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Involvement of Rap-1 activation and early termination of immune synapse in CTLA-4-mediated negative signal

Satoru Hara1, Chiaki Nakaseko, Sho Yamasaki

  • 1Laboratory for Cell Signaling, RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehirocho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.

Hematology (Amsterdam, Netherlands)
|June 4, 2009
PubMed

Insights

Cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibits T cell responses by destabilizing immunological synapses (IS). This involves Rap-1 activation, which prevents sustained T cell-APC contact and IL-2 production.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Cytotoxic T lymphocyte antigen 4 (CTLA-4) is a key T cell inhibitory receptor.
  • CTLA-4 signaling relies on the activation of the small GTPase Rap-1.
  • The exact mechanism of CTLA-4-mediated T cell suppression is not fully understood.

Purpose of the Study:

  • To elucidate the mechanism by which CTLA-4 delivers inhibitory signals.
  • To investigate the role of Rap-1 in CTLA-4-mediated T cell suppression.
  • To determine how CTLA-4 affects immunological synapse (IS) formation and stability.

Main Methods:

  • Utilized murine normal T cell clones.
  • Examined the impact of CTLA-4 engagement on IL-2 production.
  • Assessed the role of Rap-1 activation using Spa-1, a Rap-1-specific GTPase activating protein (GAP).
  • Analyzed immunological synapse formation, cell motility, and Talin accumulation at the T cell-APC interface.

Main Results:

  • CTLA-4 engagement led to decreased IL-2 production, correlating with IS destabilization.
  • Overexpression of Spa-1 blocked Rap-1 activation and CTLA-4-induced IL-2 suppression.
  • CTLA-4 engagement did not inhibit early activation signals but increased T cell motility.
  • CTLA-4 suppressed prolonged Talin accumulation at the T cell-APC contact area.

Conclusions:

  • Rap-1 activation is crucial for CTLA-4-mediated inhibition of T cell responses.
  • CTLA-4 inhibits T cell activation by preventing stable IS formation, rather than affecting early signaling events.
  • CTLA-4 signaling, via Rap-1, disrupts the T cell-APC interaction necessary for sustained activation.

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