Insight into Early-Stage Unfolding of GPI-Anchored Human Prion Protein.
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SUBMITTER: Wu EL
PROVIDER: S-EPMC4656879 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Tissue inhibitor of metalloproteinase 1 (TIMP-1) controls matrix metalloproteinase (MMP) activity through 1:1 stochiometric binding. Human TIMP-1 fused to a glycosylphosphatidylinositol (GPI) anchor (TIMP-1-GPI) shifts the activity of TIMP-1 from the extracellular matrix to the cell surface. TIMP-1-GPI treated renal cell carcinoma cells (RCC) show increased apoptosis and reduced proliferation. Transcriptomic profiling and regulatory pathway mapping were used to identify potential mechanisms driving these effects. Significant changes in inhibitor of DNA binding (IDs), TGF-β1/SMAD and BMP pathways resulted from TIMP-1-GPI treatment. These events were linked to reduced TGF-β1 signaling mediated by inhibition of proteolytic processing of latent TGF-β1 by TIMP-1-GPI. Activity of TIMP-1 from the extracellular matrix to the cell surface. TIMP-1-GPI treated renal cell carcinoma cells (RCC) show increased apoptosis and reduced proliferation. Transcriptomic profiling and regulatory pathway mapping were used to identify potential mechanisms driving these effects. Significant changes in inhibitor of DNA binding (IDs), TGF-β1/SMAD and BMP pathways resulted from TIMP-1-GPI treatment. These events were linked to reduced TGF-β1 signaling mediated by inhibition of proteolytic processing of latent TGF-β1 by TIMP-1-GPI. Renal cell carcinoma cells were transfected with empty vector, rhTimp1 and 2 concentrations of Timp1-GPI fusion protein
2012-08-23 | E-GEOD-40301 | biostudies-arrayexpress
Project description:Tissue inhibitor of metalloproteinase 1 (TIMP-1) controls matrix metalloproteinase (MMP) activity through 1:1 stochiometric binding. Human TIMP-1 fused to a glycosylphosphatidylinositol (GPI) anchor (TIMP-1-GPI) shifts the activity of TIMP-1 from the extracellular matrix to the cell surface. TIMP-1-GPI treated renal cell carcinoma cells (RCC) show increased apoptosis and reduced proliferation. Transcriptomic profiling and regulatory pathway mapping were used to identify potential mechanisms driving these effects. Significant changes in inhibitor of DNA binding (IDs), TGF-β1/SMAD and BMP pathways resulted from TIMP-1-GPI treatment. These events were linked to reduced TGF-β1 signaling mediated by inhibition of proteolytic processing of latent TGF-β1 by TIMP-1-GPI. Activity of TIMP-1 from the extracellular matrix to the cell surface. TIMP-1-GPI treated renal cell carcinoma cells (RCC) show increased apoptosis and reduced proliferation. Transcriptomic profiling and regulatory pathway mapping were used to identify potential mechanisms driving these effects. Significant changes in inhibitor of DNA binding (IDs), TGF-β1/SMAD and BMP pathways resulted from TIMP-1-GPI treatment. These events were linked to reduced TGF-β1 signaling mediated by inhibition of proteolytic processing of latent TGF-β1 by TIMP-1-GPI.
2012-08-23 | GSE40301 | GEO
Project description:BackgroundMutations in PMM2 impair phosphomannomutase-2 activity and cause the most frequent congenital disorder of glycosylation, PMM2-CDG. Mannose-1-phosphate, that is deficient in this disorder, is also implicated in the biosynthesis of glycosylphosphatidyl inositol (GPI) anchors.ObjectiveTo evaluate whether GPI-anchor and GPI-anchored proteins are defective in PMM2-CDG patients.MethodsThe expression of GPI-anchor and seven GPI-anchored proteins was evaluated by flow cytometry in different cell types from twelve PMM2-CDG patients. Additionally, neutrophil CD16 and plasma hepatic proteins were studied by Western blot. Transferrin glycoforms were evaluated by HPLC.ResultsPatients and controls had similar surface expression of GPI-anchor and most GPI-anchored proteins. Nevertheless, patients displayed a significantly diminished binding of two anti-CD16 antibodies (3G8 and KD1) to neutrophils and also of anti-CD14 (61D3) to monocytes. Interestingly, CD16 immunostaining and asialotransferrin levels significantly correlated with patients' age. Analysis by flow cytometry of CD14 with M?P9, and CD16 expression in neutrophils by Western blot using H-80 ruled out deficiencies of these antigens.ConclusionsPMM2 mutations do not impair GPI-anchor or GPI-anchored protein expression. However, the glycosylation anomalies caused by PMM2 mutations might affect the immunoreactivity of monoclonal antibodies and lead to incorrect conclusions about the expression of different proteins, including GPI-anchored proteins. Neutrophils and monocytes are sensitive to PMM2 mutations, leading to abnormal glycosylation in immune receptors, which might potentially affect their affinity to their ligands, and contribute to infection. This study also confirms less severe hypoglycosylation defects in older PMM2-CDG patients.
| S-EPMC4016514 | biostudies-literature
Project description:Endoplasmic reticulum (ER) stress and unfolded protein response are cells' survival strategies to thwart disruption of proteostasis. Tumor cells are continuously being challenged by ER stress. The prion protein, PrP, normally a glycosylphosphatidylinositol (GPI)-anchored protein exists as a pro-PrP retaining its GPI-peptide signal sequence in human pancreatic ductal cell adenocarcinoma (PDAC). Higher abundance of pro-PrP indicates poorer prognosis in PDAC patients. The reason why PDAC cells express pro-PrP is unknown. Here, we report that persistent ER stress causes conversion of GPI-anchored PrP to pro-PrP via a conserved ATF6-miRNA449c-5p-PIGV axis. Mouse neurons and AsPC-1, a PDAC cell line, express GPI-anchored PrP. However, continuous culture of these cells with the ER stress inducers thapsigargin or brefeldin A results in the conversion of a GPI-anchored PrP to pro-PrP. Such a conversion is reversible; removal of the inducers allows the cells to re-express a GPI-anchored PrP. Mechanistically, persistent ER stress increases the abundance of an active ATF6, which increases the level of miRNA449c-5p (miR449c-5p). By binding the mRNA of PIGV at its 3'-UTRs, miR449c-5p suppresses the level of PIGV, a mannosyltransferase pivotal in the synthesis of the GPI anchor. Reduction of PIGV leads to disruption of the GPI anchor assembly, causing pro-PrP accumulation and enhancing cancer cell migration and invasion. The importance of ATF6-miR449c-5p-PIGV axis is recapitulated in PDAC biopsies as the higher levels of ATF6 and miR449c-5p and lower levels of PIGV are markers of poorer outcome for patients with PDAC. Drugs targeting this axis may prevent PDAC progression.
| S-EPMC10388210 | biostudies-literature
Project description:BackgroundThe accumulation of the misfolded forms of cellular prion protein, i.e. prions (PrPSc), in the brain is one of the crucial characteristics of fatal neurodegenerative disorders, called transmissible spongiform encephalopathies (TSEs). Cellular prion protein is normally linked to the cell surface by the glycosylphosphatidylinositol (GPI) anchor. There is accumulating evidence that the GPI-anchorless prion protein may act as an accelerator of formation and propagation of prions. In the TSE affected human brain we have previously discovered a novel GPI-anchorless prion protein fragment, named PrP226*, which ends with the tyrosine 226. This fragment can be labeled specifically by the monoclonal antibody V5B2.MethodsWe developed a DELFIA based assay for quick and sensitive detection of the PrP226* fragment in human brain tissue homogenates. By calculating the ratio between the signals of native (N) and denatured (D) samples applied to the assay we were able to observe significant difference between 24 TSE affected brains and 10 control brains. The presence of PrP226* in brain tissue was confirmed by western blot.ResultsOur results demonstrate that PrP226* is present in small quantities in healthy human brain, whereas in degenerated brain it accumulates in prion aggregates, proportionally to PrPSc. Samples with high D/N ratio generally comprised more proteinase K resistant PrP, while no correlation was found between the quantity of PrP226* and standard classification of Creutzfeldt-Jakob disease (CJD).ConclusionsIn the present study we show that the PrP226* fragment accumulates in prion aggregates and after being released from them by a denaturation procedure, could serve as a proteinase K digestion independent biomarker for human TSEs. The PrP226* assay described in this paper offers a tool to follow and study this unique anchorless PrP fragment in various parts of human brain and possibly also in other tissues and body fluids.
| S-EPMC3849060 | biostudies-literature
Project description:A glycosylphosphatidylinositol (GPI) derivative with biotin linked to its mannose III 6-O-position was prepared by a convergent strategy. This biotinylated GPI was demonstrated to bind avidinated proteins readily through biotin-avidin interaction and, therefore, can serve as a universal platform to access various biologically significant GPI-anchored protein analogues.
| S-EPMC10872333 | biostudies-literature
Project description:Decline in protein homeostasis (proteostasis) is a hallmark of cellular aging and aging-related diseases. Maintaining a balanced proteostasis requires a complex network of molecular machineries that govern protein synthesis, folding, localization, and degradation. Under proteotoxic stress, misfolded proteins that accumulate in cytosol can be imported into mitochondria for degradation via 'mitochondrial as guardian in cytosol' (MAGIC) pathway. Here we report an unexpected role of yeast Gas1, a cell wall-bound glycosylphosphatidylinositol (GPI)-anchored β-1,3-glucanosyltransferase, in differentially regulating MAGIC and ubiquitin-proteasome system (UPS). Deletion of Gas1 inhibits MAGIC but elevates polyubiquitination and UPS-mediated protein degradation. Interestingly, we found that Gas1 exhibits mitochondrial localization attributed to its C-terminal GPI anchor signal. But this mitochondria-associated GPI anchor signal is not required for mitochondrial import and degradation of misfolded proteins via MAGIC. By contrast, catalytic inactivation of Gas1 via the gas1E161Q mutation inhibits MAGIC but not its mitochondrial localization. These data suggest that the glucanosyltransferase activity of Gas1 is important for regulating cytosolic proteostasis.
| S-EPMC10245992 | biostudies-literature
Project description:Prion diseases are transmissible, lethal neurodegenerative disorders caused by accumulation of the aggregated scrapie form of the prion protein (PrPSc) after conversion of the cellular prion protein (PrPC). The glycosylphosphatidylinositol (GPI) anchor of PrPC is involved in prion disease pathogenesis, and especially sialic acid in a GPI side chain reportedly affects PrPC conversion. Thus, it is important to define the location and structure of the GPI anchor in human PrPC Moreover, the sialic acid linkage type in the GPI side chain has not been determined for any GPI-anchored protein. Here we report GPI glycan structures of human PrPC isolated from human brains and from brains of a knock-in mouse model in which the mouse prion protein (Prnp) gene was replaced with the human PRNP gene. LC-electrospray ionization-MS analysis of human PrPC from both biological sources indicated that Gly229 is the ω site in PrPC to which GPI is attached. Gly229 in human PrPC does not correspond to Ser231, the previously reported ω site of Syrian hamster PrPC We found that ∼41% and 28% of GPI anchors in human PrPCs from human and knock-in mouse brains, respectively, have N-acetylneuraminic acid in the side chain. Using a sialic acid linkage-specific alkylamidation method to discriminate α2,3 linkage from α2,6 linkage, we found that N-acetylneuraminic acid in PrPC's GPI side chain is linked to galactose through an α2,3 linkage. In summary, we report the GPI glycan structure of human PrPC, including the ω-site amino acid for GPI attachment and the sialic acid linkage type.
| S-EPMC7261787 | biostudies-literature
Project description:The surface of eukaryotic cells is a multi-component fluid bilayer in which glycosylphosphatidylinositol (GPI)-anchored proteins are an abundant constituent. In this review, we discuss the complex nature of the organization and dynamics of GPI-anchored proteins at multiple spatial and temporal scales. Different biophysical techniques have been utilized for understanding this organization, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, single particle tracking, and a number of super resolution methods. Major insights into the organization and dynamics have also come from exploring the short-range interactions of GPI-anchored proteins by fluorescence (or Förster) resonance energy transfer microscopy. Based on the nanometer to micron scale organization, at the microsecond to the second time scale dynamics, a picture of the membrane bilayer emerges where the lipid bilayer appears inextricably intertwined with the underlying dynamic cytoskeleton. These observations have prompted a revision of the current models of plasma membrane organization, and suggest an active actin-membrane composite.
| S-EPMC4727430 | biostudies-literature
Project description:The decline in protein homeostasis (proteostasis) is a hallmark of cellular aging and aging-related diseases. Maintaining a balanced proteostasis requires a complex network of molecular machineries that govern protein synthesis, folding, localization, and degradation. Under proteotoxic stress, misfolded proteins that accumulate in cytosol can be imported into mitochondria for degradation through the "mitochondrial as guardian in cytosol" (MAGIC) pathway. Here, we report an unexpected role of Gas1, a cell wall-bound glycosylphosphatidylinositol (GPI)-anchored β-1,3-glucanosyltransferase in the budding yeast, in differentially regulating MAGIC and ubiquitin-proteasome system (UPS). Deletion of GAS1 inhibits MAGIC but elevates protein ubiquitination and UPS-mediated protein degradation. Interestingly, we found that the Gas1 protein exhibits mitochondrial localization attributed to its C-terminal GPI anchor signal. But this mitochondria-associated GPI anchor signal is not required for mitochondrial import and degradation of misfolded proteins through MAGIC. By contrast, catalytic inactivation of Gas1 via the gas1-E161Q mutation inhibits MAGIC but not its mitochondrial localization. These data suggest that the glucanosyltransferase activity of Gas1 is important for regulating cytosolic proteostasis.
| S-EPMC10917523 | biostudies-literature