Nishiwaki T, Maeda N, Noda M
Division of Molecular Neurobiology, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji-cho, Okazaki 444-8585, Japan.
J Biochem. 1998 Mar;123(3):458-67. doi: 10.1093/oxfordjournals.jbchem.a021959.
Protein tyrosine phosphatase zeta (PTPzeta/RPTPbeta) is a receptor-like protein tyrosine phosphatase specifically expressed in the brain. Alternative splicing produces three isoforms of this molecule: PTPzeta-A, the full-length form of PTPzeta; PTPzeta-B, the short form of PTPzeta; and PTPzeta-S, an extracellular variant. Here, we identified all these isoforms, including PTPzeta-B, as chondroitin sulfate proteoglycans, and characterized their carbohydrate modification and expression profiles in the rat brain. The level of PTPzeta-A expression was maintained during the prenatal period and decreased rapidly after birth. PTPzeta-S was expressed in a similar manner, although the postnatal decrease was gradual. In contrast, relatively constant amounts of PTPzeta-B were observed from embryonic day 13 (E13) through adulthood. PTPzeta-A and -S were constantly expressed only as proteoglycans during development, but a substantial amount of PTPzeta-B was detected in a non-proteoglycan form at E13-15. Moreover, PTPzeta-B did not contain LeX, HNK-1 carbohydrate, or keratan sulfate, although PTPzeta-A and -S were generally modified with these carbohydrates. L cells transfected with PTPzeta-A and -B cDNAs expressed these proteins as enzymatically active chondroitin sulfate proteoglycans. The PTPzeta-A and -B in L cells showed essentially similar localizations in cell cortical structures on immunofluorescence microscopy, although immature or processed forms of PTPzeta-A were accumulated additively in intracellular patchy structures. These results show that the three isoforms of PTPzeta are differentially regulated during development, and that the extracellular deleted region in PTPzeta-B is important for determination of carbohydrate modification.
蛋白酪氨酸磷酸酶ζ（PTPζ/RPTPβ）是一种在大脑中特异性表达的受体样蛋白酪氨酸磷酸酶。可变剪接产生该分子的三种同工型：PTPζ-A，PTPζ的全长形式；PTPζ-B，PTPζ的短形式；以及PTPζ-S，一种细胞外变体。在此，我们将所有这些同工型，包括PTPζ-B，鉴定为硫酸软骨素蛋白聚糖，并对它们在大鼠脑中的碳水化合物修饰和表达谱进行了表征。PTPζ-A的表达水平在产前阶段保持稳定，出生后迅速下降。PTPζ-S以类似的方式表达，尽管产后下降是渐进的。相比之下，从胚胎第13天（E13）到成年期，观察到PTPζ-B的量相对恒定。PTPζ-A和-S在发育过程中仅作为蛋白聚糖持续表达，但在E13-15时检测到大量非蛋白聚糖形式的PTPζ-B。此外，PTPζ-B不含有LeX、HNK-1碳水化合物或硫酸角质素，尽管PTPζ-A和-S通常被这些碳水化合物修饰。用PTPζ-A和-B cDNA转染的L细胞将这些蛋白表达为具有酶活性的硫酸软骨素蛋白聚糖。免疫荧光显微镜检查显示，L细胞中的PTPζ-A和-B在细胞皮质结构中的定位基本相似，尽管未成熟或加工形式的PTPζ-A在细胞内斑片状结构中累加积累。这些结果表明，PTPζ的三种同工型在发育过程中受到不同的调节，并且PTPζ-B中的细胞外缺失区域对于碳水化合物修饰的确定很重要。
