Barraud Perrine, Amrein Lilian, Dobremez Eric, Dabernat Sandrine, Masse Karine, Larou Monique, Daniel Jean-Yves, Landry Marc
EA DRED 483, Laboratoire de Biologie de la Différenciation et du Développement, Université Victor Ségalen, 33 076 Bordeaux Cedex, France.
J Comp Neurol. 2002 Mar 18;444(4):306-23. doi: 10.1002/cne.10150.
Nm23 has been identified as a gene family encoding different isoforms of nucleoside diphosphate kinase (NDPK). This protein is a key enzyme in nucleotide metabolism and has been shown to play important roles in various cellular functions. In the present study, we have investigated the expression of three isotypes in mouse dorsal root ganglia. In situ hybridization and reverse transcriptase-polymerase chain reaction analysis demonstrated high levels of nm23-M1, -M2, and -M3 mRNA expression in peripheral nervous tissue. Moreover, in situ hybridization also displayed a specific nuclear localization for nm23-M2 mRNA. Immunohistochemistry with light and electron microscopy on isoform-specific antibodies revealed a differential subcellular distribution of NDPK isoforms. Isoform A was mainly cytosolic, showing only partial association with organelles. In contrast, isoform B was also found in the nucleus, which is in agreement with its proposed role as a transcription factor. The results also indicate a preferential association of isoform C with endoplasmic reticulum and plasma membranes in neuronal cells. Furthermore, isoform C appeared to combine with other NDPK isoforms as demonstrated by double-labeling evidence by electron microscopy and might be responsible for binding NDPK oligomers to membranes. Thus, isoform C may be considered as a protein of importance for maintaining intracellular pools of GTP in the vicinity of membranes and, hence, for transmembrane signaling. The results indicate a high expression of NDPK isoforms, not only in the central but also in the peripheral nervous system. Their different subcellular compartmentalization suggests that they have isoform-specific roles in neuronal cell physiology.
Nm23已被鉴定为一个基因家族，编码核苷二磷酸激酶（NDPK）的不同亚型。这种蛋白质是核苷酸代谢中的关键酶，并且已被证明在各种细胞功能中发挥重要作用。在本研究中，我们调查了三种亚型在小鼠背根神经节中的表达。原位杂交和逆转录聚合酶链反应分析表明，nm23-M1、-M2和-M3 mRNA在外周神经组织中高水平表达。此外，原位杂交还显示nm23-M2 mRNA具有特定的核定位。使用针对亚型特异性抗体的免疫组织化学结合光镜和电镜检查揭示了NDPK亚型在亚细胞水平上的不同分布。亚型A主要位于胞质溶胶中，仅与细胞器有部分关联。相比之下，亚型B也存在于细胞核中，这与其作为转录因子的推测作用相符。结果还表明，在神经元细胞中，亚型C优先与内质网和质膜结合。此外，如电镜双标记证据所示，亚型C似乎与其他NDPK亚型结合，可能负责将NDPK寡聚体与膜结合。因此，亚型C可被视为一种对于维持膜附近的细胞内GTP池，进而对于跨膜信号传导很重要的蛋白质。结果表明，NDPK亚型不仅在中枢神经系统，而且在外周神经系统中都有高表达。它们在亚细胞水平上的不同分隔表明它们在神经元细胞生理学中具有亚型特异性作用。
