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Updated: Sep 14, 2025
Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag
Published on: December 14, 2017
PPM1M, an LRRK2-counteracting, phosphoRab12-preferring phosphatase with a potential link to Parkinson's disease
Claire Y Chiang1, Neringa Pratuseviciute2, Yu-En Lin1
1Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA; Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD, USA.
Abstract:
Leucine-rich repeat kinase 2 (LRRK2) phosphorylates a subset of Rab GTPases that regulate receptor trafficking, and LRRK2-activating mutations are linked to Parkinson's disease. Rab phosphorylation is a transient event that can be reversed by phosphatases, including protein phosphatase, Mg2+/Mn2+ dependent 1H (PPM1H), which acts on phosphorylated Rab 8A (phosphoRab8A) and phosphoRab10. Here, we report a phosphatome-wide small interfering RNA (siRNA) screen that identified PPM1M as a phosphoRab12-preferring phosphatase that also acts on phosphoRab8A and phosphoRab10. Upon knockout from cultured cells or mice, PPM1M displays selectivity for phosphoRab12. As shown previously for mice harboring LRRK2 pathway mutations, knockout of Ppm1m leads to primary cilia loss in striatal cholinergic and parvalbumin interneurons. We also identified a rare PPM1M mutation in patients with Parkinson's disease that is catalytically inactive when tested in vitro and in cells. These findings identify PPM1M as a key player in the LRRK2 signaling pathway and provide a new therapeutic target for the possible benefit of patients with Parkinson's disease.
Insights
Protein phosphatase magnesium-dependent 1M (PPM1M) dephosphorylates key Rab GTPases involved in Parkinson's disease pathogenesis. PPM1M deficiency causes neuronal defects, and its mutation is linked to Parkinson's disease, suggesting a therapeutic target.
Area of Science:
- Molecular Biology
- Neuroscience
- Biochemistry
Background:
- Leucine-rich repeat kinase 2 (LRRK2) activating mutations are linked to Parkinson's disease (PD).
- LRRK2 phosphorylates Rab GTPases, a process reversible by phosphatases like PPM1H.
- Phosphorylated Rab GTPases play roles in receptor trafficking and neuronal function.
Purpose of the Study:
- To identify phosphatases involved in the LRRK2 signaling pathway.
- To investigate the role of PPM1M in Rab GTPase dephosphorylation and its relevance to PD.
Main Methods:
- Conducted a phosphatome-wide small interfering RNA (siRNA) screen.
- Utilized knockout cell and mouse models to study PPM1M function.
- Analyzed PPM1M activity in vitro and in cells, including patient-derived mutations.
Main Results:
- Identified PPM1M as a phosphatase with preference for phosphoRab12, also acting on phosphoRab8A and phosphoRab10.
- PPM1M knockout in cells and mice led to primary cilia loss in specific neuronal populations.
- A rare, catalytically inactive PPM1M mutation was found in Parkinson's disease patients.
Conclusions:
- PPM1M is a key phosphatase in the LRRK2 signaling pathway.
- PPM1M dysfunction is implicated in Parkinson's disease pathogenesis.
- PPM1M represents a potential therapeutic target for Parkinson's disease.
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