MHC class II structural requirements for the association with Igalpha/beta, and signaling of calcium mobilization and cell death.
Emerging evidence indicates that in addition to their well-characterized role in antigen presentation, MHC II molecules transmit signals that induce death of APCs. Appropriately timed APC death is important for prevention of autoimmunity. Though the exact mechanism of MHC II-mediated cell death signaling is unknown, the response appears independent of caspase activation and does not involve Fas-FasL interaction. Here we investigated MHC II structural requirements for mediation of cell death signaling in a murine B cell lymphoma. We found that neither the transmembrane spanning regions nor the cytoplasmic tails of MHC II, which are required for MHC II-mediated cAMP production and PKC activation, are required for the death response. However, mutations in the connecting peptide region of MHC II alpha chain (alphaCP), but not the beta chain (betaCP), resulted in significant impairment of the death response. The alphaCP mutant was also unable to mediate calcium mobilization responses, and did not associate with Igalpha/beta. Knock-down of Igbeta by shRNA eliminated the MHC II-mediated calcium response but not cell death. We propose that MHC II mediates cell death signaling via association with an undefined cell surface protein(s), whose interaction is partially dependent on alphaCP region.
Jin
Lei
L
Department of Immunology, University of Colorado at Denver and Health Sciences Center and National Jewish Medical and Research Center, Denver, CO 80206, United States.
Stolpa
John C
JC
Young
Ryan M
RM
Pugh-Bernard
Aimee E
AE
Refaeli
Yosef
Y
Cambier
John C
JC
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D051925:CD79 Antigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D016923:Cell Death; D045744:Cell Line, Tumor; D000949:Histocompatibility Antigens Class II / Q000737:chemistry* / Q000276:immunology*; D051379:Mice; D008969:Molecular Sequence Data
D000911:Antibodies, Monoclonal; D051925:CD79 Antigens; C497882:Cd79a protein, mouse; C497884:Cd79b protein, mouse; D000949:Histocompatibility Antigens Class II; D002118:Calcium