Objective: This study explores the inflammatory processes in leucine-rich repeat kinase 2 (LRRK2)- microglia carrying the G2019S mutation and determines their contribution to Parkinson’s disease (PD) penetrance.

Background: Growing evidence supports an inflammatory component in PD and highlights microglia as key players in the etiology of this condition [1]. The LRRK2 G2019S mutation is the most common genetic cause of PD and is inherited with reduced penetrance [2,3]. Aside from PD, LRRK2 has been related to several chronic inflammatory disorders [2]. Hakimi et al, observed that LRRK2 protein levels are ample in immune-related cells, and LRRK2 levels can change upon pathogen detection [4]. However, to date, most of the published studies related to LRRK2 focus on its role in neurons and neglect its effects in microglia.

Method: iPSC-derived microglia were generated from manifesting and non-manifesting G2019S mutation carriers and healthy controls, as previously described [5,6]. Isogenic lines were also included. Cells were exposed to interferon gamma (IFN-γ) and the kinase inhibitor MLi-2. LRRK2 kinase activity was assessed through Western blotting. Endogenous α-synuclein levels were estimated by immunocytochemistry. Finally, RNA-sequencing was performed, and pathway enrichment analysis was implemented for the identification of dysregulated pathways.

Results: This study reveals that upon IFN-γ treatment, there is a LRRK2 G2019S-specific upregulation in the S1292 phosphorylation, a read-out of LRRK2 kinase activity, which was reversed after MLi-2 treatment. On the contrary, α-synuclein protein levels were upregulated only in manifesting G2019S LRRK2 microglia and did not respond to MLi-2 treatment, a result that was further supported by RNA-seq results.

Conclusion: Taken together, our results suggest that an inflammatory stimulus can increase LRRK2 kinase activity in a mutation-specific manner. However, this kinase activity can be downregulated by MLi-2, revealing the influence of this inhibitor on iPSC-derived microglia cells. Furthermore, the increased α-synuclein levels in manifesting LRRK2 G2019S microglia upon IFN-γ, pose α-synuclein as a main marker of LRRK2 G2019S penetrance. To further explore inflammatory mechanisms underlying LRRK2 PD penetrance, we plan to combine our RNA-seq data with metabolomics to unravel molecular signatures that may be targeted by personalized medicine approaches.

References: 1. Badanjak, K., Fixemer, S., Smajic, S., Skupin, A., Grünewald, A. (2021). The Contribution of Microglia to Neuroinflammation in Parkinson’s Disease. Int J Mol Sci. 9, 4676.
2. Berwick, D.C., Heaton, G.R., Azeggagh, S., and Harvey, K. (2019). LRRK2 Biology from structure to dysfunction: research progresses, but the themes remain the same. Mol. Neurodegener. 14, 49.
3. Trinh J, Amouri R, Duda JE, Morley JF, Read M, Donald A, Vilariño-Güell C, Thompson C, Szu Tu C, Gustavsson EK, Ben Sassi S, Hentati E, Zouari M, Farhat E, Nabli F, Hentati F, Farrer MJ. (2013). Comparative study of Parkinson’s disease and leucine-rich repeat kinase 2 p.G2019S parkinsonism. Neurobiol Aging. 5, 1125-1131.
4. Hakimi, M., Selvanantham, T., Swinton, E., Padmore, R.F., Tong, Y., Kabbach, G., Venderova, K., Girardin, S.E., Bulman, D.E., Scherzer, C.R., et al. (2011). Parkinson’s disease-linked LRRK2 is expressed in circulating and tissue immune cells and upregulated following recognition of microbial structures. J. Neural Transm. 118, 795–808.
5. van Wilgenburg, B., Browne, C., Vowles, J., and Cowley, S.A. (2013). Efficient, long-term production of monocyte-derived macrophages from human pluripotent stem cells under partly-defined and fully-defined conditions. PLoS One 8, e71098.
6. Badanjak, K., Mulica, P., Smajic, S., Delcambre, S., Tranchevent, L.-C., Diederich, N., Rauen, T., Schwamborn, J.C., Glaab, E., Cowley, S.A., et al. (2021). iPSC-Derived Microglia as a Model to Study Inflammation in Idiopathic Parkinson’s Disease. Front Cell Dev Biol 9, 740758.

« Back to 2023 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/lrrk2-g2019s-as-a-trigger-of-inflammatory-signaling-in-patient-derived-microglia/