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Revisiting the Roco G-protein cycle

Susanne Terheyden1, Franz Y Ho2, Bernd K Gilsbach1

  • 1*Department of Cell Biochemistry, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.

The Biochemical Journal
|October 16, 2014
PubMed

Insights

Mutations in leucine-rich-repeat kinase 2 (LRRK2) cause Parkinson's disease. This study reveals how LRRK2 protein dimerization regulates its activity, suggesting it doesn't need external factors for activation or GTPase activity stimulation.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Neuroscience

Background:

  • Mutations in leucine-rich-repeat kinase 2 (LRRK2) are a primary genetic cause of late-onset Parkinson's disease (PD).
  • LRRK2, a member of the Roco protein family, possesses a Roc G-domain and a COR domain, crucial for its function.
  • The precise regulatory mechanism of the LRRK2 Roc-COR tandem and its nucleotide-bound state has remained unclear due to conflicting data.

Purpose of the Study:

  • To elucidate the regulatory mechanism of the LRRK2 Roc-COR tandem.
  • To characterize the function of the Roc-COR tandem in nucleotide binding and dimerization.
  • To investigate the GTPase activity regulation in LRRK2 and related Roco proteins.

Main Methods:

  • Determined the first crystal structure of a nucleotide-bound Roc domain.
  • Utilized LRRK2 and bacterial Roco proteins for biochemical characterization.
  • Analyzed nucleotide binding affinity and dissociation rates.
  • Assessed GTPase activity of monomeric and dimeric forms.

Main Results:

  • Nucleotide binding induces significant structural changes at the Roc/COR domain interface, a key mutation site in PD.
  • The C-terminal subdomain of COR acts as a dimerization module, independent of nucleotide binding.
  • LRRK2 and Roco proteins exhibit low affinity for GDP/GTP with rapid dissociation, suggesting GEF-independent activation.
  • GTPase activity is stimulated by nucleotide-dependent dimerization, where monomers mutually enhance catalytic function, obviating the need for GAPs.

Conclusions:

  • LRRK2 dimerization is a critical regulatory mechanism for its GTPase activity.
  • Roco proteins likely activate themselves through dimerization, rather than relying on external GEFs or GAPs.
  • These findings offer new insights into LRRK2 function and potential therapeutic strategies for Parkinson's disease.

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