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A Model for the Signal Initiation Complex Between Arrestin-3 and the Src Family Kinase Fgr

Ivette Perez1, Sandra Berndt2, Rupesh Agarwal3

  • 1Department of Biochemistry, Vanderbilt University, Nashville, TN 37232-0146, USA; Center for Structural Biology, Nashville, TN 37232-0146, USA.

Journal of Molecular Biology
|December 13, 2021
PubMed

Insights

Arrestin-3 acts as a scaffold, modulating Fgr kinase activity through direct interaction. This study provides a structural basis for arrestin-dependent Fgr kinase activation, crucial for cellular growth and proliferation.

Area of Science:

  • Cellular signaling and molecular biology.
  • Protein-protein interactions in signal transduction.

Background:

  • Arrestins are key regulators of G protein-coupled receptor (GPCR) signaling.
  • Src family kinases, including Fgr kinase, are involved in cellular growth and proliferation.
  • Previous studies indicated Fgr kinase has high constitutive activity and can be activated by various pathways.

Purpose of the Study:

  • To investigate the interaction between arrestin-3 and Fgr kinase.
  • To elucidate the structural mechanisms underlying arrestin-3's modulation of Fgr kinase activity.
  • To provide a structural framework for arrestin-dependent Fgr kinase activation.

Main Methods:

  • Nuclear Magnetic Resonance (NMR) spectroscopy to identify protein-protein interactions.
  • X-ray crystallography to determine the structure of the Fgr SH3 domain.
  • Mutagenesis studies to support a proposed complex model.
  • Biochemical assays to assess kinase activity modulation.

Main Results:

  • Arrestin-3 modulates Fgr kinase activity with bell-shaped concentration dependence, suggesting a scaffold role.
  • NMR confirmed a direct interaction between arrestin-3's polyproline motif and Fgr kinase's SH3 domain.
  • The crystal structure of the Fgr SH3 domain was determined at 1.9 Å resolution.
  • A structural model of the GPCR-arrestin-3-Fgr complex was developed, supported by mutagenesis and consistent with disease-associated mutations.

Conclusions:

  • Arrestin-3 directly interacts with Fgr kinase, modulating its activity.
  • A detailed structural model explains the multi-site interaction between arrestin-3 and Fgr kinase.
  • These findings provide a structural basis for arrestin-dependent Fgr kinase activation and its role in cellular processes.
Keywords:
Fgrarrestinsignal initiation complex

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