Protein Disulphide Isomerase 6 (PDIA6) Attenuates Platelet Endoplasmic Reticulum Stress and Secretion in a Mouse Model

Abstract Background: Platelet hyperreactivity involves increased secretion of their granule content which promotes platelet aggregation and thrombosis. Platelet hyperreactivity is observed in conditions such as diabetes mellitus and is associated with decreased cardioprotective effect from antiplatelet agents in this patient group. Diabetes is associated with increased endoplasmic reticulum (ER) stress from hyperglycemia and hyperlipidemia. Protein disulphide isomerase 6 (PDIA6) is an endoplasmic reticulum protein which folds nascent proteins by reduction and oxidation of their disulphide bonds. PDIA6 has been shown to inhibit downstream ER stress pathways by inhibiting the phosphorylation of IRE-1 in fibroblasts (Eletto, Mol Cell, 2014). We hypothesized that ER stress pathways are functional in platelets and that PDIA6 may inhibit ER stress pathways leading to platelet secretion. Methods: We generated conditional PDIA6 knockout mice (PF4Cre+ Pdia6 fl/fl) (CKO) in the megakaryocyte/platelet lineage by CRISPR-Cas9 technology (Fig.1A). Megakaryopoiesis and haemostasis was assessed by bone marrow histology, coagulation assays, platelet aggregation and tail bleeding studies. We induced ER stress of purified platelets by incubation with thapsigargin and tunicamycin. Activation of the PERK and IRE1 pathways was measured by Western blot. Thrombosis was assessed in vitro by microfluidic devices and in vivo by electrolytic injury of the carotid artery. Results: PDIA6 CKO mice displayed a mild macrothrombocytopenia: the mean (+/-SD) platelet count in Pf4Cre+/Pdia6fl/fl was 775 +/- 98 x10 3/ul compared with 874 +/- 55 x10 3/ul in Pdia6fl/fl (p<0.005). The median platelet volume was 6.3 fL in Pf4Cre+/Pdia6fl/fl compared with 5.7 fL in Pdia6fl/fl (p<0.005). Megakaryopoiesis was normal at baseline. However, PDIA6 CKO mice showed significant upregulation of intracellular platelet PDIs including PDIA1, PDIA3 and PDIA4. PDIA6 deficient platelets displayed significant increase of disulphide reductase activity and the generation of free thiols on the platelet surface. Activation of the PERK and IRE-1 pathway at baseline and after induction of ER stress was increased in PDIA6 deficient platelets (Figure 1B, C). There was striking hypersecretion of PDIA1 (Figure 1D) and α-granule proteins (Figure 1E, F) in response to shear and stimulation with thrombin. PDIA6 CKO mice displayed a prothrombotic phenotype with increased platelet adhesion to fibrinogen under shear (500 s-1) and decreased time to carotid artery occlusion (mean+/SD: 10.8 +/-3.2 min in Pf4Cre+/Pdia6fl/fl compared with 15.3 +/-5.2 min in Pdia6fl/fl, n=8-10, p<0.05). Conclusion: We have identified a role for platelet PDIA6 in attenuating platelet ER stress and secretion. This opens avenues for further study into the role of platelet PDIs in conditions with increased ER stress, such as obesity and diabetes. Figure 1: PDIA6 deficient platelets have increased endoplasmic reticulum (ER) stress and are hypersecretory. A. Western blot of PDIA6 protein in platelets from Pf4Cre+/Pdia6fl/fl mice and control mice (Pdia6fl/fl) showing efficient deletion of PDIA6 in platelets. B. PDIA6 deficient platelets have increased phosphorylation of pEIF2a (PERK phosphorylation pathway) at baseline and after induction of ER stress by thapsigargin, representative image. C. Normalized band intensity (peIF2a/beta actin) in platelets treated with DMSO control or thapsigargin. D. Increased secretion of thiol isomerase PDIA1. E. alpha granule proteins: platelet factor 4 (PF4) and F. von Willebrand factor (vWF) from PDIA6 deficient platelets compared with controls after stimulation with thrombin 0.5 U/ml. n=3-5 Pf4Cre+/Pdia6fl/fl (red boxes) and n=3-5 Pdia6fl/fl mice (grey boxes). Columns are presented as mean+/-SD, *p<0.05, ** p<0.001 by Mann Whitney. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

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Endoplasmic Reticulum Stress: A Critical Molecular Driver of Endothelial Dysfunction and Cardiovascular Disturbances Associated with Diabetes

International Journal of Molecular Sciences ◽

10.3390/ijms20071658 ◽

2019 ◽

Vol 20 (7) ◽

pp. 1658 ◽

Cited By ~ 29

Author(s):

Hatem Maamoun ◽

Shahenda Abdelsalam ◽

Asad Zeidan ◽

Hesham Korashy ◽

Abdelali Agouni

Keyword(s):

Oxidative Stress ◽

Insulin Resistance ◽

Cardiovascular Disease ◽

Endoplasmic Reticulum ◽

Endothelial Cell ◽

Er Stress ◽

Cardiovascular Complications ◽

Endothelial Cell Dysfunction ◽

Cell Dysfunction ◽

Obesity And Diabetes

Physical inactivity and sedentary lifestyle contribute to the widespread epidemic of obesity among both adults and children leading to rising cases of diabetes. Cardiovascular disease complications associated with obesity and diabetes are closely linked to insulin resistance and its complex implications on vascular cells particularly endothelial cells. Endoplasmic reticulum (ER) stress is activated following disruption in post-translational protein folding and maturation within the ER in metabolic conditions characterized by heavy demand on protein synthesis, such as obesity and diabetes. ER stress has gained much interest as a key bridging and converging molecular link between insulin resistance, oxidative stress, and endothelial cell dysfunction and, hence, represents an interesting drug target for diabetes and its cardiovascular complications. We reviewed here the role of ER stress in endothelial cell dysfunction, the primary step in the onset of atherosclerosis and cardiovascular disease. We specifically focused on the contribution of oxidative stress, insulin resistance, endothelial cell death, and cellular inflammation caused by ER stress in endothelial cell dysfunction and the process of atherogenesis.

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Role of O-GlcNAcylation and endoplasmic reticulum stress on obesity and insulin resistance

Turkish Journal of Biochemistry ◽

10.1515/tjb-2018-0303 ◽

2019 ◽

Vol 44 (5) ◽

pp. 599-610 ◽

Cited By ~ 1

Author(s):

Benan Pelin Sermikli ◽

Gulizar Aydogdu ◽

Afsar Abbasi Taghidizaj ◽

Erkan Yilmaz

Keyword(s):

Insulin Resistance ◽

Endoplasmic Reticulum ◽

Western Blot ◽

Er Stress ◽

Insulin Receptor ◽

Serine Phosphorylation ◽

Wild Type ◽

Adipose Tissues ◽

Insulin Resistant

Abstract Background Obesity is a global public health problem. Obesity closely associated with various metabolic diseases such as; insulin resistance, hypertension, dyslipidemia and cardiovascular diseases. Endoplasmic reticulum (ER) stress is a critical factor for insulin resistance. O-linked N-acetyl-glucosamine (O-GlcNAc); is the post-translational modification which is has a vital role in biological processes; including cell signaling, in response to nutrients, stress and other extracellular stimuli. Materials and methods In this study, we aimed to investigate the role of O-GlcNAc modification in the context of obesity and obesity-associated insulin resistance in adipose tissue. For this purpose, first, the visceral and epididymal adipose tissues of obese and insulin resistant C57BL/6 Lepob/Lepob and wild-type mice were used to determine the O-GlcNAc modification pattern by western blot. Secondly, the external stimulation of O-GlcNAc modification in wild-type mice achieved by intraperitoneal 5 mg/kg/day glucosamine injection every 24 h for 5 days. The effect of increased O-GlcNAc modification on insulin resistance and ER stress investigated in adipose tissues of glucosamine challenged wild-type mice through regulation of the insulin signaling pathway and unfolded protein response (UPR) elements by western blot. In addition to that, the O-GlcNAc status of the insulin receptor substrate-1 (IRS1) investigated in epididymal and visceral adipose tissues of ob/ob, wild-type and glucosamine challenged mice by immunoprecipitation. Results We found that reduced O-GlcNAc levels in visceral and epididymal adipose tissues of obese and insulin-resistant ob/ob mice, although interestingly we observed that increased O-GlcNAc modification in glucosamine challenged wild-type mice resulted in insulin resistance and ER stress. Furthermore, we demonstrated that the IRS1 was modified with O-GlcNAc in visceral and epididymal adipose tissues in both ob/ob mice and glucosamine-injected mice, and was compatible with the serine phosphorylation of this modification. Conclusion Our results suggest that O-GlcNAcylation of proteins is a crucial factor for intracellular trafficking regulates insulin receptor signaling and UPR depending on the cellular state of insulin resistance.

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Activation of the Endoplasmic Reticulum (ER) Unfolded Protein Response (UPR) in Aggressive B-Cell Lymphomas.

Blood ◽

10.1182/blood.v108.11.2038.2038 ◽

2006 ◽

Vol 108 (11) ◽

pp. 2038-2038

Author(s):

Olga Balague ◽

Luis Colomo ◽

Armando Lopez-Guillermo ◽

Elias Campo ◽

Antonio Martinez

Keyword(s):

Endoplasmic Reticulum ◽

Transcription Factors ◽

Western Blot ◽

Er Stress ◽

B Cell ◽

Cell Lines ◽

Plasma Cell ◽

Plasma Cells ◽

Lymphoid Tissues ◽

B Cell Lymphomas

Abstract BACKGROUND The UPR is a prosurvival pathway activated in cells under ER stress induced by the accumulation of unfolded proteins. UPR activation in B cells normally occurs during the differentiation to antibody secreting plasma cells and requires XBP1activation. XBP-1 is a member of the TREB family of transcription factors that exists in the endoplasmic reticulum (ER) as a 33kDa protein, and in the nucleus as an active 50kDa transcription factor. The UPR stimulates two different ER proteins, ATF-6 and Ire-1, to increase XBP-1 transcription and XBP-1 mRNA splicing resulting in the accumulation of the active 50kDa nuclear protein. Moreover XBP1 is a target of proteosome inhibitors and is related to the aggressive behaviour of some carcinomas. The role of the activation of XBP-1 in lymphomas is still unknown. DESIGN: Reactive lymphoid tissues and 25 neoplastic human B-cell lines representing different stages of B-cell development were studied for XBP-1 expression by western blot and XBP-1, PAX-5, Blimp-1/prdm1, MUM-1/IRF-4 and ICSBP1/IRF-8 by immunohistochemistry. XBP-1 activation was assessed in 225 B-cell lymphomas from the archives of the laboratory of pathology by western blot, RT-PCR and immunohistochemistry . To further evaluate whether XBP-1 activation was related to the plasmacytic program or to ER stress signals we analyzed the cell lines by Western blot for XBP-1 and ATF-6 expression. RESULTS We characterize XBP-1 expression in reactive lymphoid tissues, 25 human cell lines and 225 B-cell tumors. In nearly all tonsillar lymphoid cells XBP-1 was detected as a cytoplasmic protein with a paranuclear dot pattern. Nuclear positivity was observed only in scattered centrocytes in the light zone of the germinal centers and in plasma cells, always coexpressed with plasma cell related transcription factors as MUM-1/IRF-4 and Blimp1/prdm1. Active p50XBP-1 was found in 24/25 cell lines by western blot regardless ATF-6 expression and confirmed by immunohistochemistry . Moreover p50XBP1 was found in 27/31(87%) plasmacytomas, 36/64(56%) DLBCL-ABC and in 3/10(30%) DLBCL-GCB and 22/43(51%) plasmablastic lymphomas. Intriguingly, p50XBP1 was detected also in 2/11(18%)BL and 4/25(16%)MCL with blastic features. CONCLUSIONS.XBP-1 is activated in a subset of follicular centre cells committed to plasma cell differentiation and in plasma cells.UPR prosurvival pathways in the neoplastic cell lines are activated independently of the extent of the ATF-6 activation.p50XBP1 is mostly activated in aggressive B-cell lymphomas regardless to the plasmacytic differentiation of the tumours. Thus, p50XBP-1 may be a new molecular target in the treatment of aggressive B-cell malignancies.

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Expression of Endoplasmic Reticulum Stress-Related Factors in the Retinas of Diabetic Rats

Experimental Diabetes Research ◽

10.1155/2012/743780 ◽

2012 ◽

Vol 2012 ◽

pp. 1-11 ◽

Cited By ~ 8

Author(s):

Shu Yan ◽

Cui Zheng ◽

Zhi-qi Chen ◽

Rong Liu ◽

Gui-gang Li ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Endoplasmic Reticulum Stress ◽

Western Blot ◽

Er Stress ◽

Diabetic Rats ◽

Stress Factors ◽

Diabetic Rat ◽

Related Factors ◽

Diabetes Model ◽

Polymerase Chain

Recent reports show that ER stress plays an important role in diabetic retinopathy (DR), but ER stress is a complicated process involving a network of signaling pathways and hundreds of factors, What factors involved in DR are not yet understood. We selected 89 ER stress factors from more than 200, A rat diabetes model was established by intraperitoneal injection of streptozotocin (STZ). The expression of 89 ER stress-related factors was found in the retinas of diabetic rats, at both 1- and 3-months after development of diabetes, by quantitative real-time polymerase chain reaction arrays. There were significant changes in expression levels of 13 and 12 ER stress-related factors in the diabetic rat retinas in the first and third month after the development of diabetes, Based on the array results, homocysteine- inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1(HERP), and synoviolin(HRD1) were studied further by immunofluorescence and Western blot. Immunofluorescence and Western blot analyses showed that the expression of HERP was reduced in the retinas of diabetic rats in first and third month. The expression of Hrd1 did not change significantly in the retinas of diabetic rats in the first month but was reduced in the third month.

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Lipid Infusions in Man

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648113 ◽

1973 ◽

Vol 29 (03) ◽

pp. 701-711 ◽

Cited By ~ 1

Author(s):

K. A Grøttum ◽

A Nordøy ◽

A Hellem

Keyword(s):

Platelet Aggregation ◽

Survival Time ◽

Electrophoretic Mobility ◽

Lipid Emulsion ◽

Platelet Membrane ◽

Platelet Adhesiveness ◽

Platelet Factor ◽

Platelet Surface ◽

Lipid Particles ◽

Platelet Content

SummaryThe soybean lipid emulsion Intralipid was infused during two hours in 13 volunteer individuals. Biochemically, lipid infusions increased the platelet content of triglycerides, but did not cause significant platelet aggregation, and the platelet counts and survival time were unchanged. However, the lipid infusions reduced platelet and erythrocyte electrophoric mobility, reduced the availability of platelet factor 3 by ADP or kaolin and reduced platelet adhesiveness. A coating of parts of the platelet surface by lipid particles or some other changes in the platelet membrane could explain the effects on platelet electrophoretic mobility, platelet factor 3, and adhesiveness.

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Tauroursodeoxycholic Acid Attenuates Diet-Induced and Age-Related Peripheral Endoplasmic Reticulum Stress and Cerebral Amyloid Pathology in a Mouse Model of Alzheimer’s Disease

Journal of Prevention of Alzheimer's Disease ◽

10.14283/jpad.2021.33 ◽

2021 ◽

pp. 1-12

Author(s):

T. Ochiai ◽

T. Nagayama ◽

K. Matsui ◽

K. Amano ◽

T. Sano ◽

...

Keyword(s):

Insulin Resistance ◽

Endoplasmic Reticulum ◽

Er Stress ◽

Metabolic Abnormalities ◽

Intracerebroventricular Administration ◽

Metabolic State ◽

Peripheral Tissues ◽

Age Related ◽

Obesity And Diabetes ◽

The Brain

BACKGROUND: Obesity and diabetes are well-established risk factors of Alzheimer’s disease (AD). In the brains of patients with AD and model mice, diabetes-related factors have been implicated in the pathological changes of AD. However, the molecular mechanistic link between the peripheral metabolic state and AD pathophysiology have remained elusive. Endoplasmic reticulum (ER) stress is known as one of the major contributors to the metabolic abnormalities in obesity and diabetes. Interventions aimed at reducing ER stress have been shown to improve the systemic metabolic abnormalities, although their effects on the AD pathology have not been extensively studied. OBJECTIVES: We examined whether interventions targeting ER stress attenuate the obesity/diabetes-induced Aβ accumulation in brains. We also aimed to determine whether ER stress that took place in the peripheral tissues or central nervous system was more important in the Aβ neuropathology. Furthermore, we explored if age-related metabolic abnormalities and Aβ accumulation could be suppressed by reducing ER stress. METHODS: APP transgenic mice (A7-Tg), which exhibit Aβ accumulation in the brain, were used as a model of AD to analyze parameters of peripheral metabolic state, ER stress, and Aβ pathology in the brain. Intraperitoneal or intracerebroventricular administration of taurodeoxycholic acid (TUDCA), a chemical chaperone, was performed in high-fat diet (HFD)-fed A7-Tg mice for ~1 month, followed by analyses at 9 months of age. Mice fed a normal diet were treated with TUDCA by drinking water for 4 months and intraperitoneally for 1 month in parallel, and analyzed at 15 months of age. RESULTS: Intraperitoneal administration of TUDCA suppressed ER stress in the peripheral tissues and ameliorated the HFD-induced obesity and insulin resistance. Concomitantly, Aβ levels in the brain were significantly reduced. In contrast, intracerebroventricular administration of TUDCA had no effect on the Aβ levels. Peripheral administration of TUDCA was also effective against the age-related obesity and insulin resistance, and markedly reduced amyloid accumulation. CONCLUSIONS: Interventions that target peripheral ER stress might be beneficial therapeutic and prevention strategies against brain Aβ pathology associated with metabolic overload and aging.

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Enhanced Platelet Aggregation and Thrombogenic Tendency in Adiponectin-Deficient Mice.

Blood ◽

10.1182/blood.v104.11.800.800 ◽

2004 ◽

Vol 104 (11) ◽

pp. 800-800 ◽

Cited By ~ 1

Author(s):

Hisashi Kato ◽

Hirokazu Kashiwagi ◽

Masamichi Shiraga ◽

Shigenori Honda ◽

Shigeki Miyata ◽

...

Keyword(s):

Platelet Aggregation ◽

Carotid Artery ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Thrombus Formation ◽

Atherosclerotic Lesion ◽

Blue Dye ◽

Globular Domain ◽

Wild Type ◽

Obesity And Diabetes

Abstract Adiponectin is a 30 kDa protein secreted specifically from adipocytes and structurally composed of two distinct domains, C-terminal collagen-like domain and N-terminal complement C1q-like globular domain. Adiponectin is abundantly present in plasma at high concentration ranging from 2 to 30 μg/ml. The plasma levels of adiponectin decreased in patients with obesity and diabetes. Recently it has been demonstrated that adiponectin has an anti-atherogenic activity. Hypoadiponectinemia is an independent risk factor for coronary artery disease in men. However, the role of adiponectin in hemostasis and thrombosis still remains obscure. In this study, we examined its role in hemostasis and thrombosis using adiponectin-deficient (APN-KO) mice (Nat. Med. 2002 Maeda et al.). APN-KO mice were fed by normal chaw and studied at 8–12 weeks old. There were no differences in platelet counts, PT, APTT and plasma fibrinogen levels between APN-KO and Wild-Type mice. Neither Wild-Type nor APN-KO mice showed detectable atherosclerotic lesion in carotid artery as well as whole aorta. We examined tail-bleeding times as a measure of primary hemostasis. The tail bleeding time was 96.9 ± 34.9 seconds in APN-KO mice, which was shorter than that in wild type mice (130.9 ± 52.1 seconds, n=30, p<0.05). We next studied thrombus formation in mice carotid artery using He-Ne laser induced in vivo thrombus formation model. Thrombus formation was induced by the interaction of irradiated He-Ne laser with evans blue dye injected into blood flow. The thrombus volumes formed during 10 minutes were significantly larger in APN-KO mice (6.74 ± 2.87 x 107 arbitrary units for wild-type v.s. 13.4 ± 4.25 x 107 arbitrary units for APN-KO mice, n=10, p<0.01). Adenovirus-mediated supplement of adiponectin compensated for the thrombotic tendency in APN-KO mice. In order to clarify the effects of adiponectin on platelet functon, we performed ex vivo experiments. In platelet aggregation studies under stirring conditions using platelet-rich plasma, platelet aggregation induced by low concentrations of agonists (ADP 2.5μM, collagen 2.5μg/ml, PAR4 peptide 75μM) was enhanced in APN-KO mice. Again the adenovirus-mediated supplement of adiponectin compensated for the enhancement of platelet aggregation. We next studied the thrombus formation on collagen coated surface under flow conditions. The thrombus formation was enhanced in APN-KO mice under shear rate at 250s−1. Our data provide a first evidence that adiponectin plays a role in hemostasis and thrombosis as a negative modulator of platelet function.

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Role of Endoplasmic Reticulum Stress in Atherosclerosis and Diabetic Macrovascular Complications

BioMed Research International ◽

10.1155/2014/610140 ◽

2014 ◽

Vol 2014 ◽

pp. 1-14 ◽

Cited By ~ 32

Author(s):

Dmitry A. Chistiakov ◽

Igor A. Sobenin ◽

Alexander N. Orekhov ◽

Yuri V. Bobryshev

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Macrovascular Complications ◽

Cell Organelle ◽

Unfolded Protein ◽

Homologous Protein ◽

Treatment And Prevention ◽

Age Related ◽

Obesity And Diabetes ◽

Folded Proteins

Age-related changes in endoplasmic reticulum (ER) are associated with stress of this cell organelle. Unfolded protein response (UPR) is a normal physiological reaction of a cell in order to prevent accumulation of unfolded and misfolded proteins in the ER and improve the normal ER function. However, in pathologic conditions such as atherosclerosis, obesity, and diabetes, ER function becomes impaired, leading to the development of ER stress. In chronic ER stress, defective posttranslational protein folding results in deposits of aberrantly folded proteins in the ER and the induction of cell apoptosis mediated by UPR sensors C/EBPα-homologous protein (CHOP) and inositol requiring protein-1 (IRE1). Since ER stress and ER-induced cell death play a nonredundant role in the pathogenesis of atherosclerosis and diabetic macrovascular complications, pharmaceutical targeting of ER stress components and pathways may be beneficial in the treatment and prevention of cardiovascular pathology.

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Recombinant Helicobacter pylori CagA protein induces endoplasmic reticulum stress and autophagy in human cells

10.1101/2020.06.26.174615 ◽

2020 ◽

Author(s):

Babak Nami ◽

Ali Azzawri ◽

Vasfiye B Ucar ◽

Hasan Acar

Keyword(s):

Cell Proliferation ◽

Endoplasmic Reticulum ◽

Cell Death ◽

Helicobacter Pylori ◽

Western Blot ◽

Er Stress ◽

Nuclear Localization ◽

Human Cell ◽

Human Cells ◽

Caga Protein

AbstractHelicobacter pylori (Hp) CagA protein has a key role in the development of gastric cancer by the intruding in many intracellular processes of host human cell. Endoplasmic reticulum (ER) stress is an essential process for cellular homeostasis that modulates survival and death and is linked to several complex diseases including cancer. CagA protein is found in the serum of Hp-positive individuals and also in the supernatant of Hp culture. Limited studies report that recombinant CagA can alter gene expression and signaling pathways and induce the death of human cells. In this study, we investigated the effect of exogenous recombinant CagA protein treatment on ER stress and autophagy of human cell. AGS, MKN45, and HEK293 cells were treated with 1 µg/ml of recombinant CagA protein and then ER stress was studied by quantitative-PCR of spliced XBP-1 mRNA, immunofluorescence staining of ATF6 protein nuclear localization and real-time quantitative-PCR and/or western blot expression of GRP78, GRP94, ATF4 and CHOP genes. Autophagy was studied by western blot assessment of the conversion of LC3-I to LC3-II and LC3 aggregation. Cell proliferation and death were investigated by MTT assay and trypan blue staining respectively. As result, treatment with recombinant CagA enhanced XBP-1mRNA splicing, nuclear localization of ATF6, and the expression of ER stress signaling target genes in the cells. Recombinant CagA also induced LC3 protein conversion and aggregation in the cells. Reduced cell proliferation and increased cell death were determined in the cells treated with recombinant CagA. These results show that exogenous recombinant CagA protein causes cell death by inducing ER stress and autophagy in human cells. We conclude that CagA protein exogenously localizes in/on human cells and induces ER stress via disturbing protein machinery leading the human cell to death, however, the mechanism of CagA-host cell interaction is to be investigated.

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ADP and epinephrine-induced release of platelet fibrinogen

Blood ◽

10.1182/blood.v58.4.797.797 ◽

1981 ◽

Vol 58 (4) ◽

pp. 797-802 ◽

Cited By ~ 19

Author(s):

KL Kaplan ◽

MJ Dauzier ◽

S Rose

Keyword(s):

Platelet Aggregation ◽

Bovine Serum Albumin ◽

Adenine Nucleotides ◽

Adenosine Diphosphate ◽

Human Platelets ◽

Dense Granule ◽

Fibrinogen Concentration ◽

Platelet Factor ◽

Granule Proteins ◽

Induced Aggregation

Abstract Human platelets gel-filtered into Tyrode's buffer containing 1 mM Mg++ and 0.35% bovine serum albumin were studied to determine whether they would undergo biphasic aggregation and release of alpha-granule proteins in response to adenosine diphosphate (ADP) or epinephrine without addition of exogenous fibrinogen. Fibrinogen concentration in the supernatant of unaggregated gel-filtered platelets was less than 1 pmole/ml. With addition of ADP or epinephrine, biphasic aggregation was seen, with release of platelet fibrinogen, beta-thromboglobulin, and platelet factor 4. Fibrinogen concentration in the supernatant after aggregation ranged from 15 to 70 pmole/ml. Release of the alpha-granule proteins by epinephrine was coincidental with release of the dense granule adenine nucleotides. Aggregation and alpha-granule protein release by both ADP and epinephrine were inhibited by added Ca++ at 1-- 2 mM. The ability of gel-filtered platelets to undergo ADP- and epinephrine-induced aggregation and release in the absence of exogenous fibrinogen suggests that released platelet fibrinogen may be able to fulfill the requirement for fibrinogen in ADP- and epinephrine-induced platelet aggregation and release.

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