Phuong Nguyen - Academia.edu (original) (raw)

Papers by Phuong Nguyen

Research paper thumbnail of Pharmacological and Toxicological Properties of the Potent Oral γ-Secretase Modulator BPN-15606

The Journal of pharmacology and experimental therapeutics, Jan 17, 2017

Alzheimer's disease is characterized neuropathologically by an abundance of 1) neuritic plaqu... more Alzheimer's disease is characterized neuropathologically by an abundance of 1) neuritic plaques, which are primarily composed of a fibrillar 42 amino acid amyloid β peptide, as well as 2) neurofibrillary tangles composed of aggregates of hyperphosporylated tau. Elevations in the concentrations of the Aβ42 peptide in the brain, as a result of either increased production or decreased clearance are postulated to initiate and drive the AD pathological process. We initially introduced a novel class of bridged aromatics referred to as γ-secretase modulators that inhibited the production of the Aβ42 peptide and to a lesser degree the Aβ40 peptide while concomitantly increasing the production of the carboxyl-truncated Aβ38 and Aβ37 peptides. These modulators potently lower Aβ42 levels without inhibiting the γ-secretase-mediated proteolysis of Notch or causing accumulation of carboxyl-terminal fragments of APP. Herein we report a large number of pharmacological studies and early assessme...

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Research paper thumbnail of Design and synthesis of aminothiazole modulators of the gamma-secretase enzyme

Bioorganic & medicinal chemistry letters, Jan 6, 2016

The design and construction of a series of novel aminothiazole-derived γ-secretase modulators is ... more The design and construction of a series of novel aminothiazole-derived γ-secretase modulators is described. The incorporation of heterocyclic replacements of the terminal phenyl D-ring of lead compound 1 was conducted in order to align potency with favorable drug-like properties. γ-Secretase modulator 28 displayed good activity for in vitro inhibition of Aβ42, as well as substantial improvement in ADME and physicochemical properties, including aqueous solubility. Pharmacokinetic evaluation of compound 28 in mice revealed good brain penetration, as well as good clearance, half-life, and volume of distribution which collectively support the continued development of this class of compounds.

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Research paper thumbnail of Using supported bilayers to study the spatiotemporal organization of membrane-bound proteins

Methods in cell biology, 2015

Cell division in prokaryotes and eukaryotes is commonly initiated by the well-controlled binding ... more Cell division in prokaryotes and eukaryotes is commonly initiated by the well-controlled binding of proteins to the cytoplasmic side of the cell membrane. However, a precise characterization of the spatiotemporal dynamics of membrane-bound proteins is often difficult to achieve in vivo. Here, we present protocols for the use of supported lipid bilayers to rebuild the cytokinetic machineries of cells with greatly different dimensions: the bacterium Escherichia coli and eggs of the vertebrate Xenopus laevis. Combined with total internal reflection fluorescence microscopy, these experimental setups allow for precise quantitative analyses of membrane-bound proteins. The protocols described to obtain glass-supported membranes from bacterial and vertebrate lipids can be used as starting points for other reconstitution experiments. We believe that similar biochemical assays will be instrumental to study the biochemistry and biophysics underlying a variety of complex cellular tasks, such as...

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Research paper thumbnail of Immunodominance of major histocompatibility complex class I-restricted influenza virus epitopes can be influenced by the T-cell receptor repertoire

Journal of virology, 1995

We have used T-cell receptor beta-chain transgenic mice to determine the effects of a limited T-c... more We have used T-cell receptor beta-chain transgenic mice to determine the effects of a limited T-cell receptor repertoire on major histocompatibility complex class I-restricted epitope selection during the course of an influenza virus infection. Analysis of T-cell hybridomas generated from wild-type and transgenic mice demonstrated that the viral epitope recognized depended on the available T-cell receptor repertoire. Wild-type T-cell hybridomas recognized epitopes derived from the nucleoprotein and basic polymerase molecules, whereas hybridomas generated from transgenic mice recognized epitopes derived from the nonstructural protein and the matrix protein. There was no overlap in specificity between the two panels of hybridomas. This reciprocal pattern of specificity was also apparent in cytoxicity assays with brochoalveolar lavage cells isolated from the lungs of influenza virus-infected mice. T-cell receptor usage in the transgenic hybridomas was very restricted, with only one V a...

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Research paper thumbnail of Relativizing Small Complexity Classes and Their Theories

Lecture Notes in Computer Science, 2007

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Research paper thumbnail of Pannexin2 oligomers localize in the membranes of endosomal vesicles in mammalian cells while Pannexin1 channels traffic to the plasma membrane

Frontiers in Cellular Neuroscience, 2015

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Research paper thumbnail of Client-side web mining for community formation in peer-to-peer environments

ACM SIGKDD Explorations Newsletter, 2006

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Research paper thumbnail of Scientific Services on the Cloud

Handbook of Cloud Computing, 2010

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Research paper thumbnail of ERbeta Binds N-CoR in the Presence of Estrogens via an LXXLL-like Motif in the N-CoR C-terminus

Nuclear receptor, Jan 28, 2003

Nuclear receptors (NRs) usually bind the corepressors N-CoR and SMRT in the absence of ligand or ... more Nuclear receptors (NRs) usually bind the corepressors N-CoR and SMRT in the absence of ligand or in the presence of antagonists. Agonist binding leads to corepressor release and recruitment of coactivators. Here, we report that estrogen receptor beta (ERbeta) binds N-CoR and SMRT in the presence of agonists, but not antagonists, in vitro and in vivo. This ligand preference differs from that of ERalpha interactions with corepressors, which are inhibited by estradiol, and resembles that of ERbeta interactions with coactivators. ERbeta /N-CoR interactions involve ERbeta AF-2, which also mediates coactivator recognition. Moreover, ERbeta recognizes a sequence (PLTIRML) in the N-CoR C-terminus that resembles coactivator LXXLL motifs. Inhibition of histone deacetylase activity specifically potentiates ERbeta LBD activity, suggesting that corepressors restrict the activity of AF-2. We conclude that the ER isoforms show completely distinct modes of interaction with a physiologically importa...

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Research paper thumbnail of A conserved lysine in the estrogen receptor DNA binding domain regulates ligand activation profiles at AP-1 sites, possibly by controlling interactions with a modulating repressor

Nuclear receptor, Jan 7, 2004

BACKGROUND: Estrogen receptors alpha and beta (ERalpha and ERbeta) differentially activate genes ... more BACKGROUND: Estrogen receptors alpha and beta (ERalpha and ERbeta) differentially activate genes with AP-1 elements. ERalpha activates AP-1 targets via activation functions with estrogens (the AF-dependent pathway), whereas ERbeta, and a short version of ERalpha (ERalpha DBD-LBD) activate only with anti-estrogens (AF-independent pathway). The DNA binding domain (DBD) plays an important role in both pathways, even though neither pathway requires ERE recognition. RESULTS: Mutations of a highly conserved DBD lysine (ERalpha.K206A/G), lead to super-activation of AP-1 through activation function dependent pathways, up to 200 fold. This super-activity can be elicited either through ER AFs 1 or 2, or that of a heterologous activation function (VP16). The homologous substitution in ERbeta, K170A, or in ERalpha DBD-LBD leads to estrogen-dependent AP-1 activation and loss of the usually potent anti-estrogen effects. Each of numerous K206 substitutions in ERalpha, except K206R, eliminates anti...

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Research paper thumbnail of Dual roles of the transmembrane protein p23/TMP21 in the modulation of amyloid precursor protein metabolism

Molecular neurodegeneration, Jan 8, 2007

Alzheimer's disease (AD) is characterized by cerebral deposition of beta-amyloid (Abeta) pept... more Alzheimer's disease (AD) is characterized by cerebral deposition of beta-amyloid (Abeta) peptides. Abeta is released from ectodomain cleaved amyloid precursor protein (APP) via intramembranous proteolysis by gamma-secretase, a complex consisting of presenilin and a few other proteins. p23/TMP21, a member of the p24 family type I transmembrane proteins, was recently identified as a presenilin complex component capable of modulating gamma-secretase cleavage. The p24 family proteins form oligomeric complexes and regulate vesicular trafficking in the early secretory pathway, but their role in APP trafficking has not been investigated. Here, we report that siRNA-mediated depletion of p23 in N2a neuroblastoma and HeLa cells produces concomitant knockdown of additional p24 family proteins and increases secretion of sAPP. Furthermore, intact cell and cell-free Abeta production increases following p23 knockdown, similar to data reported earlier using HEK293 cells. However, we find that p...

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Research paper thumbnail of Establishment of a critical-sized alveolar defect in the rat: a model for human gingivoperiosteoplasty

Plastic and reconstructive surgery, 2009

Despite technical advancement, treatment of congenital alveolar clefts has remained controversial... more Despite technical advancement, treatment of congenital alveolar clefts has remained controversial. Currently, primary alveolar cleft repair (i.e., gingivoperiosteoplasty) has a 41 to 73 percent success rate. However, the remaining patients have persistent alveolar bone defects requiring secondary grafting procedures. Morbidity of secondary procedures includes pain, graft resorption, extrusion or infection, and graft or tooth loss. The authors present a novel rat alveolar defect model designed to facilitate investigation of therapeutics aimed at improving bone formation following primary alveolar cleft repair in humans. Sixteen 8-week-old Sprague-Dawley rats underwent creation of a 7 x 4 x 3-mm complete alveolar defect from the maxillary incisors to the zygomatic arch. Four animals were humanely killed at each of the following time points: 0, 4, 8, and 12 weeks. Morphometric analysis of the alveolar defect was determined by means of micro-computed tomography and histology. Micro-comp...

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Research paper thumbnail of Improved diabetic wound healing through topical silencing of p53 is associated with augmented vasculogenic mediators

Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society

Diabetes is characterized by several poorly understood phenomena including dysfunctional wound he... more Diabetes is characterized by several poorly understood phenomena including dysfunctional wound healing and impaired vasculogenesis. p53, a master cell cycle regulator, is upregulated in diabetic wounds and has recently been shown to play a regulatory roles in vasculogenic pathways. We have previously described a novel method to topically silence target genes in a wound bed with small interfering (si)RNA. We hypothesized that silencing p53 results in improved diabetic wound healing and augmentation of vasculogenic mediators. Paired 4-mm stented wounds were created on diabetic db/db mice. Topically applied p53 siRNA, evenly distributed in an agarose matrix, was applied to wounds at postwound day 1 and 7 (matrix alone and nonsense siRNA served as controls). Animals were sacrificed at postwound days 10 and 24. Wound time to closure was photometrically assessed, and wounds were harvested for histology, immunohistochemistry, and immunofluorescence. Vasculogenic cytokine expression was eva...

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Research paper thumbnail of CASE REPORT Treatment of a Lower Extremity Lymphocele With Intraoperative Lymphatic Mapping

Eplasty, 2013

Lower extremity lymphoceles secondary to saphenous vein grafting are exceptionally rare and there... more Lower extremity lymphoceles secondary to saphenous vein grafting are exceptionally rare and there is only 1 previously reported case in the English literature. Data on treatment of lower extremity lymphoceles are limited and based on studies of groin lymphoceles. We discuss operative resection with selective ligation of feeding lymphatic vessels as a treatment option of lower extremity lymphoceles. A 64-year-old man who had undergone coronary artery bypass grafting 6 years prior presented with a left lower extremity mass at the site where his saphenous vein had been harvested. Examination demonstrated a 12-cm, mobile, nonpulsatile mass at his medial left calf. The findings of magnetic resonance imaging were consistent with a lymphocele. Intraoperative injection of isosulfan blue dye was used to identify feeding lymphatic vessels and the lymphocele cavity was excised. Leg drains were discontinued after 3 days, and the patient was discharged home after 6 days. Operative resection with...

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Research paper thumbnail of Xenopus egg cytoplasm with intact actin

Methods in enzymology, 2014

We report optimized methods for preparing Xenopus egg extracts without cytochalasin D, that we te... more We report optimized methods for preparing Xenopus egg extracts without cytochalasin D, that we term "actin-intact egg…

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Research paper thumbnail of Organization of early frog embryos by chemical waves emanating from centrosomes

Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 5, 2014

The large cells in early vertebrate development face an extreme physical challenge in organizing ... more The large cells in early vertebrate development face an extreme physical challenge in organizing their cytoplasm. For example, amphibian embryos have to divide cytoplasm that spans hundreds of micrometres every 30 min according to a precise geometry, a remarkable accomplishment given the extreme difference between molecular and cellular scales in this system. How do the biochemical reactions occurring at the molecular scale lead to this emergent behaviour of the cell as a whole? Based on recent findings, we propose that the centrosome plays a crucial role by initiating two autocatalytic reactions that travel across the large cytoplasm as chemical waves. Waves of mitotic entry and exit propagate out from centrosomes using the Cdk1 oscillator to coordinate the timing of cell division. Waves of microtubule-stimulated microtubule nucleation propagate out to assemble large asters that position spindles for the following mitosis and establish cleavage plane geometry. By initiating these c...

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Research paper thumbnail of Spatial organization of cytokinesis signaling reconstituted in a cell-free system

Science (New York, N.Y.), Jan 10, 2014

During animal cell division, the cleavage furrow is positioned by microtubules that signal to the... more During animal cell division, the cleavage furrow is positioned by microtubules that signal to the actin cortex at the cell midplane. We developed a cell-free system to recapitulate cytokinesis signaling using cytoplasmic extract from Xenopus eggs. Microtubules grew out as asters from artificial centrosomes and met to organize antiparallel overlap zones. These zones blocked the interpenetration of neighboring asters and recruited cytokinesis midzone proteins, including the chromosomal passenger complex (CPC) and centralspindlin. The CPC was transported to overlap zones, which required two motor proteins, Kif4A and a Kif20A paralog. Using supported lipid bilayers to mimic the plasma membrane, we observed the recruitment of cleavage furrow markers, including an active RhoA reporter, at microtubule overlaps. This system opens further approaches to understanding the biophysics of cytokinesis signaling.

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Research paper thumbnail of Ciliopathy proteins establish a bipartite signaling compartment in a C. elegans thermosensory neuron

Journal of cell science, Jan 15, 2014

How signaling domains form is an important, yet largely unexplored question. Here, we show that c... more How signaling domains form is an important, yet largely unexplored question. Here, we show that ciliary proteins help establish two contiguous, yet distinct cyclic GMP (cGMP) signaling compartments in Caenorhabditis elegans thermosensory AFD neurons. One compartment, a bona fide cilium, is delineated by proteins associated with Bardet-Biedl syndrome (BBS), Meckel syndrome and nephronophthisis at its base, and requires NPHP-2 (known as inversin in mammals) to anchor a cGMP-gated ion channel within the proximal ciliary region. The other, a subcompartment with profuse microvilli and a different lipid environment, is separated from the dendrite by a cellular junction and requires BBS-8 and DAF-25 (known as Ankmy2 in mammals) for correct localization of guanylyl cyclases needed for thermosensation. Consistent with a requirement for a membrane diffusion barrier at the subcompartment base, we reveal the unexpected presence of ciliary transition zone proteins where no canonical transition z...

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Research paper thumbnail of A Synthetic Antibody Fragment Targeting Nicastrin Affects Assembly and Trafficking of γ-Secretase

The Journal of biological chemistry, Jan 12, 2014

The γ-secretase complex, composed of presenilin, nicastrin (NCT), anterior pharynx-defective 1 (A... more The γ-secretase complex, composed of presenilin, nicastrin (NCT), anterior pharynx-defective 1 (APH-1), and presenilin enhancer 2 (PEN-2), is assembled in a highly regulated manner and catalyzes the intramembranous proteolysis of many type I membrane proteins, including Notch and amyloid precursor protein. The Notch family of receptors plays important roles in cell fate specification during development and in adult tissues, and aberrant hyperactive Notch signaling causes some forms of cancer. γ-Secretase-mediated processing of Notch at the cell surface results in the generation of the Notch intracellular domain, which associates with several transcriptional coactivators involved in nuclear signaling events. On the other hand, γ-secretase-mediated processing of amyloid precursor protein leads to the production of amyloid β (Aβ) peptides that play an important role in the pathogenesis of Alzheimer disease. We used a phage display approach to identify synthetic antibodies that specific...

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Research paper thumbnail of Microtubule nucleation remote from centrosomes may explain how asters span large cells

Proceedings of the National Academy of Sciences of the United States of America, Jan 16, 2014

A major challenge in cell biology is to understand how nanometer-sized molecules can organize mic... more A major challenge in cell biology is to understand how nanometer-sized molecules can organize micrometer-sized cells in space and time. One solution in many animal cells is a radial array of microtubules called an aster, which is nucleated by a central organizing center and spans the entire cytoplasm. Frog (here Xenopus laevis) embryos are more than 1 mm in diameter and divide with a defined geometry every 30 min. Like smaller cells, they are organized by asters, which grow, interact, and move to precisely position the cleavage planes. It has been unclear whether asters grow to fill the enormous egg by the same mechanism used in smaller somatic cells, or whether special mechanisms are required. We addressed this question by imaging growing asters in a cell-free system derived from eggs, where asters grew to hundreds of microns in diameter. By tracking marks on the lattice, we found that microtubules could slide outward, but this was not essential for rapid aster growth. Polymer trea...

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Research paper thumbnail of Pharmacological and Toxicological Properties of the Potent Oral γ-Secretase Modulator BPN-15606

The Journal of pharmacology and experimental therapeutics, Jan 17, 2017

Alzheimer's disease is characterized neuropathologically by an abundance of 1) neuritic plaqu... more Alzheimer's disease is characterized neuropathologically by an abundance of 1) neuritic plaques, which are primarily composed of a fibrillar 42 amino acid amyloid β peptide, as well as 2) neurofibrillary tangles composed of aggregates of hyperphosporylated tau. Elevations in the concentrations of the Aβ42 peptide in the brain, as a result of either increased production or decreased clearance are postulated to initiate and drive the AD pathological process. We initially introduced a novel class of bridged aromatics referred to as γ-secretase modulators that inhibited the production of the Aβ42 peptide and to a lesser degree the Aβ40 peptide while concomitantly increasing the production of the carboxyl-truncated Aβ38 and Aβ37 peptides. These modulators potently lower Aβ42 levels without inhibiting the γ-secretase-mediated proteolysis of Notch or causing accumulation of carboxyl-terminal fragments of APP. Herein we report a large number of pharmacological studies and early assessme...

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Research paper thumbnail of Design and synthesis of aminothiazole modulators of the gamma-secretase enzyme

Bioorganic & medicinal chemistry letters, Jan 6, 2016

The design and construction of a series of novel aminothiazole-derived γ-secretase modulators is ... more The design and construction of a series of novel aminothiazole-derived γ-secretase modulators is described. The incorporation of heterocyclic replacements of the terminal phenyl D-ring of lead compound 1 was conducted in order to align potency with favorable drug-like properties. γ-Secretase modulator 28 displayed good activity for in vitro inhibition of Aβ42, as well as substantial improvement in ADME and physicochemical properties, including aqueous solubility. Pharmacokinetic evaluation of compound 28 in mice revealed good brain penetration, as well as good clearance, half-life, and volume of distribution which collectively support the continued development of this class of compounds.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Using supported bilayers to study the spatiotemporal organization of membrane-bound proteins

Methods in cell biology, 2015

Cell division in prokaryotes and eukaryotes is commonly initiated by the well-controlled binding ... more Cell division in prokaryotes and eukaryotes is commonly initiated by the well-controlled binding of proteins to the cytoplasmic side of the cell membrane. However, a precise characterization of the spatiotemporal dynamics of membrane-bound proteins is often difficult to achieve in vivo. Here, we present protocols for the use of supported lipid bilayers to rebuild the cytokinetic machineries of cells with greatly different dimensions: the bacterium Escherichia coli and eggs of the vertebrate Xenopus laevis. Combined with total internal reflection fluorescence microscopy, these experimental setups allow for precise quantitative analyses of membrane-bound proteins. The protocols described to obtain glass-supported membranes from bacterial and vertebrate lipids can be used as starting points for other reconstitution experiments. We believe that similar biochemical assays will be instrumental to study the biochemistry and biophysics underlying a variety of complex cellular tasks, such as...

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Research paper thumbnail of Immunodominance of major histocompatibility complex class I-restricted influenza virus epitopes can be influenced by the T-cell receptor repertoire

Journal of virology, 1995

We have used T-cell receptor beta-chain transgenic mice to determine the effects of a limited T-c... more We have used T-cell receptor beta-chain transgenic mice to determine the effects of a limited T-cell receptor repertoire on major histocompatibility complex class I-restricted epitope selection during the course of an influenza virus infection. Analysis of T-cell hybridomas generated from wild-type and transgenic mice demonstrated that the viral epitope recognized depended on the available T-cell receptor repertoire. Wild-type T-cell hybridomas recognized epitopes derived from the nucleoprotein and basic polymerase molecules, whereas hybridomas generated from transgenic mice recognized epitopes derived from the nonstructural protein and the matrix protein. There was no overlap in specificity between the two panels of hybridomas. This reciprocal pattern of specificity was also apparent in cytoxicity assays with brochoalveolar lavage cells isolated from the lungs of influenza virus-infected mice. T-cell receptor usage in the transgenic hybridomas was very restricted, with only one V a...

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Research paper thumbnail of Relativizing Small Complexity Classes and Their Theories

Lecture Notes in Computer Science, 2007

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Research paper thumbnail of Pannexin2 oligomers localize in the membranes of endosomal vesicles in mammalian cells while Pannexin1 channels traffic to the plasma membrane

Frontiers in Cellular Neuroscience, 2015

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Research paper thumbnail of Client-side web mining for community formation in peer-to-peer environments

ACM SIGKDD Explorations Newsletter, 2006

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Research paper thumbnail of Scientific Services on the Cloud

Handbook of Cloud Computing, 2010

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Research paper thumbnail of ERbeta Binds N-CoR in the Presence of Estrogens via an LXXLL-like Motif in the N-CoR C-terminus

Nuclear receptor, Jan 28, 2003

Nuclear receptors (NRs) usually bind the corepressors N-CoR and SMRT in the absence of ligand or ... more Nuclear receptors (NRs) usually bind the corepressors N-CoR and SMRT in the absence of ligand or in the presence of antagonists. Agonist binding leads to corepressor release and recruitment of coactivators. Here, we report that estrogen receptor beta (ERbeta) binds N-CoR and SMRT in the presence of agonists, but not antagonists, in vitro and in vivo. This ligand preference differs from that of ERalpha interactions with corepressors, which are inhibited by estradiol, and resembles that of ERbeta interactions with coactivators. ERbeta /N-CoR interactions involve ERbeta AF-2, which also mediates coactivator recognition. Moreover, ERbeta recognizes a sequence (PLTIRML) in the N-CoR C-terminus that resembles coactivator LXXLL motifs. Inhibition of histone deacetylase activity specifically potentiates ERbeta LBD activity, suggesting that corepressors restrict the activity of AF-2. We conclude that the ER isoforms show completely distinct modes of interaction with a physiologically importa...

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Research paper thumbnail of A conserved lysine in the estrogen receptor DNA binding domain regulates ligand activation profiles at AP-1 sites, possibly by controlling interactions with a modulating repressor

Nuclear receptor, Jan 7, 2004

BACKGROUND: Estrogen receptors alpha and beta (ERalpha and ERbeta) differentially activate genes ... more BACKGROUND: Estrogen receptors alpha and beta (ERalpha and ERbeta) differentially activate genes with AP-1 elements. ERalpha activates AP-1 targets via activation functions with estrogens (the AF-dependent pathway), whereas ERbeta, and a short version of ERalpha (ERalpha DBD-LBD) activate only with anti-estrogens (AF-independent pathway). The DNA binding domain (DBD) plays an important role in both pathways, even though neither pathway requires ERE recognition. RESULTS: Mutations of a highly conserved DBD lysine (ERalpha.K206A/G), lead to super-activation of AP-1 through activation function dependent pathways, up to 200 fold. This super-activity can be elicited either through ER AFs 1 or 2, or that of a heterologous activation function (VP16). The homologous substitution in ERbeta, K170A, or in ERalpha DBD-LBD leads to estrogen-dependent AP-1 activation and loss of the usually potent anti-estrogen effects. Each of numerous K206 substitutions in ERalpha, except K206R, eliminates anti...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Dual roles of the transmembrane protein p23/TMP21 in the modulation of amyloid precursor protein metabolism

Molecular neurodegeneration, Jan 8, 2007

Alzheimer's disease (AD) is characterized by cerebral deposition of beta-amyloid (Abeta) pept... more Alzheimer's disease (AD) is characterized by cerebral deposition of beta-amyloid (Abeta) peptides. Abeta is released from ectodomain cleaved amyloid precursor protein (APP) via intramembranous proteolysis by gamma-secretase, a complex consisting of presenilin and a few other proteins. p23/TMP21, a member of the p24 family type I transmembrane proteins, was recently identified as a presenilin complex component capable of modulating gamma-secretase cleavage. The p24 family proteins form oligomeric complexes and regulate vesicular trafficking in the early secretory pathway, but their role in APP trafficking has not been investigated. Here, we report that siRNA-mediated depletion of p23 in N2a neuroblastoma and HeLa cells produces concomitant knockdown of additional p24 family proteins and increases secretion of sAPP. Furthermore, intact cell and cell-free Abeta production increases following p23 knockdown, similar to data reported earlier using HEK293 cells. However, we find that p...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Establishment of a critical-sized alveolar defect in the rat: a model for human gingivoperiosteoplasty

Plastic and reconstructive surgery, 2009

Despite technical advancement, treatment of congenital alveolar clefts has remained controversial... more Despite technical advancement, treatment of congenital alveolar clefts has remained controversial. Currently, primary alveolar cleft repair (i.e., gingivoperiosteoplasty) has a 41 to 73 percent success rate. However, the remaining patients have persistent alveolar bone defects requiring secondary grafting procedures. Morbidity of secondary procedures includes pain, graft resorption, extrusion or infection, and graft or tooth loss. The authors present a novel rat alveolar defect model designed to facilitate investigation of therapeutics aimed at improving bone formation following primary alveolar cleft repair in humans. Sixteen 8-week-old Sprague-Dawley rats underwent creation of a 7 x 4 x 3-mm complete alveolar defect from the maxillary incisors to the zygomatic arch. Four animals were humanely killed at each of the following time points: 0, 4, 8, and 12 weeks. Morphometric analysis of the alveolar defect was determined by means of micro-computed tomography and histology. Micro-comp...

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Research paper thumbnail of Improved diabetic wound healing through topical silencing of p53 is associated with augmented vasculogenic mediators

Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society

Diabetes is characterized by several poorly understood phenomena including dysfunctional wound he... more Diabetes is characterized by several poorly understood phenomena including dysfunctional wound healing and impaired vasculogenesis. p53, a master cell cycle regulator, is upregulated in diabetic wounds and has recently been shown to play a regulatory roles in vasculogenic pathways. We have previously described a novel method to topically silence target genes in a wound bed with small interfering (si)RNA. We hypothesized that silencing p53 results in improved diabetic wound healing and augmentation of vasculogenic mediators. Paired 4-mm stented wounds were created on diabetic db/db mice. Topically applied p53 siRNA, evenly distributed in an agarose matrix, was applied to wounds at postwound day 1 and 7 (matrix alone and nonsense siRNA served as controls). Animals were sacrificed at postwound days 10 and 24. Wound time to closure was photometrically assessed, and wounds were harvested for histology, immunohistochemistry, and immunofluorescence. Vasculogenic cytokine expression was eva...

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Research paper thumbnail of CASE REPORT Treatment of a Lower Extremity Lymphocele With Intraoperative Lymphatic Mapping

Eplasty, 2013

Lower extremity lymphoceles secondary to saphenous vein grafting are exceptionally rare and there... more Lower extremity lymphoceles secondary to saphenous vein grafting are exceptionally rare and there is only 1 previously reported case in the English literature. Data on treatment of lower extremity lymphoceles are limited and based on studies of groin lymphoceles. We discuss operative resection with selective ligation of feeding lymphatic vessels as a treatment option of lower extremity lymphoceles. A 64-year-old man who had undergone coronary artery bypass grafting 6 years prior presented with a left lower extremity mass at the site where his saphenous vein had been harvested. Examination demonstrated a 12-cm, mobile, nonpulsatile mass at his medial left calf. The findings of magnetic resonance imaging were consistent with a lymphocele. Intraoperative injection of isosulfan blue dye was used to identify feeding lymphatic vessels and the lymphocele cavity was excised. Leg drains were discontinued after 3 days, and the patient was discharged home after 6 days. Operative resection with...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Xenopus egg cytoplasm with intact actin

Methods in enzymology, 2014

We report optimized methods for preparing Xenopus egg extracts without cytochalasin D, that we te... more We report optimized methods for preparing Xenopus egg extracts without cytochalasin D, that we term "actin-intact egg…

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Organization of early frog embryos by chemical waves emanating from centrosomes

Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 5, 2014

The large cells in early vertebrate development face an extreme physical challenge in organizing ... more The large cells in early vertebrate development face an extreme physical challenge in organizing their cytoplasm. For example, amphibian embryos have to divide cytoplasm that spans hundreds of micrometres every 30 min according to a precise geometry, a remarkable accomplishment given the extreme difference between molecular and cellular scales in this system. How do the biochemical reactions occurring at the molecular scale lead to this emergent behaviour of the cell as a whole? Based on recent findings, we propose that the centrosome plays a crucial role by initiating two autocatalytic reactions that travel across the large cytoplasm as chemical waves. Waves of mitotic entry and exit propagate out from centrosomes using the Cdk1 oscillator to coordinate the timing of cell division. Waves of microtubule-stimulated microtubule nucleation propagate out to assemble large asters that position spindles for the following mitosis and establish cleavage plane geometry. By initiating these c...

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Research paper thumbnail of Spatial organization of cytokinesis signaling reconstituted in a cell-free system

Science (New York, N.Y.), Jan 10, 2014

During animal cell division, the cleavage furrow is positioned by microtubules that signal to the... more During animal cell division, the cleavage furrow is positioned by microtubules that signal to the actin cortex at the cell midplane. We developed a cell-free system to recapitulate cytokinesis signaling using cytoplasmic extract from Xenopus eggs. Microtubules grew out as asters from artificial centrosomes and met to organize antiparallel overlap zones. These zones blocked the interpenetration of neighboring asters and recruited cytokinesis midzone proteins, including the chromosomal passenger complex (CPC) and centralspindlin. The CPC was transported to overlap zones, which required two motor proteins, Kif4A and a Kif20A paralog. Using supported lipid bilayers to mimic the plasma membrane, we observed the recruitment of cleavage furrow markers, including an active RhoA reporter, at microtubule overlaps. This system opens further approaches to understanding the biophysics of cytokinesis signaling.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Ciliopathy proteins establish a bipartite signaling compartment in a C. elegans thermosensory neuron

Journal of cell science, Jan 15, 2014

How signaling domains form is an important, yet largely unexplored question. Here, we show that c... more How signaling domains form is an important, yet largely unexplored question. Here, we show that ciliary proteins help establish two contiguous, yet distinct cyclic GMP (cGMP) signaling compartments in Caenorhabditis elegans thermosensory AFD neurons. One compartment, a bona fide cilium, is delineated by proteins associated with Bardet-Biedl syndrome (BBS), Meckel syndrome and nephronophthisis at its base, and requires NPHP-2 (known as inversin in mammals) to anchor a cGMP-gated ion channel within the proximal ciliary region. The other, a subcompartment with profuse microvilli and a different lipid environment, is separated from the dendrite by a cellular junction and requires BBS-8 and DAF-25 (known as Ankmy2 in mammals) for correct localization of guanylyl cyclases needed for thermosensation. Consistent with a requirement for a membrane diffusion barrier at the subcompartment base, we reveal the unexpected presence of ciliary transition zone proteins where no canonical transition z...

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Research paper thumbnail of A Synthetic Antibody Fragment Targeting Nicastrin Affects Assembly and Trafficking of γ-Secretase

The Journal of biological chemistry, Jan 12, 2014

The γ-secretase complex, composed of presenilin, nicastrin (NCT), anterior pharynx-defective 1 (A... more The γ-secretase complex, composed of presenilin, nicastrin (NCT), anterior pharynx-defective 1 (APH-1), and presenilin enhancer 2 (PEN-2), is assembled in a highly regulated manner and catalyzes the intramembranous proteolysis of many type I membrane proteins, including Notch and amyloid precursor protein. The Notch family of receptors plays important roles in cell fate specification during development and in adult tissues, and aberrant hyperactive Notch signaling causes some forms of cancer. γ-Secretase-mediated processing of Notch at the cell surface results in the generation of the Notch intracellular domain, which associates with several transcriptional coactivators involved in nuclear signaling events. On the other hand, γ-secretase-mediated processing of amyloid precursor protein leads to the production of amyloid β (Aβ) peptides that play an important role in the pathogenesis of Alzheimer disease. We used a phage display approach to identify synthetic antibodies that specific...

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Research paper thumbnail of Microtubule nucleation remote from centrosomes may explain how asters span large cells

Proceedings of the National Academy of Sciences of the United States of America, Jan 16, 2014

A major challenge in cell biology is to understand how nanometer-sized molecules can organize mic... more A major challenge in cell biology is to understand how nanometer-sized molecules can organize micrometer-sized cells in space and time. One solution in many animal cells is a radial array of microtubules called an aster, which is nucleated by a central organizing center and spans the entire cytoplasm. Frog (here Xenopus laevis) embryos are more than 1 mm in diameter and divide with a defined geometry every 30 min. Like smaller cells, they are organized by asters, which grow, interact, and move to precisely position the cleavage planes. It has been unclear whether asters grow to fill the enormous egg by the same mechanism used in smaller somatic cells, or whether special mechanisms are required. We addressed this question by imaging growing asters in a cell-free system derived from eggs, where asters grew to hundreds of microns in diameter. By tracking marks on the lattice, we found that microtubules could slide outward, but this was not essential for rapid aster growth. Polymer trea...

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