Dual mechanism of laminin modulation of ecto‐5′‐nucleotidase activity

Abstract

The myoblast cell surface activity of ecto-5'-nucleotidase was stimulated by a laminin substrate, whereas fibronectin and gelatin did not increase the AMPase activity of ecto-5'-nucleotidase. This increase was related to a higher expression of ecto-5'-nucleotidase on the surface of cells seeded on a laminin substrate, but without the mobilization of an intracellular pool of enzyme. Furthermore, laminin and its fragments E'1 and E8 modified the AMPase activity of the ecto-5'-nucleotidase purified from chicken striated muscle and reconstituted in liposomes. Over the range of concentrations used, intact laminin and its fragment E8, consisting of the distal half of the long arm, stimulated the AMPase activity of ecto-5'-nucleotidase. By contrast, the large fragment derived from the short arms, designated E'1, inhibited the AMPase activity. Furthermore, the monoclonal anti-ecto-5'-nucleotidase antibody, CG37, abolished the stimulatory effect of fragment E8 on the AMPase activity of ecto-5'-nucleotidase but did not reverse the inhibitory effect of fragment E'1. In conclusion, laminin stimulates the AMPase activity of ecto-5'-nucleotidase by two mechanisms: inducing the expression of ecto-5'-nucleotidase to the cell surface and direct modulation of the enzymatic activity.

Inhibition of CD73 stimulates the migration and invasion of B16F10 melanoma cells in vitro, but results in impaired angiogenesis and reduced melanoma growth in vivo

“…It is possible that the conformation of ecto-5'-nucleotidase changed in the presence of inhibitory AOPCP, thus interfering with ECM binding, similar to previously indicated results for eukaryotic cells and the 5'-nucleotidase from E. coli (38). The difference between its effect on B16F10 adhesion to Matrigel and fibronectin might be explained by the presence of laminin in Matrigel and its ability to direct more CD73 to the cell surface (39). The adherence-dependent processes of migration and invasion were upregulated in AOPCP-treated B16F10 cells and downregulated by a set of adenosine receptor agonists.…”

Cellular function and molecular structure of ecto-nucleotidases

“…Antibodies directed against eN or laminin specifically perturbed the association of the two proteins. Laminin stimulated and fibronectin inhibited catalytic activity [275,276]. Moreover, laminin and fragments of fibronectin were found to activate eN on BCS-TC2 human colon adenocarcinoma cells.…”

Extracellular metabolism of ATP and other nucleotides

“…Whereas suramin and PPADS have only a small inhibitory effect on ecto-5'-nucleotidase, non-hydrolyzable analogues of ATP inhibit ecto-5'-nucleotidase (Servos et al 1998). The potential of laminin to stimulate activity of 5'-nucleotidase, of fibronectin to reduce enzyme activity of ecto-5'-nucleotidase (Dieckhoff et al 1986;Olmo et al 1992;Méhul et al 1993), or of glycosaminoglycans such as heparin and heparan sulfate to inhibit catalytic activity of NPP1 suggests that the ecto-nucleotidases may be under the control of extracellular matrix proteins (Hosoda et al 1999).…”