MPI - MS-based clinical assay for LRRK2 phosphorylated Rab10 occupancy calculation

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Recombinant pRab10 15:13:45124442
Neutrophil control 15:13:45124845 15:13:45124433
HA-pRab10 and Endo-pRab10 15:13:45124830
Accurate MS-based Rab10 phosphorylation stoichiometry determination as a readout for LRRK2 activity in Parkinson’s disease

  • Organism: Homo sapiens, Mus musculus
  • Instrument: Q Exactive HF,Q Exactive HF-X
  • SpikeIn: Yes
  • Keywords: Rab10, phosphorylation, LRRK2, Parkinson's Disease
Pathogenic mutations in the Leucine-rich repeat kinase 2 (LRRK2) are the predominant genetic cause of Parkinson’s disease (PD). They increase its activity, resulting in augmented Rab10-Thr73 phosphorylation and conversely, LRRK2 inhibition decreases pRab10 levels. Currently, there is no assay to quantify pRab10 levels for drug target engagement or patient stratification. To meet this challenge, we developed an ultra-sensitive targeted mass spectrometry (MS)-based assay for determining Rab10-Thr73 phosphorylation stoichiometry in human samples. It uses synthetic stable isotope-labeled (SIL) analogues for both phosphorylated and non-phosphorylated tryptic peptides surrounding Rab10-Thr73 to directly derive the percentage of Rab10 phosphorylation from attomole amounts of the endogenous phosphopeptide. We test the reproducibility of our assay by determining Rab10-Thr73 phosphorylation stoichiometry in neutrophils of LRRK2 mutation carriers before and after LRRK2 inhibition. Compared to healthy controls, the PD predisposing mutation carriers LRRK2 G2019S and VPS35 D620N display 1.9-fold and 3.7-fold increased pRab10 levels, respectively. Our generic MS-based assay further establishes the relevance of pRab10 as a prognostic PD marker and is a powerful tool for determining LRRK2 inhibitor efficacy and for stratifying PD patients for LRRK2 inhibitor treatment.
Created on 3/19/20, 3:14 PM