The Experts below are selected from a list of 2046 Experts worldwide ranked by ideXlab platform
David E Birk - One of the best experts on this subject based on the ideXlab platform.
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Pericellular proteins of the developing mouse tendon: a proteomic analysis.
Connective Tissue Research, 2011Co-Authors: Simone M Smith, Charles E. Thomas, David E BirkAbstract:Tendon fibroblasts synthesize and assemble collagen Fibrils, the basic structural unit of tendons. Regulation of Fibrillogenesis is essential for tendon development and function. Fibril Assembly begins within extracellular micro-domains associated with the fibroblast surface. We hypothesize that molecules crucial to the regulation of Fibril Assembly are membrane associated and/or within the pericellular micro-environment. This report defines proteins in the surfaceome, that is, plasma membrane and pericellular matrix, from mouse flexor digitorum longus tendons. Proteomic analysis identified a set of surfaceome molecules including collagens, fibronectin, integrins, proteoglycans, and receptors in extracts from mouse tendons at postnatal day 1, a developmental stage when collagen protoFibril nucleation and initial steps in Fibril Assembly predominate. The proteomic results were validated for molecules identified with a small number of unique peptides and/or low sequence coverage. For these analyses, protein...
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regulation of collagen Fibril nucleation and initial Fibril Assembly involves coordinate interactions with collagens v and xi in developing tendon
Journal of Biological Chemistry, 2011Co-Authors: Richard J Wenstrup, Jane B Florer, Guiyun Zhang, Simone M Smith, David P Beason, Robert E Seegmiller, Louis J Soslowsky, David E BirkAbstract:Collagens V and XI comprise a single regulatory type of Fibril-forming collagen with multiple isoforms. Both co-assemble with collagen I or II to form heterotypic Fibrils and have been implicated in regulation of Fibril Assembly. The objective of this study was to determine the roles of collagens V and XI in the regulation of tendon Fibrillogenesis. Flexor digitorum longus tendons from a haplo-insufficient collagen V mouse model of classic Ehlers Danlos syndrome (EDS) had decreased biomechanical stiffness compared with controls consistent with joint laxity in EDS patients. However, Fibril structure was relatively normal, an unexpected finding given the altered Fibrils observed in dermis and cornea from this model. This suggested roles for other related molecules, i.e. collagen XI, and compound Col5a1+/−,Col11a1+/− tendons had altered Fibril structures, supporting a role for collagen XI. To further evaluate this, transcript expression was analyzed in wild type tendons. During development (E18-P10) both collagen V and XI were comparably expressed; however, collagen V predominated in mature (P30) tendons. The collagens had a similar expression pattern. Tendons with altered collagen V and/or XI expression (Col5a1+/−; Col11a1+/−; Col5a1+/−,Col11a1+/−; Col11a1−/−; Col5a1+/−,Col11a1−/−) were analyzed at E18. All genotypes demonstrated a reduced Fibril number and altered structure. This phenotype was more severe with a reduction in collagen XI. However, the absence of collagen XI with a reduction in collagen V was associated with the most severe Fibril phenotype. The data demonstrate coordinate roles for collagens V and XI in the regulation of Fibril nucleation and Assembly during tendon development.
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collagens suprastructures and collagen Fibril Assembly
2011Co-Authors: David E Birk, Peter BrucknerAbstract:Extracellular matrices are composed of collagens, proteoglycans, glycosaminoglycans, glycoproteins, and elastin. Extracellular matrix not only serves as structural scaffolds in organs and tissues, but also determines cellular function through cell–matrix interactions. Accordingly, the structures and organization of extracellular matrices are diverse and adapted to tissue-specific function. This chapter focuses on the collagen family. There are 28 different types of collagen that assemble into a variety of supramolecular structures including Fibrils, microFibrils, and network-like structures. This chapter begins with a discussion of collagen molecules. This is followed by a definition of the supramolecular structure of different collagen types and their Assembly and function within extracellular matrices. A discussion of general mechanistic principles involved in the Assembly of collagen-containing suprastructures is presented. Finally, the regulation of tissue-specific collagen Fibrillogenesis is used to illustrate how these general principles are applied in different tissues to generate the diversity in extracellular matrix structures and functions observed.
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collagen Fibril Assembly during postnatal development and dysfunctional regulation in the lumican deficient murine cornea
Developmental Dynamics, 2006Co-Authors: Shukti Chakravarti, Inna Chervoneva, Guiyun Zhang, L Roberts, David E BirkAbstract:The transparent cornea is the outer barrier of the eye and is its major refractive surface. Development of a functional cornea requires a postnatal maturation phase involving development, growth and organization of the stromal extracellular matrix. Lumican, a leucine-rich proteoglycan, is implicated in regulating Assembly of collagen Fibrils and the highly organized extracellular matrix essential for corneal transparency. We investigated the regulatory role(s) of lumican in Fibril Assembly during postnatal corneal development using wild type (Lum+/+) and lumican-null (Lum−/−) mice. In Lum+/+ mice, a regular architecture of small-diameter Fibrils is achieved in the anterior stroma by postnatal day 10 (P10), while the posterior stroma takes longer to reach this developmental maturity. Thus, the anterior and the posterior stroma follow distinct developmental timelines and may be under different regulatory mechanisms. In Lum−/− mice, it is the posterior stroma where abnormal lateral associations of Fibrils and thicker Fibrils with irregular contours are evident as early as P10. In contrast, the anterior stroma is minimally perturbed by the absence of lumican. In Lum+/+ mice, lumican is expressed throughout the developing stroma at P10, with strong expression limited to the posterior stroma in the adult. Therefore, the posterior stroma, which is most vulnerable to lumican-deficiency, demonstrates an early developmental defect in Fibril structure and architecture in the Lum−/− mouse. These defects underlie the reported increased light scattering and opacity detectable in the adult. Our findings emphasize the early regulation of collagen structure by lumican during postnatal development of the cornea. Developmental Dynamics 235:2493–2506, 2006. © 2006 Wiley-Liss, Inc.
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Collagen Fibril Assembly during postnatal development and dysfunctional regulation in the lumican‐deficient murine cornea
Developmental Dynamics, 2006Co-Authors: Shukti Chakravarti, Inna Chervoneva, Guiyun Zhang, L Roberts, David E BirkAbstract:The transparent cornea is the outer barrier of the eye and is its major refractive surface. Development of a functional cornea requires a postnatal maturation phase involving development, growth and organization of the stromal extracellular matrix. Lumican, a leucine-rich proteoglycan, is implicated in regulating Assembly of collagen Fibrils and the highly organized extracellular matrix essential for corneal transparency. We investigated the regulatory role(s) of lumican in Fibril Assembly during postnatal corneal development using wild type (Lum+/+) and lumican-null (Lum−/−) mice. In Lum+/+ mice, a regular architecture of small-diameter Fibrils is achieved in the anterior stroma by postnatal day 10 (P10), while the posterior stroma takes longer to reach this developmental maturity. Thus, the anterior and the posterior stroma follow distinct developmental timelines and may be under different regulatory mechanisms. In Lum−/− mice, it is the posterior stroma where abnormal lateral associations of Fibrils and thicker Fibrils with irregular contours are evident as early as P10. In contrast, the anterior stroma is minimally perturbed by the absence of lumican. In Lum+/+ mice, lumican is expressed throughout the developing stroma at P10, with strong expression limited to the posterior stroma in the adult. Therefore, the posterior stroma, which is most vulnerable to lumican-deficiency, demonstrates an early developmental defect in Fibril structure and architecture in the Lum−/− mouse. These defects underlie the reported increased light scattering and opacity detectable in the adult. Our findings emphasize the early regulation of collagen structure by lumican during postnatal development of the cornea. Developmental Dynamics 235:2493–2506, 2006. © 2006 Wiley-Liss, Inc.
William E Van Nostrand - One of the best experts on this subject based on the ideXlab platform.
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The absence of myelin basic protein promotes neuroinflammation and reduces amyloid β-protein accumulation in Tg-5xFAD mice
Journal of Neuroinflammation, 2013Co-Authors: Ming-hsuan Ou-yang, William E Van NostrandAbstract:Background Abnormal accumulation of amyloid β-protein (Aβ) in the brain plays an important role in the pathogenesis \of Alzheimer’s disease (AD). Aβ monomers assemble into oligomers and Fibrils that promote neuronal dysfunction. This Assembly pathway is influenced by naturally occurring brain molecules, the Aβ chaperone proteins, which bind to Aβ and modulate its aggregation. Myelin basic protein (MBP) was previously identified as a novel Aβ chaperone protein and a potent inhibitor for Aβ Fibril Assembly in vitro.
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n terminal domain of myelin basic protein inhibits amyloid β protein Fibril Assembly
Journal of Biological Chemistry, 2010Co-Authors: Meichen Liao, Michael D Hoos, Darryl Aucoin, Mahiuddin Ahmed, Judianne Davis, Steven O Smith, William E Van NostrandAbstract:Abstract Accumulation of amyloid β-protein (Aβ) into brain parenchymal plaques and the cerebral vasculature is a pathological feature of Alzheimer disease and related disorders. Aβ peptides readily form β-sheet-containing oligomers and Fibrils. Previously, we reported a strong interaction between myelin basic protein (MBP) and Aβ peptides that resulted in potent inhibition of Fibril Assembly (Hoos, M. D., Ahmed, M., Smith, S. O., and Van Nostrand, W. E. (2007) J. Biol. Chem. 282, 9952–9961; Hoos, M. D., Ahmed, M., Smith, S. O., and Van Nostrand, W. E. (2009) Biochemistry 48, 4720–4727). MBP is recognized as a highly post-translationally modified protein. In the present study, we demonstrate that human MBP purified from either brain or a bacterial recombinant expression system comparably bound to Aβ and inhibited Aβ Fibril Assembly indicating that post-translational modifications are not required for this activity. We also show that purified mouse brain MBP and recombinantly expressed mouse MBP similarly inhibited Aβ Fibril formation. Through a combination of biochemical and ultrastructural techniques, we demonstrate that the binding site for Aβ is located in the N-terminal 64 amino acids of MBP and that a stable peptide (MBP1) comprising these residues was sufficient to inhibit Aβ Fibrillogenesis. Under conditions comparable with those used for Aβ, the Fibrillar Assembly of amylin, another amyloidogenic peptide, was not inhibited by MBP1, although MBP1 still bound to it. This observation suggests that the potent inhibitory effect of MBP on Fibril formation is not general to amyloidogenic peptides. Finally, MBP1 could prevent the cytotoxic effects of Aβ in primary cortical neurons. Our findings suggest that inhibition of Aβ Fibril Assembly by MBP, mediated through its N-terminal domain, could play a role in influencing amyloid formation in Alzheimer disease brain and corresponding mouse models.
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inhibition of familial cerebral amyloid angiopathy mutant amyloid β protein Fibril Assembly by myelin basic protein
Journal of Biological Chemistry, 2007Co-Authors: Michael D Hoos, Mahiuddin Ahmed, Steven O Smith, William E Van NostrandAbstract:Abstract Deposition of Fibrillar amyloid β-protein (Aβ) in the brain is a prominent pathological feature of Alzheimer disease and related disorders, including familial forms of cerebral amyloid angiopathy (CAA). Mutant forms of Aβ, including Dutch- and Iowa-type Aβ, which are responsible for familial CAA, deposit primarily as Fibrillar amyloid along the cerebral vasculature and are either absent or present only as diffuse non-Fibrillar plaques in the brain parenchyma. Despite the lack of parenchymal Fibril formation in vivo, these CAA mutant Aβ peptides exhibit a markedly increased rate and extent of Fibril formation in vitro compared with wild-type Aβ. Based on these conflicting observations, we sought to determine whether brain parenchymal factors that selectively interact with and modulate CAA mutant Aβ Fibril Assembly exist. Using a combination of immunoaffinity chromatography and mass spectrometry, we identified myelin basic protein (MBP) as a prominent brain parenchymal factor that preferentially binds to CAA mutant Aβ compared with wild-type Aβ. Surface plasmon resonance measurements confirmed that MBP bound more tightly to Dutch/Iowa CAA double mutant Aβ than to wild-type Aβ. Using a combination of biochemical and ultrastructural techniques, we found that MBP inhibited the Fibril Assembly of CAA mutant Aβ. Together, these findings suggest a possible role for MBP in regulating parenchymal Fibrillar Aβ deposition in familial CAA.
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pathologic amyloid β protein cell surface Fibril Assembly on cultured human cerebrovascular smooth muscle cells
Journal of Neurochemistry, 2002Co-Authors: William E Van Nostrand, J P Melchor, Lynda RuffiniAbstract:Cerebrovascular amyloid β-protein (Aβ) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Aβ 1-40 containing the E22Q HCHWA-D mutation, but not wild-type Aβ 1-40 , potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular Aβ precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 μM neither HCHWA-D Aβ 1-40 nor wild-type Aβ 1-40 appreciably assembles into β-pleated sheet-containing Fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D Aβ 1-40 , but not wild-type Aβ 140 , selectively binds and assembles into abundant Fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface Fibril Assembly of HCHWA-D Aβ 1-40 . Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D Aβ 1-40 in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the Assembly of pathogenic Aβ Fibrils and that cell surface Aβ Fibril formation plays an important role in causing the pathologic responses in these cells.
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Pathologic Amyloid β‐Protein Cell Surface Fibril Assembly on Cultured Human Cerebrovascular Smooth Muscle Cells
Journal of Neurochemistry, 2002Co-Authors: William E Van Nostrand, J P Melchor, Lynda RuffiniAbstract:Cerebrovascular amyloid β-protein (Aβ) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Aβ 1-40 containing the E22Q HCHWA-D mutation, but not wild-type Aβ 1-40 , potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular Aβ precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 μM neither HCHWA-D Aβ 1-40 nor wild-type Aβ 1-40 appreciably assembles into β-pleated sheet-containing Fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D Aβ 1-40 , but not wild-type Aβ 140 , selectively binds and assembles into abundant Fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface Fibril Assembly of HCHWA-D Aβ 1-40 . Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D Aβ 1-40 in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the Assembly of pathogenic Aβ Fibrils and that cell surface Aβ Fibril formation plays an important role in causing the pathologic responses in these cells.
J P Melchor - One of the best experts on this subject based on the ideXlab platform.
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Pathologic Amyloid β‐Protein Cell Surface Fibril Assembly on Cultured Human Cerebrovascular Smooth Muscle Cells
Journal of Neurochemistry, 2002Co-Authors: William E Van Nostrand, J P Melchor, Lynda RuffiniAbstract:Cerebrovascular amyloid β-protein (Aβ) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Aβ 1-40 containing the E22Q HCHWA-D mutation, but not wild-type Aβ 1-40 , potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular Aβ precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 μM neither HCHWA-D Aβ 1-40 nor wild-type Aβ 1-40 appreciably assembles into β-pleated sheet-containing Fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D Aβ 1-40 , but not wild-type Aβ 140 , selectively binds and assembles into abundant Fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface Fibril Assembly of HCHWA-D Aβ 1-40 . Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D Aβ 1-40 in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the Assembly of pathogenic Aβ Fibrils and that cell surface Aβ Fibril formation plays an important role in causing the pathologic responses in these cells.
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pathologic amyloid β protein cell surface Fibril Assembly on cultured human cerebrovascular smooth muscle cells
Journal of Neurochemistry, 2002Co-Authors: William E Van Nostrand, J P Melchor, Lynda RuffiniAbstract:Cerebrovascular amyloid β-protein (Aβ) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Aβ 1-40 containing the E22Q HCHWA-D mutation, but not wild-type Aβ 1-40 , potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular Aβ precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 μM neither HCHWA-D Aβ 1-40 nor wild-type Aβ 1-40 appreciably assembles into β-pleated sheet-containing Fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D Aβ 1-40 , but not wild-type Aβ 140 , selectively binds and assembles into abundant Fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface Fibril Assembly of HCHWA-D Aβ 1-40 . Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D Aβ 1-40 in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the Assembly of pathogenic Aβ Fibrils and that cell surface Aβ Fibril formation plays an important role in causing the pathologic responses in these cells.
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disruption of pathologic amyloid beta protein Fibril Assembly on the surface of cultured human cerebrovascular smooth muscle cells
Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis, 2001Co-Authors: Van Nostrand We, J P MelchorAbstract:Abstract Cerebral amyloid beta-protein (Abeta) angiopathy (CAA) is a common pathological feature of Alzheimer's disease and several related disorders. In this condition, the accumulation ofFibrillar Abeta deposits is associated with degeneration of smooth muscle cells within the cerebral blood vessel wall. We have been using primary cultures of human cerebrovascular smooth muscle (HCSM) cells to investigate pathogenic mechanisms of Abeta in CAA. The specific Assembly of Abeta Fibrils on the surface of these cell types initiates several pathologic responses including increased expression and cell surface accumulation of the Abeta precursor protein (AbetaPP) and induction of apoptotic cell death. These pathologic responses are not observed with preparations of Abeta that are assembled into Fibrils in solution, further underscoring the significance of the Fibril Assembly process on the cell surface. Since cell surface Abeta Fibril Assembly is the key initiator of the cerebrovascular cellular pathology that is observed in vitro, inhibition of this process remains an attractive therapeutic target for CAA. We have tested the efficacy of a variety of compounds that have been reported to inhibit Abeta Fibril Assembly in solution and block the neurotoxic properties of Abeta in vitro. The vast majority of these agents were ineffective in inhibiting the cell surface Fibrillar Assembly of Abeta and the subsequent pathologic responses in the cultured HCSM cells. This emphasizes the likely requirement of therapeutic compounds that are effective in disrupting cell surface-driven Abeta Fibril Assembly in the treatment of CAA.
Lynda Ruffini - One of the best experts on this subject based on the ideXlab platform.
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pathologic amyloid β protein cell surface Fibril Assembly on cultured human cerebrovascular smooth muscle cells
Journal of Neurochemistry, 2002Co-Authors: William E Van Nostrand, J P Melchor, Lynda RuffiniAbstract:Cerebrovascular amyloid β-protein (Aβ) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Aβ 1-40 containing the E22Q HCHWA-D mutation, but not wild-type Aβ 1-40 , potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular Aβ precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 μM neither HCHWA-D Aβ 1-40 nor wild-type Aβ 1-40 appreciably assembles into β-pleated sheet-containing Fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D Aβ 1-40 , but not wild-type Aβ 140 , selectively binds and assembles into abundant Fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface Fibril Assembly of HCHWA-D Aβ 1-40 . Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D Aβ 1-40 in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the Assembly of pathogenic Aβ Fibrils and that cell surface Aβ Fibril formation plays an important role in causing the pathologic responses in these cells.
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Pathologic Amyloid β‐Protein Cell Surface Fibril Assembly on Cultured Human Cerebrovascular Smooth Muscle Cells
Journal of Neurochemistry, 2002Co-Authors: William E Van Nostrand, J P Melchor, Lynda RuffiniAbstract:Cerebrovascular amyloid β-protein (Aβ) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Aβ 1-40 containing the E22Q HCHWA-D mutation, but not wild-type Aβ 1-40 , potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular Aβ precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 μM neither HCHWA-D Aβ 1-40 nor wild-type Aβ 1-40 appreciably assembles into β-pleated sheet-containing Fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D Aβ 1-40 , but not wild-type Aβ 140 , selectively binds and assembles into abundant Fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface Fibril Assembly of HCHWA-D Aβ 1-40 . Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D Aβ 1-40 in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the Assembly of pathogenic Aβ Fibrils and that cell surface Aβ Fibril formation plays an important role in causing the pathologic responses in these cells.
Karl E Kadler - One of the best experts on this subject based on the ideXlab platform.
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collagen Fibril Assembly and function
Current Topics in Developmental Biology, 2018Co-Authors: David F Holmes, Yinhui Lu, Tobias Starborg, Karl E KadlerAbstract:Abstract Collagen Fibrils are the major mechanical component in the extracellular matrix of a broad range of multicellular animals from echinoderms to vertebrates where they provide a stable framework for tissues. They form the key tension-resisting element of a complex fiber-composite system that has a tissue-specific hierarchical structure linked to mechanical demands. Remarkably, these tissues are self-maintaining and avoid fatigue failure over the lifetime of the animal. Collagen Fibrils can assemble spontaneously from purified solutions of collagen molecules. In developing tissues, however, in addition to the intrinsic self-Assembly properties, there is cellular machinery that regulates Fibril nucleation, spatial orientation, and Fibril size, according to the tissue and stage of development. The intricate mechanisms underlying the generation of a collagen Fibril network of defined architecture and mechanical properties are now becoming apparent. Impairment of this system leads ultimately to mechanical failure or tissue fibrosis.
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The needle in the ECM haystack
Nature Reviews Molecular Cell Biology, 2014Co-Authors: Karl E KadlerAbstract:Karl E. Kadler describes why the mechanism of collagen Fibril Assembly in vivo remains elusive.
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stem tem studies of collagen Fibril Assembly
Micron, 2001Co-Authors: David F Holmes, H K Graham, John A Trotter, Karl E KadlerAbstract:Quantitative scanning transmission electron microscopy (STEM), implemented on a conventional transmission electron microscope with STEM-attachment, has been a primary tool in our laboratory for the quantitative analysis of collagen Fibril Assembly in vivo and in vitro. Using this technique, a precise measurement of mass per unit length can be made at regular intervals along a Fibril to generate an axial mass distribution (AMD). This in turn allows the number of collagen molecules to be calculated for every transverse section of the Fibril along its entire length. All Fibrils show a near-linear AMD in their tip regions. Only Fibrils formed in tissue environments, however, show a characteristic abrupt change in mass slope along their tips. It appears that this tip growth characteristic is common to Fibrils from evolutionarily diverse systems including vertebrate tendon and the mutable tissues of the echinoderms. Computer models of collagen Fibril Assembly have now been developed based on interpretation of the STEM data. Two alternative models have so far been generated for Fibril growth by accretion; one is based on diffusion limited aggregation (DLA) and the other based on an interface-limited growth mechanism. Inter-Fibrillar fusion can also contribute to the growth of Fibrils in vertebrate tissues and STEM data indicates the presence of a tight regulation in this process. These models are fundamental for the hypotheses regarding how cells synthesise and spatially organise an extracellular matrix (ECM), rich in collagen Fibrils.
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STEM/TEM studies of collagen Fibril Assembly
Micron, 2001Co-Authors: David F Holmes, H K Graham, John A Trotter, Karl E KadlerAbstract:Quantitative scanning transmission electron microscopy (STEM), implemented on a conventional transmission electron microscope with STEM-attachment, has been a primary tool in our laboratory for the quantitative analysis of collagen Fibril Assembly in vivo and in vitro. Using this technique, a precise measurement of mass per unit length can be made at regular intervals along a Fibril to generate an axial mass distribution (AMD). This in turn allows the number of collagen molecules to be calculated for every transverse section of the Fibril along its entire length. All Fibrils show a near-linear AMD in their tip regions. Only Fibrils formed in tissue environments, however, show a characteristic abrupt change in mass slope along their tips. It appears that this tip growth characteristic is common to Fibrils from evolutionarily diverse systems including vertebrate tendon and the mutable tissues of the echinoderms. Computer models of collagen Fibril Assembly have now been developed based on interpretation of the STEM data. Two alternative models have so far been generated for Fibril growth by accretion; one is based on diffusion limited aggregation (DLA) and the other based on an interface-limited growth mechanism. Inter-Fibrillar fusion can also contribute to the growth of Fibrils in vertebrate tissues and STEM data indicates the presence of a tight regulation in this process. These models are fundamental for the hypotheses regarding how cells synthesise and spatially organise an extracellular matrix (ECM), rich in collagen Fibrils.