6533b7d4fe1ef96bd1262a2b

RESEARCH PRODUCT

Integrin-mediated Cell Adhesion to Type I Collagen Fibrils

subject

description

In the integrin family, the collagen receptors form a structurally and functionally distinct subgroup. Two members of this subgroup, α1β1 and α2β1 integrins, are known to bind to monomeric form of type I collagen. However, in tissues type I collagen monomers are organized into large fibrils immediately after they are released from cells. Here, we studied collagen fibril recognition by integrins. By an immunoelectron microscopy method we showed that integrin α2I domain is able to bind to classical D-banded type I collagen fibrils. However, according to the solid phase binding assay, the collagen fibril formation appeared to reduce integrin α1I and α2I domain avidity to collagen and to lower the number of putative αI domain binding sites on it. Respectively, cellular α1β1 integrin was able to mediate cell spreading significantly better on monomeric than on fibrillar type I collagen matrix, whereas α2β1 integrin appeared still to facilitate both cell spreading on fibrillar type I collagen matrix and also the contraction of fibrillar type I collagen gel. Additionally, α2β1 integrin promoted the integrin-mediated formation of long cellular projections typically induced by fibrillar collagen. Thus, these findings suggest that α2β1 integrin is a functional cellular receptor for type I collagen fibrils, whereas α1β1 integrin may only effectively bind type I collagen monomers. Furthermore, when the effect of soluble αI domains on type I collagen fibril formation was tested in vitro, the observations suggest that integrin type collagen receptors might guide or even promote pericellular collagen fibrillogenesis.