Mutations in the X-linked ATP6AP2 cause a glycosylation disorder with autophagic defects

The biogenesis of the multi-subunit vacuolar-type H+-ATPase (V-ATPase) is initiated in the endoplasmic reticulum with the assembly of the proton pore V0, which is controlled by a group of assembly factors. Here, we identify two hemizygous missense mutations in the extracellular domain of the accessory V-ATPase subunit ATP6AP2 (also known as the [pro]renin receptor) responsible for a glycosylation disorder with liver disease, immunodeficiency, cutis laxa, and psychomotor impairment. We show that ATP6AP2 deficiency in the mouse liver caused hypoglycosylation of serum proteins and autophagy defects. The introduction of one of the missense mutations into Drosophila led to reduced survival and altered lipid metabolism. We further demonstrate that in the liver-like fat body, the autophagic dysregulation was associated with defects in lysosomal acidification and mammalian target of rapamycin (mTOR) signaling. Finally, both ATP6AP2 mutations impaired protein stability and the interaction with ATP6AP1, a member of the V0 assembly complex. Collectively, our data suggest that the missense mutations in ATP6AP2 lead to impaired V-ATPase assembly and subsequent defects in glycosylation and autophagy.

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Lysosomal calcium homeostasis defects, not proton pump defects, cause endo-lysosomal dysfunction in PSEN-deficient cells

The Journal of Cell Biology ◽

10.1083/jcb.201201076 ◽

2012 ◽

Vol 198 (1) ◽

pp. 23-35 ◽

Cited By ~ 123

Author(s):

Katrijn Coen ◽

Ronald S. Flannagan ◽

Szilvia Baron ◽

Luciene R. Carraro-Lacroix ◽

Dong Wang ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Drosophila Melanogaster ◽

Alternative Hypothesis ◽

Atpase Subunit ◽

Lysosomal Dysfunction ◽

Calcium Storage ◽

And Function ◽

Lysosomal Acidification

Presenilin (PSEN) deficiency is accompanied by accumulation of endosomes and autophagosomes, likely caused by impaired endo-lysosomal fusion. Recently, Lee et al. (2010. Cell. doi: http://dx.doi.org/10.1016/j.cell.2010.05.008) attributed this phenomenon to PSEN1 enabling the transport of mature V0a1 subunits of the vacuolar ATPase (V-ATPase) to lysosomes. In their view, PSEN1 mediates the N-glycosylation of V0a1 in the endoplasmic reticulum (ER); consequently, PSEN deficiency prevents V0a1 glycosylation, compromising the delivery of unglycosylated V0a1 to lysosomes, ultimately impairing V-ATPase function and lysosomal acidification. We show here that N-glycosylation is not a prerequisite for proper targeting and function of this V-ATPase subunit both in vitro and in vivo in Drosophila melanogaster. We conclude that endo-lysosomal dysfunction in PSEN−/− cells is not a consequence of failed N-glycosylation of V0a1, or compromised lysosomal acidification. Instead, lysosomal calcium storage/release is significantly altered in PSEN−/− cells and neurons, thus providing an alternative hypothesis that accounts for the impaired lysosomal fusion capacity and accumulation of endomembranes that accompanies PSEN deficiency.

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Suitability of L-[35S]methionine for studying the biosynthesis of the polypeptides of mouse liver endoplasmic reticulum membrane fractions in vivo

Canadian Journal of Biochemistry ◽

10.1139/o79-079 ◽

1979 ◽

Vol 57 (6) ◽

pp. 625-638 ◽

Cited By ~ 3

Author(s):

Monique Behar-Bannelier ◽

Rajendra N. Sharma ◽

Robert K. Murray

Keyword(s):

Endoplasmic Reticulum ◽

Mouse Liver ◽

Serum Proteins ◽

Sodium Dodecyl ◽

Endoplasmic Reticulum Membrane ◽

Membrane Flow ◽

Adult Mice ◽

Coomassie Blue ◽

Er Membrane

The use of L-[35S]methionine (500–700 Ci/mmol (1 Ci = 37 GBq)) for labelling the polypeptides of liver rough (R) and smooth (S) endoplasmic reticulum (ER) membrane fractions in vivo was studied. Adult mice were injected intraperitoneally with 400 μCi of the isotope and killed at various times (2 min to 24 h) thereafter. RER and SER fractions were prepared, stripped of ribosomes, and treated with Triton X-100 to remove intravesicular contents. Sufficient radioactivity was present in individual aliquots (75 μg protein) of the ER membrane fractions to permit their analysis by fluorography after separation by electrophoresis in polyacrylamide gels containing sodium dodecyl sulphate. By 3 min, although the majority of the labelled components were of intravesicular origin, some 12 membrane polypeptides were labelled in the RER fraction (including one corresponding in migration to cytochrome P-450); some 6 of these latter polypeptides were labelled to a lesser degree in the SER membrane fraction at this time. By 5 min, the patterns of radioactive polypeptides of the RER and SER fractions (including both membrane and intravesicular components) were identical. By 7 min, some 28 labelled membrane polypeptides were detectable in the total microsomal membrane. Analysis of the 24-h samples revealed that all the membrane polypeptides seen by staining with Coomassie blue were visualised by fluorography. Other studies revealed the applicability of the approach used for producing highly labelled cell sap and serum proteins. The overall results demonstrate the suitability of L-[35S]methionine administered in vivo for producing mouse liver ER membrane polypeptides of relatively high radioactivity and are consistent with a rapid conversion of RER to SER by ribosome detachment or membrane flow.

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Inhibition of Glycogen Synthase Kinase-3 Ameliorates β-Amyloid Pathology and Restores Lysosomal Acidification and Mammalian Target of Rapamycin Activity in the Alzheimer Disease Mouse Model

Journal of Biological Chemistry ◽

10.1074/jbc.m112.409250 ◽

2012 ◽

Vol 288 (2) ◽

pp. 1295-1306 ◽

Cited By ~ 122

Author(s):

Limor Avrahami ◽

Dorit Farfara ◽

Maya Shaham-Kol ◽

Robert Vassar ◽

Dan Frenkel ◽

...

Keyword(s):

Alzheimer Disease ◽

Mouse Model ◽

Glycogen Synthase ◽

Mammalian Target Of Rapamycin ◽

Glycogen Synthase Kinase ◽

Target Of Rapamycin ◽

Glycogen Synthase Kinase 3 ◽

Amyloid Pathology ◽

Β Amyloid ◽

Lysosomal Acidification

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Integrated Metabolomics and Transcriptomics Analyses Reveal Altered Lipid Metabolism in Mouse Placentas Exposed to Alcohol

Placenta ◽

10.1016/j.placenta.2021.07.108 ◽

2021 ◽

Vol 112 ◽

pp. e33

Author(s):

Sze Ting (Cecilia) Kwan ◽

Manjot Virdee ◽

Nipun Saini ◽

Kaylee Helfrich ◽

Susan Smith

Keyword(s):

Lipid Metabolism ◽

Altered Lipid Metabolism ◽

Altered Lipid ◽

Integrated Metabolomics

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Aromadendrin Protects Neuronal Cells from Methamphetamine-Induced Neurotoxicity by Regulating Endoplasmic Reticulum Stress and PI3K/Akt/mTOR Signaling Pathway

International Journal of Molecular Sciences ◽

10.3390/ijms22052274 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2274

Author(s):

Hyun-Su Lee ◽

Eun-Nam Kim ◽

Gil-Saeng Jeong

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Signaling Pathway ◽

Neuronal Cells ◽

Mammalian Target Of Rapamycin ◽

Mtor Signaling ◽

Mtor Signaling Pathway ◽

Irreversible Damage ◽

Pre Treatment ◽

Apoptotic Pathways

Methamphetamine (METH) is a highly addictive drug that induces irreversible damage to neuronal cells and pathological malfunction in the brain. Aromadendrin, isolated from the flowers of Chionanthus retusus, has been shown to have anti-inflammatory or anti-tumor activity. Nevertheless, it has been reported that METH exacerbates neurotoxicity by inducing endoplasmic reticulum (ER) stress via the phosphoinositide 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway in neuronal cells. There is little evidence that aromadendrin protects cells from neurotoxicity induced by METH. In this study, we found that aromadendrin partially suppressed the METH-induced cell death in SH-SY5y cells without causing cytotoxicity. Aromadendrin regulated METH-induced ER stress by preserving the phosphorylation of the PI3K/Akt/mTOR signaling pathway in METH-exposed SH-SY5y cells. In addition, aromadendrin mitigated METH-induced autophagic and the apoptotic pathways in METH-exposed SH-SY5y cells. Mechanistic studies revealed that pre-treatment with aromadendrin restored the expression of anti-apoptotic proteins in METH-exposed conditions. The inhibitor assay confirmed that aromadendrin-mediated restoration of mTOR phosphorylation protected cells from autophagy and apoptosis in METH-exposed cells. Therefore, these findings suggest that aromadendrin relatively has a protective effect on SH-SY5y cells against autophagy and apoptosis induced by METH via regulation of ER stress and the PI3K/Akt/mTOR signaling pathway.

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Role of mTOR1 and mTOR2 complexes in MEG-01 cell physiology

Thrombosis and Haemostasis ◽

10.1160/th14-09-0727 ◽

2015 ◽

Vol 114 (11) ◽

pp. 969-981 ◽

Cited By ~ 4

Author(s):

Esther López ◽

Alejandro Berna-Erro ◽

Javier J. López ◽

María P. Granados ◽

Nuria Bermejo ◽

...

Keyword(s):

Cell Proliferation ◽

Endoplasmic Reticulum ◽

Endoplasmic Reticulum Stress ◽

Mammalian Target Of Rapamycin ◽

Target Of Rapamycin ◽

Cell Physiology ◽

Cell Stimulation ◽

Intracellular Location ◽

Macromolecular Complexes

SummaryThe function of the mammalian target of rapamycin (mTOR) is upregulated in response to cell stimulation with growing and differentiating factors. Active mTOR controls cell proliferation, differentiation and death. Since mTOR associates with different proteins to form two functional macromolecular complexes, we aimed to investigate the role of the mTORI and mTOR2 complexes in MEG-01 cell physiology in response to thrombopoietin (TPO). By using mTOR antagonists and overexpressing FKBP38, we have explored the role of both mTOR complexes in proliferation, apoptosis, maturation-like mechanisms, endoplasmic reticulum-stress and the intracellular location of both active mTOR complexes during MEG-01 cell stimulation with TPO. The results demonstrate that mTOR1 and mTOR2 complexes play different roles in the physiology of MEG-01 cells and in the maturation-like mechanisms; hence, these findings might help to understand the mechanism underlying generation of platelets.

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The Decline of the Immune Response during Aging: the Role of an Altered Lipid Metabolism

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1991.tb16986.x ◽

1991 ◽

Vol 621 (1 Physiological) ◽

pp. 277-290 ◽

Cited By ~ 22

Author(s):

GEORG WICK ◽

LUKAS A. HUBER ◽

XU QING-BO ◽

ELMAR JAROSCH ◽

DIETHER SCHÖNITZER ◽

...

Keyword(s):

Immune Response ◽

Lipid Metabolism ◽

Altered Lipid Metabolism ◽

Altered Lipid

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Furin controls β cell function via mTORC1 signaling

10.1101/2020.04.09.027839 ◽

2020 ◽

Cited By ~ 1

Author(s):

Bas Brouwers ◽

Ilaria Coppola ◽

Katlijn Vints ◽

Bastian Dislich ◽

Nathalie Jouvet ◽

...

Keyword(s):

Secretory Pathway ◽

Cell Function ◽

Mammalian Target Of Rapamycin ◽

Human Islets ◽

Β Cells ◽

Β Cell ◽

Differential Proteomics ◽

Atpase Subunit ◽

Proteolytic Activation ◽

Mtorc1 Signaling

AbstractFurin is a proprotein convertase (PC) responsible for proteolytic activation of a wide array of precursor proteins within the secretory pathway. It maps to the PRC1 locus, a type 2 diabetes susceptibility locus, yet its specific role in pancreatic β cells is largely unknown. The aim of this study was to determine the role of furin in glucose homeostasis. We show that furin is highly expressed in human islets, while PCs that potentially could provide redundancy are expressed at considerably lower levels. β cell-specific furin knockout (βfurKO) mice are glucose intolerant, due to smaller islets with lower insulin content and abnormal dense core secretory granule morphology. RNA expression analysis and differential proteomics on βfurKO islets revealed activation of Activating Transcription Factor 4 (ATF4), which was mediated by mammalian target of rapamycin C1 (mTORC1). βfurKO cells show impaired cleavage of the essential V-ATPase subunit Ac45, and by blocking this pump in β cells the mTORC1 pathway is activated. Furthermore, βfurKO cells show lack of insulin receptor cleavage and impaired response to insulin. Taken together, these results suggest a model of mTORC1-ATF4 hyperactivation in β cells lacking furin, which causes β cell dysfunction.

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Relationship between some variables of protein profile and indicators of lipomobilization in dairy cows after calving

Archives Animal Breeding ◽

10.7482/0003-9438-57-019 ◽

2014 ◽

Vol 57 (1) ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

Csilla Tóthová ◽

Oskar Nagy ◽

Gabriel Kováč

Keyword(s):

Dairy Cows ◽

Serum Amyloid A ◽

Acute Phase Proteins ◽

Protein Profile ◽

Total Proteins ◽

Amyloid A ◽

Esterified Fatty Acids ◽

Positive Correlations ◽

Altered Lipid Metabolism ◽

Altered Lipid

Abstract. The objective of this study was to determine the concentrations of the main indicators of lipomobilization and selected variables of protein profile in dairy cows after calving, including immunoglobulins and acute phase proteins, as well as to evaluate the relationships between the altered lipid metabolism and changes in protein profile. Into the evaluation we included 54 clinically healthy dairy cows of a Slovak spotted breed, low-land black spotted breed and their crossbreeds in the period of 1-2 weeks after parturition. Blood samples were analysed for non-esterified fatty acids (NEFA, mmol/l), β-hydroxybutyrate (BHB, mmol/l), total proteins (TP, g/l), albumin (Alb, g/l), immunoglobulin G (IgG, g/l), haptoglobin (Hp, g/l) and serum amyloid A (SAA, mg/l). In cows with concentrations of NEFA above 0.35 mmol/l (n=20) we found significantly lower mean serum concentrations of total proteins, albumin and IgG than in cows with serum NEFA concentrations below 0.35 mmol/l (n=34) (P<0.001). On the other hand, cows with higher values of NEFA showed significantly higher mean concentrations of BHB, Hp and SAA (P<0.001). The concentrations of NEFA significantly negatively correlated with the values of TP (P<0.001), albumin (P<0.01) and IgG (P<0.001). Significant positive correlations were found between the concentrations of NEFA and BHB, Hp, as well as SAA (P<0.001). Similar correlations were also found between the values of BHB and the variables of protein profile except for albumin. This study indicates strong relationships between NEFA and selected variables of protein profile in cows after parturition.

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