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Novel isoform of lymphoid adaptor FYN-T-binding protein (FYB-130) interacts with SLP-76 and up-regulates interleukin 2 production.

T-cell activation involves the participation of protein-tyrosine kinases p56(lck) and ZAP-70/SYK as well as lymphoid proteins such as SLP-76 and FYB/SLAP. FYB/SLAP has the hallmarks of an adaptor protein that binds to the SH2 domains of the Src kinase FYN-T and SLP-76. Whereas two forms of FYB at 120 and 130 kDa have been identified biochemically, a cDNA encoding only the lower molecular weight isoform has been cloned (termed FYB-120 or SLAP-130). In this study, we report the isolation of an alternative isoform of FYB with a molecular mass of 130 kDa (FYB-130) that has the same structure as FYB-120 except for an insertion of 46 amino acids toward the carboxyl-terminal region of the protein. FYB-120 and FYB-130 share an ability to bind to the SH2 domains of FYN-T and SLP-76, to act as substrates for p59(FYN-T), and to be expressed in the cytoplasm and nucleus of T-cells. Differences were noted between the isoforms in the efficiency of binding to SLP-76 and in the preferential expression of FYB-130 in mature T-cells. When co-expressed together with FYN-T and SLP-76, FYB-130 caused a significant increase in anti-CD3-driven NF-AT transcription. Finally, fluorescence in situ hybridization analysis localized the FYB gene to human chromosome 5 at position p13.1. FYB-130 therefore represents a novel variant of FYB protein that can up-regulate T-cell receptor-driven interleukin 2 production in mature T-cells.

Pubmed ID: 10497204


  • Veale M
  • Raab M
  • Li Z
  • da Silva AJ
  • Kraeft SK
  • Weremowicz S
  • Morton CC
  • Rudd CE


The Journal of biological chemistry

Publication Data

October 1, 1999

Associated Grants


Mesh Terms

  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Base Sequence
  • Carrier Proteins
  • Cell Nucleus
  • Chromosome Mapping
  • Chromosomes, Human, Pair 5
  • Cloning, Molecular
  • Cytoplasm
  • Humans
  • Interleukin-2
  • Molecular Sequence Data
  • Phosphoproteins
  • Protein Binding
  • Protein Isoforms
  • Sequence Homology, Amino Acid
  • T-Lymphocytes
  • Thymus Gland
  • Up-Regulation