Cathepsin L expression is directed to secretory vesicles for enkephalin neuropeptide biosynthesis and secretion
Cathepsin L expression is directed to secretory vesicles for enkephalin neuropeptide biosynthesis and secretion
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DOI：
10.1074/jbc.m605510200
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发表时间：
2007-03-30
影响因子：
4.8
通讯作者：
Hook, Vivian
中科院分区：
文献类型：
--
作者：
Hwang, Shin-Rong;Garza, Christina;Hook, Vivian
分泌囊泡内的蛋白酶是将神经肽前体转化为活性肽神经递质和激素所必需的。这项研究表明，新的细胞的半胱氨酸蛋白酶组织蛋白酶L的作用，从脑啡肽原（PE）的调节分泌途径的神经内分泌PC 12细胞产生（Met）脑啡肽肽神经递质。这些发现是通过在PC 12细胞中共表达PE和组织蛋白酶L cDNA并分析PE衍生的肽产物来实现的。组织蛋白酶L的表达导致（Met）脑啡肽的细胞水平高度增加，这是由于PE转化为与体内存在的那些类似的23、18-19、8-9和4.5 kDa的含脑啡肽的中间体。此外，组织蛋白酶L与PE的表达导致尼古丁诱导的（Met）脑啡肽分泌量增加。这些结果表明增加水平的（Met）脑啡肽内的分泌囊泡的调节分泌途径。重要的是，组织蛋白酶L的表达是针对分泌囊泡，证明了共定位的组织蛋白酶L-DsRed融合蛋白与脑啡肽和嗜铬粒蛋白A的神经肽，是存在于分泌囊泡。体内研究还表明，组织蛋白酶L在体内与脑啡肽共定位。新定义的分泌囊泡功能的组织蛋白酶L的活性脑啡肽阿片肽的生物合成与其功能的溶酶体蛋白质降解。这些研究结果表明，组织蛋白酶L作为一个独特的半胱氨酸蛋白酶途径产生脑啡肽成员的神经肽。
Proteases within secretory vesicles are required for conversion of neuropeptide precursors into active peptide neurotransmitters and hormones. This study demonstrates the novel cellular role of the cysteine protease cathepsin L for producing the (Met)enkephalin peptide neurotransmitter from proenkephalin (PE) in the regulated secretory pathway of neuroendocrine PC12 cells. These findings were achieved by coexpression of PE and cathepsin L cDNAs in PC12 cells with analyses of PE-derived peptide products. Expression of cathepsin L resulted in highly increased cellular levels of (Met)enkephalin, resulting from the conversion of PE to enkephalin-containing intermediates of 23, 18-19, 8-9, and 4.5 kDa that were similar to those present in vivo. Furthermore, expression of cathepsin L with PE resulted in increased amounts of nicotine-induced secretion of (Met)enkephalin. These results indicate increased levels of (Met)enkephalin within secretory vesicles of the regulated secretory pathway. Importantly, cathespin L expression was directed to secretory vesicles, demonstrated by colocalization of cathepsin L-DsRed fusion protein with enkephalin and chromogranin A neuropeptides that are present in secretory vesicles. In vivo studies also showed that cathepsin L in vivo was colocalized with enkephalin. The newly defined secretory vesicle function of cathepsin L for biosynthesis of active enkephalin opioid peptide contrasts with its function in lysosomes for protein degradation. These findings demonstrate cathepsin L as a distinct cysteine protease pathway for producing the enkephalin member of neuropeptides.