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Stable Adhesion (stable + adhesion)
Selected AbstractsMyopodia (postsynaptic filopodia) participate in synaptic target recognitionDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2003Sarah Ritzenthaler Abstract Synaptic partner cells recognize one another by utilizing a variety of molecular cues. Prior to neuromuscular synapse formation, Drosophila embryonic muscles extend dynamic actin-based filopodia called "myopodia." In wild-type animals, myopodia are initially extended randomly from the muscle surface but become gradually restricted to the site of motoneuron innervation, a spatial redistribution we call "clustering." Previous experiments with prospero mutant embryos demonstrated that myopodia clustering does not occur in the absence of motoneuron outgrowth into the muscle field. However, whether myopodia clustering is due to a general signal from passing axons or is a result of the specific interactions between synaptic partners remained to be investigated. Here, we have examined the relationship of myopodia to the specific events of synaptic target recognition, the stable adhesion of synaptic partners. We manipulated the embryonic expression of ,PS2 integrin and Toll, molecules known to affect synaptic development, to specifically alter synaptic targeting on identified muscles. Then, we used a vital single-cell labeling approach to visualize the behavior of myopodia in these animals. We demonstrate a strong positive correlation between myopodia activity and synaptic target recognition. The frequency of myopodia clustering is lowered in cases where synaptic targeting is disrupted. Myopodia clustering seems to result from the adherence of a subset of myopodia to the innervating growth cone while the rest are eliminated. The data suggest that postsynaptic cells play a dynamic role in the process of synaptic target recognition. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 31,40, 2003 [source] Manipulating CD4+ T cells by optical tweezers for the initiation of cell-cell transfer of HIV-1JOURNAL OF BIOPHOTONICS, Issue 4 2010Gregory P. McNerney Abstract Cell-cell interactions through direct contact are very important for cellular communication and coordination , especially for immune cells. The human immunodeficiency virus type I (HIV-1) induces immune cell interactions between CD4+ cells to shuttle between T cells via a virological synapse. A goal to understand the process of cell-cell transmission through virological synapses is to determine the cellular states that allow a chance encounter between cells to become a stable cell-cell adhesion. We demonstrate the use of optical tweezers to manipulate uninfected primary CD4+ T cells near HIV Gag-iGFP transfected Jurkat T cells to probe the determinants that induce stable adhesion. When combined with fast 4D confocal fluorescence microscopy, optical tweezers can be utilized not only to facilitate cell-cell contact, but also to simultaneously track the formation of a virological synapse, and ultimately to probe the events that precede virus transfer. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nitric oxide specifically inhibits integrin-mediated platelet adhesion and spreading on collagenJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2008W. ROBERTS Summary.,Background:,Nitric oxide (NO) inhibits platelet adhesion to collagen, although the precise molecular mechanisms underlying this process are unclear. Objectives:,Collagen-mediated adhesion is a multifaceted event requiring multiple receptors and platelet-derived soluble agonists. We investigated the influence of NO on these processes. Results:,S-nitrosoglutathione (GSNO) induced a concentration-dependent inhibition of platelet adhesion to immobilized collagen. Maximal adhesion to collagen required platelet-derived ADP and TxA2. GSNO-mediated inhibition was lost in the presence of apyrase and indomethacin, suggesting that NO reduced the availability of, or signaling by, ADP and TxA2. Exogenous ADP, but not the TxA2 analogue U46619, reversed the inhibitory actions of GSNO on adhesion. Under adhesive conditions NO inhibited dense granule secretion but did not influence TxA2 generation. These data indicated that NO may block signaling by TxA2 required for dense granule secretion, thereby reducing the availability of ADP. Indeed, we found TxA2 -mediated activation of PKC was required to drive dense granule secretion, a pathway that was inhibited by NO. Because our data demonstrated that NO only inhibited the activation-dependent component of adhesion, we investigated the effects of NO on individual collagen receptors. GSNO inhibited platelet adhesion and spreading on ,2,1 specific peptide ligand GFOGER. In contrast, GSNO did not inhibit GPVI-mediated adhesion to collagen, or adhesion to the GPVI specific ligand, collagen related peptide (CRP). Conclusions:,NO targets activation-dependent adhesion mediated by ,2,1, possibly by reducing bioavailability of platelet-derived ADP, but has no effect on activation-independent adhesion mediated by GPVI. Thus, NO regulates platelet spreading and stable adhesion to collagen. [source] Role of ,4,1 Integrins in Chemokine-Induced Monocyte Arrest under Conditions of Shear StressMICROCIRCULATION, Issue 1 2009SHARON J. HYDUK ABSTRACT Monocyte recruitment or emigration to tissues is an essential component of host defense in both acute and chronic inflammatory responses. Sequential molecular interactions mediate a cascade of tethering, rolling, arrest, stable adhesion, and intravascular crawling that culminates in monocyte diapedesis across the vascular endothelium and migration through the basement membrane of postcapillary venules. Integrins are complex adhesion and signaling molecules. Dynamic alterations in their conformation and distribution on the monocyte cell surface are required for many steps of monocyte emigration. Intracellular signaling initiated by chemokine receptors induces conformational changes in integrins that upregulate their affinity for ligands, and this is essential for monocyte arrest. This review focuses on the activation of monocyte ,4,1 integrins by endothelial chemokines, which is required for the arrest of monocytes rolling on vascular cell adhesion molecule 1 under shear flow. Using soluble ligand-binding assays and adhesion assays in parallel-plate flow chambers, critical signaling mediators in chemokine-induced ,4,1 integrin affinity upregulation and monocyte arrest have been identified, including phospholipase C, calcium, and calmodulin. [source] Structure of the Calx-, domain of the integrin ,4 subunit: insights into function and cation-independent stabilityACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Noelia Alonso-García The integrin ,6,4 is a receptor for laminins and provides stable adhesion of epithelial cells to the basement membranes. In addition, ,6,4 is important for keratinocyte migration during wound healing and favours the invasion of carcinomas into surrounding tissue. The cytoplasmic domain of the ,4 subunit is responsible for most of the intracellular interactions of the integrin; it contains four fibronectin type III domains and a Calx-, motif. The crystal structure of the Calx-, domain of ,4 was determined to 1.48,Å resolution. The structure does not contain cations and biophysical data support the supposition that the Calx-, domain of ,4 does not bind calcium. Comparison of the Calx-, domain of ,4 with the calcium-binding domains of Na+/Ca2+ -exchanger 1 reveals that in ,4 Arg1003 occupies a position equivalent to that of the calcium ions in the Na+/Ca2+ -exchanger. By combining mutagenesis and thermally induced unfolding, it is shown that Arg1003 contributes to the stability of the Calx-, domain. The structure of the Calx-, domain is discussed in the context of the function and intracellular interactions of the integrin ,4 subunit and a putative functional site is proposed. [source] Talin2 is induced during striated muscle differentiation and is targeted to stable adhesion complexes in mature muscleCYTOSKELETON, Issue 3 2007Melissa A. Senetar Abstract The cytoskeletal protein talin serves as an essential link between integrins and the actin cytoskeleton in several similar, but functionally distinct, adhesion complexes, including focal adhesions, costameres, and intercalated disks. Vertebrates contain two talin genes, TLN1 and TLN2, but the different roles of Talin1 and Talin2 in cell adhesion are unclear. In this report we have analyzed Talin1 and Talin2 in striated muscle. Using isoform-specific antibodies, we found that Talin2 is highly expressed in mature striated muscle. Using mouse C2C12 cells and primary human skeletal muscle myoblasts as models of muscle differentiation, we show that Talin1 is expressed in undifferentiated myoblasts and that Talin2 expression is upregulated during muscle differentiation at both the mRNA and protein levels. We have also identified regulatory sequences that may be responsible for the differential expression of Talin1 and Talin2. Using GFP-tagged Talin1 and Talin2 constructs, we found that GFP-Talin1 targets to focal adhesions while GFP-Talin2 targets to abnormally large adhesions in myoblasts. We also found that ectopic expression of Talin2 in myoblasts, which do not contain appreciable levels of Talin2, dysregulates the actin cytoskeleton. Finally we demonstrate that Talin2, but not Talin1, localizes to costameres and intercalated disks, which are stable adhesions required for the assembly of mature striated muscle. Our results suggest that Talin1 is the primary link between integrins and actin in dynamic focal adhesions in undifferentiated, motile cells, but that Talin2 may serve as the link between integrins and the sarcomeric cytoskeletonin stable adhesion complexes in mature striated muscle. Cell Motil. Cytoskeleton 2007. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||