Shen P, Canoll P D, Sap J, Musacchio J M
Department of Pharmacology, New York University Medical Center, 550 First Avenue, New York, NY 10016, USA.
Brain Res. 1999 May 1;826(2):157-71. doi: 10.1016/s0006-8993(99)01179-8.
Receptor protein tyrosine phosphatases (RPTPs) comprise a family of proteins that feature intracellular phosphatase domains and an ectodomain with putative ligand-binding motifs. Several RPTPs are expressed in the brain, including RPTP-kappa which participates in homophilic cell-cell interactions in vitro [Y.-P. Jiang, H. Wang, P. D'Eustachio, J.M. Musacchio, J. Schlessinger, J. Sap, Cloning and characterization of R-PTP-kappa, a new member of the receptor protein tyrosine phosphatase family with a proteolytically cleaved cellular adhesion molecule-like extracellular region, Mol. Cell. Biol. 13 (1993) 2942-2951; J. Sap, Y.-P. Jiang, D. Friedlander, M. Grumet, J. Schlessinger, Receptor tyrosine phosphatase R-PTP-kappa mediates homophilic binding, Mol. Cell. Biol. 14 (1994) 1-9]. The homology of RPTP-kappa's ectodomain to neural cell adhesion molecules indicates potential roles in developmental processes such as axonal growth and target recognition, as has been demonstrated for certain Drosophila RPTPs. The brain distribution of RPTP-kappa-expressing cells has not been determined, however. In a gene-trap mouse model with a beta-gal+neo (beta-geo) insertion in the endogenous RPTP-kappa gene, the consequent loss of RPTP-kappa's enzymatic activity does not produce any obvious phenotypic defects [W.C. Skarnes, J.E. Moss, S.M. Hurtley, R.S.P. Beddington, Capturing genes encoding membrane and secreted proteins important for mouse development, Proc. Natl. Acad. Sci. U.S.A. 92 (1995) 6592-6596]. Nevertheless, since the transgene's expression is driven by the endogenous RPTP-kappa promoter, distribution of the truncated RPTP-kappa/beta-geo fusion protein should reflect the regional and cellular expression of wild-type RPTP-kappa, and thus may identify sites where RPTP-kappa is important. Towards that goal, we have used this mouse model to map the distribution of the truncated RPTP-kappa/beta-geo fusion protein in the adult mouse brain using beta-galactosidase as a marker enzyme. Visualization of the beta-galactosidase activity revealed a non-random pattern of expression, and identified cells throughout the CNS that display RPTP-kappa promoter activity. Several neural systems highly expressed the transgene-most notably cortical, olfactory, hippocampal, hypothalamic, amygdaloid and visual structures. These well-characterized brain regions may provide a basis for future studies of RPTP-kappa function.
受体蛋白酪氨酸磷酸酶（RPTPs）是一类蛋白质家族，其特点是具有细胞内磷酸酶结构域和带有假定配体结合基序的胞外结构域。几种RPTPs在大脑中表达，包括RPTP-κ，它在体外参与同嗜性细胞间相互作用[蒋玉平、王浩、P. 德尤斯塔基奥、J.M. 穆萨基奥、J. 施莱辛格、J. 萨普，R-PTP-κ的克隆与特性分析，受体蛋白酪氨酸磷酸酶家族的一个新成员，其细胞外区域具有蛋白水解切割的细胞粘附分子样结构，《分子细胞生物学》13（1993）2942 - 2951；J. 萨普、蒋玉平、D. 弗里德兰德、M. 格鲁梅特、J. 施莱辛格，受体酪氨酸磷酸酶R-PTP-κ介导同嗜性结合，《分子细胞生物学》14（1994）1 - 9]。RPTP-κ的胞外结构域与神经细胞粘附分子的同源性表明其在轴突生长和靶标识别等发育过程中可能发挥作用，某些果蝇RPTPs已证明了这一点。然而，表达RPTP-κ的细胞在大脑中的分布尚未确定。在内源性RPTP-κ基因中插入β-半乳糖苷酶 + 新霉素（β-geo）的基因捕获小鼠模型中，RPTP-κ酶活性的丧失并未产生任何明显的表型缺陷[W.C. 斯卡恩斯、J.E. 莫斯、S.M. 赫特利、R.S.P. 贝丁顿，捕获对小鼠发育重要的编码膜蛋白和分泌蛋白的基因，《美国国家科学院院刊》92（1995）6592 - 6596]。尽管如此，由于转基因的表达由内源性RPTP-κ启动子驱动，截短的RPTP-κ/β-geo融合蛋白的分布应反映野生型RPTP-κ的区域和细胞表达情况，因此可能确定RPTP-κ发挥重要作用的位点。为实现这一目标，我们利用该小鼠模型，以β-半乳糖苷酶作为标记酶，绘制成年小鼠大脑中截短的RPTP-κ/β-geo融合蛋白的分布图。β-半乳糖苷酶活性的可视化显示出非随机的表达模式，并识别出整个中枢神经系统中显示RPTP-κ启动子活性的细胞。几个神经系统高度表达转基因，最显著的是皮质、嗅觉、海马、下丘脑、杏仁核和视觉结构。这些特征明确的脑区可能为未来研究RPTP-κ的功能提供基础。
