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The integrins
Yoshikazu Takada, Xiaojing Ye, Scott Simon
Genome Biology , 2007, DOI: 10.1186/gb-2007-8-5-215
Abstract: The integrins are a superfamily of cell adhesion receptors that recognize mainly extracellular matrix ligands and cell-surface ligands, although some soluble ligands have been identified [1]. They are transmembrane αβ heterodimers, and at least 18 α and eight β subunits are known in humans [2] (Figure 1; lists of the integrin subunits present in mouse, chicken, zebrafish, Caenorhabditis elegans, Xenopus laevis and Drosophila melanogaster are given in Additional data file 1). Integrin α and β subunits are totally distinct, with no detectable homology between them; sequence identity among α subunits is about 30% and among β subunits 45%, indicating that both the α and the β gene families evolved by gene duplication (Figure 2). In humans, genes for both α and β subunits are located on various chromosomes. However, genes for integrins expressed in leukocytes (subunits αL, αM, αD, and αX) are clustered at 16p11, while for those expressed in platelets and endothelial cells, the αIIb and β3 genes are at 17q21.32, and the α6, α4, and αV cluster at 2q31 (Table 1). Some integrin ? subunits (?1, ?2, ?10, ?11, ?M, ?L, ?D, and ?X) contain a so-called I (insertion or interaction), or A, domain, while others do not. The I-domain integrin α subunits are closely related to each other (Figure 2a). Also closely related to each other are the family of non-I-domain α subunits that recognize the RGD motif (αV, α8, α5, and αIIb) and the family of laminin-binding α subunits (α3, α6, and α7). Studies on integrin genes from lower and higher eukaryotes clearly indicate that integrin genes (both α and β) derived from a common ancestral gene by gene duplications. A genomic analysis among 24 invertebrate and vertebrate species revealed that the α and β integrin structure, along with the inserted α I domain, has been highly conserved during the evolution of vertebrates [3].The crystal structures of human integrins αVβ3 [4,5] and αIIbβ3 [6] show that the extracellular portion of an integrin hetero
HIV and tuberculosis: Partners in crime  [cached]
Maniar Janak,Kamath Ratnakar,Mandalia Sundhiya,Shah Keyur
Indian Journal of Dermatology, Venereology and Leprology , 2006,
Abstract: Background: Tuberculosis is the commonest infection detected in HIV-infected individuals worldwide. Aim: The aim of this study is to describe the clinical, bacteriologic and radiological spectrum of tuberculosis (TB) in the setting of human immunodeficiency virus (HIV) infection in a tertiary care centre in Mumbai. Methods: A total of 8640 HIV-infected individuals were screened for tuberculosis routinely from January 1998 to December 2003, using clinical examination, chest X-ray and abdominal ultrasonography, sputum smears for acid-fast bacilli (AFB) and culture on Lowenstein-Jensen medium. Results: TB was detected in 8078 (93.5%) patients of whom 3393 (42%) had pulmonary, 3514 (43.5%) had extrapulmonary TB and 1171 (14.5%) had disseminated disease. One thousand two hundred thirty eight patients (36.5%) showed AFB in sputum, while 1154 (34%) showed growth on culture medium and 4174 had radiographic involvement. In 781 (67%) individuals disseminated disease coexisted with pulmonary involvement. All 8078 coinfected patients were treated with anti-TB therapy (ATT), of whom 6422 patients (79.5%) showed one or more adverse events. Gastritis was the commonest complaint followed by hepatitis and skin rashes. ATT resistance was detected in 482 individuals. Conclusion: Tuberculosis is the commonest opportunistic infection (OI) in HIV positive patients in India, showing a higher prevalence of extrapulmonary and disseminated TB and adverse events due to ATT. Early recognition of concurrent OIs and their adequate treatment and prophylaxis is essential.
Integrins are required for cardioblast polarisation in Drosophila
Jessica Vanderploeg, L Lourdes Vazquez Paz, Allison MacMullin, J Roger Jacobs
BMC Developmental Biology , 2012, DOI: 10.1186/1471-213x-12-8
Abstract: As with vertebrates, the Drosophila heart arises from lateral mesoderm that migrates medially to meet their contralateral partners, to then assemble a midline vessel. During migration, Integrins are among the first proteins restricted to the presumptive luminal domain of cardioblasts. Integrins are required for normal levels of leading edge membrane motility. Apical accumulation of Integrins is enhanced by Robo, and reciprocally, apicalisation of luminal factors like Slit and Robo requires Integrin function. Integrins may provide a template for the formation of a lumen by stabilising lumen factors like Robo. Subsequent to migration, Integrin is required for normal cardioblast alignment and lumen formation. This phenotype is most readily modified by other mutations that affect adhesion, such as Talin and extracellular matrix ligands.Our findings reveal an instructive role for Integrins in communicating polarising information to cells during migration, and during transition to an epithelial tube structure.Vascular endothelia are characterised by a polarised cell architecture, wherein Cadherin based cell junctions establish the integrity of the vessel walls, while the lumen of the vessel is defined by Integrins and an extracellular matrix (ECM) [1,2]. When these vessels first form, grow or are remodeled, the progenitor cells must be less polarised, as they will change neighbours, migrate through other tissues, and respond to local growth cues. During vessel formation, progenitors may have a more mesenchymal organisation, while the differentiated vessel must have stable epithelial polarisation of membrane domains. Vasculogenesis, therefore, can be interpreted in the framework of mesenchymal to epithelial transition [3].Integrins are transmembrane receptors comprised of pairs of α and β subunits, which link the ECM to the cell cytoskeleton, and mediate cell locomotion, adhesion and signals that affect differentiation and survival [4,5]. There are at least 7 different Int
Violence, Crime, and Violent Crime  [cached]
Richard B. Felson
International Journal of Conflict and Violence , 2009,
Abstract: I propose a dual conceptualization of violent crime. Since violent crime is both violence and crime, theories of aggression and deviance are required to understand it. I argue that both harm-doing and rule breaking are instrumental behaviors and that a bounded rational choice approach can account for both behaviors. However, while some of the causes of harm-doing and deviance (and violent and nonviolent crime) are the same, some are different. Theories of crime and deviance cannot explain why one only observes individual and group differences in violent crime and theories of aggression and violence cannot explain why one observes differences in all types of crimes. Such theories are “barking up the wrong tree.”
COMPUTER CRIME  [PDF]
SANTOSH GOBRU JADHAO
Indian Streams Research Journal , 2013,
Abstract: Computer crime or Cyber crime refers to any crime that involves a computer and a network. The computer may have been used in the commission of a crime or it may be the target. Netcrime refers to criminal exploitation of the Internet
Integrins in vascular development
Hynes, R.O.;Bader, B.L.;Hodivala-Dilke, K.;
Brazilian Journal of Medical and Biological Research , 1999, DOI: 10.1590/S0100-879X1999000500002
Abstract: many growth factors and their protein kinase receptors play a role in regulating vascular development. in addition, cell adhesion molecules, such as integrins and their ligands in the extracellular matrix, play important roles in the adhesion, migration, proliferation, survival and differentiation of the cells that form the vasculature. some integrins are known to be regulated by angiogenic growth factors and studies with inhibitors of integrin functions and using strains of mice lacking specific integrins clearly implicate some of these molecules in vasculogenesis and angiogenesis. however, the data are incomplete and sometimes discordant and it is unclear how angiogenic growth factors and integrin-mediated adhesive events cooperate in the diverse cell biological processes involved in forming the vasculature. consideration of the results suggests working hypotheses and raises questions for future research directions.
Integrins in vascular development  [cached]
Hynes R.O.,Bader B.L.,Hodivala-Dilke K.
Brazilian Journal of Medical and Biological Research , 1999,
Abstract: Many growth factors and their protein kinase receptors play a role in regulating vascular development. In addition, cell adhesion molecules, such as integrins and their ligands in the extracellular matrix, play important roles in the adhesion, migration, proliferation, survival and differentiation of the cells that form the vasculature. Some integrins are known to be regulated by angiogenic growth factors and studies with inhibitors of integrin functions and using strains of mice lacking specific integrins clearly implicate some of these molecules in vasculogenesis and angiogenesis. However, the data are incomplete and sometimes discordant and it is unclear how angiogenic growth factors and integrin-mediated adhesive events cooperate in the diverse cell biological processes involved in forming the vasculature. Consideration of the results suggests working hypotheses and raises questions for future research directions.
Integrins Are the Necessary Links to Hypertrophic Growth in Cardiomyocytes  [PDF]
Rebecca K. Harston,Dhandapani Kuppuswamy
Journal of Signal Transduction , 2011, DOI: 10.1155/2011/521742
Abstract: To compensate for hemodynamic overload of the heart, an event which stretches the myocardium, growth and survival signaling are activated in cardiac muscle cells (cardiomyocytes). Integrins serve as the signaling receptors of cardiomyocytes responsible for mechanotransduction toward intracellular signaling. The main integrin heterodimers on the cardiomyocyte surface are α5β1 and , and elimination of either β1 or β3 integrins impedes pressure-induced hypertrophic signaling and leads to increased mortality. The growth signaling pathways downstream of β1 and β3 integrins are well characterized. However, new integrin pathways responsible for inhibiting apoptosis induced by hemodynamic overload are emerging. β1 and β3 integrins activate differential survival signaling, yet both integrins initiate survival signaling downstream of ubiquitination and the kinase pathway including phosphoinositol-3-kinase (PI3K)/Akt. Further characterization of these integrin-signaling mechanisms may lead to drug targets to prevent decompensation to heart failure. 1. Cardiac Hypertrophy Cardiac hypertrophy begins as a compensatory response to hemodynamic overload, such as from increased pressure with hypertension. Several cell types are present in the ventricular wall that provide diverse contributions for optimal organ performance. Cardiomyocytes are the muscle cells in the heart which make up myofibrils that contract to pump blood to the body. Like skeletal muscle cells, cardiomyocytes are striated, but only cardiomyocytes have intercalated discs, which connect adjacent cells and help them simultaneously contract. While all cell types in the heart differentially respond to hemodynamic changes, the cardiomyocytes ultimately regulate cardiac performance through pump function and must change intracellular signaling pathways most substantially. Hypertrophy is defined by the increase in protein synthesis, cardiomyocyte size, and cytoskeletal remodeling, which are important to increase the ventricle wall thickness to normalize against the mechanical stress [1] and optimize contractility (reviewed in [2]). Cardiomyocytes are terminally differentiated and, therefore, have limited proliferative potential. Thus, cell growth and initiation of survival signaling are their means of increasing ventricle muscle mass. As cardiomyocytes reenter a growth phase not initiated since development, there is an immediate early gene induction of proto-oncogenes, and heat shock protein genes are activated first, followed by induction of a “fetal” gene program similar to developmental expression patterns.
The role of integrins in pulmonary fibrosis
D. Sheppard
European Respiratory Review , 2008,
Abstract: Integrins are a large family of transmembrane glycoprotein receptors initially identified as mediators of cell adhesion and tissue integrity. However, it is now known that the primary function of integrins in mammals is to act as signalling proteins. Signals from integrins are known to play critical roles in virtually every aspect of the behaviour of epithelial cells and in the development of certain pathological conditions, including pulmonary fibrosis. In this respect, the interaction between transforming growth factor-β, which is known to be pivotal in the development of pulmonary fibrosis, and the integrin alphaVβ6 is of particular interest. Integrin alphaVβ6 is responsible for the activation of constitutively expressed latent transforming growth factor-β by a mechanism that allows for temporal and spatial activity control. There is increasing evidence that this mechanism plays a critical role in the pathological activity of transforming growth factor-β. Although other activation mechanisms have been identified, studies suggest that alphaVβ6-mediated activation of transforming growth factor-β is necessary for the development of fibrosis in lung-disease models. The data from such studies imply that integrins may be attractive targets for intervention in pulmonary fibrotic diseases, such as idiopathic pulmonary fibrosis.
Integrins and their ligands in rheumatoid arthritis
Torsten Lowin, Rainer H Straub
Arthritis Research & Therapy , 2011, DOI: 10.1186/ar3464
Abstract: Integrins are a large group of transmembrane proteins that anchor the cell to the extracellular matrix (ECM) or other cells. Upon binding, integrins remodel the ECM by inducing the expression of certain proteases. Integrins control cellular proliferation, migration, and invasion. Whereas in some cases integrins can mediate these effects on their own, they usually signal in the context of growth factor or cytokine receptors [1]. Ligand binding to integrin controls adhesion-dependent proliferation, whereas unligated integrins enhance apoptotic pathways [2]. This is one reason why dysregulated integrin expression or downstream signaling pathways can be observed in almost all forms of cancer, and integrin levels often determine the aggressiveness or propensity to metastasize.Migration, invasion, and proliferation of synovial cells are major problems in rheumatoid arthritis (RA) [3]. This debilitating disease is characterized by an inflamed synovial tissue with a massive influx of immune cells and an inflated synovial lining consisting mainly of synovial fibroblasts (SFs) and macrophages that adhere to the adjacent ECM. These SFs are highly proliferative and contribute significantly to cartilage and bone destruction. In some aspects, they can be considered 'tumor-like' as SFs are resistant to many apoptotic pathways, show increased proliferation, and produce high amounts of matrix metalloproteinases (MMPs) because of dysregulation of the transcription factors AP-1, p53, and nuclear factor-kappa-B (NF-κB) [4]. Fibroblasts, macrophages, but also endothelial cells in synovial tissue show high levels of integrin expression [5]. In RA, not only integrins but also their ligands (for example, fibronectin and collagen as well as their degradation products) are up-regulated [6]. This 'overstimulation' of cells by integrin-mediated signals increases basal secretion of proinflammatory cytokines like interleukin-6 (IL-6) and IL-8 but also levels of various MMPs [7-9].This review int
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