Elevated In Vitro Kinase Activity in Peripheral Blood Mononuclear Cells of Leucine-Rich Repeat Kinase 2 G2019S Carriers: A Novel Enzyme-Linked Immunosorbent Assay-Based Method.

BACKGROUND: Leucine-rich repeat kinase 2 kinase inhibitors are being vigorously pursued as potential therapeutic options; however, there is a critical need for sensitive and quantitative assays of leucine-rich repeat kinase 2 function and target engagement. OBJECTIVES: Our objective was to compare collection and storage protocols for peripheral blood mononuclear cells, and to determine the optimal conditions for downstream analyses of leucine-rich repeat kinase 2 in PD cohorts. METHODS: Here, we describe enzyme-linked immunosorbent assay-based assays capable of detecting multiple aspects of leucine-rich repeat kinase 2 function at endogenous levels in human tissues. RESULTS: In peripheral blood mononuclear cells from both healthy and affected carriers of the G2019S mutation in leucine-rich repeat kinase 2, we report, for the first time, significantly elevated in vitro kinase activity, while detecting a significant increase in pS935/leucine-rich repeat kinase 2 in idiopathic PD patients. CONCLUSIONS: Quantitative assays such as these described here could potentially uncover specific markers of leucine-rich repeat kinase 2 function that are predictive of disease progression, aid in patient stratification, and be a critical component of upcoming clinical trials. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

An Assessment of LRRK2 Serine 935 Phosphorylation in Human Peripheral Blood Mononuclear Cells in Idiopathic Parkinson's Disease and G2019S LRRK2 Cohorts.

The phosphorylated form of LRRK2, pS935 LRRK2, has been proposed as a target modulation biomarker for LRRK2 inhibitors. The primary aim of the study was to characterize and qualify this biomarker for therapeutic trials of LRRK2 inhibitors in Parkinson's disease (PD). To this end, analytically validated assays were used to monitor levels of pS935 LRRK2 and total LRRK2 in peripheral blood mononuclear cells (PBMCs) from the following donor groups: healthy controls, idiopathic PD, and G2019S carriers with and without PD. Neither analyte correlated with age, gender, or disease severity. While total LRRK2 levels were similar across the four groups, there was a significant reduction in pS935 LRRK2 levels in disease-manifesting G2019S carriers compared to idiopathic PD. In aggregate, these data indicate that phosphorylation of LRRK2 at S935 may reflect a state marker for G2019S LRRK2-driven PD, the underlying biology for which requires investigation in future studies. This study also provides critical foundational data to inform the integration of pS935 and total LRRK2 levels as biomarkers in therapeutic trials of LRRK2 kinase inhibitors.