Elevated LRRK2 autophosphorylation in brain-derived and peripheral exosomes in LRRK2 mutation carriers

Shijie Wang,Andrew B West,Zhiyong Liu,Omar S Mabrouk,Jan Aasly,Tao Ye,Tyler Maltbie

doi:10.1186/s40478-017-0492-y

Abstract

Missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene can cause late-onset Parkinson disease (PD). LRRK2 mutations increase LRRK2 kinase activities that may increase levels of LRRK2 autophosphorylation at serine 1292 (pS1292) and neurotoxicity in model systems. pS1292-LRRK2 protein can be packaged into exosomes and measured in biobanked urine. Herein we provide evidence that pS1292-LRRK2 protein is robustly expressed in cerebral spinal fluid (CSF) exosomes. In a novel cohort of Norwegian subjects with and without the G2019S-LRRK2 mutation, with and without PD, we quantified levels of pS1292-LRRK2, total LRRK2, and other exosome proteins in urine from 132 subjects and in CSF from 82 subjects. CSF and urine were collected from the same morning clinic visit in 55 of the participants. We found that total LRRK2 protein concentration was similar in exosomes purified from either CSF or urine but the levels did not correlate. pS1292-LRRK2 levels were higher in urinary exosomes from male and female subjects with a LRRK2 mutation. Male LRRK2 mutation carriers without PD had intermediate pS1292-LRRK2 levels compared to male carriers with PD and controls. However, female LRRK2 mutation carriers without PD had the same pS1292-LRRK2 levels compared to female carriers with PD. pS1292-LRRK2 levels in CSF exosomes were near saturated in most subjects, ten-fold higher on average than pS1292-LRRK2 levels in urinary exosomes, irrespective of LRRK2 mutation status or PD diagnosis. These results provide insights into the effects of LRRK2 mutations in both the periphery and brain in a well-characterized clinical population and show that LRRK2 protein in brain exosomes may be much more active than in the periphery in most subjects.

Highlights

Genetic variation in the leucine-rich repeat kinase 2 (LRRK2) gene associates with Parkinson disease (PD) susceptibility [21, 34]
Exosome pS1292-LRRK2 levels correlate with cellular LRRK2 kinase activity Previously, we demonstrated that heterozygous G2019SLRRK2 mutations increased the ratio of pS1292-LRRK2 to total LRRK2 protein ~4-fold in urinary exosomes of G2019S carriers as compared to non-carriers [6]
These and other measurements from model systems have not revealed the proportion of LRRK2 protein phosphorylated at pS1292, as only relative ratios of signal have been presented in past studies [6, 8, 14, 23]

Summary

Introduction

Genetic variation in the leucine-rich repeat kinase 2 (LRRK2) gene associates with Parkinson disease (PD) susceptibility [21, 34]. Rare pathogenic missense mutations in exons encoding the GTPase domain (termed ROC) and linking COR (C-terminal of ROC) domains strongly predispose to late-onset PD [29]. The more common mutation in the kinase domain that may be present in 0.1% of Western populations, G2019S, has more variable and typically lower penetrance [32]. Studies analyzing Aβ, tau, and αsynuclein proteins in cerebral spinal fluid (CSF) from LRRK2 mutations carriers have identified nominal differences compared to idiopathic PD [1, 30]. Genome-wide association studies have identified common polymorphisms in LRRK2 that associate with idiopathic PD, implicating LRRK2 function in susceptibility to late-onset PD in individuals without pathogenic mutations [19]. Few studies have yet biochemically analyzed LRRK2 protein in clinical samples from individuals with LRRK2 mutations or in the general idiopathic PD population

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