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Query: UMLS:C0001511 (Adhesion)
 5,955 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelet adhesion has been measured to type-I monomeric collagen, collagen fibres, alpha 1(I) and alpha 2(I) chains and the chain fragments alpha 1(I)CB3, alpha 1(I)CB6, alpha 1(I)CB7 and alpha 1(I)CB8, and alpha 2(I)CB3,5 and alpha 2(I)CB4. Little if any adhesion occurred to any denatured species at 37 degrees C, demonstrating the importance of the collagen helix. However, on coating at 4 degrees C to promote helix formation, and assaying at room temperature to avoid denaturation, adhesion was observed to both alpha-chain types and all fragments, the exact level of which depended on the identity of the species in question. Adhesion was strongly Mg(2+)-dependent. Antibodies against the integrin alpha 2 beta 1 partially inhibited adhesion to alpha-chains and all fragments except alpha 1(I)CB6, indicating a wide distribution of alpha 2 beta 1-binding sites in the collagen molecule. 'Activation-dependent' adhesion to monomeric collagen, totally secondary to alpha 2 beta 1-mediated adhesion, involved at least two mechanisms, one mediated by integrin alpha IIb beta 3 and insensitive to prostaglandin E1, the other inhibitable by prostaglandin E1 but independent of integrin alpha IIb beta 3. alpha IIb beta 3-mediated adhesion to fragments was, at least in part, independent of the alpha 2 beta 1-mediated adhesion. Adhesion to fibres was largely bivalent-cation-independent with only minor involvement of integrin alpha 2 beta 1. Some alpha IIb beta 3-mediated adhesion occurred but was independent of any alpha 2 beta 1-initiated adhesion. Total 'activation-dependent' adhesion to fibres was less than to monomeric collagen. Affinity chromatography revealed bivalent-cation-independent binding to fibres of three main platelet surface proteins, 90, 150 and 190 kDa in size.
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PMID:Conformation-dependent platelet adhesion to collagen involving integrin alpha 2 beta 1-mediated and other mechanisms: multiple alpha 2 beta 1-recognition sites in collagen type I. 751 71

A large variety of cells adhere to and spread on specific regions within the triple helix of collagens, mainly via alpha 1 beta 1 and alpha 2 beta 1 integrins. Disruption of collagen triple helical integrity generally affects the efficiency of cell adhesion on different collagens including collagen V. This report addresses the question of the importance of the linear sequence of the constitutive alpha-chains versus the triple helical conformation in the recognition of collagen V binding sites. To investigate this question, in vitro renaturation of the isolated alpha 1 (V) and alpha 2 (V) chains was performed according to the annealing procedure and formation of the triple helix was monitored by rotary shadowing and by mild trypsin digestion followed by electrophoretic analysis. The results indicate that the alpha 1 (V) and alpha 2 (V) homotrimeric reassociation can occur up to a full-length triple helix but intermediate forms of 50-200 nm long rod-like segments are also observed. We have previously shown that alpha 1 beta 1 and alpha 2 beta 1 integrins, the major collagen receptors, are also involved in cell adhesion to native collagen V. Therefore we chose the following two different cell lines for this study: HT1080 (a human fibrosarcoma cell line) expressing alpha 2 beta 1 and HBL100 (a human mammary epithelial cell line) containing significant amounts of alpha 1 beta 1 and alpha 2 beta 1 integrins. We showed that both alpha 1 (V) and alpha 2(V) homotrimers induced cell adhesion but refolded alpha2(V) chains were more efficient and promoted cell adhesion as well as native collagen V. Thermal stability of refolded alpha-chains was monitored by adhesion promoting activity and showed that cell adhesion was dependent on triple helical conformation of the substrates. Adhesion in all cases was strongly Mg2+ and Mn(2+)-dependent and Ca2+ ions alone were ineffective. Antibodies against alpha 2 and beta 1 integrin subunits completely inhibited HT1080 cell adhesion to all substrates. Moreover, addition of cyclic RGD peptides, which had been shown to interact with alpha 2 beta 1, dramatically affected HT1080 cell adhesion to native collagen V and to the refolded alpha-chains. Antibody to beta 1 subunits abolished HBL100 cell adhesion to all substrates. A complete inhibition of HBL100 cell adhesion to native collagen V was achieved only by simultaneous addition of function-blocking specific monoclonal antibodies against alpha 1 and alpha 2 integrin subunits. However, only alpha 2 beta 1 was engaged obviously in HBL100 cell adhesion to refolded alpha-chains. These data indicate that triple helical conformation is particularly critical for alpha 2 beta 1- and alpha 1 beta 1-dependent adhesion and that the integrin alpha 2 beta 1 is a dominant functional receptor for refolded alpha-chains. We conclude that alpha 2 beta 1-dependent adhesion seems to involve multiple different conformational binding sites while alpha 1 beta 1-dependent adhesion is more restricted to the heterotrimeric native form of the molecule.
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PMID:Structural requirements for alpha 1 beta 1 and alpha 2 beta 1 integrin mediated cell adhesion to collagen V. 883 9