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Literatura académica sobre el tema "Vacuolar acidification"
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Artículos de revistas sobre el tema "Vacuolar acidification"
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Yamashiro, C. T., P. M. Kane, D. F. Wolczyk, R. A. Preston, and T. H. Stevens. "Role of vacuolar acidification in protein sorting and zymogen activation: a genetic analysis of the yeast vacuolar proton-translocating ATPase." Molecular and Cellular Biology 10, no. 7 (1990): 3737–49. http://dx.doi.org/10.1128/mcb.10.7.3737-3749.1990.
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Vacuolar acidification has been proposed to play a key role in a number of cellular processes, including protein sorting, zymogen activation, and maintenance of intracellular pH. We investigated the significance of vacuolar acidification by cloning and mutagenizing the gene for the yeast vacuolar proton-translocating ATPase 60-kilodalton subunit (VAT2). Cells carrying a vat2 null allele were viable; however, these cells were severely defective for growth in medium buffered at neutral pH. Vacuoles isolated from cells bearing the vat2 null allele were completely devoid of vacuolar ATPase activity. The pH of the vacuolar lumen of cells bearing the vat2 mutation was 7.1, compared with the wild-type pH of 6.1, as determined by a flow cytometric pH assay. These results indicate that the vacuolar proton-translocating ATPase complex is essential for vacuolar acidification and that the low-pH state of the vacuole is crucial for normal growth. The vacuolar acidification-defective vat2 mutant exhibited normal zymogen activation but displayed a minor defect in vacuolar protein sorting.
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Yamashiro, C. T., P. M. Kane, D. F. Wolczyk, R. A. Preston, and T. H. Stevens. "Role of vacuolar acidification in protein sorting and zymogen activation: a genetic analysis of the yeast vacuolar proton-translocating ATPase." Molecular and Cellular Biology 10, no. 7 (1990): 3737–49. http://dx.doi.org/10.1128/mcb.10.7.3737.
Texto completoResumen
Vacuolar acidification has been proposed to play a key role in a number of cellular processes, including protein sorting, zymogen activation, and maintenance of intracellular pH. We investigated the significance of vacuolar acidification by cloning and mutagenizing the gene for the yeast vacuolar proton-translocating ATPase 60-kilodalton subunit (VAT2). Cells carrying a vat2 null allele were viable; however, these cells were severely defective for growth in medium buffered at neutral pH. Vacuoles isolated from cells bearing the vat2 null allele were completely devoid of vacuolar ATPase activity. The pH of the vacuolar lumen of cells bearing the vat2 mutation was 7.1, compared with the wild-type pH of 6.1, as determined by a flow cytometric pH assay. These results indicate that the vacuolar proton-translocating ATPase complex is essential for vacuolar acidification and that the low-pH state of the vacuole is crucial for normal growth. The vacuolar acidification-defective vat2 mutant exhibited normal zymogen activation but displayed a minor defect in vacuolar protein sorting.
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Morano, K. A., and D. J. Klionsky. "Differential effects of compartment deacidification on the targeting of membrane and soluble proteins to the vacuole in yeast." Journal of Cell Science 107, no. 10 (1994): 2813–24. http://dx.doi.org/10.1242/jcs.107.10.2813.
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Lysosomal/vacuolar protein targeting is dependent on compartment acidification. In yeast, sorting of soluble vacuolar proteins such as carboxypeptidase Y is sensitive to acute changes in vacuolar pH. In contrast, the vacuolar membrane protein alkaline phosphatase is missorted only under conditions of chronic deacidification. We have undertaken a temporal analysis to define further the relationship between compartment acidification and sorting of soluble and membrane vacuolar proteins. Depletion of either the Vma3p or Vma4p subunits of the yeast vacuolar ATPase over time resulted in loss of vacuolar ATPase activity and vacuolar acidification. A kinetic delay in processing of carboxypeptidase Y occurred concomitant with these physiological changes while transport of alkaline phosphatase remained unaffected. Carboxypeptidase S, another vacuolar hydrolase that transits through the secretory pathway as an integral membrane protein, displayed a pH sensitivity similar to that of soluble vacuolar proteins. These results indicate that compartment acidification is tightly coupled to efficient targeting of proteins to the vacuole and that there may be multiple distinct mechanisms for targeting of vacuolar membrane proteins.
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Chen, Shuliang, Maureen Tarsio, Patricia M. Kane, and Miriam L. Greenberg. "Cardiolipin Mediates Cross-Talk between Mitochondria and the Vacuole." Molecular Biology of the Cell 19, no. 12 (2008): 5047–58. http://dx.doi.org/10.1091/mbc.e08-05-0486.
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Cardiolipin (CL) is an anionic phospholipid with a dimeric structure predominantly localized in the mitochondrial inner membrane, where it is closely associated with mitochondrial function, biogenesis, and genome stability ( Daum, 1985 ; Janitor and Subik, 1993 ; Jiang et al., 2000 ; Schlame et al., 2000 ; Zhong et al., 2004 ). Previous studies have shown that yeast mutant cells lacking CL due to a disruption in CRD1, the structural gene encoding CL synthase, exhibit defective colony formation at elevated temperature even on glucose medium ( Jiang et al., 1999 ; Zhong et al., 2004 ), suggesting a role for CL in cellular processes apart from mitochondrial bioenergetics. In the current study, we present evidence that the crd1Δ mutant exhibits severe vacuolar defects, including swollen vacuole morphology and loss of vacuolar acidification, at 37°C. Moreover, vacuoles from crd1Δ show decreased vacuolar H+-ATPase activity and proton pumping, which may contribute to loss of vacuolar acidification. Deletion mutants in RTG2 and NHX1, which mediate vacuolar pH and ion homeostasis, rescue the defective colony formation phenotype of crd1Δ, strongly suggesting that the temperature sensitivity of crd1Δ is a consequence of the vacuolar defects. Our results demonstrate the existence of a novel mitochondria-vacuole signaling pathway mediated by CL synthesis.
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Raymond, C. K., I. Howald-Stevenson, C. A. Vater, and T. H. Stevens. "Morphological classification of the yeast vacuolar protein sorting mutants: evidence for a prevacuolar compartment in class E vps mutants." Molecular Biology of the Cell 3, no. 12 (1992): 1389–402. http://dx.doi.org/10.1091/mbc.3.12.1389.
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The collection of vacuolar protein sorting mutants (vps mutants) in Saccharomyces cerevisiae comprises of 41 complementation groups. The vacuoles in these mutant strains were examined using immunofluorescence microscopy. Most of the vps mutants were found to possess vacuolar morphologies that differed significantly from wild-type vacuoles. Furthermore, mutants representing independent vps complementation groups were found to share aberrant morphological features. Six distinct classes of vacuolar morphology were observed. Mutants from eight vps complementation groups were defective both for vacuolar segregation from mother cells into developing buds and for acidification of the vacuole. Another group of mutants, represented by 13 complementation groups, accumulated a novel organelle distinct from the vacuole that contained a late-Golgi protein, active vacuolar H(+)-ATPase complex, and soluble vacuolar hydrolases. We suggest that this organelle may represent an exaggerated endosome-like compartment. None of the vps mutants appeared to mislocalize significant amounts of the vacuolar membrane protein alkaline phosphatase. Quantitative immunoprecipitations of the soluble vacuolar hydrolase carboxypeptidase Y (CPY) were performed to determine the extent of the sorting defect in each vps mutant. A good correlation between morphological phenotype and the extent of the CPY sorting defect was observed.
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Raymond, C. K., P. J. O'Hara, G. Eichinger, J. H. Rothman, and T. H. Stevens. "Molecular analysis of the yeast VPS3 gene and the role of its product in vacuolar protein sorting and vacuolar segregation during the cell cycle." Journal of Cell Biology 111, no. 3 (1990): 877–92. http://dx.doi.org/10.1083/jcb.111.3.877.
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vps3 mutants of the yeast Saccharomyces cerevisiae are impaired in the sorting of newly synthesized soluble vacuolar proteins and in the acidification of the vacuole (Rothman, J. H., and T. H. Stevens. Cell. 47:1041-1051; Rothman, J. H., C. T. Yamashiro, C. K. Raymond, P. M. Kane, and T. H. Stevens. 1989. J. Cell Biol. 109:93-100). The VPS3 gene, which was cloned using a novel selection procedure, encodes a low abundance, hydrophilic protein of 117 kD that most likely resides in the cytoplasm. Yeast strains bearing a deletion of the VPS3 gene (vps3-delta 1) are viable, yet their growth rate is significantly reduced relative to wild-type cells. Temperature shift experiments with strains carrying a temperature conditional vps3 allele demonstrate that cells rapidly lose the capacity to sort the vacuolar protein carboxypeptidase Y upon loss of VPS3 function. Vacuolar morphology was examined in wild-type and vps3-delta 1 yeast strains by fluorescence microscopy. The vacuoles in wild-type yeast cells are morphologically complex, and they appear to be actively partitioned between mother cells and buds during an early phase of bud growth. Vacuolar morphology in vps3-delta 1 mutants is significantly altered from the wild-type pattern, and the vacuolar segregation process seen in wild-type strains is defective in these mutants. With the exception of a vacuolar acidification defect, the phenotypes of vps3-delta 1 strains are significantly different from those of mutants lacking the vacuolar proton-translocating ATPase. These data demonstrate that the acidification defect in vps3-delta 1 cells is not the primary cause of the pleiotropic defects in vacuolar function observed in these mutants.
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Rothman, J. H., C. T. Yamashiro, C. K. Raymond, P. M. Kane, and T. H. Stevens. "Acidification of the lysosome-like vacuole and the vacuolar H+-ATPase are deficient in two yeast mutants that fail to sort vacuolar proteins." Journal of Cell Biology 109, no. 1 (1989): 93–100. http://dx.doi.org/10.1083/jcb.109.1.93.
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Organelle acidification plays a demonstrable role in intracellular protein processing, transport, and sorting in animal cells. We investigated the relationship between acidification and protein sorting in yeast by treating yeast cells with ammonium chloride and found that this lysosomotropic agent caused the mislocalization of a substantial fraction of the newly synthesized vacuolar (lysosomal) enzyme proteinase A (PrA) to the cell surface. We have also determined that a subset of the vpl mutants, which are deficient in sorting of vacuolar proteins (Rothman, J. H., and T. H. Stevens. 1986. Cell. 47:1041-1051; Rothman, J. H., I. Howald, and T. H. Stevens. EMBO [Eur. Mol. Biol. Organ.] J. In press), failed to accumulate the lysosomotropic fluorescent dye quinacrine within their vacuoles, mimicking the phenotype of wild-type cells treated with ammonium. The acidification defect of vpl3 and vpl6 mutants correlated with a marked deficiency in vacuolar ATPase activity, diminished levels of two immunoreactive subunits of the protontranslocating ATPase (H+-ATPase) in purified vacuolar membranes, and accumulation of the intracellular portion of PrA as the precursor species. Therefore, some of the VPL genes are required for the normal function of the yeast vacuolar H+-ATPase complex and may encode either subunits of the enzyme or components required for its assembly and targeting. Collectively, these findings implicate a critical role for acidification in vacuolar protein sorting and zymogen activation in yeast, and suggest that components of the yeast vacuolar acidification system may be identified by examining mutants defective in sorting of vacuolar proteins.
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Klionsky, D. J., H. Nelson, N. Nelson, and D. S. Yaver. "Mutations in the yeast vacuolar ATPase result in the mislocalization of vacuolar proteins." Journal of Experimental Biology 172, no. 1 (1992): 83–92. http://dx.doi.org/10.1242/jeb.172.1.83.
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The vacuolar ATPase of the yeast Saccharomyces cerevisiae acidifies the vacuolar lumen and generates an electrochemical gradient across the vacuole membrane. We have investigated the role of compartment acidification of the vacuolar system in the sorting of vacuolar proteins. Strains with chromosomal disruptions of genes (delta vat) encoding the A (69 x 10(3) M(r)), B (57 x 10(3) M(r)) or c (16 x 10(3) M(r)) subunits of the vacuolar ATPase accumulate and secrete precursor forms of the soluble vacuolar hydrolases carboxypeptidase Y and proteinase A. A kinetic analysis suggests that these precursor proteins accumulate in, and are secreted from, the Golgi complex or post-Golgi vesicles. In addition, subcellular fractionation shows that vacuolar hydrolase-invertase hybrid proteins are inefficiently localized to the vacuole in delta vat strains. This result suggests that the vat mutations cause a steady-state defect in vacuolar protein sorting. The vat mutations also affect the sorting of vacuolar membrane proteins. Precursor forms of alkaline phosphatase are accumulated in vat mutant cells, but to a lesser extent than is seen for the soluble vacuolar hydrolases. This finding, coupled with the insensitivity of alkaline phosphatase to the ATPase inhibitor bafilomycin A1, suggests that vacuolar membrane protein sorting is less sensitive to changes in lumenal pH when compared with the targeting of soluble vacuolar proteins. These results indicate that acidification of the vacuolar system is important for efficient sorting of soluble proteins to the vacuole.
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Banta, L. M., J. S. Robinson, D. J. Klionsky, and S. D. Emr. "Organelle assembly in yeast: characterization of yeast mutants defective in vacuolar biogenesis and protein sorting." Journal of Cell Biology 107, no. 4 (1988): 1369–83. http://dx.doi.org/10.1083/jcb.107.4.1369.
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Yeast vacuole protein targeting (vpt) mutants exhibit defects in the sorting and processing of multiple vacuolar hydrolases. To evaluate the impact these vpt mutations have on the biogenesis and functioning of the lysosome-like vacuole, we have used light and electron microscopic techniques to analyze the vacuolar morphology in the mutants. These observations have permitted us to assign the vpt mutants to three distinct classes. The class A vpt mutants (26 complementation groups) contain 1-3 large vacuoles that are morphologically indistinguishable from those in the parental strain, suggesting that only a subset of the proteins destined for delivery to this compartment is mislocalized. One class A mutant (vpt13) is very sensitive to low pH and exhibits a defect in vacuole acidification. Consistent with a potential role for vacuolar pH in protein sorting, we found that bafilomycin A1, a specific inhibitor of the vacuolar ATPase, as well as the weak base ammonium acetate and the proton ionophore carbonyl cyanide m-chlorophenylhydrazone, collapse the pH gradient across the vacuolar membrane and cause the missorting and secretion of two vacuolar hydrolases in wild-type cells. Mutants in the three class B vpt complementation groups exhibit a fragmented vacuole morphology. In these mutants, no large normal vacuoles are observed. Instead, many (20-40) smaller vacuole-like organelles accumulate. The class C vpt mutants, which constitute four complementation groups, exhibit extreme defects in vacuole biogenesis. The mutants lack any organelle resembling a normal vacuole but accumulate other organelles including vesicles, multilamellar membrane structures, and Golgi-related structures. Heterozygous class C zygotes reassemble normal vacuoles rapidly, indicating that some of the accumulated aberrant structures may be intermediates in vacuole formation. These class C mutants also exhibit sensitivity to osmotic stress, suggesting an osmoregulatory role for the vacuole. The vpt mutants should provide insights into the normal physiological role of the vacuole, as well as allowing identification of components required for vacuole protein sorting and/or vacuole assembly.
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Steele-Mortimer, Olivia, Maryse St-Louis, Martin Olivier, and B. Brett Finlay. "Vacuole Acidification Is Not Required for Survival ofSalmonella enterica Serovar Typhimurium within Cultured Macrophages and Epithelial Cells." Infection and Immunity 68, no. 9 (2000): 5401–4. http://dx.doi.org/10.1128/iai.68.9.5401-5404.2000.
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ABSTRACT Phagosome acidification is an important component of the microbicidal response by infected eukaryotic cells. Thus, intracellular pathogens that reside within phagosomes must either block phagosome acidification or be able to survive at low pH. In this work, we studied the effect of phagosomal acidification on the survival of intracellular Salmonella enterica serovar Typhimurium in different cell types. Bafilomycin A1, a specific inhibitor of the vacuolar proton-ATPases, was used to block acidification of salmonella-containing vacuoles. We found that in several epithelial cell lines, treatment with bafilomycin A1 had no effect on intracellular survival or replication. Furthermore, although acidification was essential for Salmonella intracellular survival in J774 cultured macrophages, as reported previously (13), it is not essential in other macrophage cell lines. These data suggest that vacuolar acidification may play a role in intracellular survival of salmonellae only under certain conditions and in specific cell types.