Cloning and analysis of protein tyrosine phosphatases expressed in lymphoid organs.

酪氨酸残基的可逆磷酸化在包括淋巴细胞的分化和增殖在内的各种细胞事件中起着至关重要的调节作用。为了筛选小鼠淋巴器官中的蛋白酪氨酸磷酸酶（PTPs），我们用变性引物通过PCR扩增cDNA。我们发现了七种新的小鼠PTP，并进一步分析了其中的四种。mRPTP-sigma（以前称为PTPT 9）是一种跨膜PTP，其胞外结构域由作为N-CAM家族细胞粘附分子的Ig样结构域和FN-111样结构域组成。观察到至少三种选择性剪接转录物（T、B和S），mRPTP-σ T在胸腺中占优势，而mRPTP-σ B在脑中占优势。PTP 36的C-末端磷酸酶结构域和N-末端结构域与条带4.1（一种细胞内相关蛋白）具有同源性。此外，我们发现PTP 36中存在一个推测的SH 3结合基序。mRPTP-sigma和PTP 36在未成熟胸腺细胞和胸腺基质细胞中都有表达。在发育中的T淋巴细胞中，mRPTP-sigma和PTP 36分别在CD 4 ^-CD 8 ^-和CD 4 ^+ CD 8 ^+亚群中占优势。mRPTP-sigma和PTP 36的发育调节表达表明其参与T淋巴细胞分化的控制。DPZPTP（以前称为PTPST 8）是在果蝇肿瘤抑制基因dlg中发现的一个含有5个GLGF重复序列的胞质PTP。在胸腺中，DPZPTP主要表达于基质部分。PTPBR 7是一个新的PTP受体，其胞浆内只有一个磷酸酶结构域，其胞外结构域与已知分子没有明显的结构相似性。因此，PTPBR 7定义了一个新的受体型蛋白酪氨酸磷酸酶亚家族。PTPBR 7几乎只在脑中表达，尤其是在小脑中。PTPBR 7的独特结构及其在脑中的主要表达表明其在神经元细胞中的关键调节作用。

Reversible phosphorylation of tyrosine residues plays a crucial regulatory role in various cellular events including differentiation and proliferation of lymphocytes. To screen PTPs (protein tyrosine phosphatases) in the murine lymphoid organs, we amplified the cDNA by PCR with degenerative primers. We found seven novel murine PTPs and further analyzed four of them. mRPTP-sigma(formerly called as PTPT9) was a transmembrane PTP,whose extracellular domain was composed of lg-like and FN-lll-like domains as N-CAM family cell-adhesion molecules. At least three alternatively spliced transcripts (T,B,and S) were observed and mRPTP-sigma T was dominant in thymus whereas mRPTP-sigma B was dominant in brain. PTP36 had a C-terminal phosphatase domain and an N-terminal domain with homology to band 4.1, a cytoskeletal-associated protein. In addition, we found a putative SH3-binding motif in PTP36.mRPTP-sigma and PTP36 were expressed both in immature thymocytes and thymic stroma cells. In developing T lymphocytes, mRPTP-sigma and PTP36 were expressed dominantly in CD4^-CD8^- and CD4^+CD8^+ subpopulations, respectively. Developmentally regulated expression of mRPTP-sigma and PTP36 suggests its involvement in the control of T lymphocyte differentiation. DPZPTP (formerly called as PTPST8) was a cytoplasmic PTP with five GLGF repeats, which had been found in a Drosophila tumor suppresser gene, dlg. In the thymus, DPZPTP was expressed dominantly in the stroma fraction. PTPBR7 was a novel receptor PTP with only one cytoplasmic phosphatase domain and its extracellular domain revealed no obvious structural similarity to known molecules. Thus, PTPBR7 defined a new subfamily of receptor-type protein tyrosine phosphatase. PTPBR7 was expressed almost exclusively in the brain and especially in the cerebellum. The unique structure of PTPBR7 and its predominant expression in the brain suggested its crucial regulatory role in neuronal cells.