Abstract
Abstract: :
Purpose: Opticin is a member of the extracellular matrix small leucine-rich repeat protein (SLRP) family that was initially identified closely related to vitreous collagen fibrils (JBC, 2000, 275: 2123-2129). Opticin is almost exclusively expressed by the eye and in the mouse its expression is confined to the non-pigmented ciliary epithelium. To date, very little is known about its function. The purpose of this study was to investigate the potential interaction of opticin with cellular receptors such as integrins. Methods: Purified recombinant bovine opticin was used to study its interaction with A375-SM melanoma cells by cell spreading assay. The A375-SM human melanoma cells expressed a variety of integrins. As controls, vascular cell adhesion molecule (VCAM) and a 50-kDa fragment of fibronectin were used as ligands. In order to identify the integrins responsible for interactions, anti-functional antibodies raised against various α and ß chains were used as inhibitors during cell spreading assays. Results: The cell spreading assays showed 30-40% of the cells spreading when opticin was coated on the wells at 100 µg/ml. Inhibition assays revealed that the interaction between A375-SM cells and opticin could be blocked by using anti-functional antibodies raised against α4 (HP1/2), αV (17E6), ß1 (mAb13) and ß3 (14D12.D3) chains. Conclusions: These results suggest that opticin is a ligand for the α4ß1 and αVß3 integrins. Therefore, opticin could be a key regulator of physiological and pathological processes within the eye, including angiogenesis within the vitreous cavity.
Keywords: cell adhesions/cell junctions • extracellular matrix • vitreous