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Berlin Brandenburg

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  • Membrane Transport Proteins
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  • 1
    Language: English
    In: The Prostate, July 2011, Vol.71(10), pp.1074-83
    Description: We previously reported that over-expression of the SEC62 gene is a widespread phenomenon in prostate cancer. Since the use of endoplasmic reticulum (ER) stress-inducing substances such as thapsigargin in prostate cancer therapy is widely discussed in the literature, we investigated the influence of Sec62 protein content on the cellular response to these drugs. Growth effects were analyzed by real-time cell analysis and viability tests in DU145-cells representing an increased SEC62 expression or PC3- and LNCaP-cells representing a similar SEC62 expression compared to non-tumor cells. Ca(2+) -imaging in an established HeLa-system with fluorescent dye was used to study molecular effects of Sec62 depletion. We found a lower propensity toward apoptotic cell death after thapsigargin treatment for DU145 cells compared to PC3 or LNCaP and siRNA-mediated silencing of SEC62 resulted in a reduced viability of thapsigargin-treated PC3 cells, indicating that Sec62 functions in cellular stress response. Measurement of cytosolic [Ca(2+) ] demonstrated the influence of Sec62 on the cellular response to thapsigargin on a molecular level. Using real-time cell analysis, we observed the loss of androgen stimulation of LNCaP cells in the presence of thapsigargin, and an additional negative effect on cell growth of Sec62 depletion. Also, for PC3- and DU145-cells Sec62 depletion inhibited growth after thapsigargin treatment. Our data indicate a crucial function of Sec62 in the response to thapsigargin-induced ER stress. This will be of great significance on the background of elevated Sec62 protein levels in prostate cancer cells when treatment with thapsigargin analogs is considered.
    Keywords: Apoptosis -- Physiology ; Cell Survival -- Physiology ; Endoplasmic Reticulum -- Metabolism ; Membrane Transport Proteins -- Metabolism
    ISSN: 02704137
    E-ISSN: 1097-0045
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  • 2
    In: European Journal of Immunology, April 2012, Vol.42(4), pp.831-841
    Description: T‐cell activation and the subsequent transformation of activated cells into ‐cell blasts require profound changes in cell volume. However, the impact of cell volume regulation for ‐cell immunology has not been characterized. Here we studied the role of the cell‐volume regulating osmolyte transporter aut for ‐cell activation in aut‐deficient mice. T‐cell mediated recall responses were severely impaired in mice as shown with 16 melanoma rejection and hapten‐induced contact hypersensitivity. CD4 and CD8 cells were unequivocally located within peripheral lymph nodes of unprimed mice but significantly decreased in compared with mice following in vivo activation. Further analysis revealed that aut is critical for rescuing cells from activation‐induced cell death in vitro and in vivo as shown with , superantigen, and antigen‐specific activation. Consequently, reduction of CD4 and CD8 cells in mice upon antigen challenge resulted in impaired in vivo generation of ‐cell memory. These findings disclose for the first time that volume regulation in cells is an element in the regulation of adaptive immune responses and that the osmolyte transporter aut is crucial for ‐cell survival and ‐cell mediated immune reactions.
    Keywords: Activation‐Induced Cell Death ; Cell Volume Regulation ; Taurine Transporter ; T‐Cell Response
    ISSN: 0014-2980
    E-ISSN: 1521-4141
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  • 3
    Language: English
    In: Journal of cell science, 15 April 2012, Vol.125(Pt 8), pp.1958-69
    Description: Co-translational transport of polypeptides into the endoplasmic reticulum (ER) involves the Sec61 channel and additional components such as the ER lumenal Hsp70 BiP and its membrane-resident co-chaperone Sec63p in yeast. We investigated whether silencing the SEC61A1 gene in human cells affects co- and post-translational transport of presecretory proteins into the ER and post-translational membrane integration of tail-anchored proteins. Although silencing the SEC61A1 gene in HeLa cells inhibited co- and post-translational transport of signal-peptide-containing precursor proteins into the ER of semi-permeabilized cells, silencing the SEC61A1 gene did not affect transport of various types of tail-anchored protein. Furthermore, we demonstrated, with a similar knockdown approach, a precursor-specific involvement of mammalian Sec63 in the initial phase of co-translational protein transport into the ER. By contrast, silencing the SEC62 gene inhibited only post-translational transport of a signal-peptide-containing precursor protein.
    Keywords: DNA Helicases -- Metabolism ; Endoplasmic Reticulum -- Metabolism ; Membrane Proteins -- Metabolism ; Membrane Transport Proteins -- Metabolism ; Peptides -- Metabolism
    ISSN: 00219533
    E-ISSN: 1477-9137
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  • 4
    Language: English
    In: Methods in enzymology, 2007, Vol.428, pp.439-58
    Description: This chapter reports present knowledge on the properties of mice with disrupted gene coding for the taurine transporter (taut-/- mice). Study of those mice unraveled some of the roles of taurine and its membrane transport for the development and maintenance of normal organ functions and morphology. When compared with wild-type controls, taut-/- mice have decreased taurine levels in skeletal and heart muscle by about 98%, in brain, kidney, plasma, and retina by 80 to 90%, and in liver by about 70%. taut-/- mice exhibit a lower body mass as well as a strongly reduced exercise capacity compared with taut+/- and wild-type mice. Furthermore, taut-/- mice show a variety of pathological features, for example, subtle derangement of renal osmoregulation, changes in neuroreceptor expression, and loss of long-term potentiation in the striatum, and they develop clinically relevant age-dependent disorders, for example, visual, auditory, and olfactory dysfunctions, unspecific hepatitis, and liver fibrosis. Taurine-deficient animal models such as acutely dietary-manipulated foxes and cats, pharmacologically induced taurine-deficient rats, and taurine transporter knockout mouse are powerful tools allowing identification of the mechanisms and complexities of diseases mediated by impaired taurine transport and taurine depletion (Chapman et al., 1993; Heller-Stilb et al., 2002; Huxtable, 1992; Lake, 1993; Moise et al., 1991; Novotny et al., 1991; Pion et al., 1987; Timbrell et al., 1995; Warskulat et al., 2004, 2006b). Taurine, which is the most abundant amino acid in many tissues, is normally found in intracellular concentrations of 10 to 70 mmol/kg in mammalian heart, brain, skeletal muscle, liver, and retina (Chapman et al., 1993; Green et al., 1991; Huxable, 1992; Timbrell et al., 1995). These high taurine levels are maintained by an ubiquitous expression of Na(+)-dependent taurine transporter (TAUT) in the plasma membrane (Burg, 1995; Kwon and Handler, 1995; Lang et al., 1998; Liu et al., 1992; Ramamoorthy et al., 1994; Schloss et al., 1994; Smith et al., 1992; Uchida et al., 1992; Vinnakota et al., 1997; Yancey et al., 1975). Taurine is not incorporated into proteins. It is involved in cell volume regulation, neuromodulation, antioxidant defense, protein stabilization, stress responses, and via formation of taurine-chloramine in immunomodulation (Chapman et al., 1993; Green et al., 1991; Huxtable, 1992; Timbrell et al., 1995). On the basis of its functions, taurine may protect cells against various types of injury (Chapman et al., 1993; Green et al., 1991; Huxtable, 1992; Kurz et al., 1998; Park et al., 1995; Stapleton et al., 1998; Timbrell et al., 1995; Welch and Brown, 1996; Wettstein and Häussinger, 1997). In order to examine the multiple taurine functions, murine models have several intrinsic advantages for in vivo research compared to other animal models, including lower cost, maintenance, and rapid reproduction rate. Further, experimental reagents for cellular and molecular studies are widely available for the mouse. In particular, mice can be easily genetically manipulated by making transgene and knockout mice. This chapter focuses on the phenotype of the TAUT-deficient murine model (taut-/-; Heller-Stilb et al., 2002), which may help researchers elucidate the diverse roles of taurine in development and maintenance of normal organ functions and morphology.
    Keywords: Membrane Glycoproteins -- Genetics ; Membrane Transport Proteins -- Genetics ; Taurine -- Physiology
    ISSN: 0076-6879
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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  • 5
    Language: English
    In: Cellular Physiology and Biochemistry, 2003, Vol.13(6), pp.337-346
    Description: In nucleated cells cellular taurine is released prior to DNA fragmentation and the breakdown of phosphatidylserine asymmetry within the plasma membrane. Similar to what is seen in nucleated cells, phosphatidylserine asymmetry is also abolished in erythrocytes exposed to osmotic shock or oxidative stress. The present study has been performed to explore the sensitivity of erythrocytes from a taurine transporter knockout mouse (taut-/-) against osmotic shock and oxidative stress. Erythrocyte cell volume was estimated from forward scatter and breakdown of phosphatidylserine asymmetry was identified by determination of annexin binding using FACS analysis. Erythrocytes from taut-/- mice were compared to erythrocytes from wild type littermates (taut+/ +). Plasma concentration and erythrocyte content of taurine was significantly lower in taut-/- than in taut+/ + mice, but the intraerythrocyte taurine concentration did not exceed the plasma concentration. Hyperosmotic shock (exposure to 700 mOsm) and oxidative stress (exposure to 0.1 mM tert-butyl-hydroperoxide) significantly decreased the cell volume and increased the number of annexin binding sites of erythrocytes from both, taut-/- and taut+/ + mice. However, decrease of cell volume and increase of annexin binding was significantly blunted in erythrocytes from taut-/- mice as compared to their taut+/ + littermates. Stimulation of erythropoiesis by prior hemorrhage did not abrogate the difference between taut+/ + and taut-/- erythrocytes. The present observations point to a decreased sensitivity of mature erythrocytes from taut-/- mice to osmotic shock and oxidative stress, rendering them more resistant to apoptosis.
    Keywords: Original Paper ; Biology ; Chemistry
    ISSN: 1015-8987
    E-ISSN: 1421-9778
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  • 6
    Language: English
    In: Pflügers Archiv, 2006, Vol.451(5), pp.668-677
    Description: Cellular taurine uptake or release counteracts alterations of cell volume. Na + -coupled taurine transporter TAUT mediates concentrative cellular uptake of taurine. Inhibition of vasopressin secretion by hypotonicity may involve taurine release from glial cells of supraoptic nucleus. We compared renal function of mice lacking TAUT ( taut −/− ) and wild-type littermates ( taut +/+ ). We observed renal taurine loss and subsequent hypotaurinemia in taut −/− mice. With free access to water, plasma and urine osmolality, urinary flow rate as well as urinary excretion and plasma concentrations of Na + and K + were similar in taut −/− and taut +/+ mice, whereas plasma concentrations of urea were enhanced in taut −/− mice. An oral water load (1 ml/16 g body weight) induced a similar diuresis in both genotypes. Repeating the oral water load immediately after normalization of urine flow rate, however, resulted in delayed diuresis and higher urinary vasopressin/creatinine ratios in taut −/− mice. In comparison, the repeated diuretic response to vasopressin V 2 receptor blockade was not different between genotypes. Water deprivation for 36 h led to similar antidiuresis and increases of urinary osmolality in both genotypes. Upon free access to water after deprivation, taut −/− mice continued to concentrate urine up to 6 days, while taut +/+ mice rapidly returned to normal urinary osmolality. Urinary vasopressin/creatinine ratios and plasma aldosterone concentrations were not different under basal conditions but were significantly higher in taut −/− mice than in taut +/+ mice at 6 days after water deprivation. In conclusion, taut −/− mice suffer from renal taurine loss and impaired ability to lower urine osmolality and to increase urinary water excretion. The latter defect could reside extrarenally and result from a role of taurine in the suppression of vasopressin release which may be attenuated in taut −/− mice.
    Keywords: Lifesciences ; Medicine ; Anatomy & Physiology;
    ISSN: 0031-6768
    E-ISSN: 1432-2013
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