Article

Leucine-rich repeat kinase 2 (LRRK2) interacts with parkin, and mutant LRRK2 induces neuronal degeneration

Department of Psychiatry, Division of Neurobiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 01/2006; 102(51):18676-81. DOI: 10.1073/pnas.0508052102
Source: PubMed

ABSTRACT Parkinson's disease (PD) is a disorder of movement, cognition, and emotion, and it is characterized pathologically by neuronal degeneration with Lewy bodies, which are cytoplasmic inclusion bodies containing deposits of aggregated proteins. Most PD cases appear to be sporadic, but genetic forms of the disease, caused by mutations in alpha-synuclein, parkin, and other genes, have helped elucidate pathogenesis. Mutations in leucine-rich repeat kinase 2 (LRRK2) cause autosomal-dominant Parkinsonism with clinical features of PD and with pleomorphic pathology including deposits of aggregated protein. To study expression and interactions of LRRK2, we synthesized cDNAs and generated expression constructs coding for human WT and mutant LRRK2 proteins. Expression of full-length LRRK2 in cells in culture suggests that the protein is predominately cytoplasmic, as is endogenous protein by subcellular fractionation. Using coimmunoprecipitation, we find that LRRK2, expressed in cells in culture, interacts with parkin but not with alpha-synuclein, DJ-1, or tau. A small proportion of the cells overexpressing LRRK2 contain protein aggregates, and this proportion is greatly increased by coexpression of parkin. In addition, parkin increases ubiquitination of aggregated protein. Also, mutant LRRK2 causes neuronal degeneration in both SH-SY5Y cells and primary neurons. This cell model may be useful for studies of PD cellular pathogenesis and therapeutics. These findings suggest a gain-of-function mechanism in the pathogenesis of LRRK2-linked PD and suggest that LRRK2 may be involved in a pathogenic pathway with other PD-related proteins such as parkin, which may help illuminate both familial and sporadic PD.

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    • "It is possible that manipulating individual functional domains or single genes is not sufficient. For example, other studies indicate that interactions between two (e.g., LRRK2 and Parkin [34]; LRRK2 and alpha-synuclein [27]; LRRK2 and RAB7L1 (PARK16 locus) [35]) or more [1] [3] of the PD risk genes may be essential. Also, of course, PD is a late adult neurodegenerative disorder and, with the exception of the rodent models, the above discussed approaches can not recreate normal mammalian aging. "
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    ABSTRACT: It has been 10 years and more since associations between specific genes and Parkinson's disease (PD) were discovered, and it is now assumed that mutations in such PD (risk) genes, probably in interaction with other factors, are a major cause for PD [1–4]. These PD risk genes include alpha-synuclein (SNCA), LRRK2, Parkin, PINK1 and others. Yet after a decade of intense research it is still unclear how most mutations in these genes contribute to the PD pathology. This is likely due to a number of reasons, including that some of these genes seem to encode complex molecules with multiple functions; that mutations may lead to toxic gain-of-function and/or loss-of-function defects; that mutated molecules may need to interact with one another or other influences to be effective; or that some of these molecules or their products may need to migrate from other brain structures or even from the periphery to the dopamine neurons that they are supposed to kill. These factors all complicate the analysis of the mechanisms of action of PD risk genes. LRRK2 Perhaps most is known about the potential mechanisms of action of LRRK2 (e.g., [3,5–11]), which can serve as an example to highlight the many complexities encountered in the search of a function. With the first mutation discovered a decade ago in familial cases of PD [12–14], many mutations have since been described in the LRRK2 gene and several are considered pathogenic [3,5,6,9]. These are missense mutations. The most prevalent of these mutations, G2019S, was found in 1-2% of sporadic PD cases (in a Caucasian population) [15], but in up to 37% of familial PD cases in specific ethnic groups (Ashkenazi Jews, North African Arabs; c.f. [5]). The LRRK2 gene has 51 exons and encodes a large (286 kDa) protein with several predicted functional domains. These include a MAPKKK-like kinase domain and a ROC GTPase domain, as well as COR, leucine-rich repeat (LRR), ankyrin, armadillo and WD40 domains [5–7]. Wildtype LRRK2 binds/affects a variety of proteins, including Parkin, HSP90, moesin, tubulin, as well as presynaptic proteins involved in vesicle trafficking such as NSF, syntaxin 1, actin and others [5,7,16]. The mutations occur throughout LRRK2 [5,6]. Several mutations, including G2019S, are in the kinase domain [5,7,17]; G2019S, for example, abnormally increases kinase activity in in vitro [5,7] and in mouse models [17]. Models To study the function of the wildtype protein or one of these mutations, researchers have used a variety of approaches and expression systems, including targeted deletion (knock-out), or overexpression of wildtype or mutant LRRK2 in bacterial systems, cell lines (e.g., HEK-293, Cos-7, SH-SY5Y), primary neuron cultures or invertebrate models (C. elegans, Drosophila) [3,5,8,9,11], as well as in mouse lines [3,5,18]. Hypotheses as to what could be wrong in these mutants are typically derived from the predicted protein functions (e.g., kinase, GTPase), or from what is now known to be amiss in PD (e.g., loss of dopamine neurons, mitochondrial vulnerability, inflammation, etc.). These studies yielded a plethora of findings on potential LRRK2 (mal)functions, including effects on synaptic vesicle recycling, neurite morphology/outgrowth, autop-hagy, pro-inflammatory factors, susceptibility to oxidative stress, cell death via accumulation of alpha-synuclein, and others [5– 9,17,19]. Yet it is not clear whether or to what extent these mutations make dopamine neurons sick in mammals. For one, in PD their association remains correlative. In animal models, degeneration of dopamine neurons after deletion of LRRK2 (e.g., [20]) or over-expression of LRRK2 or LRRK2-G2019S [21] was reported in some (but not all) Drosophila and other invertebrate models. However, transgenic mice display surprisingly subtle or no effects on the dopamine transmission [3,5,11,18]. Indeed, a lack of significant degeneration of dopamine neurons seems to be a common feature of most mouse models of PD risk genes [3]. For LRRK2, mouse lines with a variety of constructs (knock-out, knock-in, BAC) have been developed [3,5,11,18]. These include lines that lack the LRRK2 protein (whole or part), or overexpress human wildtype LRRK2, the LRRK2-G2019S mutation or a LRRK2 kinase-dead mutation. In some cases, neither of these lines showed changes in markers of dopamine neuron health, dopamine levels or dopaminergic drug-evoked behaviors (while displaying pro-nounced histopathological changes in the kidney and lung where LRRK2 is also highly expressed) [22,23]. In other cases, such transgenics did display modest alterations in dopamine function/ release and/or related behaviors, but, with one exception [24], none showed dopamine neuron degeneration [25–31]. In contrast to these transgenic models, substantial degenera-tion of dopamine neurons could be achieved by virally driven overexpression of pathogenic LRRK2 (G2019S) in dopamine neurons of rodents [32,33]. However, while providing a valuable
    07/2013; 3(2):73-76. DOI:10.1016/j.baga.2013.04.002
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    • "Actually, several groups reported that LRKK2 is able to modulate several signal transduction pathways, such as the ERK1/2, TNFα/FasL and Wnt signaling pathways (Berwick & Harvey 2011), and the microRNA pathway, which regulates protein synthesis (Gehrke et al. 2010). The interaction between LRRK2 and parkin is also reported, but there is no evidence to associate LRRK2 with other genes, such as -synuclein, tau, and DJ-1 (Smith et al. 2005). Further investigations may reveal how LRRK2 participates in pathways of other PARK gene-related dopaminergic neuronal degeneration. "
    Etiology and Pathophysiology of Parkinson's Disease, 10/2011; , ISBN: 978-953-307-462-7
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    • "Association of parkin and LRRK2 with elements of the secretory and endocytic pathways (see text) raise the possibility that they affect synaptic structure and function by regulating synaptic protein trafficking. LRRK2, which has been reported to interact with parkin (Smith et al., 2005), is hypothesized to induce the formation or stabilization of excitatory synapses. Downstream effects of LRRK2 and parkin mutations would thus increase vulnerability to synaptic glutamate stress (Helton et al., 2008) and could influence neuronal activity. "
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    ABSTRACT: The past decade in Parkinson's disease (PD) research has been punctuated by numerous advances in understanding genetic factors that contribute to the disease. Common to most of the genetic models of Parkinsonian neurodegeneration are pathologic mechanisms of mitochondrial dysfunction, secretory vesicle dysfunction and oxidative stress that likely trigger common cell death mechanisms. Whereas presynaptic function is implicated in the function/dysfunction of α-synuclein, the first gene shown to contribute to PD, synaptic function has not comprised a major focus in most other genetic models. However, recent advances in understanding the impact of mutations in parkin and LRRK2 have also yielded insights into synaptic dysfunction as a possible early pathogenic mechanism. Autophagy is a common neuronal response in each of these genetic models of PD, participating in the clearance of protein aggregates and injured mitochondria. However, the potential consequences of autophagy upregulation on synaptic structure and function remain unknown. In this review, we discuss the evidence that supports a role for synaptic dysfunction in the neurodegenerative cascade in PD, and highlight unresolved questions concerning a potential role for autophagy in either pathological or compensatory synaptic remodeling. This article is part of a Special Issue entitled "Autophagy and protein degradation in neurological diseases."
    Neurobiology of Disease 10/2010; 43(1):60-7. DOI:10.1016/j.nbd.2010.10.011 · 5.20 Impact Factor
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