Identification of GEFs and GAPS modulating phosphorylation and abundance of Rab10 by LRRK2-G2019S in neurons

The Parkinson s Disease associated kinase LRRK2 is proposed to act through phosphorylation of Rab proteins, most notably Rab10. All Rabs participate in a GTPase cycle, in which GEFs (Guanine nucleotide exchange factors) promote membrane binding, and GAPs (GTPase-activating proteins) promote release into the cytoplasm. LRRK2 is proposed to phosphorylate membrane bound Rab10. The hypothesis is that phosphoRab10 is less sensitive to GAP action and may remain membrane bound. To test how LRRK2 and Rab10 function in the GTPase cycle, we used an immunoblotting strategy in fly brains to show that a putative GEF Crag/DENND4C and three possible GAPs (pollux (plx), GAPcenA and Evi5, orthologs of AS160) interact with LRRK2 controlling the phosphorylation and abundance of Rab10. Crag behaves similarly to a Rab10 GEF and additionally modulates the level of panRab10. Only plx acts as a conventional GAP. GAPcenA seems to act as a GAP for phosphoRab10 more than panRab10. It is likely that Evi5 acts as a GAP for another Rab, possibly Rab11.