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Expansion of the Genomic Encyclopedia of Bacteria and Archaea

Description: To date the vast majority of bacterial and archaeal genomes sequenced are of rather limited phylogenetic diversity as they were chosen based on their physiology and/ or medical importance. The Genomic Encyclopedia of Bacteria and Archaea (GEBA) project (Wu et al. 2009) is aimed to systematically filling the gaps of the tree of life with phylogenetically diverse reference genomes. However more than 99percent of microorganisms elude current culturing attempts, severely limiting the ability to recover complete or even partial genomes of these largely mysterious species. These limitations gave rise to the GEBA uncultured project. Here we propose to use single cell genomics to massively expand the Genomic Encyclopedia of Bacteria and Archaea by targeting 80 single cell representatives of uncultured candidate phyla which have no or very few cultured representatives. Generating these reference genomes of uncultured microbes will dramatically increase the discovery rate of novel protein families and biological functions, shed light on the numerous underrepresented phyla that likely play important roles in the environment, and will assist in improving the reconstruction of the evolutionary history of Bacteria and Archaea. Moreover, these data will improve our ability to interpret metagenomics sequence data from diverse environments, which will be of tremendous value for microbial ecology and evolutionary studies to come.
Date: March 20, 2011
Creator: Rinke, Christian; Sczyrba, Alex; Malfatti, Stephanie; Lee, Janye; Cheng, Jan-Fang; Stepanauskas, Ramunas et al.
Partner: UNT Libraries Government Documents Department

Proteomics: Technology and Applications

Description: This meeting took place at the Keystone, Colorado resort from March 25-30, 2003. It was attended by 206 participants, of which 35 were students; 39% of attendees submitted abstracts. The meeting had 30% returning attendees and 70% new attendees. The group of speakers was composed of internationally recruited junior and senior experts in their respective fields. The group included representatives from academia and the private sector, highlights the convergence of proteomics efforts in the two sectors. The completion of the genome sequences of a large number of prokaryotic and eukaryotic species has catalyzed new research approaches to study the structure, function and control of biological processes. They are characterized by the systematic and in many cases quantitative analysis of all the molecules of a particular type expressed by a cell or tissue. The systematic analysis of proteins has been terms ''proteomics''. In an initial phase, most of the proteomics efforts were focused on large-scale protein identification. More recently, the objectives and technologies of proteomics have been diversified and expanded. Current proteomics research attempts to systematically and, where applicable, quantitatively determine the many properties of proteins and their biological function, including: protein abundance, state of modification, specific activity, interaction with other biomolecules, half-life, subcelluar location, structure and more. Significant current challenges include the development of suitable technologies to determine these properties on a proteome-wide scale, the interpretation of the large amounts of data obtained, and the integration of different types of data into a coherent model describing a biological process. The scientific program of the meeting intended to provide an up-to-date overview of the breadth of proteomics research and of emerging and mature technologies. Special emphasis was placed on discussing how proteomics technologies intersect with biological and clinical research. This was accomplished by bringing together leading experts from the different areas ...
Date: March 25, 2003
Creator: Aebersold, Ruedi
Partner: UNT Libraries Government Documents Department

From Microstructure to Macrostructure and Function in thePhotochemical Apparatus

Description: A discussion is presented of the macrostructure of the chloroplast insofar as it is known and knowable by means of microscopy (visible, ultraviolet and electron). This leads to a number of principles of structure to be found in the granum universally distributed throughout the plant kingdom. A chemical analysis of the constitution of these lamellar structures leads to a deduction of structural principles for such molecules as are found therein. The application of these structural principles to the visible structure of the lamella leads to a microstructure on a molecular level of these lamellae which, in turn, leads to a theory of their function.
Date: October 22, 1958
Creator: Calvin, Melvin
Partner: UNT Libraries Government Documents Department

Modeling cortical circuits.

Description: The neocortex is perhaps the highest region of the human brain, where audio and visual perception takes place along with many important cognitive functions. An important research goal is to describe the mechanisms implemented by the neocortex. There is an apparent regularity in the structure of the neocortex [Brodmann 1909, Mountcastle 1957] which may help simplify this task. The work reported here addresses the problem of how to describe the putative repeated units ('cortical circuits') in a manner that is easily understood and manipulated, with the long-term goal of developing a mathematical and algorithmic description of their function. The approach is to reduce each algorithm to an enhanced perceptron-like structure and describe its computation using difference equations. We organize this algorithmic processing into larger structures based on physiological observations, and implement key modeling concepts in software which runs on parallel computing hardware.
Date: September 1, 2010
Creator: Rohrer, Brandon Robinson; Rothganger, Fredrick H.; Verzi, Stephen J. & Xavier, Patrick Gordon
Partner: UNT Libraries Government Documents Department

Final Report on LDRD project 130784 : functional brain imaging by tunable multi-spectral Event-Related Optical Signal (EROS).

Description: Functional brain imaging is of great interest for understanding correlations between specific cognitive processes and underlying neural activity. This understanding can provide the foundation for developing enhanced human-machine interfaces, decision aides, and enhanced cognition at the physiological level. The functional near infrared spectroscopy (fNIRS) based event-related optical signal (EROS) technique can provide direct, high-fidelity measures of temporal and spatial characteristics of neural networks underlying cognitive behavior. However, current EROS systems are hampered by poor signal-to-noise-ratio (SNR) and depth of measure, limiting areas of the brain and associated cognitive processes that can be investigated. We propose to investigate a flexible, tunable, multi-spectral fNIRS EROS system which will provide up to 10x greater SNR as well as improved spatial and temporal resolution through significant improvements in electronics, optoelectronics and optics, as well as contribute to the physiological foundation of higher-order cognitive processes and provide the technical foundation for miniaturized portable neuroimaging systems.
Date: September 1, 2009
Creator: Speed, Ann Elizabeth; Spahn, Olga Blum & Hsu, Alan Yuan-Chun
Partner: UNT Libraries Government Documents Department

Enzyme catalysts for a biotechnology-based chemical industry. Final report, September 29, 1993--September 28, 1998

Description: Enzymes have enormous potential for reducing energy requirements and environmental problems in the chemicals and pharmaceutical industries. The explosion of tools that has come out of molecular biology during the last 20 years has made it possible to evolve enzymes for features never required in nature. Scientists can speed up the rate and channel the direction of evolution by controlling mutagenesis and the accompanying selection pressures. Darwinian evolution carried out in the test tube offers a unique opportunity for biotechnology: the ability to tailor enzymes for optimal performance in a wide range of applications. Thus it is possible, for example, to evolve enzymes that carry out reactions on nonnatural substrates or even to carry out reactions for which there is no counterpart in nature. Due to the vast size of the potential sequence space, however, explorations by directed evolution must be guided by sound principles and workable strategies. During the course of this group, this laboratory has continued to make significant progress in the evolution of industrial enzymes as well as in developing general methods for in vitro evolution.
Date: November 16, 1998
Creator: Arnold, F.H.
Partner: UNT Libraries Government Documents Department

Parallel continuation-based global optimization for molecular conformation and protein folding

Description: This paper presents the authors` recent work on developing parallel algorithms and software for solving the global minimization problem for molecular conformation, especially protein folding. Global minimization problems are difficult to solve when the objective functions have many local minimizers, such as the energy functions for protein folding. In their approach, to avoid directly minimizing a ``difficult`` function, a special integral transformation is introduced to transform the function into a class of gradually deformed, but ``smoother`` or ``easier`` functions. An optimization procedure is then applied to the new functions successively, to trace their solutions back to the original function. The method can be applied to a large class of nonlinear partially separable functions including energy functions for molecular conformation and protein folding. Mathematical theory for the method, as a special continuation approach to global optimization, is established. Algorithms with different solution tracing strategies are developed. Different levels of parallelism are exploited for the implementation of the algorithms on massively parallel architectures.
Date: December 31, 1994
Creator: Coleman, T. F. & Wu, Z.
Partner: UNT Libraries Government Documents Department

Programmed cell death

Description: The purpose of this conference to provide a multidisciplinary forum for exchange of state-of-the-art information on the role programmed cell death plays in normal development and homeostasis of many organisms. This volume contains abstracts of papers in the following areas: invertebrate development; immunology/neurology; bcl-2 family; biochemistry; programmed cell death in viruses; oncogenesis; vertebrate development; and diseases.
Date: December 31, 1995
Partner: UNT Libraries Government Documents Department

The biology of novel animal genes: Mouse APEX gene knockout

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The controlled breeding of novel genes into mice, including the gene knockout (KO), or conversely by adding back transgenes provide powerful genetic technologies that together suffice to determine in large part the biological role(s) of novel genes. Inbred mouse remains the best understood and most useful mammalian experimental system available for tackling the biology of novel genes. The major mammalian apurinic/apyrimidinic (AP) endonuclease (APE), is involved in a key step in the repair of spontaneous and induced AP sites in DNA. Efficient repair of these lesions is imperative to prevent the stable incorporation of mutations into the cellular genome which may lead to cell death or transformation. Loss or modulation of base excison repair activity in vivo may elevate the spontaneous mutation rate in cells, and may lead to a substantial increase in the incidence of cancer. Despite extensive biochemical analysis, however, the significance of these individual APE functions in vivo has not been elucidated. Mouse embryonic stem (ES) cells heterozygous for a deletion mutation in APE have been generated and whole animals containing the APE mutation have been derived from these ES cells. Animals homozygous for the APE null mutation die early in gestation, underscoring the biological significance of this DNA repair gene.
Date: July 1, 1997
Creator: MacInnes, M.; Altherr, M.R.; Ludwig, D.; Pedersen, R. & Mold, C.
Partner: UNT Libraries Government Documents Department

Structures and Functions of Oligosaccharins

Description: We have made considerable progress during the 2.5 year funding period just ending in our studies of the structures and functions of oligosaccharide signal molecules (oligosaccharins). We have emphasized studies of the enzymes that solubilize, process, and degrade oligosaccharins and of the proteins that inhibit those enzymes. We have been especially interested in elucidating how oligosaccharins and their processing enzymes participate in determining the outcome of challenges to plants by pathogenic microbes. We have studied, to a lesser extent, the roles of oligosaccharins in plant growth and development. Abstracts of papers describing results acquired with support from this grant that have been published, submitted, or in preparation are presented to summarize the progress made during the last two and one half years. The report highlights the most important contributions made in our oiigosaccharin research during this time period, and the corresponding abstract is referenced. Results of work in progress are described primarily in conjunction with our application for continued support.
Date: December 1, 1995
Creator: Albersheim, Peter
Partner: UNT Libraries Government Documents Department

Importance of protamine phosphorylation to histone displacement in spermatids: can the disruption of this process be used for male contraception

Description: Protamine is a small protein that packages DNA in the sperm of most vertebrates. Shortly after its synthesis, the serine and threonine residues in each protamine are phosphorylated and the modified proteins are deposited onto DNA, displacing the histones and other chromatin proteins. We have hypothesized that the phosphorylation of protamine 1 induces protamine dimerization and these dimers are required for efficient histone displacement. Histone displacement by protamines in late-step spermatids appears to be essential for the production of fertile sperm in man and other mammals, and the disruption of this process could provide a new approach for male contraception. As a first step towards testing this theory, we have initiated a set of in vitro experiments to determine whether of not protamine phosphorylation is essential for histone displacement. Thee results of these experiments, although incomplete, confirm that unphosphorylated protamine cannot effectively displace histone from DNA. Polyarginine molecules twice the size of a protamine molecule and salmine dimer were found to be more effective. These results are consistent with the theory that the disruption of protamine phosphorylation may prove to be a useful new approach for male contraception if it can be shown to facilitate or induce protamine dimerization.
Date: June 1, 1995
Creator: Balhorn, R.; Hud, N.V.; Corzett, M. & Mazrimas, J.
Partner: UNT Libraries Government Documents Department

Dynamic neurotransmitter interactions measured with PET

Description: Positron emission tomography (PET) has become a valuable interdisciplinary tool for understanding physiological, biochemical and pharmacological functions at a molecular level in living humans, whether in a healthy or diseased state. The utility of tracing chemical activity through the body transcends the fields of cardiology, oncology, neurology and psychiatry. In this, PET techniques span radiochemistry and radiopharmaceutical development to instrumentation, image analysis, anatomy and modeling. PET has made substantial contributions in each of these fields by providing a,venue for mapping dynamic functions of healthy and unhealthy human anatomy. As diverse as the disciplines it bridges, PET has provided insight into an equally significant variety of psychiatric disorders. Using the unique quantitative ability of PET, researchers are now better able to non-invasively characterize normally occurring neurotransmitter interactions in the brain. With the knowledge that these interactions provide the fundamental basis for brain response, many investigators have recently focused their efforts on an examination of the communication between these chemicals in both healthy volunteers and individuals suffering from diseases classically defined as neurotransmitter specific in nature. In addition, PET can measure the biochemical dynamics of acute and sustained drug abuse. Thus, PET studies of neurotransmitter interactions enable investigators to describe a multitude of specific functional interactions in the human brain. This information can then be applied to understanding side effects that occur in response to acute and chronic drug therapy, and to designing new drugs that target multiple systems as opposed to single receptor types. Knowledge derived from PET studies can be applied to drug discovery, research and development (for review, see (Fowler et al., 1999) and (Burns et al., 1999)). Here, we will cover the most substantial contributions of PET to understanding biologically distinct neurochemical systems that interact to produce a variety of behaviors and disorders. Neurotransmitters are neither static nor ...
Date: April 2, 2001
Creator: Schiffer, W. K. & Dewey, S. L.
Partner: UNT Libraries Government Documents Department

2004 Structural, Function and Evolutionary Genomics

Description: This Gordon conference will cover the areas of structural, functional and evolutionary genomics. It will take a systematic approach to genomics, examining the evolution of proteins, protein functional sites, protein-protein interactions, regulatory networks, and metabolic networks. Emphasis will be placed on what we can learn from comparative genomics and entire genomes and proteomes.
Date: March 23, 2005
Creator: Gray, Douglas L. Brutlag Nancy Ryan
Partner: UNT Libraries Government Documents Department

Plant, cell, and molecular mechanisms of abscisic-acid regulation of stomatal apertures. In vivo phosphorylation of phosphoenolpyruvate carboxylase in guard cells of Vicia faba L. is enhanced by fusicoccin and suppressed by abscisic acid

Description: Plants regulate water loss and CO{sub 2} gain by modulating the aperture sizes of stomata that penetrate the epidermis. Aperture size itself is increased by osmolyte accumulation and consequent turgor increase in the pair of guard cells that flank each stoma. Guard-cell phosphoenolpyruvate carboxylase, which catalyzes the regulated step leading to malate synthesis, is crucial for charge and pH maintenance during osmolyte accumulation. Regulation of this cytosolic enzyme by effectors is well documented, but additional regulation by posttranslational modification is predicted by the alteration of PEPC kinetics during stomatal opening. In this study, the authors have investigated whether this alteration is associated with the phosphorylation status of this enzyme. Using sonicated epidermal peels (isolated guard cells) pre-loaded with {sub 32}PO{sub 4}, the authors induced stomatal opening and guard-cell malate accumulation by incubation with 5 {micro}M fusicoccin (FC). In corroboratory experiments, guard cells were incubated with 5 {micro}M fusicoccin (FC). In corroboratory experiments, guard cells were incubated with the FC antagonist, 10 {micro}M abscisic acid (ABA). The phosphorylation status of PEPC was assessed by immunoprecipitation, electrophoresis, immunoblotting, and autoradiography. PEPC was phosphorylated when stomata were stimulated to open, and phosphorylation was lessened by incubation with ABA.
Date: 1996~
Creator: Du, Z.; Aghoram, K. & Outlaw, W. H., Jr.
Partner: UNT Libraries Government Documents Department

Neuromagnetic source reconstruction

Description: In neuromagnetic source reconstruction, a functional map of neural activity is constructed from noninvasive magnetoencephalographic (MEG) measurements. The overall reconstruction problem is under-determined, so some form of source modeling must be applied. We review the two main classes of reconstruction techniques-parametric current dipole models and nonparametric distributed source reconstructions. Current dipole reconstructions use a physically plausible source model, but are limited to cases in which the neural currents are expected to be highly sparse and localized. Distributed source reconstructions can be applied to a wider variety of cases, but must incorporate an implicit source, model in order to arrive at a single reconstruction. We examine distributed source reconstruction in a Bayesian framework to highlight the implicit nonphysical Gaussian assumptions of minimum norm based reconstruction algorithms. We conclude with a brief discussion of alternative non-Gaussian approachs.
Date: December 31, 1994
Creator: Lewis, P. S.; Mosher, J. C. & Leahy, R. M.
Partner: UNT Libraries Government Documents Department

The Exosporium of B.cereus Contains a Binding Site for gC1qR/p33: Implication in Spore Attachment and/or Entry.

Description: B. cereus, is a member of a genus of aerobic, gram-positive, spore-forming rod-like bacilli, which includes the deadly, B. anthracis. Preliminary experiments have shown that gC1qR binds to B.cereus spores that have been attached to microtiter plates. The present studies were therefore undertaken, to examine if cell surface gC1qR plays a role in B.cereus spore attachment and/or entry. Monolayers of human colon carcinoma (Caco-2) and lung cells were grown to confluency on 6 mm coverslips in shell vials with gentle swirling in a shaker incubator. Then, 2 {micro}l of a suspension of strain SB460 B.cereus spores (3x10{sup 8}/ml, in sterile water), were added and incubated (1-4 h; 36{sup 0} C) in the presence or absence of anti-gC1qR mAb-carbon nanoloops. Examination of these cells by EM revealed that: (1) When B. cereus endospores contacted the apical Caco-2 cell surface, or lung cells, gClqR was simultaneously detectable, indicating upregulation of the molecule. (2) In areas showing spore contact with the cell surface, gClqR expression was often adjacent to the spores in association with microvilli (Caco-2 cells) or cytoskeletal projections (lung cells). (3) Furthermore, the exosporia of the activated and germinating spores were often decorated with mAb-nanoloops. These observations were further corroborated by experiments in which B.cereus spores were readily taken up by monocytes and neutrophils, and this uptake was partially inhibited by mAb 60.11, which recognizes the C1q binding site on gC1qR. Taken together, the data suggest a role, for gC1qR at least in the initial stages of spore attachment and/or entry.
Date: January 1, 2008
Partner: UNT Libraries Government Documents Department

Low Dose Radiation Response Curves, Networks and Pathways in Human Lymphoblastoid Cells Exposed from 1 to 10 cGy of Acute Gamma Radiation

Description: We investigated the low dose dependency of the transcriptional response of human cells to characterize the shape and biological functions associated with the dose response curve and to identify common and conserved functions of low dose expressed genes across cells and tissues. Human lymphoblastoid (HL) cells from two unrelated individuals were exposed to graded doses of radiation spanning the range of 1-10 cGy were analyzed by transcriptome profiling, qPCR and bioinformatics, in comparison to sham irradiated samples. A set of {approx}80 genes showed consistent responses in both cell lines; these genes were associated with homeostasis mechanisms (e.g., membrane signaling, molecule transport), subcellular locations (e.g., Golgi, and endoplasmic reticulum), and involved diverse signal transduction pathways. The majority of radiation-modulated genes had plateau-like responses across 1-10 cGy, some with suggestive evidence that transcription was modulated at doses below 1 cGy. MYC, FOS and TP53 were the major network nodes of the low-dose response in HL cells. Comparison our low dose expression findings in HL cells with those of prior studies in mouse brain after whole body exposure, in human keratinocyte cultures, and in endothelial cells cultures, indicates that certain components of the low dose radiation response are broadly conserved across cell types and tissues, independent of proliferation status.
Date: April 18, 2011
Creator: Wyrobek, A. J.; Manohar, C. F.; Nelson, D. O.; Furtado, M. R.; Bhattacharya, M. S.; Marchetti, F. et al.
Partner: UNT Libraries Government Documents Department


Description: Irradiation of benzo[a]pyrene 1 with 1-methylcytosine hydrochloride 2a (molar ratio 1:10) at 3500 {angstrom} in methanol-acetone produces the 6-(1-methylcytos-5-yl)-benzo[pa]pyrene 3. The structure of the photoproduct shows the hydrocarbon bound through the most active 6-carbon atom to the nucleophilic 5-position of the base. The specific substitution of both moieties combined with other data allows them to understand the carcinogenic activity of the hydrocarbon and thereby to propose a possible mechanism of their linkage in vivo. In this model, the K region does not play a role in triggering the cancer process.
Date: August 1, 1970
Creator: Cavalieri, E. & Calvin, M
Partner: UNT Libraries Government Documents Department

Structures and functions of oligosaccharins. Progress report, June 15, 1993--March 14, 1995

Description: This research focuses on the following: Purification, characterization, and cell wall localization of an {alpha}-fucosidase that inactivates a xyloglucan oligosaccharin; Oligogalacturonides inhibit the formation of roots on tobacco explants; Activation of a tobacco glycine-rich protein gene by a fungal glucan preparation; Fusarium moniliforme secretes four endopolygalacturonases derived from a single gene product; Polygalacturonase-inhibiting protein accumulates in Phaseolus vulgaris L. in response to wounding, elicitors and fungal infection; Generation of {beta}-glucan elicitors by plant enzymes and inhibition of the enzymes by a fungal protein; Polygalacturonase inhibitor proteins from bean (Phaseolus vulgaris L.), pear (Pyrus communis L.) and tomato (Lycopersicon esculentum): Immunological relatedness and specificity of polygalacturonase inhibition; Fungi protect themselves against plant pathogenesis-related glycanases; Purification, cloning, and characterization of two xylanases from Magnaporthe grisea, the rice blast fungus; and Molecular cloning and expression pattern of an {alpha}-fucosidase gene from pea seedlings.
Date: March 1, 1995
Creator: Albersheim, P.
Partner: UNT Libraries Government Documents Department

Chaperonin polymers in archaea: The cytoskeleton of prokaryotes?

Description: Chaperonins are protein complexes that play a critical role in folding nascent polypeptides under normal conditions and refolding damaged proteins under stress conditions. In all organisms these complexes are composed of evolutionarily conserved 60-kDa proteins arranged in double-ring structures with between 7 and 9 protein subunits per ring. These double ring structures are assumed to be the functional units in vivo, although they have never been observed inside cells. Here the authors show that the purified chaperonin from the hyperthermophilic archaeon Sulfolobus shibatae, which is closely related to chaperonins in eukaryotes, has a double ring structure at low concentrations (0.1 mg/ml), but at more physiological concentrations, the rings stack end to end to form polymers. The polymers are stable at physiological temperatures (75 C) and closely resemble structures observed inside unfixed S. shibatae cells. The authors suggest that in vivo chaperonin activity may be regulated by polymerization and that chaperonin polymers may act as a cytoskeleton-like structure in archaea and bacteria.
Date: July 1, 1997
Creator: Trent, J.D.; Kagawa, H.K. & Zaluzec, N.J.
Partner: UNT Libraries Government Documents Department

Measuring dopamine release in the human brain with PET

Description: The dopamine system is involved in the regulation of brain regions that subserve motor, cognitive and motivational behaviors. Disruptions of dopamine (DA) function have ben implicated in neurological and psychiatric illnesses including substance abuse as well as on some of the deficits associated with aging of the human brain. This has made the DA system an important topic in research in the neurosciences and neuroimaging as well as an important molecular target for drug development. Positron Emission Tomography (PET), was the first technology that enabled direct measurement of components of the DA system in the living human brain. Imaging studies of DA in the living brain have been indirect, relying on the development of radiotracers to label DA receptors, DA transporters, compounds which have specificity for the enzymes which degrade synaptic DA. Additionally, through the use of tracers that provide information on regional brain activity (ie brain glucose metabolism and cerebral blood flow) and of appropriate pharmacological interventions, it has been possible to assess the functional consequences of changes in brain DA activity. DA specific ligands have been useful in the evaluation of patients with neuropsychiatric illnesses as well as to investigate receptor blockade by antipsychotic drugs. A limitation of strategies that rely on the use of DA specific ligands is that the measures do not necessarily reflect the functional state of the dopaminergic system and that there use to study the effects of drugs is limited to the investigation of receptor or transporter occupancy. Newer strategies have been developed in an attempt to provide with information on dopamine release and on the functional responsivity of the DA system in the human brain. This in turn allows to investigate the effects of pharmacological agent in an analogous way to what is done with microdialysis techniques.
Date: December 1, 1995
Creator: Volkow, N.D.; Fowler, J.S.; Logan, J. & Wang, G.J.
Partner: UNT Libraries Government Documents Department

CD147 is a regulatory subunit of the gamma-secretase complex inAlzheimer's disease amyloid beta-peptide production

Description: {gamma}-secretase is a membrane protein complex that cleaves the {beta}-amyloid precursor protein (APP) within the transmembrane region, following prior processing by {beta}-secretase, producing amyloid {beta}-peptides (A{beta}{sub 40} and A{beta}{sub 42}). Errant production of A{beta}-peptides that substantially increases A{beta}{sub 42} production has been associated with the formation of amyloid plaques in Alzheimer's disease patients. Biophysical and genetic studies indicate that presenilin-1 (Psn-1), which contains the proteolytic active site, and three other membrane proteins, nicastrin (Nct), APH-1, and PEN-2 are required to form the core of the active {gamma}-secretase complex. Here, we report the purification of the native {gamma}-secretase complexes from HeLa cell membranes and the identification of an additional {gamma}-secretase complex subunit, CD147, a transmembrane glycoprotein with two immunoglobulin-like domains. The presence of this subunit as an integral part of the complex itself was confirmed through co-immunoprecipitation studies of the purified protein from HeLa cells and solubilized complexes from other cell lines such as neural cell HCN-1A and HEK293. Depletion of CD147 by RNA interference was found to increase the production of A{beta} peptides without changing the expression level of the other {gamma}-secretase components or APP substrates while CD147 overexpression had no statistically significant effect on amyloid {beta}-peptide production, other {gamma}-secretase components or APP substrates, indicating that the presence of the CD147 subunit within the {gamma}-secretase complex directly down-modulates the production of A{beta}-peptides. {gamma}-secretase was first recognized through its role in the production of the A{beta} peptides that are pathogenic in Alzheimer's disease (AD) (1). {gamma}-secretase is a membrane protein complex with unusual aspartyl protease activity that cleaves a variety of type I membrane proteins, such as APP, CD44, DCC, ErbB4, E-cadherin, LRP, N-cadherin, Nectin-1, and Notch, within their transmembranous regions (2-11); therefore, in addition to its role in AD, {gamma}-secretase has been found to participate in other important biological functions, ...
Date: April 6, 2005
Creator: Zhou, Shuxia; Zhou, Hua; Walian, Peter J. & Jap, Bing K.
Partner: UNT Libraries Government Documents Department