Nexin-1 inhibits the activity of human brain trypsin

Trypsin and other trypsin-like serine proteases have been shown to play important roles in neural development, plasticity and neurodegeneration. Their activity is modulated by serine protease inhibitors, serpins. However, for human brain trypsin, trypsin-4, no brain-derived inhibitors have been described. Here, we report that nexin-1 inhibits trypsin-4, and forms stable complexes only with this trypsin-isoenzyme. This result suggests that nexin-1 could modulate trypsin activity in brain where both nexin-1 and trypsin-4 are expressed.