Loss of leucine-rich repeat kinase 2 causes age-dependent bi-phasic alterations of the autophagy pathway

Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital, Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA.
Molecular Neurodegeneration (Impact Factor: 6.56). 01/2012; 7(1):2. DOI: 10.1186/1750-1326-7-2
Source: PubMed


Dominantly inherited missense mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of Parkinson's disease, but its normal physiological function remains unclear. We previously reported that loss of LRRK2 causes impairment of protein degradation pathways as well as increases of apoptotic cell death and inflammatory responses in the kidney of aged mice.
Our analysis of LRRK2-/- kidneys at multiple ages, such as 1, 4, 7, and 20 months, revealed unique age-dependent development of a variety of molecular, cellular, and ultrastructural changes. Gross morphological abnormalities of the kidney, including altered size, weight, texture, and color, are evident in LRRK2-/- mice at 3-4 months of age, along with increased accumulation of autofluorescent granules in proximal renal tubules. The ratio of kidney/body weight in LRRK2-/- mice is increased at 1, 4, and 7 months of age (-10% at 1 month, and -20% at 4 and 7 months), whereas the ratio is drastically decreased at 20 months of age (-50%). While kidney filtration function evaluated by levels of blood urea nitrogen and serum creatinine is not significantly affected in LRRK2-/- mice at 12-14 months of age, expression of kidney injury molecule-1, a sensitive and specific biomarker for epithelial cell injury of proximal renal tubules, is up-regulated (-10-fold). Surprisingly, loss of LRRK2 causes age-dependent bi-phasic alterations of the autophagic activity in LRRK2-/- kidneys, which is unchanged at 1 month of age, enhanced at 7 months but reduced at 20 months, as evidenced by corresponding changes in the levels of LC3-I/II, a reliable autophagy marker, and p62, an autophagy substrate. Levels of α-synuclein and protein carbonyls, a general oxidative damage marker, are also decreased in LRRK2-/- kidneys at 7 months of age but increased at 20 months. Interestingly, the age-dependent bi-phasic alterations in autophagic activity in LRRK2-/- kidneys is accompanied by increased levels of lysosomal proteins and proteases at 1, 7, and 20 months of age as well as progressive accumulation of autolysosomes and lipofuscin granules at 4, 7-10, and 20 months of age.
LRRK2 is important for the dynamic regulation of autophagy function in vivo.

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    • "It has been recently reported that the most common LRRK2 point mutation, G2019S, initiates and enhances the formation of α-syn aggregates (Lin et al., 2009), possibly by impairing degradation pathways such as the autophagy-lysosomal pathway (Ferree et al., 2012; Tong et al., 2012). Overall, the potential interactions of LRRK2 and α-syn have not been clearly established. "
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    ABSTRACT: Mutations in the leucine-rich repeat kinase 2 gene are the most common cause of autosomal dominant Parkinson's disease (PD). To assess the cerebrospinal fluid (CSF) levels of α-synuclein oligomers in symptomatic and asymptomatic leucine-rich repeat kinase 2 mutation carriers, we used enzyme-linked immunosorbent assays (ELISA) to investigate total and oligomeric forms of α-synuclein in CSF samples. The CSF samples were collected from 33 Norwegian individuals with leucine-rich repeat kinase 2 mutations: 13 patients were clinically diagnosed with PD and 20 patients were healthy, asymptomatic leucine-rich repeat kinase 2 mutation carriers. We also included 35 patients with sporadic PD (sPD) and 42 age-matched healthy controls. Levels of CSF α-synuclein oligomers were significantly elevated in healthy asymptomatic individuals carrying leucine-rich repeat kinase 2 mutations (n = 20; P < 0.0079) and in sPD group (n = 35; P < 0.003) relative to healthy controls. Increased α-synuclein oligomers in asymptomatic leucine-rich repeat kinase 2 mutation carriers showed a sensitivity of 63.0% and a specificity of 74.0%, with an area under the curve of 0.66, and a sensitivity of 65.0% and a specificity of 83.0%, with an area under the curve of 0.74 for sPD cases. An inverse correlation between CSF levels of α- synuclein oligomers and disease severity and duration was observed. Our study suggests that quantification of α-synuclein oligomers in CSF has potential value as a tool for PD diagnosis and presymptomatic screening of high-risk individuals.
    Frontiers in Aging Neuroscience 09/2014; 6:248. DOI:10.3389/fnagi.2014.00248 · 4.00 Impact Factor
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    • "Different reasons have been proposed for the impact of deficient GCase activity on DA neurons, for example dominant inheritance of the mutation may be due to increased cell stress caused by excessive ER-associated degradation [68] of the unfolded mutant protein [82], while other groups found evidence that the accumulation of lysosomal lipids (glucocerebrosides ) is the main cause of neuronal dysfunction [83]. Mutations of the a-synuclein gene, SNCA, have also been shown to compromise lysosomal cargo clearance [84e87], and mutations that prolong the active state of the autophagy suppressing kinase, LRRK2, increase PD risk in an agedependent manner [88] [89]. Other mutations that affect cargo clearance through autophagiclysosomal routes include those found in Parkin and PINK1, which disrupt mitophagy (the autophagic clearance of expired mitochondria) [90] [91] and the predominantly neuronal P-type ATPase, ATP13A2, which maintains lysosomal pH, and whose entire loss of function causes Kufor-Rakeb syndrome (Table 1) [92e94]. "
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    ABSTRACT: For over a century, researchers have observed similar neurodegenerative hallmarks in brains of people affected by rare early-onset lysosomal storage diseases and late-onset neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Increasing evidence suggests these apparently disparate diseases share a common underlying feature, namely, a dysfunctional clearance of cellular cargo through the secretory-endosomal-autophagic-lysosomal-exocytic (SEALE) network. By providing examples of rare and common neurodegenerative diseases known to have pathologically altered cargo flux through the SEALE network, we explore the unifying hypothesis that impaired catabolism or exocytosis of SEALE cargo, places a burden of stress on neurons that initiates pathogenesis. We also describe how a growing understanding of genetic, epigenetic and age-related modifications of the SEALE network, has inspired a number of novel disease-modifying therapeutic approaches aimed at alleviating SEALE storage and providing therapeutic benefit to people affected by these devastating diseases across the age spectrum. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Best Practice & Research: Clinical Endocrinology & Metabolism 09/2014; 29(2). DOI:10.1016/j.beem.2014.08.009 · 4.60 Impact Factor
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    • "In addition , SNCA and protein carbonyls (a general marker of oxidative stress) levels also decrease whereas lysosomal proteins and proteases increase (Tong et al., 2012). However, neither autophagic nor lysosome-related structures accumulate in the brains of LRRK2 knockout mice, which suggests LRRK2 may have different roles in different tissues , or that in the absence of LRRK2, homologeus such as LRRK1 may compensate (Tong et al., 2010). "
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    ABSTRACT: Leucine-rich repeat kinase 2 (LRRK2) is a large, ubiquitous protein of unknown function. Mutations in the gene encoding LRRK2 have been linked to familial and sporadic Parkinson disease (PD) cases. The LRRK2 protein is a single polypeptide that displays GTPase and kinase activity. Kinase and GTPase domains are involved in different cellular signalling pathways. Despite several experimental studies associating LRRK2 protein with various intracellular membranes and vesicular structures such as endosomal/lysosomal compartments, the mitochondrial outer membrane, lipid rafts, microtubule-associated vesicles, the golgi complex, and the endoplasmic reticulum its broader physiologic function(s) remain unidentified. Additionally, the cellular distribution of LRRK2 may indicate its role in several different pathways, such as the ubiquitin-proteasome system, the autophagic-lysosomal pathway, intracellular trafficking, and mitochondrial dysfunction. This review discusses potential mechanisms through which LRRK2 may mediate neurodegeneration and cause PD.
    Experimental Neurology 06/2014; 261. DOI:10.1016/j.expneurol.2014.05.025 · 4.70 Impact Factor
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