[Fragmentation of fibronectin in cystic fibrosis]

Fibronectin (FN) plays an important role in mediating cell-matrix interactions and also as an opsonin in the phagocytosis of some microorganisms. Due to its domain structure FN is easily attacked by proteolytic enzymes and especially by elastases. Some of the fragments possess original properties as potentiation of viral transformation or proteolytic activity absent in the intact molecule. Cystic fibrosis is frequently accompanied by infection with protease generating microorganisms, such as Pseudomonas aeruginosa. Polyacrylamide gel electrophoresis and immunoblotting revealed the presence of FN fragments in the plasma of patients with molecular weight between 30 and 100 kD. Purified plasma FN was rapidly hydrolyzed in fragments by the sputum of patients as well as by purified Pseudomonas elastase. The comparison of fragments detected in patients' plasma with those produced by in vitro proteolysis confirms the probability of in vivo fragmentation of FN in cystic fibrosis and suggests that several proteolytic enzymes, endogenous and of bacterial origin, might be involved.