We show here that SAP mutants found in XLP patients are defective in binding its physiological ligands signaling lymphocyte activating molecule (SLAM), a co-receptor in T cell activation, and Fyn, a Src family protein tyrosine kinase.
These findings suggest that association of SAP with 2B4 is necessary for optimal NK/lymphokine-activated killer cytotoxicity and imply that alterations in SAP/2B4 signaling contribute to the immune dysfunction observed in XLP.
Deficiency of the proapoptotic SAP function in X-linked lymphoproliferative disease aggravates Epstein-Barr virus (EBV) induced mononucleosis and promotes lymphoma development.
In addition, the 2B4-induced signal was absolutely dependent on coexpression of SAP, a Src homology 2 (SH2) domain-containing adaptor associating with SLAM-related receptors and mutated in X-linked lymphoproliferative disease.
X-linked lymphoproliferative disease (XLP1) is a rare immunodeficiency characterized by severe immune dysregulation and caused by mutations in the SH2D1A/SAP gene.
A phosphopeptide library screen and analysis of mutations identified in XLP patients confirm that these extended interactions are required for SAP function.
To delineate the role of SAP in the pathophysiology of X-linked lymphoproliferative disease, a strain of sap-deficient mice has been generated by deleting exon 2 of the gene.
Several years ago, the gene defective in XLP was identified as SAP (SLAM-associated protein), and recent data suggest that SAP plays a broad role in immune signaling.
HSCT is the only curative therapy for XLP and this therapy should be urgently considered.What is Known:• SAP and XIAP deficiencies share common clinical feature, HLH, whereas they also have their own specific manifestations.• IBD affects 25-30% of XIAP-deficient patients, which has been reported in other countries especially in European country and Japan.What is New:• This is the largest patient cohort study of XLP in China.• We firstly summarized the clinical features and outcomes of Chinese XIAP-deficient patients and found only 1 in 22 patients developed IBD and diet background may contribute to it; Asian SAP-deficient patients carrying SH2D1A R55X mutation were more prone to HLH.
Mutations in <i>SH2D1A</i> gene that encodes SAP (SLAM-associated protein) result in X-linked lymphoproliferative disease (XLP), a rare primary immunodeficiency disease defined by exquisite sensitivity to the B-lymphotropic Epstein-Barr virus (EBV) and B cell lymphomas.
Among them is the X-linked lymphoproliferative syndrome (XLP) which was shown to be caused by either mutations in the gene SH2D1a/SAP or, more recently, in the BIRC4/XIAP gene.