ABSTRACT
CD26 is a widely distributed 110-kDa cell surface glycoprotein with an important role in T-cell costimulation. We demonstrated previously that CD26 binds to caveolin-1 in antigen-presenting cells, and following exogenous CD26 stimulation, Tollip and IRAK-1 disengage from caveolin-1 in antigen-presenting cells. IRAK-1 is then subsequently phosphorylated to up-regulate CD86 expression, resulting in subsequent T-cell proliferation. However, it is unclear whether caveolin-1 is a costimulatory ligand for CD26 in T-cells. Using soluble caveolin-1-Fc fusion protein, we now show that caveolin-1 is the costimulatory ligand for CD26, and that ligation of CD26 by caveolin-1 induces T-cell proliferation and NF-kappaB activation in a T-cell receptor/CD3-dependent manner. We also demonstrated that the cytoplasmic tail of CD26 interacts with CARMA1 in T-cells, resulting in signaling events that lead to NF-kappaB activation. Ligation of CD26 by caveolin-1 recruits a complex consisting of CD26, CARMA1, Bcl10, and IkappaB kinase to lipid rafts. Taken together, our findings provide novel insights into the regulation of T-cell costimulation via the CD26 molecule.
Subject(s)
Adenosine Deaminase/physiology , Apoptosis Regulatory Proteins/physiology , CARD Signaling Adaptor Proteins/physiology , Caveolin 1/physiology , Dipeptidyl Peptidase 4/physiology , Glycoproteins/physiology , Guanylate Cyclase/physiology , Lymphocyte Activation/immunology , Signal Transduction/physiology , T-Lymphocytes/metabolism , Humans , Jurkat Cells , T-Lymphocytes/immunologyABSTRACT
CD26 is a T-cell costimulatory molecule with dipeptidyl peptidase IV enzyme activity in its extracellular region. We have previously reported that the addition of recombinant soluble CD26 resulted in enhanced proliferation of human T lymphocytes induced by the recall antigen tetanus toxoid (TT) via upregulation of CD86 on monocytes and that caveolin-1 was a binding protein of CD26, and the CD26-caveolin-1 interaction resulted in caveolin-1 phosphorylation (p-cav-1) as well as TT-mediated T-cell proliferation. However, the mechanism involved in this immune enhancement has not yet been elucidated. In the present work, we perform experiments to identify the molecular mechanisms by which p-cav-1 leads directly to the upregulation of CD86. Through proteomic analysis, we identify Tollip (Toll-interacting protein) and IRAK-1 (interleukin-1 receptor-associated serine/threonine kinase 1) as caveolin-1-interacting proteins in monocytes. We also demonstrate that following stimulation by exogenous CD26, Tollip and IRAK-1 dissociate from caveolin-1, and IRAK-1 is then phosphorylated in the cytosol, leading to the upregulation of CD86 via activation of NF-kappaB. Binding of CD26 to caveolin-1 therefore regulates signaling pathways in antigen-presenting cells to induce antigen-specific T-cell proliferation.
Subject(s)
Antigen-Presenting Cells/metabolism , Antigens, CD/metabolism , Caveolins/metabolism , Dipeptidyl Peptidase 4/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Membrane Glycoproteins/metabolism , Protein Kinases/metabolism , Up-Regulation , Animals , Antigens, CD/genetics , B7-2 Antigen , Caveolin 1 , Caveolins/chemistry , Caveolins/genetics , Cell Line , Cell Membrane/metabolism , Cell Proliferation/drug effects , Chlorocebus aethiops , Dipeptidyl Peptidase 4/genetics , Humans , Interleukin-1 Receptor-Associated Kinases , Intracellular Signaling Peptides and Proteins/chemistry , Intracellular Signaling Peptides and Proteins/genetics , Membrane Glycoproteins/genetics , Monocytes/metabolism , Phosphotyrosine/metabolism , Promoter Regions, Genetic/genetics , Protein Binding , Protein Kinases/chemistry , Protein Kinases/genetics , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , T-Lymphocytes/cytology , T-Lymphocytes/drug effects , T-Lymphocytes/immunology , T-Lymphocytes/metabolism , Tetanus Toxoid/immunology , Tetanus Toxoid/pharmacologyABSTRACT
Membrane type 1 matrix metalloproteinase (MT1-MMP) is a potent modulator of the pericellular environment and promotes tumor cell invasion and proliferation in many types of tumor. The activation of proMMP-2 and processing of collagen I by MT1-MMP have been thought to be important for its tumor-promoting function. These activities can be inhibited by mutant forms of MT1-MMP lacking the catalytic domain. However, the effect of such dominant-negative mutants has never been evaluated in vivo. Various mutants lacking the catalytic domain (dCAT) were prepared and confirmed to inhibit MT1-MMP activity in human fibrosarcoma HT1080 cells, and tumor cells expressing these mutants were implanted s.c. into nude mice to monitor tumor formation. Only the membrane-anchored form of a dCAT construct through the transmembrane domain [dCAT(1)] showed potent antitumor activity not only in HT1080 cells but also in gastric carcinoma MKN28 and MKN45 cells expressing MT1-MMP. A soluble form of dCAT lacking the transmembrane domain did not show such activity. The expression of dCAT(1) in MKN28 or MKN45 further prevented the metastatic spread of tumor cells into the peritoneal cavity; however, dCAT(1) showed no effect against TMK-1, another gastric carcinoma cell line expressing no MT1-MMP. It is of note that the tumorigenicity of TMK-1 cells enhanced by MT1-MMP overexpression was, in turn, canceled by the additional expression of dCAT(1). Thus, MT1-MMP expressed in tumor cells seems to play a pivotal role in tumor growth in mice. The results also suggest new possibilities to abrogate the tumor-promoting function of MT1-MMP other than the conventional protease inhibitor-based approach.
Subject(s)
Carcinoma/therapy , Fibrosarcoma/therapy , Genetic Therapy , Metalloendopeptidases/antagonists & inhibitors , Stomach Neoplasms/therapy , Animals , Carcinoma/enzymology , Carcinoma/genetics , Catalytic Domain/genetics , Fibrosarcoma/enzymology , Fibrosarcoma/genetics , Humans , Matrix Metalloproteinase 14 , Matrix Metalloproteinases, Membrane-Associated , Metalloendopeptidases/genetics , Mice , Mice, Inbred BALB C , Mutation , Neoplasm Transplantation , Stomach Neoplasms/enzymology , Stomach Neoplasms/genetics , Tumor Cells, CulturedABSTRACT
CD26 is a T cell costimulatory molecule with dipeptidyl peptidase IV activity in its extracellular region. We previously reported that recombinant soluble CD26 enhanced T cell proliferation induced by the recall antigen tetanus toxoid (TT). However, the mechanism involved in this enhancement is not yet elucidated. We now demonstrate that CD26 binds Caveolin-1 on antigen-presenting cells, and that residues 201-211 of CD26 along with the serine catalytic site at residue 630 contribute to binding to caveolin-1 scaffolding domain. In addition, after CD26-caveolin-1 interaction on TT-loaded monocytes, caveolin-1 is phosphorylated, which links to activate NF-kappaB, followed by up-regulation of CD86. Finally, reduced caveolin-1 expression on monocytes inhibits CD26-mediated CD86 up-regulation and abrogates CD26 effect on TT-induced T cell proliferation. Taken together, these results strongly suggest that CD26-caveolin-1 interaction plays a role in the up-regulation of CD86 on TT-loaded monocytes and subsequent engagement with CD28 on T cells, leading to antigen-specific T cell activation.
