title: Internalization of CD26 by mannose 6-phosphate/insulin-like growth factor II receptor contributes to T cell activation.
abstract: CD26 is a T cell activation antigen known to bind adenosine deaminase and have dipeptidyl peptidase IV activity. Cross-linking of CD26 and CD3 with immobilized mAbs can deliver a costimulatory signal that contributes to T cell activation. Our earlier studies revealed that cross-linking of CD26 induces its internalization, the phosphorylation of a number of proteins involved in the signaling pathway, and subsequent T cell proliferation. Although these findings suggest the importance of internalization in the function of CD26, CD26 has only 6 aa residues in its cytoplasmic region with no known motif for endocytosis. In the present study, we have identified the mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGFIIR) as a binding protein for CD26 and that mannose 6-phosphate (M6P) residues in the carbohydrate moiety of CD26 are critical for this binding. Activation of peripheral blood T cells results in the mannose 6 phosphorylation of CD26. In addition, the cross-linking of CD26 with an anti-CD26 antibody induces not only capping and internalization of CD26 but also colocalization of CD26 with M6P/IGFIIR. Finally, both internalization of CD26 and the T cell proliferative response induced by CD26-mediated costimulation were inhibited by the addition of M6P, but not by glucose 6-phosphate or mannose 1-phosphate. These results indicate that internalization of CD26 after cross-linking is mediated in part by M6P/IGFIIR and that the interaction between mannose 6-phosphorylated CD26 and M6P/IGFIIR may play an important role in CD26-mediated T cell costimulatory signaling.
authors.affiliation: Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: H
authors.initials: H
authors.lastname: Ikushima
authors.forename: Y
authors.initials: Y
authors.lastname: Munakata
authors.forename: T
authors.initials: T
authors.lastname: Ishii
authors.forename: S
authors.initials: S
authors.lastname: Iwata
authors.forename: M
authors.initials: M
authors.lastname: Terashima
authors.forename: H
authors.initials: H
authors.lastname: Tanaka
authors.forename: S F
authors.initials: SF
authors.lastname: Schlossman
authors.forename: C
authors.initials: C
authors.lastname: Morimoto
mesh_terms: D050260:Carbohydrate Metabolism; D002455:Cell Division; D018819:Dipeptidyl Peptidase 4 / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D008213:Lymphocyte Activation; D008360:Mannosephosphates / Q000378:metabolism; D010766:Phosphorylation; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*
chemical_list: D008360:Mannosephosphates; D017527:Receptor, IGF Type 2; C027693:mannose-6-phosphate; D018819:Dipeptidyl Peptidase 4