LRRK2 exonic variants associated with Parkinson’s disease augment phosphorylation levels for LRRK2-Ser1292 and Rab10-Thr73

Abstract

AbstractLeucine-rich repeat kinase 2 (LRRK2) is associated to Parkinson’s disease (PD). The most common form of LRRK2 PD is caused by the G2019S variant. Besides G2019S, eight other LRRK2 variants causing familial PD also have amino acid substitutions located in a LRRK2 enzymatic domainsuggesting that enzymatic activity is at the core of mechanisms underlying disease risk. Common LRRK2 polymorphic risk variations such as G2385R, A419V, R1628 and M1646T all reside in other LRRK2 domains. Prior knowledge is limited on how these variants influence LRRK2 function. To investigate the impact on enzymatic function of both rare and common LRRK2 variation a comprehensive profiling of nineteen LRRK2 exonic variants was pursued. Six LRRK2 phosphorylation sites were identified by mass spectrometry. Besides already known phosphorylation sites such as Ser910, Ser935, Ser955, Ser973 and Ser1292 also Thr826 was confirmed by a targeted MRM assay as a LRRK2 phosphorylation site in mammalian cells. Phosphorylation site occupancy for all six LRRK2 sites was obtained but no obvious correlation to risk of disease was found. Instead, application of phospho-specific antibodies targeting LRRK2 phosphorylation sites confirmed that autophosphorylation at Ser1292 was significantly increased for all disease-causing variants whereas no significant differences could be observed for the common intermediate risk variants. Recently, Rab10 and Rab12 have been shown to be bona fide LRRK2 substrates and we find that both rare and common LRRK2 exonic variants augment the phosphorylation of Rab10. This was not observed with Rab12. Furthermore, the protective variant N551K has reduced Rab10 phosphorylation compared to LRRK2 WT. This was not observed with the protective variant R1398H. Our findings support the hypothesis that increased LRRK2 kinase function is associated with increased PD risk but also highlights the need for more sensitive tools for detection of increases in kinase activity in carriers of LRRK2 PD risk variants.AbbreviationsPDParkinson’s diseaseLRRK2leucine-rich repeat kinase 2MRMmultiple mass spectrometryMSmass spectrometryLC-MSliquid chromatography mass spectrometryLODlimit of detectionMAFminor allele frequencyCV%coefficient of variationSDS-PAGESDS-polyacrylamide gel electrophoresisRocRas of complexCORC-terminal of RocPRLpleomorphic risk loci.