Structural basis for the interaction of the free SH2 domain EAT-2 with SLAM receptors in hematopoietic cells

Massimo Morra¹, Jun Lu², Florence Poy², Margarita Martin³, Joan Sayos, Silvia Calpe, Charles Gullo, Duncan Howie, Svend Rietdijk, Andrew Thompson⁴, Anthony J. Coyle⁵, Christopher Denny⁴, Michael B. Yaffe⁶, Pablo Engel³, Michael J. Eck², and Cox Terhorst¹

Division of Immunology, Beth Israel Deaconess Medical Center, Harvard Medical School and ²Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, ⁴Molecular Biology Institute, University of California, Los Angeles, CA 90095, ⁵Millennium Pharmaceuticals Inc., Inflammation Division, Cambridge, MA 02139, ⁶Center for Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA and ³Department of Cellular Biology and Pathology, Faculty of Medicine, University of Barcelona, Spain ¹Corresponding authors e-mail: terhorst{at}caregroup.harvard.edu or mmorra{at}caregroup.harvard.edu

Abstract: The T and natural killer (NK) cell-specific gene SAP (SH2D1A) encodes a ‘free SH2 domain’ that binds a specific tyrosine motif in the cytoplasmic tail of SLAM (CD150) and related cell surface proteins. Mutations in SH2D1A cause the X-linked lymphoproliferative disease, a primary immunodeficiency. Here we report that a second gene encoding a free SH2 domain, EAT-2, is expressed in macrophages and B lympho cytes. The EAT-2 structure in complex with a phosphotyrosine peptide containing a sequence motif with Tyr281 of the cytoplasmic tail of CD150 is very similar to the structure of SH2D1A complexed with the same peptide. This explains the high affinity of EAT-2 for the pTyr motif in the cytoplasmic tail of CD150 but, unlike SH2D1A, EAT-2 does not bind to non-phosphorylated CD150. EAT-2 binds to the phosphorylated receptors CD84, CD150, CD229 and CD244, and acts as a natural inhibitor, which interferes with the recruitment of the tyrosine phosphatase SHP-2. We conclude that EAT-2 plays a role in controlling signal transduction through at least four receptors expressed on the surface of professional antigen-presenting cells.

Key Words: Keywords: antigen-presenting cells/crystal structure/EAT-2/SAP/XLP