Marcinkiewicz M, Savaria D, Marcinkiewicz J
Laboratory of Molecular Neuroendocrinology, Clinical Research Institute of Montreal, University of Montreal, 110 Pine Avenue West, Montreal, Quebec, Canada.
Brain Res Mol Brain Res. 1998 Aug 31;59(2):229-46. doi: 10.1016/s0169-328x(98)00141-7.
Injury of peripheral nerves induces expression of several pro-protein convertases (PCs) involved in processing of precursor proteins into their diverse active end-products. In this study, the focus was on convertase PC1 which, although undetectable in control nerves, is strongly induced in injured nerves. High concentrations of PC1 mRNA of 9.0, 5.5, 3.0, 2.5 and 1.6 kb were observed on day 4 post-lesion in proximal and distal segments. By in situ hybridization PC1 mRNA was detected in most of endoneurial cells, which were further identified by immunocytochemistry as myelin 2', 3'-cyclic nucleotide 3'-phosphodiesterase containing Schwann cells. PC1 mRNA and protein were also present in cultured Schwann cells also containing convertases PC5, furin and PC7 as well as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Mostly unprocessed pro-NGF of 35 kDa and pro-BDNF of 35 kDa were found on Western blotting of Schwann cells. Expression of exogenous neurotrophins by infection with vaccinia virus vector showed that mouse pro-NGF and rat pro-BDNF are cleaved intracellularly on smaller forms of 13.5 kDa NGF and 14 kDa BDNF. Infection experiments demonstrated that Schwann cells contain active processing enzymes. In conclusion, this work provides in vivo evidence of the presence of several PCs in the injured rat sciatic nerve and ex vivo in cultured Schwann cells.
外周神经损伤会诱导几种前体蛋白转化酶（PCs）的表达，这些酶参与将前体蛋白加工成各种活性终产物。在本研究中，重点是转化酶PC1，它在对照神经中无法检测到，但在损伤神经中强烈诱导表达。在损伤后第4天，在近端和远端节段观察到9.0、5.5、3.0、2.5和1.6 kb的高浓度PC1 mRNA。通过原位杂交在大多数神经内膜细胞中检测到PC1 mRNA，通过免疫细胞化学进一步鉴定为含有髓鞘2',3'-环核苷酸3'-磷酸二酯酶的施万细胞。PC1 mRNA和蛋白也存在于培养的施万细胞中，这些细胞还含有转化酶PC5、弗林蛋白酶和PC7以及神经生长因子（NGF）和脑源性神经营养因子（BDNF）。在施万细胞的蛋白质印迹中发现了大部分未加工的35 kDa前体NGF和35 kDa前体BDNF。用痘苗病毒载体感染来表达外源性神经营养因子表明，小鼠前体NGF和大鼠前体BDNF在细胞内被切割成13.5 kDa的NGF和14 kDa的BDNF较小形式。感染实验证明施万细胞含有活性加工酶。总之，这项工作提供了体内证据，证明在损伤的大鼠坐骨神经中存在几种PCs，并且在体外培养的施万细胞中也存在。
