefeldin A treatment, indicating a Golgi-independent mechanism for Hook3 localization. Because overexpression of Hook3 caused fragmentation of the Golgi complex, we propose that Hook3 participates in defining the architecture and localization of the mammalian Golgi complex.

scholarly journals Direct methylation of FXR by Set7/9, a lysine methyltransferase, regulates the expression of FXR target genes

2012 ◽  
Vol 302 (9) ◽  
pp. G937-G947 ◽  
Author(s):  
Natarajan Balasubramaniyan ◽  
Meena Ananthanarayanan ◽  
Frederick J. Suchy
Keyword(s):  
Bile Acid ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Farnesoid X Receptor ◽  
Mutant Form ◽  
Wild Type ◽  
Associated Proteins ◽  
Transcriptional Complex

The farnesoid X receptor (FXR) is a ligand (bile acid)-dependent nuclear receptor that regulates target genes involved in every aspect of bile acid homeostasis. Upon binding of ligand, FXR recruits an array of coactivators and associated proteins, some of which have intrinsic enzymatic activity that modify histones or even components of the transcriptional complex. In this study, we show chromatin occupancy by the Set7/9 methyltransferase at the FXR response element (FXRE) and direct methylation of FXR in vivo and in vitro at lysine 206. siRNA depletion of Set7/9 in the Huh-7 liver cell line decreased endogenous mRNAs of the FXR target genes, the short heterodimer partner (SHP) and bile salt export pump (BSEP). Mutation of the methylation site at K206 of FXR to an arginine prevented methylation by Set7/9. A pan-methyllysine antibody recognized the wild-type FXR but not the K206R mutant form. An electromobility shift assay showed that methylation by Set7/9 enhanced binding of FXR/retinoic X receptor-α to the FXRE. Interaction between hinge domain of FXR (containing K206) and Set7/9 was confirmed by coimmunoprecipitation, GST pull down, and mammalian two-hybrid experiments. Set7/9 overexpression in Huh-7 cells significantly enhanced transactivation of the SHP and BSEP promoters in a ligand-dependent fashion by wild-type FXR but not the K206R mutant FXR. A Set7/9 mutant deficient in methyltransferase activity was also not effective in increasing transactivation of the BSEP promoter. These studies demonstrate that posttranslational methylation of FXR by Set7/9 contributes to the transcriptional activation of FXR-target genes.

Preparation of cultured astrocytes for x-ray microanalysis

1989 ◽  
Vol 47 ◽  
pp. 988-989
Author(s):  
N.K.R. Smith ◽  
K.E. Hunter ◽  
P. Mobley ◽  
L.P. Felpel
Keyword(s):  
Cultured Cells ◽  
Elemental Content ◽  
Elemental Distribution ◽  
Sprague Dawley ◽  
X Ray ◽  
Cultured Astrocytes ◽  
Freeze Dried ◽  
Ultimate Objective

Electron probe energy dispersive x-ray microanalysis (XRMA) offers a powerful tool for the determination of intracellular elemental content of biological tissue. However, preparation of the tissue specimen , particularly excitable central nervous system (CNS) tissue , for XRMA is rather difficult, as dissection of a sample from the intact organism frequently results in artefacts in elemental distribution. To circumvent the problems inherent in the in vivo preparation, we turned to an in vitro preparation of astrocytes grown in tissue culture. However, preparations of in vitro samples offer a new and unique set of problems. Generally, cultured cells, growing in monolayer, must be harvested by either mechanical or enzymatic procedures, resulting in variable degrees of damage to the cells and compromised intracel1ular elemental distribution. The ultimate objective is to process and analyze unperturbed cells. With the objective of sparing others from some of the same efforts, we are reporting the considerable difficulties we have encountered in attempting to prepare astrocytes for XRMA.Tissue cultures of astrocytes from newborn C57 mice or Sprague Dawley rats were prepared and cultured by standard techniques, usually in T25 flasks, except as noted differently on Cytodex beads or on gelatin. After different preparative procedures, all samples were frozen on brass pins in liquid propane, stored in liquid nitrogen, cryosectioned (0.1 μm), freeze dried, and microanalyzed as previously reported.

scholarly journals Stu2p binds tubulin and undergoes an open-to-closed conformational change

2006 ◽  
Vol 172 (7) ◽  
pp. 1009-1022 ◽  
Author(s):  
Jawdat Al-Bassam ◽  
Mark van Breugel ◽  
Stephen C. Harrison ◽  
Anthony Hyman
Keyword(s):  
Conformational Change ◽  
Conformational Transition ◽  
Budding Yeast ◽  
Microtubule Dynamics ◽  
Open Structure ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
The Common

Stu2p from budding yeast belongs to the conserved Dis1/XMAP215 family of microtubule-associated proteins (MAPs). The common feature of proteins in this family is the presence of HEAT repeat–containing TOG domains near the NH2 terminus. We have investigated the functions of the two TOG domains of Stu2p in vivo and in vitro. Our data suggest that Stu2p regulates microtubule dynamics through two separate activities. First, Stu2p binds to a single free tubulin heterodimer through its first TOG domain. A large conformational transition in homodimeric Stu2p from an open structure to a closed one accompanies the capture of a single free tubulin heterodimer. Second, Stu2p has the capacity to associate directly with microtubule ends, at least in part, through its second TOG domain. These two properties lead to the stabilization of microtubules in vivo, perhaps by the loading of tubulin dimers at microtubule ends. We suggest that this mechanism of microtubule regulation is a conserved feature of the Dis1/XMAP215 family of MAPs.

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