Metalloprotease MP100: a synaptic protease in rat brain

Proteases are expressed widely throughout the nervous system and perform es sential functions. We have earlier characterized and cloned the metalloprot ease MP100, an enzyme originally described as a beta-amyloid precursor prot ein (beta-APP) processing candidate. In the present study we describe the c ellular and subcellular localization of MP100 in rat brain. A punctuate int racellular immunostaining in cortical, hippocampal and cerebellar neurons s uggests its high abundance in vesicular intracellular structures. The MP100 staining pattern resembled that of the presynaptic protein synaptophysin. In gel filtration chromatography of isolated rat brain synaptosomal membran es, MP100 co-fractionated with synaptophysin and beta-APP. Furthermore, pre -embedding immunoelectron microscopy of the cerebellum revealed MP100 to be localized at synaptic sites. All together, these data might indicate a rol e for MP100 in functions such as proteolytic modification of synaptic prote ins. (C) 1999 Elsevier Science B.V. All rights reserved.