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Integrin Function (integrin + function)
Selected AbstractsL1, ,1 integrin, and cadherins mediate axonal regeneration in the embryonic spinal cordDEVELOPMENTAL NEUROBIOLOGY, Issue 14 2006Murray Blackmore Abstract Embryonic birds and mammals are capable of axon regeneration after spinal cord injury, but this ability is lost during a discrete developmental transition. We recently showed that changes within maturing neurons, as opposed to changes solely in the spinal cord environment, significantly restrict axon regeneration during development. The developmental changes within neurons that limit axon regeneration remain unclear. One gap in knowledge is the identity of the adhesive receptors that embryonic neurons use to extend axons in the spinal cord. Here we test the roles of L1/NgCAM, ,1 integrin, and cadherins, using a coculture system in which embryonic chick brainstem neurons regenerate axons into an explant of embryonic spinal cord. By in vivo and in vitro methods, we found that brainstem neurons reduce axonal expression of L1 as they mature. Disrupting either L1 or ,1 integrin function individually in our coculture system partially inhibited growth of brainstem axons in spinal cords, while disrupting cadherin function alone had no effect. However, when all three adhesive receptors were blocked simultaneously, axon growth in the spinal cord was reduced by 90%. Using immunohistochemistry and in situ hybridization we show that during the period when neurons lose their regenerative capacity they reduce expression of mRNA for N-cadherin, and reduce axonal L1/NgCAM protein through a post-transcriptional mechanism. These data show that embryonic neurons use L1/NgCAM, ,1 integrin, and cadherin receptors for axon regeneration in the embryonic spinal cord, and raise the possibility that a reduced expression of these essential receptors may contribute to the low-regenerative capacity of older neurons. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Zinc, copper and manganese enhanced keratinocyte migration through a functional modulation of keratinocyte integrinsEXPERIMENTAL DERMATOLOGY, Issue 6 2000I. Tenaud Abstract: The migration of keratinocytes plays an important role in the re-epithelialization of cutaneous wounds. Zinc, copper and manganese are used in vivo for their healing properties and their mechanism of action is still only partially known. Thus, they have been shown both to promote keratinocyte proliferation and to modulate integrins expression. The aim of this study was to determine if trace elements induce an increase of the migration of keratinocytes and if this effect is related to the modulation of integrins. Two independent migration assays were used to study keratinocyte migration: the scratch assay using normal human keratinocytes and the modified Boyden chamber using HaCaT cells. Inhibition studies using function-blocking antibodies directed to ,3, ,6, ,V and ,1 subunits were performed to investigate the modulator effect of trace elements on integrin function. In this way, zinc and copper gluconates increased ,3, ,V and ,1 function whereas manganese gluconate seems mainly able to modulate the function of ,3 and ,1. The stimulating effect of these trace elements on keratinocyte migration does not appear related to ,6 subunit. Thus, zinc, copper and manganese enhanced keratinocyte migration and one of the mechanisms was going through a modulation of integrin functions. [source] Compact spheroid formation by ovarian cancer cells is associated with contractile behavior and an invasive phenotypeINTERNATIONAL JOURNAL OF CANCER, Issue 9 2009Katharine L. Sodek Abstract Ovarian cancer cells are present in malignant ascites both as individual cells and as multicellular spheroid aggregates. Although spheroid formation affords protection of cancer cells against some chemotherapeutic agents, it has not been established whether a relationship exists between invasive behavior and predisposition to spheroid formation. Aspects of spheroid formation, including cell-matrix adhesion, remodeling and contractility are characteristic myofibroblast-like behaviors associated with fibrosis that contribute to tumor growth and dissemination. We explored the possibility that cell behaviors that promote spheroid formation also facilitate invasion. Our analysis of 6 human ovarian cancer cell lines indicated that ovarian cancer cells possessing myofibroblast-like properties formed compact spheroids and invaded 3D matrices. These cells readily contracted collagen I gels, possessed a spindle-like morphology, and had elevated expression of genes associated with the TGF,-mediated fibrotic response and/or ,1 integrin function, including fibronectin (FN), connective tissue growth factor (CTGF/CCN2), lysyl oxidase (LOX1), tissue transglutaminase 2 (TGM2) and urinary plasminogen activator receptor (uPAR). Whereas cell aggregation was induced by TGF,, and by ,1-integrin overexpression and activation, these treatments did not stimulate the contractile activity required for spheroid compaction. The positive relationship found between compact spheroid formation and invasive behavior implies a preferential survival of an invasive subpopulation of ovarian cancer cells, as cells in spheroids are more resistant to several chemotherapeutics. Preventing the formation of ovarian cancer spheroids may represent a novel strategy to improve the efficacy of existing therapeutics. © 2008 Wiley-Liss, Inc. [source] Critical amino acid residues of the ,4 subunit for ,4,7 integrin functionJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2001Yvonka Zeller Abstract A characteristic feature of integrin,ligand interactions is the requirement for divalent cations. Putative cation binding sites have been identified in the , and , subunit of the ,4 integrins, ,4,1 and ,4,7, and within their ligands which display the tripeptide LDV in fibronectin and homologous motifs in VCAM-1 and MAdCAM-1. The extracellular domain of the murine and human ,4-subunit contains three conserved LDV motifs, designated LDV-1 to -3. Using site directed mutagenesis and transfection studies, we now examined the functional relevance of the LDV motifs for ,4,7 integrins. We present evidence that LDV-1 mutants (D489N) behave like ,4 wt cells, but LDV-3 mutants (D811N) are impaired in ,4,7 integrin-triggered homotypic cell aggregation and in adhesion and spreading on ,4 specific ligands. Further characterization of LDV-3 mutants revealed a defect in mAb-induced ,4,7-cell surface cluster formation. Mutation of the LDV-2 motif (D698N) caused loss of ,4,7 integrin cell surface expression. Our results indicate: (i) that LDV-3, located proximal to the cell membrane, is important for ,4,7 integrin-triggered functions and for lateral clustering and (ii) that LDV-2 affects ,4,7 heterodimer stability. J. Cell. Biochem. 83: 304,319, 2001. © 2001 Wiley-Liss, Inc. [source] Megakaryocytes derived from human embryonic stem cells: a genetically tractable system to study megakaryocytopoiesis and integrin functionJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2006M. GAUR Summary.,Background:,The platelet fibrinogen receptor, a heterodimer consisting of integrin subunits ,IIb and ,3, is required for platelet aggregation, spreading, and hemostasis. Platelet agonists such as thrombin and adenosine diphosphate (ADP) lead to the activation of ,IIb,3, thereby enhancing its affinity and avidity for binding fibrinogen (inside-out signaling). Furthermore, fibrinogen binding to ,IIb,3 triggers cytoskeletal changes and granule release (outside-in signaling).Aim:,Genetic approaches to characterize the molecular pathways involved in ,IIb,3 signaling are not possible with anucleate blood platelets. Therefore, we have established an OP9 stromal cell co-culture system to generate megakaryocytes from human embryonic stem cells (hESCs).Results:,,IIb,3 activation, measured by soluble fibrinogen binding to hESC-derived megakaryocytes, /GPIb,+ cells, is readily detectable following stimulation with known platelet agonists. Dose,response curves for peptide agonists specific for the two platelet thrombin receptors, protease-activated receptor 1 (PAR1) and PAR4, show a relative responsiveness that mirrors that of human platelets, and sub-maximal ADP responses are augmented by epinephrine. Moreover, hESC-derived megakaryocytes undergo lamellipodia formation, actin filament assembly, and vinculin localization at focal adhesions when plated on a fibrinogen-coated surface, characteristic of ,IIb,3 outside-in signaling. Undifferentiated hESCs genetically modified by lentiviral infection can be cloned and maintained in an undifferentiated state and then differentiated into megakaryocytes capable of ,IIb,3 activation.Conclusion:,Using hESCs, we have developed a renewable source of human megakaryocytes, and a genetically tractable system for studying megakaryocytopoiesis and ,IIb,3 signaling in the native cellular environment. [source] Zinc, copper and manganese enhanced keratinocyte migration through a functional modulation of keratinocyte integrinsEXPERIMENTAL DERMATOLOGY, Issue 6 2000I. Tenaud Abstract: The migration of keratinocytes plays an important role in the re-epithelialization of cutaneous wounds. Zinc, copper and manganese are used in vivo for their healing properties and their mechanism of action is still only partially known. Thus, they have been shown both to promote keratinocyte proliferation and to modulate integrins expression. The aim of this study was to determine if trace elements induce an increase of the migration of keratinocytes and if this effect is related to the modulation of integrins. Two independent migration assays were used to study keratinocyte migration: the scratch assay using normal human keratinocytes and the modified Boyden chamber using HaCaT cells. Inhibition studies using function-blocking antibodies directed to ,3, ,6, ,V and ,1 subunits were performed to investigate the modulator effect of trace elements on integrin function. In this way, zinc and copper gluconates increased ,3, ,V and ,1 function whereas manganese gluconate seems mainly able to modulate the function of ,3 and ,1. The stimulating effect of these trace elements on keratinocyte migration does not appear related to ,6 subunit. Thus, zinc, copper and manganese enhanced keratinocyte migration and one of the mechanisms was going through a modulation of integrin functions. [source] The microanatomy of the distal arrector pili: possible role for ,1,1 and ,5,1 integrins in mediating cell-cell adhesion and anchorage to the extracellular matrixJOURNAL OF CUTANEOUS PATHOLOGY, Issue 2 2000Jeri Kersten Mendelson The arrector pili (AP) muscle is a small band of smooth muscle that attaches proximally to the bulge area of the pilosebaceous apparatus in the reticular dermis and extends up toward the epidermis. The distal anatomy of the AP and the anchorage mechanism allowing hair erection have not been previously described. Integrins are likely candidates mediating this attachment. Immunohistochemical techniques were used to determine the distribution of the following integrins: ,1, ,2, ,3, ,4, ,5, ,6 and ,1 as well as fibronectin. Frozen human scalp tissue was sectioned in traditional planes, obliquely and horizontally to visualize microanatomy in three dimensions. Histological examination revealed that the distal portions of smooth muscle fibers splay extensively between collagen bundles of the upper dermis. Integrin subunits ,1, ,5 and ,1 were expressed by the AP muscle. Analysis of the relative density of immunoreactivity in digitized sections revealed increased ,5 subunit expression at the extracellular matrix (ECM)-muscle interface. These data suggest that anchorage of the AP muscle to the ECM is via ,5,1 integrin and ,1,1 integrin functions in muscle cell-cell adhesion. Extensive splaying of smooth muscle fibers may allow increased surface area contact between the ECM and smooth muscle cells expressing peripherally situated ,5 integrin. [source] What is vinculin needed for in platelets?JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2010J. V. MITSIOS Summary.,Background: Vinculin links integrins to the cell cytoskeleton by virtue of its binding to proteins such as talin and F-actin. It has been implicated in the transmission of mechanical forces from the extracellular matrix to the cytoskeleton of migrating cells. Vinculin's function in platelets is unknown. Objective: To determine whether vinculin is required for the functions of platelets and their major integrin, ,IIb,3. Methods: The murine vinculin gene (Vcl) was deleted in the megakaryocyte/platelet lineage by breeding Vcl fl/fl mice with Pf4,Cre mice. Platelet and integrin functions were studied in vivo and ex vivo. Results: Vinculin was undetectable in platelets from Vcl fl/fl Cre+ mice, as determined by immunoblotting and fluorescence microscopy. Vinculin-deficient megakaryocytes exhibited increased membrane tethers in response to mechanical pulling on ,IIb,3 with laser tweezers, suggesting that vinculin helps to maintain membrane cytoskeleton integrity. Surprisingly, vinculin-deficient platelets displayed normal agonist-induced fibrinogen binding to ,IIb,3, aggregation, spreading, actin polymerization/organization, clot retraction and the ability to form a procoagulant surface. Furthermore, vinculin-deficient platelets adhered to immobilized fibrinogen or collagen normally, under both static and flow conditions. Tail bleeding times were prolonged in 59% of vinculin-deficient mice. However, these mice exhibited no spontaneous bleeding and they formed occlusive platelet thrombi comparable to those in wild-type littermates in response to carotid artery injury with FeCl3. Conclusion: Despite promoting membrane cytoskeleton integrity when mechanical force is applied to ,IIb,3, vinculin is not required for the traditional functions of ,IIb,3 or the platelet actin cytoskeleton. [source] ADAMs in cancer cell proliferation and progressionCANCER SCIENCE, Issue 5 2007Satsuki Mochizuki A disintegrin and metalloproteinases (ADAMs) are a new gene family of proteins with sequence similarity to the reprolysin family of snake venomases that share the metalloproteinase domain with matrix metalloproteinases (MMPs). They are structurally classified into two groups: the membrane-anchored ADAM and ADAM with thrombospondin motifs (ADAMTS). These molecules are involved in various biological events such as cell adhesion, cell fusion, cell migration, membrane protein shedding and proteolysis. Studies on the biochemical characteristics and biological functions of ADAMs are in progress, and accumulated lines of evidence have shown that some ADAMs are expressed in malignant tumors and participate in the pathology of cancers. The activities of ADAMs are regulated by gene expression, intracytoplasmic and pericellular regulation, activation of the zymogens and inhibition of activities by inhibitors. Many ADAM species, including ADAM8, ADAM9, ADAM10, ADAM12, ADAM15, ADAM17, ADAM19, ADAM28, ADAMTS1, ADAMTS4 and ADAMTS5, are expressed in human malignant tumors. Many of them are involved in the regulation of growth factor activities and integrin functions, leading to promotion of cell growth and invasion, although the precise mechanisms of these are not clear at the present time. In this article, we review recent information about ADAM family members and their implications for cancer cell proliferation and progression. (Cancer Sci 2007; 98: 621,628) [source] | |||||||||||||||||||||||||