PROLIDASE ACTIVITY IN FIBROBLASTS IS REGULATED BY INTERACTION OF EXTRACELLULAR-MATRIX WITH CELL-SURFACE INTEGRIN RECEPTORS

Prolidase (EC 3.4.13.9) is a ubiquitously distributed imidodipeptidase that catalyzes the hydrolysis of C-terminal proline or hydroxyproline containing dipeptides. The enzyme plays an important role in the recy cling of proline for collagen synthesis and cell growth. An increase i n enzyme activity is correlated with increased rates of collagen turno ver indicative of extracellular matrix (ECM) remodeling, but the mecha nism linking prolidase activity and ECM is poorly understood. Thus, th e effect of ECM-cell interaction on intracellular prolidase activity i s of special interest. In cultured human skin fibroblasts, the interac tion with ECM and, more specifically, type I collagen mediated by the beta(1) integrin receptor regulates cellular prolidase activity. Suppo rting evidence comes from the following observations: 1) in sparse cel ls with a low amount of ECM collagen or in confluent cells in which EC M collagen was removed by collagenase (but not by trypsin or elastase) treatment, prolidase activity was decreased; 2) this effect was rever sed by the addition of type I collagen or beta(1) integrin antibody (a gonist for beta(1) integrin receptor); 3) sparse cells (with typically low prolidase activity) showed increased prolidase activity when grow n on plates coated with type I collagen or on type IV collagen and lam inin, constituents of basement membrane; 4) the relative differences i n prolidase activity due to collagenase treatment and subsequent recov ery of the activity by beta(1) integrin antibody or type I collagen tr eatment were accompanied by parallel differences in the amount of the enzyme protein recovered from these cells, as shown by Western immunob lot analysis. Thus, we conclude that prolidase activity responded to E CM metabolism (tissue remodeling) through signals mediated by the inte grin receptor. (C) 1997 Wiley-Liss, Inc.