A role for a 70-kDa amino-terminal fibronectin fragment in supporting soluble gelatin interactions with rat peritoneal macrophages

Abstract

Seventy-kilodalton amino-terminal and 180-kDa cell-binding fibronectin fragments were used to determine which fibronectin domains support soluble gelatin interactions with macrophages. At each time measured, intact and 180-kDa fibronectin supported significantly larger quantities of cell-associated gelatin than control levels (P < 0.05). Throughout the time course fibronectin supported more binding than 180 kDa. Seventy kilodalton did not augment gelatin binding until 2 h, but by 6 h 70 kDa supported more binding than intact fibronectin (P < 0.01). This appeared to result from a cellular response initiated by 70-kDa-gelatin interactions with the macrophages. Within 4 h the majority of gelatin associated with cells under control conditions, and in the presence of fibronectin or 180 kDa, was internalized. Seventy-kilodalton-mediated binding remained localized primarily to the cell surfaces at all times. The macrophages partially degraded the internalized and external gelatin fractions. These results demonstrate that intact fibronectin and specific fibronectin fragments support soluble gelatin interactions with macrophages.

A 70-kDa amino-terminal fibronectin fragment supports gelatin binding to macrophages and decreases gelatinase activity

“…Preincubation of macrophage cell layers with a 70-kDa aminoterminal fibronectin fragment and nonlabeled gelatin induces a unique cellular response that initiates augmented 125 I-DLTgelatin binding to macrophages [1]. To determine whether this macrophage response required protein synthesis, cell layers were treated with cycloheximide or puromycin before preincubation with nonlabeled gelatin and 70-kDa fibronectin fragment ( Fig.…”

“…Plasma fibronectin was isolated from the blood of healthy human volunteers or from Slime A preparations provided by Hyland Laboratories, San Francisco, CA as previously described [1,30]. All fibronectin fragments used were prepared as previously described [1].…”

“…All fibronectin fragments used were prepared as previously described [1]. Bovine denatured collagen (Sigma) was prepared and conjugated with 125 I-dilactitol tyramine (DLT) according to the method of Strobel et al [32] and modified by Penc et al [1].…”

“…For instance, the interaction between fibronectin and cells from the mononuclear phagocyte system affects chemotaxis, adherence, secretion, and phagocytosis [3][4][5][6][7][8]. We previously reported that association of macrophages with a 70-kDa amino-terminal fibronectin fragment and gelatin initiated a cellular response that induced 125 I-radiolabeled gelatin binding to the cells [1]. Such interactions may be important after injury when soluble gelatin is formed and released into the vasculature [9].…”

“…Proteases are certainly required for wound repair and the formation of fibronectin fragments may optimize such processes by initiating biological responses that can be quite different from those expressed by the intact fibronectin molecule [7,[21][22][23][24]. We recently reported that intact fibronectin and two gelatin-binding fibronectin fragments supported in vitro interaction between soluble 125 I-radiolabeled gelatin and macrophages [1]. A 180-kDa integrin-binding fibronectin fragment supported less gelatin binding than intact fibronectin.…”