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.

Download full-text


Available from: Emilie Giaime,

Click to see the full-text of:

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

8 MB

See full-text
  • Source
    • "While some of the discrepancies could be because of technical differences between studies, such as the use of slightly different measures in different cell lines, it is also possible that some important biology could be discerned by investigating the mechanism(s) underlying how LRRK2 impacts macroautophagy. For example, the observation that LRRK2 knockout results in autophagy markers can be both increased or decreased in vivo depending on the age of the animals (Tong et al. 2012) shows that some autophagy markers are potentially regulated at stages downstream of LRRK2 itself. In other words, measurement of any given marker of macroautophagy could reflect both primary consequences of LRRK2 alterations and compensatory changes that follow. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Substantial progress has been made in the genetic basis of Parkinson's disease (PD). In particular, by identifying genes that segregate with inherited PD or show robust association with sporadic disease, and by showing the same genes are found on both lists, we have generated an outline of the cause of this condition. Here, we will discuss what those genes tell us about the underlying biology of PD. We specifically discuss the relationships between protein products of PD genes and show that common links include regulation of the autophagy-lysosome system, an important way by which cells recycle proteins and organelles. We also discuss whether all PD genes should be considered to be in the same pathway and propose that in some cases the relationships are closer while in other cases the interactions are more distant and might be considered separate. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 07/2015; DOI:10.1111/jnc.13266 · 4.28 Impact Factor
  • Source
    • "Although these studies suggest a role for LRRK2 in endolysosomal processes, what is lacking is strong evidence for a physiological role for LRRK2 in endolysosomal functions in vivo. The strongest evidence to date comes from analysis of renal epithelial cells in LRRK2 knockout mice, showing changes in the numbers of autophagosomes and autolysosomes, as well as accumulation of lipofuscin granules, which can be suggestive of lysosome dysfunction (Tong et al., 2012). Loss-of-function of Drosophila lrrk has been reported to cause defects in synaptic vesicle endocytosis at the larval neuromuscular junction (NMJ) that is associated with decreased uptake of the tracer FM1-43, which is internalized via endocytosis (Matta et al., 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Mutations in LRRK2 cause a dominantly inherited form of Parkinson's disease (PD), and are the most common known genetic determinant of PD. As inhibitor-based therapies targeting LRRK2 have emerged as a key therapeutic strategy in PD, understanding the consequences of inhibiting the normal cellular functions of LRRK2 is vital. Despite much interest, the physiologic functions of LRRK2 remain unclear. Several recent studies have linked the toxicity caused by overexpression of pathogenic mutant forms of LRRK2 to defects in the endolysosomal and autophagy pathways, raising the question of whether endogenous LRRK2 might play a role in these processes. Here we report the characterization of multiple novel nonsense alleles in the Drosophila LRRK2 homolog lrrk. Using these alleles, we show that lrrk loss-of-function causes striking defects in the endolysosomal and autophagy pathways, including accumulation of markedly enlarged lysosomes that are laden with undigested contents, consistent with a defect in lysosomal degradation. lrrk loss-of-function also results in accumulation of autophagosomes, as well as enlarged early endosomes laden with mono-ubiquitinated cargo proteins, suggesting an additional defect in lysosomal substrate delivery. Interestingly, the lysosomal abnormalities in these lrrk mutants can be suppressed by a constitutively active form of the small GTPase rab9, which promotes retromer-dependent recycling from late endosomes to the Golgi. Collectively, our data provides compelling evidence of a vital role for lrrk in lysosomal function and endolysosomal membrane transport in vivo, and suggests a link between lrrk and retromer-mediated endosomal recycling.
    Disease Models and Mechanisms 10/2014; 7(12). DOI:10.1242/dmm.017020 · 4.97 Impact Factor
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    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
Show more