Mutations in LRRK2 are a common cause of genetic Parkinson’s disease (PD). LRRK2 is a multi-domain Roco protein, harbouring kinase and GTPase activity. In analogy with a bacterial homologue, LRRK2 was proposed to act as a GTPase activated by dimerization (GAD), while recent reports suggest LRRK2 to exist under a monomeric and dimeric form in vivo. It is however unknown how LRRK2 oligomerization is regulated. Here, we show that oligomerization of a homologous bacterial Roco protein depends on the nucleotide load. The protein is mainly dimeric in the nucleotide-free and GDP-bound states, while it forms monomers upon GTP binding, leading to a monomer-dimer cycle during GTP hydrolysis. An analogue of a PD-associated mutation stabilizes the dimer and decreases the GTPase activity. This work thus provides insights into the conformational cycle of Roco proteins and suggests a link between oligomerization and disease-associated mutations in LRRK2.

Background: Methods: Conclusion:

Roco proteins have come into focus after mutations in the gene coding for the human Roco protein Leucine-rich repeat kinase 2 (LRRK2) were discovered to be one of the most common genetic causes of late onset Parkinson’s disease. Roco proteins are characterized by a Roc domain responsible for GTP binding and hydrolysis, followed by a COR dimerization device. The regulation and function of this RocCOR domain tandem is still not completely understood. To fully biochemically characterize Roco proteins, we performed a systematic survey of the kinetic properties of several Roco protein family members, including LRRK2. Together, our results show that Roco proteins have a unique G-protein cycle. Our results confirm that Roco proteins have a low nucleotide affinity in the micromolar range and thus do not strictly depend on G-nucleotide exchange factors. Measurement of multiple and single turnover reactions shows that neither P_i nor GDP release are rate-limiting, while this is the case for the GAP-mediated GTPase reaction of some small G-proteins like Ras and for most other high affinity Ras-like proteins, respectively. The K _M values of the reactions are in the range of the physiological GTP concentration, suggesting that LRRK2 functioning might be regulated by the cellular GTP level.

Mutations in the gene coding for the multi-domain protein leucine-rich repeat kinase 2 (LRRK2) are the leading cause of genetically inherited Parkinson's disease (PD). Two of the common found mutations are the R1441C and G2019S. In this study we identified protein phosphatase 2A (PP2A) as an interacting partner of LRRK2. We were able to demonstrate that the Ras of complex protein (ROC) domain is sufficient to interact with the three subunits of PP2A in human neuroblastoma SH-SY5Y cells and in HeLa cells. The alpha subunit of PP2A is interacting with LRRK2 in the perinuclear region of HeLa cells. Silencing the catalytic subunit of PP2A by shRNA aggravated cellular degeneration induced by the pathogenic R1441C-LRRK2 mutant expressed in neuroblastoma SH-SY5Y cells. A similar enhancement of apoptotic nuclei was observed by downregulation of the catalytic subunit of PP2A in cultured cortical cells derived from neurons overexpressing the pathogenic mutant G2019S-LRRK2. Conversely, pharmacological activation of PP2A by sodium selenate showed a partial neuroprotection from R1441C-LRRK2-induced cellular degeneration. All these data suggest that PP2A is a new interacting partner of LRRK2 and reveal the importance of PP2A as a potential therapeutic target in PD.

Mutations in human leucine-rich-repeat kinase 2 (LRRK2) have been found to be the most frequent cause of late-onset Parkinson’s Disease (PD). LRRK2 is a large protein with two enzymatic domains, a GTPase and a kinase domain. A cluster of (auto)-phosphorylation sites within the N-terminus of LRRK2 have been shown to be crucial for the localization of LRRK2 and is important for PD pathogenesis. In addition, phosphorylation of sites within the G-domain of the protein affect GTPase activity. Here we discuss the role of these (auto)-phosphorylation sites of LRRK2 and their regulation by phosphatases and upstream kinases.

The Leucine Rich Repeat Kinase 2 (LRRK2) gene is a major genetic determinant of Parkinson’s disease (PD), encoding a homonymous multi-domain protein with two catalytic activities, GTPase and Kinase, involved in intracellular signaling and trafficking. LRRK2 is phosphorylated at multiple sites, including a cluster of autophosphorylation sites in the GTPase domain and a cluster of heterologous phosphorylation sites at residues 860 to 976. Phosphorylation at these latter sites is found to be modified in brains of PD patients, as well as for some disease mutant forms of LRRK2. The main aim of this study is to investigate the functional consequences of LRRK2 phosphorylation or dephosphorylation at LRRK2’s heterologous phosphorylation sites. To this end, we generated LRRK2 phosphorylation site mutants and studied how these affected LRRK2 catalytic activity, neurite outgrowth and lysosomal physiology in cellular models. We show that phosphorylation of RAB8a and RAB10 substrates are reduced with phosphomimicking forms of LRRK2, while RAB29 induced activation of LRRK2 kinase activity is enhanced for phosphodead forms of LRRK2. Considering the hypothesis that PD pathology is associated to increased LRRK2 kinase activity, our results suggest that for its heterologous phosphorylation sites LRRK2 phosphorylation correlates to healthy phenotypes and LRRK2 dephosphorylation correlates to phenotypes associated to the PD pathological processes.