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Detection of Small GTPase Prenylation and GTP Binding Using Membrane Fractionation and GTPase-linked Immunosorbent Assay
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Published on: November 11, 2018

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CDC42 binds PAK4 via an extended GTPase-effector interface

Byung Hak Ha1, Titus J Boggon2,3

  • 1Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520.

Proceedings of the National Academy of Sciences of the United States of America
|January 4, 2018
PubMed

Insights

The p21-activated kinase 4 (PAK4) interacts with CDC42 through its CRIB domain and other regions. These interactions uniquely regulate PAK4 kinase activity and binding affinity.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Structural Biology

Background:

  • p21-activated kinases (PAK) are serine/threonine kinases crucial for cellular functions.
  • PAKs are downstream effectors of RHO GTPases, regulating cytoskeleton, growth, survival, and polarity.
  • PAK4 is a type II PAK implicated in various cellular processes.

Purpose of the Study:

  • To investigate the interaction between PAK4 and RHO GTPases, specifically CDC42.
  • To elucidate the structural basis and functional consequences of PAK4-CDC42 binding.

Main Methods:

  • Solution scattering (SAXS) to determine the overall organization of the PAK4-CDC42 complex.
  • X-ray crystallography to resolve the atomic details of the interaction interface.
  • Biochemical assays to assess kinase activity and binding affinity.

Main Results:

  • Full-length PAK4 forms a compact heterodimer with CDC42.
  • X-ray crystallography revealed canonical CRIB domain binding and additional interactions involving the PAK4 kinase C-lobe and polybasic region.
  • These novel interactions enhance CDC42 binding affinity and modulate PAK4 kinase activity.

Conclusions:

  • The interaction between PAK4 and CDC42 is more complex than previously understood.
  • Additional binding sites beyond the CRIB domain significantly influence PAK4's functional regulation.
  • This provides new insights into the intricate mechanisms of RHO GTPase signaling and kinase regulation.
Keywords:
crystal structureprotein kinaseprotein–protein interactionsignal transductionsmall GTPase

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