Watanabe Y, Shiozuka K, Ikeda T, Hoshi N, Hiraki H, Suzuki T, Hashimoto S, Kawashima H
Molecular Medicine Research Laboratories, Yamanouchi Institute for Drug Discovery Research, 21 Miyukigaoka, Tsukuba, Ibaraki 305, Japan.
Brain Res Mol Brain Res. 1998 Jul 15;58(1-2):83-94. doi: 10.1016/s0169-328x(98)00100-4.
Recently, cDNAs encoding brain-specific transmembrane-type protein tyrosine phosphatases (PTPs) with single catalytic domain have been cloned. These include PC12-PTP, PCPTP1, PTPBR7, and PTP-SL, whose cytoplasmic domains had high similarity to STEP, a brain-specific nontransmembrane-type PTP. Based on the high similarity and expression pattern, PCPTP1 seems to be identical with PC12-PTP1 and to be the rat homologue of murine PTPBR7. Here, we report the molecular cloning and expression profile of PCPTP1-Ce, a variant of PCPTP1. Both PCPTP1 mRNA and PCPTP1-Ce mRNA seem to be derived from a single common region gene. Nucleotide and deduced amino acid sequence comparison between PCPTP1-Ce and PCPTP1 revealed that the predicted protein product of PCPTP1-Ce is identical with that translated from the third initiation methionine of the longest ORF of PCPTP1, and that these two clones differ in the 5'-untranslated sequences. Northern blot analyses with specific probes for PCPTP1 and PCPTP1-Ce confirmed our previous observation that PCPTP1-Ce mRNA was almost exclusively expressed in the cerebellum, whereas PCPTP1 was widely expressed in various brain regions dissected including cerebellum. In situ hybridization study demonstrated that PCPTP1-Ce mRNA was exclusively expressed in Purkinje cells of the cerebellum. In contrast, PCPTP1 mRNA was predominantly expressed in granule cells and less in Purkinje cells. Moreover, immunohistochemical analysis using an affinity-purified polyclonal antibody raised against the cytoplasmic region of PCPTP1/PCPTP1-Ce demonstrated that Purkinje cells were strongly immunostained, whereas granule cells were stained only faintly in the cerebellum. These observations clearly demonstrated that PCPTP1-Ce mRNA and its protein products are expressed in Purkinje cells and suggest that PCPTP1-Ce may play an important role in Purkinje cell function in the rat cerebellum.
最近，编码具有单个催化结构域的脑特异性跨膜型蛋白酪氨酸磷酸酶（PTP）的cDNA已被克隆。这些包括PC12-PTP、PCPTP1、PTPBR7和PTP-SL，它们的胞质结构域与STEP（一种脑特异性非跨膜型PTP）具有高度相似性。基于高度相似性和表达模式，PCPTP1似乎与PC12-PTP1相同，并且是小鼠PTPBR7的大鼠同源物。在此，我们报告PCPTP1的一个变体PCPTP1-Ce的分子克隆和表达谱。PCPTP1 mRNA和PCPTP1-Ce mRNA似乎都来自一个单一的共同区域基因。PCPTP1-Ce与PCPTP1之间的核苷酸和推导氨基酸序列比较表明，PCPTP1-Ce的预测蛋白产物与从PCPTP1最长ORF的第三个起始甲硫氨酸翻译而来的产物相同，并且这两个克隆在5'-非翻译序列上有所不同。用PCPTP1和PCPTP1-Ce的特异性探针进行的Northern印迹分析证实了我们之前的观察结果，即PCPTP1-Ce mRNA几乎只在小脑中表达，而PCPTP1在包括小脑在内的各种解剖脑区中广泛表达。原位杂交研究表明，PCPTP1-Ce mRNA只在小脑的浦肯野细胞中表达。相比之下，PCPTP1 mRNA主要在颗粒细胞中表达，在浦肯野细胞中较少表达。此外，使用针对PCPTP1/PCPTP1-Ce胞质区域产生的亲和纯化多克隆抗体进行的免疫组织化学分析表明，浦肯野细胞被强烈免疫染色，而颗粒细胞在小脑中仅被微弱染色。这些观察结果清楚地表明，PCPTP1-Ce mRNA及其蛋白产物在浦肯野细胞中表达，并表明PCPTP1-Ce可能在大鼠小脑浦肯野细胞功能中发挥重要作用。
