Collagen can modulate cell interactions with fibronectin.

Abstract

The effects of soluble collagen on the function of fibronectin in baby hamster kidney (BHK) cells was examined. Collagen and its purified .alpha.1(I) chain noncompetitively inhibited cell spreading on substrates precoated with fibronectin or a 75,000-D [dalton] cell-binding fragment of fibronectin. Neither preincubation of cells with collagen followed by washing nor the addition of collagen to previously spread cells had any inhibitory effect on cell spreading, which indicates a requirement for the concurrent presence of collagen during the process of spreading. Treatment of collagen or .alpha.1(I) chain with collagenase abolished the inhibitory effect on fibronectin-mediated cell spreading. Direct attachment of BHK cells to fibronectin-coated or 75,000-D fragment-coated substrates was not inhibited by collagen or by the .alpha.1(I) chain. The binding of [3H]fibronectin or the 3H-75,000-D fragment to cell surfaces was not inhibited by the presence of soluble collagen, whereas soluble fibronectin inhibited binding. Although the binding of [3H]fibronectin-coated beads to BHK cell surfaces was also not inhibited by collagen, the phagocytosis of such beads was inhibited by the presence of collagen. Soluble fibronectin partially inhibited the binding of fibronectin-coated beads but did not inhibit phagocytosis of the beads that did bind. The mechanism of the inhibition of fibronectin function by collagen and the possible interactions of 2 different kinds of receptors on the cell surface are discussed.