title: SAP facilitates recruitment and activation of LCK at NTB-A receptors during restimulation-induced cell death.
abstract: Upon TCR restimulation, activated, cycling T cells can undergo a self-regulatory form of apoptosis known as restimulation-induced cell death (RICD). We previously demonstrated that RICD is impaired in T cells from patients with X-linked lymphoproliferative disease, which lack SLAM-associated protein (SAP) expression. Both SAP and the specific SLAM receptor NK, T, and B cell Ag (NTB-A) are required for RICD, but the mechanism by which these molecules promote a strong, proapoptotic signal through the TCR remains unclear. In this article, we show that the Src-family kinase LCK, but not FYN, associates with NTB-A in activated human T cells. This association increased after TCR restimulation in a SAP-dependent manner, requiring both immunoreceptor tyrosine-based switch motifs in the NTB-A cytoplasmic tail. Both NTB-A-associated LCK phosphorylation and kinase activity were enhanced in restimulated T cells, amplifying proximal TCR signaling. In contrast, TCR-induced LCK association with NTB-A, as well as phosphorylation and kinase activity, was reduced in T cells from patients with X-linked lymphoproliferative disease or normal T cells transfected with SAP-specific small interfering RNA, consistent with RICD resistance. Collectively, our data reveal how SAP nucleates a previously unknown signaling complex involving NTB-A and LCK to potentiate RICD of activated human T cells.
authors.affiliation: Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.
authors.forename: Gil
authors.initials: G
authors.lastname: Katz
authors.forename: Scott M
authors.initials: SM
authors.lastname: Krummey
authors.forename: Sasha E
authors.initials: SE
authors.lastname: Larsen
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Stinson
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Snow
mesh_terms: D015703:Antigens, CD / Q000276:immunology* / Q000378:metabolism; D017209:Apoptosis / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000276:immunology* / Q000378:metabolism; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D000071179:Signaling Lymphocytic Activation Molecule Associated Protein; D000071176:Signaling Lymphocytic Activation Molecule Family; D000071177:Signaling Lymphocytic Activation Molecule Family Member 1; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D014162:Transfection
chemical_list: D015703:Antigens, CD; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; C114953:SH2D1A protein, human; C000604060:SLAMF6 protein, human; D000071179:Signaling Lymphocytic Activation Molecule Associated Protein; D000071176:Signaling Lymphocytic Activation Molecule Family; D000071177:Signaling Lymphocytic Activation Molecule Family Member 1; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)