Neuropsin--a possible modulator of synaptic plasticity.

Accumulating evidence has suggested pivotal roles for neural proteases in development, maturation, aging, and cognitive functions. Among such proteases, neuropsin, a kallikrein gene-related (KLK) endoprotease, appears to have a significant plasticity function that has been analyzed primarily in the hippocampal Schaffer-collateral pathway. In this article, after reviewing the general features of neuropsin, its role in Schaffer-collateral synaptic plasticity is discussed in some detail. Enzymatically active neuropsin is necessary to establish the early phase of long-term potentiation (LTP). This type of LTP, which can be elicited by rather weak tetanic stimulation, is significant in synaptic late association between two independent hippocampal synapses. Neuropsin deficiency completely impaired the early phase of LTP, leading to the absence of late associativity. Associations between early and persistent-LTP synapses may be related to mammalian working memory and consequently integration in learning and memory.