Cloning and sequencing of the cDNA encoding human neurotrypsin.

cDNA clones encoding human neurotrypsin have been isolated from a human fetal brain cDNA library using a PCR-amplified probe. The assembled cDNA sequence contains a 2625 bp open reading frame encoding a multidomain serine protease with an overall sequence identity of 82.5% to murine neurotrypsin. Surprisingly, the human neurotrypsin exhibits an additional scavenger receptor cysteine-rich repeat.

Expression of neuroserpin, an inhibitor of tissue plasminogen activator, in the developing and adult nervous system of the mouse.

Neuroserpin is a serine protease inhibitor of the serpin family that has been identified as an axonally secreted glycoprotein in neuronal cultures of chicken dorsal root ganglia. To obtain an indication for possible functions of neuroserpin, we analyzed its expression in the developing and the adult CNS of the mouse. In the adult CNS, neuroserpin was most strongly expressed in the neocortex, the hippocampal formation, the olfactory bulb, and the amygdala. In contrast, most thalamic nuclei, the caudate putamen, and the cerebellar granule cells were devoid of neuroserpin mRNA. During embryonic development, neuroserpin mRNA was not detectable in neuroepithelia, but it was expressed in the differentiating fields of most CNS regions concurrent with their appearance. In the cerebellum, the granule cells and a subgroup of Purkinje cells were neuroserpin-positive during postnatal development. As a further step toward the elucidation of neuroserpin function, we performed a study to identify potential target proteases. In vitro, neuroserpin formed SDS-stable complexes and inhibited the amidolytic activity of tissue plasminogen activator, urokinase, and plasmin. In contrast, no complex formation with or inhibition of thrombin was found. Expression pattern and inhibitory specificity implicate neuroserpin as a candidate regulator of plasminogen activators, which have been suggested to participate in the modulation or reorganization of synaptic connections in the adult. During development, neuroserpin may attenuate extracellular proteolysis related to processes such as neuronal migration, axogenesis, or the formation of mature synaptic connections.

Neurotrypsin, a novel multidomain serine protease expressed in the nervous system.

We have cloned a novel murine cDNA encoding a multidomain serine protease, termed neurotrypsin, which exhibits an unprecedented domain composition. The deduced amino acid sequence defines a mosaic protein of 761 amino acids consisting of a kringle domain, followed by three scavenger receptor cysteine-rich repeats, and a serine protease domain. Based on comparisons of the primary structure, the protease domain belongs to the subfamily of trypsin-like serine proteases. In situ hybridization revealed that the expression of neurotrypsin in the adult murine nervous system is confined to distinct subsets of neurons. The most prominent expression was found in the cerebral cortex, the hippocampus, and the amygdala. Le., structures engaged in the processing and storage of learned behaviors and memories. Together with the recently obtained evidence that extracellular serine proteases play a role in neural plasticity, this expression pattern suggests that the extracellular proteolytic action of neurotrypsin subserves structural reorganizations associated with learning and memory operations.