GLIA-DERIVED NEXIN PROTEASE NEXIN-1 IS EXPRESSED BY A SUBSET OF NEURONS IN THE RAT-BRAIN/

Glia-derived nexin/protease nexin-1 (GDN/PN-1) is a serine protease in hibitor that is secreted by glial cells and fibroblasts in culture. In the adult mammalian nervous system it has been shown to be expressed in the olfactory system and by some glial cells in response to neurona l injury. In situ hybridization and immunocytochemical studies were pe rformed to identify the structures expressing GDN/PN-1 in the developi ng and adult rat brain. In contrast to a transient widespread expressi on during pre- and postnatal development, some brain structures consti tutively express GDN/PN-1. These include the olfactory nerve layer of the olfactory bulb, basal forebrain, striatum, pyramidal neurons of la yer V in the cortex, thalamic nuclei, pars compacta of the substantia nigra, inferior and superior colliculi, and deep cerebellar nuclei. Al l of these parts, excluding the olfactory nerve layer, are characteriz ed by a high neuronal cell density. Neurons in these regions were immu noreactive for GDN/PN-1. Furthermore GDN/PN-1 expression in cell lines showed that the active protein was synthesized and secreted from B104 but not from NB2a neuroblastoma cells. Although GDN/PN-1 has only bee n reported to be synthesized by glia, the results presented here demon strate that in addition, a subset of neurons express this protease inh ibitor. (C) 1994 Wiley-Liss, Inc.