Regulation of acid-sensing ion channel 1a function by tissue kallikrein may be through channel cleavage

Recently, we have demonstrated that serine protease tissue kallikrein (TK) can protect cortical neurons against ischemia-acidosis/reperfusion-induced injury, and that this effect might be mediated by acid-sensing ion channels (ASICs). However, little is known about how TK regulates the function of ASICs. Here we provided evidence that the regulation of ASIC1a function by TK was probably correlated with its cleavage. High concentration of TK (3μM) partially cleaved the extracellular loop of ASIC1a, followed by a marked decrease of LDH release and an increase of cell survival at pH 6.2. Pretreatment with a protease inhibitor aprotinin inhibited the cleavage of ASIC1a and prevented functional regulation by TK. However, the cleavage of ASIC2a, which was not functionally modified by TK, was not observed. Therefore, we propose that the limited proteolysis of extracellular loop within ASIC1a might be one of the potential regulatory mechanisms of ASIC1a function by TK.