scholarly journals Mitochondria supply ATP to the ER through a mechanism antagonized by cytosolic Ca2+

2019 ◽  
Author(s):  
Jing Yong ◽  
Helmut Bischof ◽  
Marina Siirin ◽  
Anne Murphy ◽  
Roland Malli ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Warburg Effect ◽  
Transport Process ◽  
Protein Misfolding ◽  
Atp Hydrolysis ◽  
Atp Level ◽  
Physiological Conditions ◽  
Atp Supply ◽  
Atp Regeneration ◽  
Er Membrane

AbstractThe endoplasmic reticulum (ER) imports ATP and uses energy from ATP hydrolysis for protein folding and trafficking. However, little is known about this vital ATP transport process across the ER membrane. Here, using three commonly used cell lines (CHO, INS1 and HeLa), we report that ATP enters the ER lumen through a cytosolic Ca2+-antagonized mechanism, or CaATiER (Ca2+-Antagonized Transport into ER) mechanism for brevity. Significantly, we observed that a Ca2+ gradient across the ER membrane is necessary for ATP transport into the ER. Therefore Ca2+ signaling in the cytosol is inevitably coupled with ATP supply to the ER. We propose that under physiological conditions, cytosolic Ca2+ inhibits ATP import into the ER lumen to limit ER ATP consumption. Furthermore, the ATP level in the ER is readily depleted by oxidative phosphorylation (OxPhos) inhibitors, and that ER protein misfolding increases ATP trafficking from mitochondria into the ER. These findings suggest that ATP usage in the ER may increase mitochondrial OxPhos while decreasing glycolysis, i.e., an “anti-Warburg” effect.Significance StatementWe report that ATP enters the ER lumen through an AXER-dependent, cytosolic Ca2+-antagonized mechanism, or CaATiER (Ca2+-Antagonized Transport into ER) mechanism. In addition, our findings suggest that ATP usage in the ER may render an “anti-Warburg” effect by increasing ATP regeneration from mitochondrial OxPhos while decreasing the portion of ATP regeneration from glycolysis.

scholarly journals Mitochondria supply ATP to the ER through a mechanism antagonized by cytosolic Ca2+

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Jing Yong ◽  
Helmut Bischof ◽  
Sandra Burgstaller ◽  
Marina Siirin ◽  
Anne Murphy ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Folding ◽  
Oxidative Phosphorylation ◽  
Cell Lines ◽  
Warburg Effect ◽  
Protein Misfolding ◽  
Atp Hydrolysis ◽  
Atp Level ◽  
Physiological Conditions ◽  
Er Membrane

The endoplasmic reticulum (ER) imports ATP and uses energy from ATP hydrolysis for protein folding and trafficking. However, little is known about how this vital ATP transport occurs across the ER membrane. Here, using three commonly used cell lines (CHO, INS1 and HeLa), we report that ATP enters the ER lumen through a cytosolic Ca2+-antagonized mechanism, or CaATiER (Ca2+-Antagonized Transport into ER). Significantly, we show that mitochondria supply ATP to the ER and a SERCA-dependent Ca2+ gradient across the ER membrane is necessary for ATP transport into the ER, through SLC35B1/AXER. We propose that under physiological conditions, increases in cytosolic Ca2+ inhibit ATP import into the ER lumen to limit ER ATP consumption. Furthermore, the ATP level in the ER is readily depleted by oxidative phosphorylation (OxPhos) inhibitors and that ER protein misfolding increases ATP uptake from mitochondria into the ER. These findings suggest that ATP usage in the ER may increase mitochondrial OxPhos while decreasing glycolysis, i.e. an ‘anti-Warburg’ effect.

The Wiskott-Aldrich Syndrome (WAS): Studies On A Possible Defect In Mitochondrial ATP Regeneration In Platelets

1981 ◽  
Author(s):  
W van Brederode ◽  
G Gorter ◽  
J W N Akkerman
Keyword(s):  
Co2 Production ◽  
Bleeding Tendency ◽  
Atp Level ◽  
Atp Production ◽  
Clinically Normal ◽  
Platelet Defects ◽  
Atp Supply ◽  
Induced Aggregation ◽  
Normal Controls ◽  
Atp Regeneration

WAS is a severe, X-linked disorder, characterized by eczema, immunodeficiency and an increased bleeding tendency caused by thrombocytopenia and platelet malfunction. There is a diminished epinephrine-induced aggregation response and an abnormal mitochondrial CO2 production during platelet activation. From this, Shapiro et al (The Lancet 1978) concluded that WAS-platelets have a defect in mitochondrial ATP regeneration, which could be employed for detection of WAS- carriers, who are clinically normal and have only minor platelet defects. The test consists of an epinephrine-induced aggregation in the presence of an inhibitor of glycolytic ATP production (deoxyglucose, 2 DG), and showed impaired second wave aggregation in obligate carriers but not in normal controls. We tested 4 unrelated obligate WAS-carriers and found impaired aggregations in all. Five out of 7 female relatives also showed aggregation abnormalities, suggestive for WAS-carriership. However, in 8 out of 15 normal controls (males and females) the test was also positive. The nature of a possible defect in mitochondrial ATP supply was further studied in gel-filtered platelets by analyzing the metabolic ATP level before and during epinephrine-induced aggregation in the presence of inhibitors of glycolysis and glycogenoly- sis and during incubation in substrate-depleted medium. These studies showed that mitochondrial energy generation depended on sugar supply either from glycolysis or glycoge- nolysis and was unable to maintain a normal metabolic ATP level when these pathways were inhibited. Incubation with 2DG led to a fall in metabolic ATP and - consequently - to an impaired epinephrine-induced aggregation. The fall of metabolic ATP (2DG present) was much steeper in platelets from 2 unrelated WAS-patients than in cells from normal controls; most (but not all) obligate carriers showed intermediate values. It is concluded that the impaired epinephrine-induced aggregation in the presence of 2DG in WAS reflects disturbances in ATP homeostasis, which are consistent with a mitochondrial defect.

Topological and Enzymatic Analysis of Human Alg2 Mannosyltransferase

2021 ◽  
Author(s):  
Meng-Hai Xiang ◽  
Xin-Xin Xu ◽  
Chun-Di Wang ◽  
Shuai Chen ◽  
Si Xu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Biosynthetic Pathway ◽  
Membrane Binding ◽  
Binding Domain ◽  
Enzymatic Analysis ◽  
Kinetic Assay ◽  
Physiological Conditions ◽  
Single Membrane ◽  
Er Membrane

Abstract N-glycosylation starts with the biosynthesis of lipid-linked oligosaccharide (LLO) on the endoplasmic reticulum. Alg2 mannosyltransferase adds both the α1,3- and α1,6-Man onto ManGlcNAc2-pyrophosphate-dolichol (M1Gn2-PDol) in either order to generate the branched M3Gn2-PDol product. The well-studied yeast Alg2 interacts with ER membrane through four hydrophobic domains. Unexpectedly, we show that Alg2 structure has diverged significantly between yeast and humans. Human Alg2 (hAlg2) associates with the ER via a single membrane-binding domain and is markedly more stable in vitro. These properties were exploited to develop an LC-MS quantitative kinetic assay for studying purified hAlg2. Under physiological conditions, hAlg2 prefers to transfer α1,3-Man on to M1Gn2 before adding the α1,6-Man. However, this bias is altered by an excess of GDP-Man donor or an increased level of M1Gn2 substrate, both of which trigger production of the M2Gn2 (α-1,6)-PDol. These results suggest that Alg2 may regulate the LLO biosynthetic pathway by controlling accumulation of M2Gn2 (α-1,6) intermediate.

TMCC3 localizes at the three-way junctions for the proper tubular network of the endoplasmic reticulum

2019 ◽  
Vol 476 (21) ◽  
pp. 3241-3260
Author(s):  
Sindhu Wisesa ◽  
Yasunori Yamamoto ◽  
Toshiaki Sakisaka
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Mammalian Cells ◽  
Coiled Coil ◽  
Transmembrane Domains ◽  
Domain Family ◽  
Coiled Coil Domain ◽  
U2os Cells ◽  
Er Membrane

The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.

Spatial localization of unknown proteins in the endoplasmic reticulum predicts functions

2007 ◽  
Vol 30 (4) ◽  
pp. 84
Author(s):  
Michael D. Jain ◽  
Hisao Nagaya ◽  
Annalyn Gilchrist ◽  
Miroslaw Cygler ◽  
John J.M. Bergeron
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Folding ◽  
Protein Synthesis ◽  
Protein Function ◽  
Protein Translocation ◽  
Spatial Localization ◽  
Predict Protein Function ◽  
Insight Into ◽  
Soluble Fractions ◽  
Er Membrane

Protein synthesis, folding and degradation functions are spatially segregated in the endoplasmic reticulum (ER) with respect to the membrane and the ribosome (rough and smooth ER). Interrogation of a proteomics resource characterizing rough and smooth ER membranes subfractionated into cytosolic, membrane, and soluble fractions gives a spatial map of known proteins involved in ER function. The spatial localization of 224 identified unknown proteins in the ER is predicted to give insight into their function. Here we provide evidence that the proteomics resource accurately predicts the function of new proteins involved in protein synthesis (nudilin), protein translocation across the ER membrane (nicalin), co-translational protein folding (stexin), and distal protein folding in the lumen of the ER (erlin-1, TMX2). Proteomics provides the spatial localization of proteins and can be used to accurately predict protein function.

scholarly journals Endoplasmic Reticulum Stress Regulators: New Drug Targets for Parkinson’s Disease

2021 ◽  
pp. 1-10
Author(s):  
Vera Kovaleva ◽  
Mart Saarma
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Endoplasmic Reticulum ◽  
Protein Folding ◽  
Er Stress ◽  
Protein Misfolding ◽  
Drug Targets ◽  
Dopamine Neurons ◽  
Drug Candidates ◽  
The Unfolded Protein Response

Parkinson’s disease (PD) pathology involves progressive degeneration and death of vulnerable dopamine neurons in the substantia nigra. Extensive axonal arborisation and distinct functions make this type of neurons particularly sensitive to homeostatic perturbations, such as protein misfolding and Ca2 + dysregulation. Endoplasmic reticulum (ER) is a cell compartment orchestrating protein synthesis and folding, as well as synthesis of lipids and maintenance of Ca2 +-homeostasis in eukaryotic cells. When misfolded proteins start to accumulate in ER lumen the unfolded protein response (UPR) is activated. UPR is an adaptive signalling machinery aimed at relieving of protein folding load in the ER. When UPR is chronic, it can either boost neurodegeneration and apoptosis or cause neuronal dysfunctions. We have recently discovered that mesencephalic astrocyte-derived neurotrophic factor (MANF) exerts its prosurvival action in dopamine neurons and in animal model of PD through the direct binding to UPR sensor inositol-requiring protein 1 alpha (IRE1α) and attenuation of UPR. In line with this, UPR targeting resulted in neuroprotection and neurorestoration in various preclinical PD animal models. Therefore, growth factors (GFs), possessing both neurorestorative activity and restoration of protein folding capacity are attractive as drug candidates for PD treatment especially their blood-brain barrier penetrating analogs and small molecule mimetics. In this review, we discuss ER stress as a therapeutic target to treat PD; we summarize the existing preclinical data on the regulation of ER stress for PD treatment. In addition, we point out the crucial aspects for successful clinical translation of UPR-regulating GFs and new prospective in GFs-based treatments of PD, focusing on ER stress regulation.

scholarly journals Septin-dependent compartmentalization of the endoplasmic reticulum during yeast polarized growth

2005 ◽  
Vol 169 (6) ◽  
pp. 897-908 ◽  
Author(s):  
Cosima Luedeke ◽  
Stéphanie Buvelot Frei ◽  
Ivo Sbalzarini ◽  
Heinz Schwarz ◽  
Anne Spang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Proteins ◽  
Diffusion Barriers ◽  
Yeast Cells ◽  
Dependent Manner ◽  
Protein Diffusion ◽  
Ultrastructural Studies ◽  
Bud Neck ◽  
Er Membrane

Polarized cells frequently use diffusion barriers to separate plasma membrane domains. It is unknown whether diffusion barriers also compartmentalize intracellular organelles. We used photobleaching techniques to characterize protein diffusion in the yeast endoplasmic reticulum (ER). Although a soluble protein diffused rapidly throughout the ER lumen, diffusion of ER membrane proteins was restricted at the bud neck. Ultrastructural studies and fluorescence microscopy revealed the presence of a ring of smooth ER at the bud neck. This ER domain and the restriction of diffusion for ER membrane proteins through the bud neck depended on septin function. The membrane-associated protein Bud6 localized to the bud neck in a septin-dependent manner and was required to restrict the diffusion of ER membrane proteins. Our results indicate that Bud6 acts downstream of septins to assemble a fence in the ER membrane at the bud neck. Thus, in polarized yeast cells, diffusion barriers compartmentalize the ER and the plasma membrane along parallel lines.

COULD PROTEIN MISFOLDING IN THE ENDOPLASMIC RETICULUM BE THE CAUSE OF ARTHRITIS IN SPONDYLOARTHROPATHIES

2006 ◽  
Vol 12 (Supplement) ◽  
pp. S72
Author(s):  
U Sittichai ◽  
M C. Romero ◽  
L M. Avila ◽  
J D. Londo??o ◽  
R Valle ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Misfolding

scholarly journals Endoplasmic reticulum stress in lung disease

2017 ◽  
Vol 26 (144) ◽  
pp. 170018 ◽  
Author(s):  
Stefan J. Marciniak
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Folding ◽  
Pulmonary Fibrosis ◽  
Endoplasmic Reticulum Stress ◽  
Lung Disease ◽  
Cigarette Smoke ◽  
Protein Misfolding ◽  
Fine Particulates ◽  
Disease Protein

Exposure to inhaled pollutants, including fine particulates and cigarette smoke is a major cause of lung disease in Europe. While it is established that inhaled pollutants have devastating effects on the genome, it is now recognised that additional effects on protein folding also drive the development of lung disease. Protein misfolding in the endoplasmic reticulum affects the pathogenesis of many diseases, ranging from pulmonary fibrosis to cancer. It is therefore important to understand how cells respond to endoplasmic reticulum stress and how this affects pulmonary tissues in disease. These insights may offer opportunities to manipulate such endoplasmic reticulum stress pathways and thereby cure lung disease.

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