Maier Olaf, van der Heide Tiemen, Johnson Richard, de Vries Hans, Baron Wia, Hoekstra Dick
University Medical Center Groningen, University of Groningen, Department of Cell Biology/Section Membrane Cell Biology, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
Exp Cell Res. 2006 Feb 15;312(4):500-11. doi: 10.1016/j.yexcr.2005.11.014.
Formation of the paranodal axo-glial junction requires the oligodendrocyte-specific 155-kDa isoform of neurofascin (NF155). Here, we report the presence of two peptides in cultured oligodendrocytes, which are recognized by distinct NF155-specific antibodies and correspond to a membrane anchor of 30 kDa and a 125 kDa peptide, which is shed from the cells, indicating that it consists of the NF155 ectodomain. Transfection of OLN-93 cells with NF155 verified that both peptides originate from NF155 cleavage, and we present evidence that metalloproteases mediate NF155 processing. Interestingly, metalloprotease activity is required for NF155 transport into oligodendrocyte processes supporting the functional significance of NF155 cleavage. To further characterize NF155 cleavage and function, we transfected MDCK cells with NF155. Although ectodomain shedding was observed in polarized and non-polarized MDCK cells, surface localization of NF155 was restricted to the lateral membrane of polarized cells consistent with a role in cell-cell adhesion. Aggregation assays performed with OLN-93 cells confirmed that NF155 accelerates cell-cell adhesion in a metalloprotease-dependent manner. The physiological relevance of NF155 processing is corroborated by the presence of NF155 cleavage products in heavy myelin, suggesting a role of NF155 ectodomain shedding for the generation and/or stabilization of the nodal/paranodal architecture.
结旁轴突 - 神经胶质连接的形成需要少突胶质细胞特异性的155 kDa神经束蛋白异构体（NF155）。在此，我们报告在培养的少突胶质细胞中存在两种肽段，它们可被不同的NF155特异性抗体识别，分别对应一个30 kDa的膜锚定肽段和一个从细胞中脱落的125 kDa肽段，这表明该125 kDa肽段由NF155的胞外结构域组成。用NF155转染OLN - 93细胞证实这两种肽段均源自NF155的裂解，并且我们提供证据表明金属蛋白酶介导NF155的加工过程。有趣的是，NF155转运至少突胶质细胞突起需要金属蛋白酶活性，这支持了NF155裂解的功能重要性。为了进一步表征NF155的裂解和功能，我们用NF155转染了MDCK细胞。尽管在极化和非极化的MDCK细胞中均观察到胞外结构域脱落，但NF155的表面定位仅限于极化细胞的侧膜，这与它在细胞间黏附中的作用一致。用OLN - 93细胞进行的聚集试验证实，NF155以金属蛋白酶依赖性方式加速细胞间黏附。重髓鞘中存在NF155裂解产物，这证实了NF155加工的生理相关性，表明NF155胞外结构域脱落对节点/结旁结构的形成和/或稳定起作用。
