Latent fibronectin‐degrading serine proteinase activity in N‐terminal heparin‐binding domain of human plasma fibronectin

Abstract

The N-terminal 70-kDa fragment of human plasma fibronectin, purified from a cathepsin D digest, is characterized by lack of stability. It is processed proteolytically during incubation in the presence of Ca2' into 27-kDa N-terminal heparin-binding and 45-kDa collagen-binding domains. The N-terminal residue in the 27-kDa fragment was blocked as in native fibronectin. The 45-kDa fragments began with the sequences AAVYQP, AVYQP and VYQP (residues 260, 261, 262 -265 of fibronectin) that correspond to the beginning of the collagen-binding domain. In the presence of Ca2+ the purified 27-kDa fragment underwent further processing finally leading to the cleavage of the bond KS5-DS6 and to the simultaneous appearance of a specific proteolytic activity. Inhibition studies suggests that the newly generated enzyme is a Ca2+-dependent serine proteinase. Among all assayed matrix proteins, the newly generated enzyme cleaves native fibronectin and its fragments. It is proposed that this fibronectinase may originate from the N-terminal domain of fibronectin.Fibronectin is the best known cell adhesion protein that can also be incorporated into the extracellular matrix. It occurs at high level in plasma and other body fluids. Fibronectin contains several structural domains, each of which exhibits various biological functions. The fibronectin molecule (550 kDa) is composed of two almost identical polypeptide chains linked by two disulfide bonds near the COOH-terminus. Each chain bears a number of structural repeats named type I, 11, and 111. The type I and 11 repeats are characterized by a high content of disulfide bonds that are absent in the type I11 repeats (Fig. 1).The N-terminal 29-kDa domain of fibronectin is composed by five type I repeats which are organized into a finger structure. It bears one of the fibrin-binding sites, one of the heparin-binding sites of fibronectin and one of the sites for transglutaminase-activated crosslinking. The N-terminal domain binds Staphylococcus aureus, DNA and the C-terminal heparin-binding domain of adjacent fibronectin molecules to form polymers (reviewed in [l -31).In our previous work we described the isolation and characterization of two matrix-degrading proteinases, FNgelatinase and FN-laminase. The enzymes were localized in the central and C-terminal domains, respectively 14-71. In this paper we describe the generation of a new proteolytic activity during the degradation process of the N-terminal fibronectin fragment.

Immunopurification and characterization of a collagenase/gelatinase domain issued from basement membrane fibronectin

“…3c). The proteolytic potential of plasma fibronectin has been investigated in some previous reports [6,7]. However, these properties could be more important at the cellular level [8,13].…”

“…Plasma fibronectin has been described as a potent proteolytic system activated by limited proteolysis [6,7]. Comparison between both plasma and cellular fibronectin could be very useful to understand some aspects of the molecular mechanisms of tissue remodeling in normal and pathological processes.…”

Matrix Assembly Induction and Cell Migration and Invasion Inhibition by a 13-Amino Acid Fibronectin Peptide

“…integrin receptors), for other ECM components, and for FN itself; through these interactions FN participates in many physiological and pathological processes (3,7). The proteolysis of purified FN with several enzymes, as well as the construction and expression of recombinant FNfgs, has provided evidence that FNfgs can perform activities that are not present in the intact molecule (32)(33)(34)(35)(36).…”

“…The study of proteolytic FNfgs has disclosed cryptic biological activities not shared by the native protein (32)(33)(34)(35)(36). In particular, the FN collagen binding domain (COL-domain), in addition to binding with collagens and gelatin (3,(37)(38)(39)(40), has been shown to possess a number of other biological activities including the expression of collagenase activity (35,(41)(42), the promotion of odontoblast differentiation (43), and the substratum-dependent stimulation of fibroblast migration (44).…”

Matrix degrading properties of sperm serine proteinase, acrosin

“…The intent of this study was to examine the direct effect of the serine proteinase acrosin on various matrix proteins and the possibility of an indirect effect of activation of a matrix-degrading activity from fibronectin [10,11].…”