Enzymatic properties of rat myelencephalon-specific protease
Enzymatic properties of rat myelencephalon-specific protease
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DOI：
10.1021/bi015781a
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发表时间：
2002-01-29
期刊：
影响因子：
2.9
通讯作者：
Blaber, M
中科院分区：
文献类型：
--
作者：
Blaber, SI;Scarisbrick, IA;Blaber, M
髓脑特异性蛋白酶（MSP），首先在大鼠中发现，现在已知有一个人类同源物（人激肽释放酶6），优先表达在中枢神经系统（CNS），相比非神经组织。MSP被假定具有胰蛋白酶样活性，在CNS中响应于谷氨酸受体介导的兴奋性毒性损伤而上调，并且在阿尔茨海默病患者的脑中下调。CNS白色物质中的少突胶质细胞优先表达这种酶，表明其在髓鞘稳态中发挥作用。为了进一步表征这种新鉴定的酶的活性和底物特异性，我们在杆状病毒/昆虫细胞系系统中异源表达MSP。我们证明，重组MSP表现出广泛的特异性切割后，精氨酸，但不是赖氨酸残基，胰蛋白酶和胰激肽释放酶之间的动力学特征的中间。我们表明，MSP的前形式不自我激活，而是需要裂解后赖氨酸，表明成熟的活性MSP是由一个不同的蛋白酶调节。MSP可以部分地通过自溶调节，因为活性蛋白通过在特定的内部精氨酸位置处的自溶容易地失活。此外，我们表明，MSP是大量表达的炎性细胞在泰勒的小鼠脑脊髓炎病毒（TMEV）模型的多发性硬化症（MS）的脱髓鞘的网站。结合证明MSP降解髓鞘相关蛋白以及几种细胞外基质蛋白的能力的数据，这些发现将MSP描述为具有在免疫介导的脱髓鞘中发挥关键作用的潜力的广泛特异性髓鞘特异性蛋白酶。
Myelencephalon-specific protease (MSP), first identified in the rat and now known to have a human homologue (human kallikrein 6), is preferentially expressed in the central nervous system (CNS), compared with nonneural tissues. MSP has been postulated to have trypsin-like activity, is upregulated in response to glutamate receptor-mediated excitotoxic injury in the CNS, and is downregulated in the brain of Alzheimer's patients. The preferential expression of this enzyme by oligodendrocytes in CNS white matter points to a role in myelin homeostasis. To further characterize the activity and substrate specificity of this newly identified enzyme, we have heterologously expressed MSP in a baculovirus/insect cell line system. We demonstrate that recombinant MSP exhibits a broad specificity for cleavage after arginine but not lysine residues, with kinetic characteristics intermediate between trypsin and pancreatic kallikrein. We show that the pro form of MSP does not self-activate but, rather, requires cleavage after lysine, indicating that mature active MSP is regulated by a distinct protease. MSP may be regulated in part by autolysis, since the active protein is readily inactivated through autolysis at specific internal arginine positions. Additionally, we show that MSP is abundantly expressed in inflammatory cells at sites of demyelination in the Theiler's murine encephalomyelitis virus (TMEV) model of multiple sclerosis (MS). In conjunction with data demonstrating the ability of MSP to degrade myelin-associated as well as several extracellular matrix proteins, these findings delineate MSP as a broad-specificity arginine-specific protease with the potential to play a key role in immune-mediated demyelination.