Browsing by Subject "Endoplasmic reticulum"

Now showing 1 - 3 of 3
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    Involvement of endoplasmic reticulum stress and activation of MAP kinases in B-lapachone-induced human prostate cancer cell apoptosis
    (Murcia : F. Hernández, 2008) Lien, Yi-Chen; Kung, Hsiu-Ni; Lu, Kuo-Shyan; Jeng, Chung-Jiuan; Chau, Yat-Pang
    ß-Lapachone, an o-naphthoquinone, induces various carcinoma cells to undergo apoptosis, but the mechanism is poorly understood. In the present study, we found that the ß-lapachone-induced apoptosis of DU145 human prostate carcinoma cells was associated with endoplasmic reticulum (ER) stress, as shown by increased intracellular calcium levels and induction of GRP-78 and GADD-153 proteins, suggesting that the endoplasmic reticulum is a target of ß-lapachone. ß- Lapachone-induced DU145 cell apoptosis was dosedependent and accompanied by cleavage of procaspase- 12 and phosphorylation of p38, ERK, and JNK, followed by activation of the executioner caspases, caspase-7 and calpain. However, pretreatment with the general caspase inhibitor, z-VAD-FMK, or calpain inhibitors, including ALLM or ALLN, failed to prevent ß-lapachone-induced apoptotic cell death. Blocking the enzyme activity of NQO1 with dicoumarol, a known NQO1 inhibitor, or preventing an increase in intracellular calcium levels using BAPTA-AM, an intracellular calcium chelator, substantially inhibited MAPK phosphorylation, abolished the activation of calpain, caspase-12 and caspase-7, and provided significant protection of ßlapachone- treated cells. These findings show that ßlapachone- induced ER stress and MAP kinase phosphorylation is a novel signaling pathway underlying the molecular mechanism of the anticancer effect of ßlapachone.
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    The glucose-6-phosphatase system in human development
    (Murcia : F. Hernández, 1995) Burchell, A.; Hume, R.
    The classical role of glucose-6-phosphatase in liver and kidney is the production of glucose for release into blood. In liver, glucose-6-phosphatase catalyses the terminal step of glycogenolysis and gluconeogenesis. Abnormally low hepatic glucose-6- phosphatase activity is found in human genetic deficiencies i.e. glycogen storage disease type 1 and in cases of developmental delay, found predominantly in preterm infants. In contrast, abnormally high liver glucose-6-phosphatase occurs in poorly controlled or untreated diabetes mellitus. Hepatic glucose-6-phosphatase is an integral endoplasmic reticulum (and nuclear membrane) protein and it is part of a multicomponent system. Its active site is situated inside the lumen of the endoplasmic reticulum and transport proteins are needed to allow its substrates glucose-~6-phosphate (and pyrophosphate) and its products phosphate and glucose to cross the endoplasmic reticulum membrane. In addition, a calcium binding protein is also associated with the glucose-6-phosphatase enzyme. Immunohistochemical studies, in combination with image analysis, have shown that glucose-6- phosphatase is present in liver and kidney and also in specific cell types in a variety of human tissues, for example Leydig cells in the testis and some astrocytes in the brain. Where practicable, enzymatic analysis, direct transport assays andlor immunological detection of the endoplasmic reticulum glucose and phosphate transport proteins have been used to demonstrate the presence and activity of the whole glucose-6-phosphatase system. The distribution of the human glucose-6-phosphatase system changes dramatically during development with a different spatial and temporal pattern in each tissue. The most unexpected localization was in circulating, predominantly nucleated, embryonic and early fetal red blood cells.
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    Tricalbin-Mediated contact sites control ER curvature to maintain plasma membrane integrity
    (Elsevier, ) Collado, Javier; Kalemanov, Maria; Campelo, Felix; Bourgoint, Clelia; Thomas, Ffion; Loewith, Robbie; Martínez Sánchez, Antonio; Baumeister, Wolgang; Stefan, Christopher J.; Fernandez-Busnadiego, Ruben; Ingeniería de la Información y las Comunicaciones
    Membrane contact sites (MCS) between the endoplasmic reticulum (ER) and the plasma membrane (PM) play fundamental roles in all eukaryotic cells. ER-PM MCS are particularly abundant in Saccharomyces cerevisiae, where approximately half of the PM surface is covered by cortical ER (cER). Several proteins, including Ist2, Scs2/22, and Tcb1/2/3 are implicated in cER formation, but the specific roles of these molecules are poorly understood. Here, we use cryo-electron tomography to show that ER-PM tethers are key determinants of cER morphology. Notably, Tcb proteins (tricalbins) form peaks of extreme curvature on the cER membrane facing the PM. Combined modeling and functional assays suggest that Tcb-mediated cER peaks facilitate the transport of lipids between the cER and the PM, which is necessary to maintain PM integrity under heat stress. ER peaks were also present at other MCS, implying that membrane curvature enforcement may be a widespread mechanism to regulate MCS function.