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    ABSTRACT: Mammalian oocytes are surrounded by a highly hydrated hyaluronan (HA)-rich extracellular matrix with embedded cumulus cells, forming the cumulus cell-oocyte complex (COC) matrix. The correct assembly, stability and mechanical properties of this matrix, which are crucial for successful ovulation, transport of the COC to the oviduct and its fertilization, depend on the interaction between HA and specific HA-organizing proteins. Although the proteins inter-αinhibitor (IαI), pentraxin 3 (PTX3) and TNF-stimulated gene-6 (TSG-6) have been identified as being critical for COC matrix formation, its supramolecular organization and the molecular mechanism of COC matrix stabilization remain unknown. Here we used films of end-grafted HA as a model system to investigate the molecular interactions involved in the formation and stabilization of HA matrices containing TSG-6, IαI and PTX3. We found that PTX3 binds neither to HA alone nor to HA films containing TSG-6. This long pentraxin also failed to bind to products of the interaction between IαI, TSG-6 and HA, among which are the covalent HC·HA and HC·TSG-6 complexes, despite the fact that both IαI and TSG-6 are ligands of PTX3. Interestingly, prior encounter with IαI was required for effective incorporation of PTX3 into TSG-6-loaded HA films. Moreover, we demonstrated that this ternary protein mixture made of IαI, PTX3 and TSG-6 is sufficient to promote formation of a stable (i.e. cross-linked) yet highly hydrated HA matrix. We propose that this mechanism is essential for correct assembly of the COC matrix, and may also have general implications in other inflammatory processes that are associated with HA-crosslinking.
    Journal of Biological Chemistry 09/2014; · 4.60 Impact Factor
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    ABSTRACT: Under inflammatory conditions and in the matrix of the cumulus-oocyte complex (COC), the polysaccharide hyaluronan (HA) becomes decorated covalently with heavy chains (HCs) of the serum glycoprotein inter-α-inhibitor (IαI). This alters the functional properties of the HA as well as its structural role within extracellular matrices. The covalent transfer of HCs from IαI to HA is catalyzed by tumor necrosis factor-stimulated gene-6 (TSG-6) but TSG-6 is also known as a HA cross-linker that induces condensation of the HA matrix. Here, we investigate the interplay of these two distinct functions of TSG-6 by studying the ternary interactions of IαI and TSG-6 with well defined films of end-grafted HA chains. We demonstrate that TSG-6 mediated cross-linking of HA films is impaired in the presence of IαI, and that this effect suppresses the TSG-6-mediated enhancement of HA binding to CD44 positive cells. Furthermore, we find that the interaction of TSG-6 and IαI in the presence of HA gives rise to two types of complexes that independently promote the covalent transfer of heavy chains to HA. One type of complex interacts very weakly with HA and is likely to correspond to the previously reported covalent HC·TSG-6 complexes. The other type of complex is novel and binds stably but non-covalently to HA. Prolonged incubation with TSG-6 and IαI leads to HA films that contain, in addition to covalently HA-bound HCs, several tightly but non-covalently bound molecular species. These findings have important implications for understanding how the biological activities of TSG-6 are regulated, such that the presence or absence of IαI will dictate its function.
    Journal of Biological Chemistry 09/2013; · 4.60 Impact Factor
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    ABSTRACT: Cell adhesion is a paradigm of the ubiquitous interplay of cell signalling, modulation of material properties and biological functions of cells. It is controlled by competition of short range attractive forces, medium range repellant forces and the elastic stresses associated with local and global deformation of the composite cell envelopes. We review the basic physical rules governing the physics of cell adhesion learned by studying cell-mimetic systems and demonstrate the importance of these rules in the context of cellular systems. We review how adhesion induced micro-domains couple to the intracellular actin and microtubule networks allowing cells to generate strong forces with a minimum of attractive cell adhesion molecules (CAMs) and to manipulate other cells through filopodia over micrometer distances. The adhesion strength can be adapted to external force fluctuations within seconds by varying the density of attractive and repellant CAMs through exocytosis and endocytosis or protease-mediated dismantling of the CAM-cytoskeleton link. Adhesion domains form local end global biochemical reaction centres enabling the control of enzymes. Actin-microtubule crosstalk at adhesion foci facilitates the mechanical stabilization of polarized cell shapes. Axon growth in tissue is guided by attractive and repulsive clues controlled by antagonistic signalling pathways.
    Soft Matter 02/2014; 10(11):1644-59. · 4.15 Impact Factor

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May 15, 2014