Re-evaluation of protease activity of reelin.

Reelin is a very large secreted glycoprotein that is essential for brain formation and function, but the mechanism by which it affects the dynamics and morphology of neuronal cells remains unsolved. One previous study claimed that Reelin has a proteolytic activity against extracellular matrix proteins, which might explain many of the actions of Reelin. Therefore, in this study wild-type Reelin protein and its mutant in which a supposedly critical serine residue was replaced were expressed and tested for their self-degrading and laminin-degrading activities. We found that both of these proteins generated totally the same cleaved fragments and that neither of them is capable of degrading laminin. It is thus likely that Reelin is not a serine protease and is unable to degrade extracellular matrix.