CD26-mediated signaling for T cell activation occurs in lipid rafts through its association with CD45RO

Abstract

CD26 is a T cell activation antigen that contains dipeptidyl peptidase IV activity and is known to bind adenosine deaminase. The mechanism by which CD26 costimulation potentiates T cell receptor-mediated T cell activation, leading to subsequent exertion of T cell effector function, is still not clearly defined. In this article, we demonstrate that CD26 localizes into lipid rafts, and targeting of CD26 to rafts is necessary for signaling events through CD26. Importantly, aggregation of CD26 by anti-CD26 mAb crosslinking also causes coaggregation of CD45 into rafts. Moreover, we show that CD26 directly binds to the cytoplasmic domain of CD45. Our results therefore indicate a mechanism whereby CD26 engagement promotes aggregation of lipid rafts and facilitates colocalization of CD45 to T cell receptor signaling molecules p56 Lck , ZAP-70, and TCR, thereby enhancing protein tyrosine phosphorylation of various signaling molecules and subsequent interleukin-2 production.T he CD26 is a 110-kDa cell-surface glycoprotein that possesses dipeptidyl peptidase IV (EC 3.4.14.5) activity in its extracellular domain (1, 2) and has an important role in T cell activation (3). Although constitutively expressed in the liver, intestine, and kidney, CD26 expression level is tightly regulated on T cells, and its density is markedly enhanced after T cell activation (4). In the resting state of human T lymphocytes, CD26 is expressed on a subset of CD4 ϩ memory T cells, and this CD4 ϩ CD26 high T cell population has been shown to respond maximally to recall antigens (5). In fact, CD26 itself is involved in the processes of T cell signal transduction.Activation of resting T cells requires two independent signals, the first stemming from recognition by the T cell receptor (TCR) complex of processed antigen peptides plus major histocompatibility complex molecules on antigen-presenting cells, with the second signal being provided by other receptor-ligand interactions between T cells and antigen-presenting cells (6, 7). Intensive work over the past several years has characterized the T cell surface molecule CD26 as a receptor capable of generating T cell costimulatory signals (8, 9). Crosslinking of CD26 and CD3 with immobilized mAbs induced T cell activation and IL-2 production (5). Moreover, anti-CD26 antibody treatment of T cells led to decreased surface expression of CD26 via its internalization, and this modulation of CD26 resulted in an enhanced proliferative response to anti-CD3 or anti-CD2 stimulation (9). We also demonstrated previously that ligation of CD26 by the anti-CD26 mAb 1F7 induced increased tyrosine phosphorylation of signaling molecules such as c-Cbl, mitogen-activated protein kinase [MAP kinase, or extracellularregulated kinase (ERK1͞2)], Zap70, p56 Lck , and CD3 (10). However, the exact mechanism responsible for CD26-mediated tyrosine phosphorylation and costimulation is unclear, particularly in view of the fact that CD26 has a short conserved cytoplasmic domain consisting of only six amino acid residues, without intrins...

Differential Regulation of CXCR4-mediated T-cell Chemotaxis and Mitogen-activated Protein Kinase Activation by the Membrane Tyrosine Phosphatase, CD45

“…It has been observed that CD45 is excluded from the lipid raft domain upon TCR signaling (54). However, cross-linking of the CD26 receptor induced an interaction between CD26 and the cytoplasmic domain of CD45 that resulted in the coaggregation of CD45 and CD26 in lipid rafts (55). The role of CD45 in CXCR4-mediated lipid raft formation is a subject for further studies.…”

CD26 up-regulates expression of CD86 on antigen-presenting cells by means of caveolin-1

“…To produce GST-caveolin-1 and its deletion mutants, the plasmid constructs were transformed into BL21 (DE3); pT-Trx Escherichia coli (a kind gift from S. Ishii, RIKEN Tsukuba Institute, Ibaraki, Japan) (23). GST fusion proteins and pulldown assay were generated as previously described (24). GST-CD26 and its deletion mutants were produced by the mammalian cell line COS-7, and purified as described elsewhere (25).…”

CD26-Mediated Induction of EGR2 and IL-10 as Potential Regulatory Mechanism for CD26 Costimulatory Pathway

“…We have previously shown that CD26 localizes into lipid rafts, and stimulation with anti-CD3 plus anti-CD26 promotes aggregation of lipid rafts, leading to colocalization of CD45 to TCR signaling molecules such as p56 Lck , ZAP-70, or TCRz (30). Our present data strongly suggest that persistent NFAT-AP-1 cooperation is responsible for CD26-mediated T cell activation, and sustained activation of NFAT and ERK1/2 is possibly due to the aggregation of signaling molecules in lipid rafts following CD26-mediated costimulation.…”

“…Each sample was resolved by SDS-PAGE in reducing condition. SDS-PAGE and Western blot analysis were conducted as described previously (30). The images were taken using luminescent image analyzer LAS 4000 (GE Healthcare), and data were analyzed with image reader LAS 4000 and Multi Gauge software (GE Healthcare).…”