SLAM-associated protein deficiency causes imbalanced early signal transduction and blocks downstream activation in T cells from X-linked lymphoproliferative disease patients

Ornella Parolini, Silvia Sanzone, Maximilian Zeyda, Marcus D. Saemann, Maddalena Soncini, Wolfgang Holter, Gerhard Fritsch, Walter Knapp, Fabio Candotti, Thomas M. Stulnig

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Deficiency of SAP (SLAM (signaling lymphocyte activation molecule)-associated protein) protein is associated with a severe immunodeficiency, the X-linked lymphoproliferative disease (XLP) characterized by an inappropriate immune reaction against Epstein-Barr virus infection often resulting in a fatal clinical course. Several studies demonstrated altered NK and T cell function in XLP patients; however, the mechanisms underlying XLP disease are still largely unknown. Here, we show that non-transformed T cell lines obtained from XLP patients were defective in several activation events such as IL-2 production, CD25 expression, and homotypic cell aggregation when cells were stimulated via T cell antigen receptor (TCR).CD3 but not when early TCR-dependent events were bypassed by stimulation with phorbol 12-myristate 13-acetate/ionomycin. Analysis of proximal T cell signaling revealed imbalanced TCR.CD3-induced signaling in SAP-deficient T cells. Although phospholipase C gamma 1 phosphorylation and calcium response were both enhanced in T cells from XLP patients, phosphorylation of VAV and downstream signal transduction events such as mitogen-activated protein kinase phosphorylation and IL-2 production were diminished. Importantly, reconstitution of SAP expression by retroviral-mediated gene transfer completely restored abnormal signaling events in T cell lines derived from XLP patients. In conclusion, SAP mutation or deletion in XLP patients causes profound defects in T cell activation, resulting in immune deficiency. Moreover, these data provide evidence that SAP functions as an essential integrator in early TCR signal transduction.
Original languageEnglish
Pages (from-to)29593-29599
Number of pages7
JournalTHE JOURNAL OF BIOLOGICAL CHEMISTRY
Volume278
DOIs
Publication statusPublished - 2003

Keywords

  • Antigens, CD3
  • Calcium
  • Carrier Proteins
  • Cell Adhesion
  • Cell Division
  • Cell Line, Transformed
  • Chromosomes, Human, X
  • Cytoplasm
  • Flow Cytometry
  • Humans
  • I-kappa B Proteins
  • Interleukin-2
  • Intracellular Signaling Peptides and Proteins
  • Ionomycin
  • Lymphoproliferative Disorders
  • MAP Kinase Signaling System
  • Mutagens
  • Mutation
  • Phospholipase C gamma
  • Phosphorylation
  • Receptors, Antigen, T-Cell
  • Receptors, Interleukin-2
  • Retroviridae
  • Signal Transduction
  • T-Lymphocytes
  • Tetradecanoylphorbol Acetate
  • Time Factors
  • Type C Phospholipases

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