Regulation of spinal neurons through proteolytic actions by serine proteases.

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In order to understand physiological function of a serine protease, motopsin/neurotrypsin (PRSS12), which we previously isolated from brain cDNA, mice lacking motopsin gene were prepared. We also characterized enzymatic property of recombinant motopsin and analyzed the localization of motopsin in the central nervous system. After mutation of motopsin gene has been reported to cause mental retardation just on starting this project, we focused motopsin in the cerebral cortex.1)Preparation of motopsin targeting miceThe first exon of mouse motopsin gene was replaced to pGKneo cassette. Gene targeting was confirmed by Southern hybridization, Northern hybridization and immunohistochemistry using anti-motopsin IgG. The mutant mice showed no deficit on motor on beam walking and foot print tests. Light-dark box test and elevated plus maze showed tendency that mutant mice had less anxiety than wild type. Interestingly, dendritic spine was decreased at pyramidal neurons of cingulate cortex and hi … More ppocampal CA1 region, at which motopsin was preferentially expressed. Our results suggest that motopsin have significant function for the development of emotion rather than motor behavior.2)Characterization of motopsinWe found that motopsin activates tissue plasminogen activator (WA) in vitro last year. The co-localization of motopsin and tPA. When motopsin and tPA were co-expressed in HEK293 cells, both proteases were localized in secretary vesides. Immunohistochemical technique dearly showed oo-localiation of motopsin and tPA at pyramidal neurons of cingulate cortex and hippcampus at postnatal day 10. Further, 12 candidate genes which interact with motopsin were isolated by yeast two hybrid system. Among them, mRNAs for a few genes were detected at motopsin-expressing cells.3)Regulation of the expression of spinesinFour types of spinesin isoforms were generated by alternative splicing. Type 1 and 2 lack the transmembrane domain, whereas type 3 and 4 are type II transmembrane proteins. Interestingly, only type 3 and 4 mRNAs were detected in spinal cord although type 1 and 2 mRNAs were expressed in various tissues including the CNS. Less