The adaptor molecule SAP is required for T cell receptor induced-invariant natural killer T (iNKT) cell killing of T and B cell targets
SAP-null iNKT cells adhere poorly to T lymphoid targets and exhibit reduced polarization of lytic machinery to the immunological synapse
The adaptor molecule Signaling Lymphocytic Activation Molecule (SLAM)-associated protein (SAP) plays critical roles during invariant natural killer T (iNKT) cell ontogeny. As a result, SAP-deficient humans and mice lack iNKT cells. The strict developmental requirement for SAP has made it difficult to discern its possible involvement in mature iNKT cell functions. Using temporal Cre recombinase-mediated gene deletion to ablate SAP expression after completion of iNKT cell development, we demonstrate that SAP is essential for T cell receptor (TCR)-induced iNKT cell cytotoxicity against T and B leukemia targets in vitro and iNKT cell-mediated control of T leukemia growth in vivo. These findings are not restricted to the murine system, as siRNA-mediated silencing of SAP in human iNKT cells also significantly impairs TCR-induced cytolysis. Mechanistic studies reveal that iNKT cell killing requires the tyrosine kinase Fyn, a known SAP-binding protein. Furthermore, SAP expression is required within murine and human iNKTs to facilitate interaction of iNKT cells with T cell targets and induce reorientation of the microtubule-organizing center to the immunological synapse (IS). Collectively, these studies highlight a novel and essential role for SAP during iNKT cell cytotoxicity and formation of a functional iNKT cell IS.
- Submitted November 21, 2012.
- Accepted February 15, 2013.
- Copyright © 2005 American Society of Hematology