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Dynamic interaction of CD2 with the GYF and the SH3 domain of compartmentalized effector molecules

Christian Freund1, Ronald Kühne, Hailin Yang

  • 1Protein Engineering Group and Molecular Modeling Group, Forschungsinstitut für Molekulare Pharmakologie and Freie Universität Berlin, Robert-Rössle-Strasse 10, D-13125 Berlin, Germany. freund@fmp-berlin.de

The EMBO Journal
|November 12, 2002
PubMed

Insights

The GYF domain of CD2BP2 binds CD2, regulating T cell signaling. Upon CD2 clustering, Fyn SH3 replaces CD2BP2, switching CD2 function.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Structural Biology

Background:

  • Intracellular protein interaction domains are crucial for eukaryotic cell signaling pathways.
  • The CD2BP2 adaptor protein plays a role in T cell activation by binding to the CD2 cytoplasmic tail, influencing interleukin-2 production.

Purpose of the Study:

  • To elucidate the structural basis of the interaction between the CD2BP2 GYF domain and the CD2 cytoplasmic tail.
  • To investigate the competitive binding of tyrosine kinases to the CD2 proline-rich sequence and its functional implications in T cells.

Main Methods:

  • X-ray crystallography to determine the structure of the CD2BP2 GYF domain bound to a CD2 peptide.
  • Nuclear Magnetic Resonance (NMR) spectroscopy to analyze protein-protein interactions and competition assays.
  • Co-immunoprecipitation experiments to assess in vivo protein interactions within different cellular compartments.

Main Results:

  • The GYF domain utilizes conserved hydrophobic residues to form a unique interaction surface for proline-rich motifs, distinct from SH3 domains.
  • Fyn SH3 domain, but not Lck SH3, competes with CD2BP2 for binding to the CD2 proline-rich sequence in vitro.
  • In vivo, CD2BP2 binds CD2 in soluble compartments, but Fyn SH3 replaces it in lipid rafts after CD2 ectodomain clustering.

Conclusions:

  • The study reveals a novel binding mechanism for the GYF domain involving a single hydrophobic surface.
  • A functional switch in CD2 signaling is demonstrated, mediated by competition between CD2BP2 and Fyn SH3 for CD2 binding, triggered by extracellular signals and lipid raft translocation.

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