Analysis of α-synuclein levels related to LRRK2 kinase activity: from substantia nigra to urine of patients with Parkinson's disease

Research on Parkinson's disease (PD) has been focused on the development of PD diagnostic tools as much as the development of PD therapeutics. Several genetic culprits of PD, including DJ-1, Leucine-rich repeat kinase 2 (LRRK2), and alpha-synuclein (alpha-syn), have been investigated as markers of PD in human biofluids. Unfortunately, the approaches to develop PD diagnostic tools are impractical, and there is a considerable demand for an appropriate marker of PD. The measurement of alpha-syn in biofluids has recently been made more accurate by examining monomers and aggregates separately using enzyme-linked immunosorbent assay (ELISA). Previously, we reported on the development of two types of sandwich ELISA for total alpha-syn and MJFR-14-6-4-2 antibody-specific alpha-syn fibrillar oligomers. The pathogenic LRRK2 G2019S mutation is related to increased alpha-syn secretion in the extracellular space. We tested our established ELISA using differentiated SH-SH5Y cells transfected with LRRK2 G2019S. The secretory levels of fibrillar oligomeric alpha-syn divided by total alpha-syn were significantly increased in LRRK2 G2019S-expressing cells. Additionally, substantia nigra lysates or concentrated urine from PD patients and non-PD subjects were analyzed. We observed ambiguous changes in the levels of total or fibrillar oligomeric alpha-syn and their ratio between PD and non-PD. Despite the insignificant increase in the relative levels of fibrillar oligomeric alpha-syn to total alpha-syn in PD, the duration of disease progression after diagnosis significantly corresponded to the relative levels of fibrillar oligomeric alpha-syn to total alpha-syn in the urine. These results might provide greater understanding for the next stage of development of alpha-syn ELISAs.

Automated summary

Research on Parkinson's disease has focused on developing diagnostic tools and therapeutics. Genetic culprits like DJ-1, LRRK2, and alpha-syn have been studied as markers of PD. ELISA technology has been used to improve the accuracy of measuring alpha-syn in biofluids.