Differential Requirement for the SAP-Fyn Interaction during NK T Cell Development and Function

• Published in: The Journal of immunology (1950) Vol. 181; no. 4; pp. 2311 - 2320
• Main Authors: Nunez-Cruz, Selene, Yeo, W. C. Janice, Rothman, Jennifer, Ojha, Priti, Bassiri, Hamid, Juntilla, Marisa, Davidson, Dominique, Veillette, Andre, Koretzky, Gary A, Nichols, Kim E
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15.08.2008
• Subjects: Animals; Cell Differentiation - genetics; Cell Differentiation - immunology; Cell Line; Coculture Techniques; Intracellular Signaling Peptides and Proteins - deficiency; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Intracellular Signaling Peptides and Proteins - physiology; Killer Cells, Natural - cytology; Killer Cells, Natural - immunology; Killer Cells, Natural - metabolism; Lymphocyte Activation - genetics; Lymphocyte Activation - immunology; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Mutant Strains; Proto-Oncogene Proteins c-fyn - deficiency; Proto-Oncogene Proteins c-fyn - genetics; Proto-Oncogene Proteins c-fyn - metabolism; Proto-Oncogene Proteins c-fyn - physiology; Signal Transduction - genetics; Signal Transduction - immunology; Signaling Lymphocytic Activation Molecule Associated Protein; T-Lymphocyte Subsets - cytology; T-Lymphocyte Subsets - immunology; T-Lymphocyte Subsets - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.181.4.2311

The adaptor molecule SAP (signaling lymphocytic activation molecule-associated protein) plays a critical role during NK T (NKT) cell development in humans and mice. In CD4(+) T cells, SAP interacts with the tyrosine kinase Fyn to deliver signals required for TCR-induced Th2-type cytokine production. To determine whether the SAP-dependent signals controlling NKT cell ontogeny rely on its binding to Fyn, we used the OP9-DL1 system to initiate structure function studies of SAP in murine NKT cell development. In cultures containing wild-type (WT) hematopoietic progenitors, we noted the transient emergence of cells that reacted with the NKT cell-specific agonist alpha-galactosyl ceramide and its analog PBS57. Sap(-/-) cells failed to give rise to NKT cells in vitro; however, their development could be rescued by re-expression of WT SAP. Emergence of NKT cells was also restored by a mutant version of SAP (SAP R78A) that cannot bind to Fyn, but with less efficiency than WT SAP. This finding was accentuated in vivo in Sap(R78A) knock-in mice as well as Sap(R78A) competitive bone marrow chimeras, which retained NKT cells but at significantly reduced numbers compared with controls. Unlike Sap(R78A) CD4(+) T cells, which produce reduced levels of IL-4 following TCR ligation, alpha-galactosyl ceramide-stimulated NKT cells from the livers and spleens of Sap(R78A) mice produced Th2 cytokines and activated NK cells in a manner mimicking WT cells. Thus, SAP appears to use differential signaling mechanisms in NKT cells, with optimal ontogeny requiring Fyn binding, while functional responses occur independently of this interaction.