Morimoto C, Schlossman S F
Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, Massachussetts 02115, USA.
Immunol Rev. 1998 Feb;161:55-70. doi: 10.1111/j.1600-065x.1998.tb01571.x.
CD26 is a widely distributed 110 kD cell-surface glycoprotein with known dipeptidyl-peptidase IV (DPP-IV) activity in its extracellular domain. This ecto-enzyme is capable of cleaving amino terminal dipeptides from polypeptides with either L-proline or L-alanine in the penultimate position. On human T cells, CD26 expression appears late in thymic differentiation and is preferentially restricted to the CD4+ helper/memory population, and CD26 can deliver a potent co-stimulatory T-cell activation signal. The cDNA sequence of CD26 predicts a type II membrane protein with only 6 amino acids in its cytoplasmic region, suggesting that, in addition to DPP-IV enzyme activity, other signal-inducing molecules may be associated with CD26. Considerable evidence exists that CD26 interacts, presumably in its extracellular domain, with both CD45, a protein tyrosine phosphatase, and adenosine deaminase (ADA), each of which is capable of functioning in a signal transduction pathway. In addition, CD26 is the receptor for ADA, and ADA on the cell surface is involved in an important immunoregulatory mechanism by which released ADA binds to the cell-surface ADA. This multifunctional molecule may be involved in cell migration and the HIV-1-associated loss of CD4+ cells through the process of programmed cell death. Thus, CD26 appears to play a key role in a number of aspects of lymphocyte function.
CD26是一种广泛分布的110 kD细胞表面糖蛋白，其胞外结构域具有已知的二肽基肽酶IV（DPP-IV）活性。这种胞外酶能够从倒数第二位带有L-脯氨酸或L-丙氨酸的多肽上切割氨基末端二肽。在人类T细胞上，CD26的表达在胸腺分化后期出现，并且优先局限于CD4+辅助/记忆细胞群体，而且CD26能够传递有效的共刺激T细胞激活信号。CD26的cDNA序列预测其为一种II型膜蛋白，其胞质区域仅有6个氨基酸，这表明除了DPP-IV酶活性外，其他信号诱导分子可能与CD26相关联。有大量证据表明，CD26可能在其胞外结构域与蛋白酪氨酸磷酸酶CD45和腺苷脱氨酶（ADA）相互作用，这两种分子都能够在信号转导途径中发挥作用。此外，CD26是ADA的受体，细胞表面的ADA通过释放的ADA与细胞表面ADA结合这一重要的免疫调节机制发挥作用。这种多功能分子可能通过程序性细胞死亡过程参与细胞迁移以及与HIV-1相关的CD4+细胞丢失。因此，CD26似乎在淋巴细胞功能的多个方面发挥关键作用。
