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The Semaphorin 4D receptor Plexin-B1 is a GTPase activating protein for R-Ras

Izumi Oinuma1, Yukio Ishikawa, Hironori Katoh

  • 1Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.

Science (New York, N.Y.)
|August 7, 2004
PubMed

Insights

Plexin-B1, a Semaphorin 4D receptor, activates R-Ras GTPase activity. This interaction is crucial for Semaphorin 4D-induced repulsive axon guidance signaling in neurons.

Area of Science:

  • Neuroscience
  • Cell Biology
  • Molecular Biology

Background:

  • Plexins are cell surface receptors binding semaphorins, regulating cell adhesion and migration.
  • Ras superfamily proteins, like R-Ras, are critical for cell adhesion and neurite outgrowth.

Purpose of the Study:

  • To investigate the interaction between Plexin-B1 and R-Ras.
  • To elucidate the role of Plexin-B1-R-Ras signaling in Semaphorin 4D-mediated neuronal guidance.

Main Methods:

  • Investigated the direct interaction between Plexin-B1 and R-Ras.
  • Examined the role of Rnd1 in Plexin-B1-R-Ras complex formation.
  • Assessed the effect of this complex on R-Ras GTPase activity.
  • Studied Sema4D-induced growth cone collapse in hippocampal neurons.

Main Results:

  • Plexin-B1 directly stimulates the GTPase activity of R-Ras.
  • This activation requires the interaction of Plexin-B1 with Rnd1.
  • The Plexin-B1-Rnd1 complex down-regulates R-Ras activity.
  • This down-regulation is essential for Sema4D-induced growth cone collapse.

Conclusions:

  • Plexin-B1 acts as a GTPase activating protein for R-Ras.
  • Plexin-B1 mediates Sema4D-induced repulsive axon guidance signaling via R-Ras regulation.
  • This pathway is critical for neuronal development and guidance.

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