Prion propagation involves a templating reaction in which the infectious form of the prion protein (PrPSc) binds to the cellular form (PrPC), generating additional molecules of PrPSc. While several ...regions of the PrPC molecule have been suggested to play a role in PrPSc formation based on in vitro studies, the contribution of these regions in vivo is unclear. Here, we report that mice expressing PrP deleted for a short, polybasic region at the N terminus (residues 23-31) display a dramatically reduced susceptibility to prion infection and accumulate greatly reduced levels of PrPSc. These results, in combination with biochemical data, demonstrate that residues 23-31 represent a critical site on PrPC that binds to PrPSc and is essential for efficient prion propagation. It may be possible to specifically target this region for treatment of prion diseases as well as other neurodegenerative disorders due to beta -sheet-rich oligomers that bind to PrPC.
Prion propagation involves a templating reaction in which the infectious form of the prion protein (PrP(Sc)) binds to the cellular form (PrP(C)), generating additional molecules of PrP(Sc). While ...several regions of the PrP(C) molecule have been suggested to play a role in PrP(Sc) formation based on in vitro studies, the contribution of these regions in vivo is unclear. Here, we report that mice expressing PrP deleted for a short, polybasic region at the N terminus (residues 23-31) display a dramatically reduced susceptibility to prion infection and accumulate greatly reduced levels of PrP(Sc). These results, in combination with biochemical data, demonstrate that residues 23-31 represent a critical site on PrP(C) that binds to PrP(Sc) and is essential for efficient prion propagation. It may be possible to specifically target this region for treatment of prion diseases as well as other neurodegenerative disorders due to β-sheet-rich oligomers that bind to PrP(C).
Estrogen (E2) signaling is conveyed by the transcription factors estrogen receptor (ER) α and β. ERs modulate the expression of genes involved in cellular proliferation, motility, and death. The ...regulation of transcription by E2-ERα through binding to estrogen-responsive elements (EREs) in DNA constitutes the ERE-dependent signaling pathway. E2-ERα also modulates gene expression by interacting with transregulators bound to cognate DNA-regulatory elements, and this regulation is referred to as the ERE-independent signaling pathway. The relative importance of the ERE-independent pathway in E2-ERα signaling is unclear. To address this issue, we engineered an ERE-binding defective ERα mutant (ERαEBD) by changing residues in an α-helix of the protein involved in DNA binding to render the receptor functional only through the ERE-independent signaling pathway. Using recombinant adenovirus-infected ER-negative MDA-MB-231 cells derived from a breast adenocarcinoma, we found that E2-ERαEBD modulated the expression of a subset of ERα-responsive genes identified by microarrays and verified by quantitative PCR. However, E2-ERαEBD did not affect cell cycle progression, cellular growth, death, or motility in contrast to E2-ERα.ERαEBD in the presence of E2 was also ineffective in inducing phenotypic alterations in ER-negative U-2OS cells derived from an osteosarcoma. E2-ERα, on the other hand, effectively repressed growth in this cell line. Our findings suggest that genomic responses from the ERE-dependent signaling pathway are required for E2-ERα to induce alterations in cellular responses.
Estrogen hormone (E2) signaling is primarily conveyed by the estrogen receptors (ER) α and β. ERs are encoded by two distinct genes and share varying degrees of domain-specific structural/functional ...similarities. ERs mediate a complex array of nuclear and non-nuclear events critical for the homeodynamic regulation of various tissue functions. The canonical nuclear signaling involves the interaction of ERα and ERβ with specific DNA sequences, the so-called estrogen responsive elements (EREs). This interaction constitutes the initial step in ERE-dependent signaling in which ERβ is a weaker transcription factor than ERα in response to E2. However, it remains unclear why transactivation potencies of ER subtypes differ. Studies suggest that the amino-terminus, the least conserved structural region, of ERβ, but not that of ERα, impairs the ability of the receptor to bind to ERE independent of E2. Although the impaired ERβ–ERE interaction contributes, it is not sufficient to explain the weak transactivation potency of the receptor. It appears that the lack of transactivation ability and of the capability of the amino-terminus of ERβ, as opposed to that of ERα, to functionally interact with the carboxyl-terminal hormone-dependent activation domain is also critical for the receptor-specific activity. Thus, the structurally distinct amino-termini of ERs are important determinants in defining the function of ER-subtypes in the ERE-dependent pathway. This could differentially affect the physiology and pathophysiology of E2 signaling.
Estrogen (E2) signaling is conveyed by the transcription factors estrogen
receptor (ER) α and β. ERs modulate the expression of genes
involved in cellular proliferation, motility, and death. The ...regulation of
transcription by E2-ERα through binding to estrogen-responsive elements
(EREs) in DNA constitutes the ERE-dependent signaling pathway. E2-ERα
also modulates gene expression by interacting with transregulators bound to
cognate DNA-regulatory elements, and this regulation is referred to as the
ERE-independent signaling pathway. The relative importance of the
ERE-independent pathway in E2-ERα signaling is unclear. To address this
issue, we engineered an ERE-binding defective ERα mutant
(ERα
EBD
) by changing residues in an α-helix of the
protein involved in DNA binding to render the receptor functional only through
the ERE-independent signaling pathway. Using recombinant adenovirus-infected
ER-negative MDA-MB-231 cells derived from a breast adenocarcinoma, we found
that E2-ERα
EBD
modulated the expression of a subset of
ERα-responsive genes identified by microarrays and verified by
quantitative PCR. However, E2-ERα
EBD
did not affect cell
cycle progression, cellular growth, death, or motility in contrast to
E2-ERα.ERα
EBD
in the presence of E2 was also
ineffective in inducing phenotypic alterations in ER-negative U-2OS cells
derived from an osteosarcoma. E2-ERα, on the other hand, effectively
repressed growth in this cell line. Our findings suggest that genomic
responses from the ERE-dependent signaling pathway are required for
E2-ERα to induce alterations in cellular responses.
Estrogen (E2) signaling is conveyed by the transcription factors estrogen receptor (ER) α and β. ERs modulate the expression
of genes involved in cellular proliferation, motility, and death. The ...regulation of transcription by E2-ERα through binding
to estrogen-responsive elements (EREs) in DNA constitutes the ERE-dependent signaling pathway. E2-ERα also modulates gene
expression by interacting with transregulators bound to cognate DNA-regulatory elements, and this regulation is referred to
as the ERE-independent signaling pathway. The relative importance of the ERE-independent pathway in E2-ERα signaling is unclear.
To address this issue, we engineered an ERE-binding defective ERα mutant (ERα EBD ) by changing residues in an α-helix of the protein involved in DNA binding to render the receptor functional only through
the ERE-independent signaling pathway. Using recombinant adenovirus-infected ER-negative MDA-MB-231 cells derived from a breast
adenocarcinoma, we found that E2-ERα EBD modulated the expression of a subset of ERα-responsive genes identified by microarrays and verified by quantitative PCR.
However, E2-ERα EBD did not affect cell cycle progression, cellular growth, death, or motility in contrast to E2-ERα.ERα EBD in the presence of E2 was also ineffective in inducing phenotypic alterations in ER-negative U-2OS cells derived from an
osteosarcoma. E2-ERα, on the other hand, effectively repressed growth in this cell line. Our findings suggest that genomic
responses from the ERE-dependent signaling pathway are required for E2-ERα to induce alterations in cellular responses.
Estrogen (E2) signaling is conveyed by the transcription factors estrogen receptor (ER) {alpha} and b. ERs modulate the expression of genes involved in cellular proliferation, motility, and death. ...The regulation of transcription by E2-ER{alpha} through binding to estrogen-responsive elements (EREs) in DNA constitutes the ERE-dependent signaling pathway. E2-ER{alpha} also modulates gene expression by interacting with transregulators bound to cognate DNA-regulatory elements, and this regulation is referred to as the ERE- independent signaling pathway. The relative importance of the ERE-independent pathway in E2-ER{alpha} signaling is unclear. To address this issue, we engineered an ERE-binding defective ER{alpha} mutant (ER{alpha} sub(EBD)) by changing residues in an {alpha}-helix of the protein involved in DNA binding to render the receptor functional only through the ERE-independent signaling pathway. Using recombinant adenovirus- infected ER-negative MDA-MB-231 cells derived from a breast adenocarcinoma, we found that E2- ER{alpha} sub(EBD) modulated the expression of a subset of ER{alpha}-responsive genes identified by microarrays and verified by quantitative PCR. However, E2-ER{alpha} sub(EBD) did not affect cell cycle progression, cellular growth, death, or motility in contrast to E2-ER{alpha}.ER{alpha} sub(EBD) in the presence of E2 was also ineffective in inducing phenotypic alterations in ER-negative U-2OS cells derived from an osteosarcoma. E2-ER{alpha}, on the other hand, effectively repressed growth in this cell line. Our findings suggest that genomic responses from the ERE-dependent signaling pathway are required for E2- ER{alpha} to induce alterations in cellular responses.
Estrogen hormone (E2) signaling is primarily conveyed by the estrogen receptors (ER) alpha and beta. ERs are encoded by two distinct genes and share varying degrees of domain-specific ...structural/functional similarities. ERs mediate a complex array of nuclear and non-nuclear events critical for the homeodynamic regulation of various tissue functions. The canonical nuclear signaling involves the interaction of ERalpha and ERbeta with specific DNA sequences, the so-called estrogen responsive elements (EREs). This interaction constitutes the initial step in ERE-dependent signaling in which ERbeta is a weaker transcription factor than ERalpha in response to E2. However, it remains unclear why transactivation potencies of ER subtypes differ. Studies suggest that the amino-terminus, the least conserved structural region, of ERbeta, but not that of ERalpha, impairs the ability of the receptor to bind to ERE independent of E2. Although the impaired ERbeta-ERE interaction contributes, it is not sufficient to explain the weak transactivation potency of the receptor. It appears that the lack of transactivation ability and of the capability of the amino-terminus of ERbeta, as opposed to that of ERalpha, to functionally interact with the carboxyl-terminal hormone-dependent activation domain is also critical for the receptor-specific activity. Thus, the structurally distinct amino-termini of ERs are important determinants in defining the function of ER-subtypes in the ERE-dependent pathway. This could differentially affect the physiology and pathophysiology of E2 signaling.
This overview compares and synthesizes the articles of this theme issue. It highlights that progress has been made toward the goals of marine ecosystem-based management (EBM) in tropical regions. ...Four key findings are presented: (1) Tailoring EBM to specific contexts ultimately determines success. (2) Employment of a wide variety of marine management tools is necessary and complementary to spatial management through marine protected areas (MPAs). (3) Although EBM approaches may be usefully defined using oceanographic and ecological principles, the design and implementation of feasible EBM will require, at least, equal consideration of governance and social conditions. (4) Interest in EBM has grown rapidly; however, this approach only improves ocean resource management if sustained by commitments from, at least, policymakers, resource users, and donors. Practical program design principles stressing the importance of leadership development, awareness raising, institutional reform, conflict resolution, adaptation, and evaluation are derived from these case studies and comparative analyses. A suite of empirically based EBM evaluative criteria, which can be adapted to local contexts, are suggested to fostered learning and progress.
Cerebroside sulfate activator (CS-Act) is a small compact protein which binds and solubilizes certain glycosphingolipids. Following the recent publication of the purification and preliminary sequence ...of pig kidney CS-Act Fluharty, A.L., Katona, Z., Meek, W.E., Frei, K., & Fowler, A.V. (1992) Biochem. Med. Metab. Biol. 47, 66-85, we now report the primary sequence of the C-terminal portion of this protein and the assignment of the three disulfide bonds. Cyanogen bromide (CNBr) treatment of native CS-Act produced three major and several minor peptide fragments. Analysis of one HPLC-purified fragment revealed the C-terminus 14 amino acid sequence. This established the length of the native protein at 79 residues. In conjunction with the sequence data for one other major HPLC-purified CNBr fragment, it could be concluded that the three intrachain disulfide bonds were located at half-cystine residues 4 and 77, 7 and 71, and 36 and 47. Mass spectrometry (fast atom bombardment and electrospray ionization) showed the molecular weight of the major component of the CS-Act preparation to be 9720.5 Da, which was in close agreement with the calculated mass of the 79 amino acid peptide with five covalently attached sugar residues and three internal disulfide bonds. The mass spectrometric molecular weight measurements also showed that the CS-Act preparation possessed microheterogeneity in its carbohydrate moiety, as less intense signals corresponded to species containing (in decreasing order of abundance) two, one, four, and three sugar residues.
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