Ishigami Shoji, Sandkvist Maria, Tsui Foon, Moore Elizabeth, Coleman Timothy A, Lawrence Daniel A
Center for Vascular and Inflammatory Diseases, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
Biochem J. 2007 Feb 15;402(1):25-34. doi: 10.1042/BJ20061170.
Ns (neuroserpin) is a member of the serpin (serine protease inhibitor) gene family that is primarily expressed within the central nervous system. Its principal target protease is tPA (tissue plasminogen activator), which is thought to contribute to synaptic plasticity and to be secreted in a stimulus-dependent manner. In the present study, we demonstrate in primary neuronal cultures that Ns co-localizes in LDCVs (large dense core vesicles) with the regulated secretory protein chromogranin B. We also show that Ns secretion is regulated and can be specifically induced 4-fold by secretagogue treatment. A novel 13-amino-acid sorting signal located at the C-terminus of Ns is identified that is both necessary and sufficient to target Ns to the regulated secretion pathway. Its deletion renders Ns no longer responsive to secretagogue stimulation, whereas PAI-Ns [Ns (neuroserpin)-PAI-1 (plasminogen activator inhibitor-1) chimaera appending the last 13 residues of Ns sequence to the C-terminus of PAI-1] shifts PAI-1 secretion into a regulated secretory pathway.
神经丝氨酸蛋白酶抑制剂（Ns）是丝氨酸蛋白酶抑制剂（serpin）基因家族的成员，主要在中枢神经系统中表达。其主要靶蛋白酶是组织型纤溶酶原激活剂（tPA），tPA被认为有助于突触可塑性，并以刺激依赖的方式分泌。在本研究中，我们在原代神经元培养物中证明，Ns与受调节分泌蛋白嗜铬粒蛋白B共定位于大致密核心囊泡（LDCVs）中。我们还表明，Ns的分泌是受调节的，并且促分泌剂处理可特异性诱导其分泌增加4倍。我们鉴定出位于Ns C末端的一个新的13个氨基酸的分选信号，该信号对于将Ns靶向受调节的分泌途径既必要又充分。删除该信号会使Ns不再对促分泌剂刺激产生反应，而PAI-Ns [Ns（神经丝氨酸蛋白酶抑制剂）-PAI-1（纤溶酶原激活剂抑制剂-1）嵌合体，将Ns序列的最后13个残基附加到PAI-1的C末端]会将PAI-1的分泌转变为受调节的分泌途径。
