Yang Y, Gil M C, Choi E Y, Park S H, Pyun K H, Ha H
Immune Cell Signal Transduction Research Unit, Korea Research Institute of Bioscience and Biotechnology, KIST, Taejon, South Korea.
Gene. 1997 Feb 20;186(1):77-82. doi: 10.1016/s0378-1119(96)00684-1.
Tyrosine phosphorylation of proteins plays an important role in cellular signaling and many cellular activities. The levels of cellular phosphorylation are reversibly controlled by protein tyrosine kinases and protein tyrosine phosphatases. The murine R-PTP-kappa, a receptor-type protein tyrosine phosphatase, has recently been cloned (Jiang et al. (1993) Mol. Cell. Biol. 13, 2942-2951). In order to identify the protein tyrosine phosphatases critical to the cellular signal transduction in human keratinocytes, a polymerase chain reaction (PCR)-based strategy was employed, and we have cloned a human homologue of the murine R-PTP-kappa. Here, we report the isolation of a complementary DNA encoding a human R-PTP-kappa. Of the several overlapping cDNA clones, one clone, which we originally termed p55-7, was found to encode a transmembrane protein of 1440 amino acids and was highly conserved with murine R-PTP-kappa with 98% identity at the amino-acid levels. The human R-PTP-kappa gene was localized to chromosome 6 by southern hybridization of DNA from a rodent/human somatic cell mapping panel. Northern blot analysis of RNA from several human tissues revealed, like the murine R-PTP-kappa, the presence of a major mRNA of approx. 7.0 kb and a minor mRNA of approx. 5.3 kb. In contrast to the expression of murine R-PTP-kappa which was highly expressed in liver and kidney, the human R-PTP-kappa was predominantly expressed in spleen, prostate, and ovary. However, the transcripts were detectable at various levels in all examined tissues (thymus, testis, small intestine, and colon) except for PBL (peripheral blood leukocytes). In addition, human R-PTP-kappa displayed a restricted pattern of expression among a series of cell lines, and was apparently expressed in an epidermal cells and cell lines (human normal keratinocytes, HaCaT, and A431), but was not detectable in other cell lines tested after longer exposure.
蛋白质的酪氨酸磷酸化在细胞信号传导和许多细胞活动中发挥着重要作用。细胞磷酸化水平由蛋白酪氨酸激酶和蛋白酪氨酸磷酸酶可逆性控制。鼠源R-PTP-κ是一种受体型蛋白酪氨酸磷酸酶，最近已被克隆（Jiang等人，（1993年）《分子与细胞生物学》13卷，2942 - 2951页）。为了鉴定对人角质形成细胞中细胞信号转导至关重要的蛋白酪氨酸磷酸酶，采用了基于聚合酶链反应（PCR）的策略，我们克隆了鼠源R-PTP-κ的人同源物。在此，我们报告了编码人R-PTP-κ的互补DNA的分离。在几个重叠的cDNA克隆中，一个最初被称为p55-7的克隆被发现编码一个由1440个氨基酸组成的跨膜蛋白，并且在氨基酸水平上与鼠源R-PTP-κ高度保守，同一性达98%。通过对来自啮齿动物/人类体细胞定位板的DNA进行Southern杂交，将人R-PTP-κ基因定位到6号染色体。对来自几种人类组织的RNA进行Northern印迹分析显示，与人R-PTP-κ一样，存在一条约7.0 kb的主要mRNA和约5.3 kb的次要mRNA。与在肝脏和肾脏中高表达的鼠源R-PTP-κ的表达情况不同，人R-PTP-κ主要在脾脏、前列腺和卵巢中表达。然而，除了外周血白细胞（PBL）外，在所有检测的组织（胸腺、睾丸、小肠和结肠）中都能检测到不同水平的转录本。此外，人R-PTP-κ在一系列细胞系中表现出有限的表达模式，并且明显在表皮细胞和细胞系（人正常角质形成细胞、HaCaT和A431）中表达，但在延长曝光时间后检测其他测试细胞系时未检测到。
