Clinical and pathological characteristics of patients with Leucine‐rich repeat kinase‐2 mutations

Mutations in LRRK2 are the single most common known cause of Parkinson's disease (PD). Two new PD patients with LRRK2 mutation were identified from a cohort with extensive postmortem assessment. One of these patients harbors the R793M mutation and presented with the typical clinical and pathological features of PD. A novel L1165P mutation was identified in a second patient. This patient had the classical and pathological features of PD, but additionally developed severe neuropsychological symptoms and dementia associated with abundant neurofibrillary tangles in the hippocampal formation; features consistent with a secondary diagnosis of tangle‐predominant dementia. α‐Synuclein‐containing pathological inclusions in these patients also were highly phosphorylated at Ser‐129, similar to other patients with idiopathic PD. These two PD patients also were characterized by the presence of occasional cytoplasmic TDP‐43 inclusions in the temporal cortex, a finding that was not observed in three other patients with the G2019S mutation in LRRK2. These findings extend the clinical and pathological features that may be associated with LRRK2 mutations. © 2008 Movement Disorder Society     

Physiologically relevant factors influence tau phosphorylation by leucine‐rich repeat kinase 2

Hyperphosphorylation and aggregation of tau are observed in multiple neurodegenerative diseases termed tauopathies. Tau has also been implicated in the pathogenesis of Parkinson's disease (PD) and parkinsonisms. Some PD patients with mutations in the leucine‐rich repeat kinase 2 (LRRK2) gene exhibit tau pathology. Mutations in LRRK2 are a major risk factor for PD, but LRRK2 protein function remains unclear. The most common mutation, G2019S, is located in the kinase domain of LRRK2 and enhances kinase activity in vitro. This suggests that the kinase activity of LRRK2 may underlie its cellular toxicity. Recently, in vitro studies have suggested a direct interaction between tubulin‐bound tau and LRRK2 that results in tau phosphorylation at one identified site. Here we present data suggesting that microtubules (MTs) enhance LRRK2‐mediated tau phosphorylation at three different epitopes. We also explore the effect of divalent cations as catalytic cofactors for G2019S LRRK2‐mediated tau phosphorylation and show that manganese does not support kinase activity but inhibits the efficient ability of magnesium to catalyze LRRK2‐mediated phosphorylation of tau. These results suggest that cofactors such as MTs and cations in the cellular milieu have an important impact on LRRK2‐tau interactions and resultant tau phosphorylation. © 2015 Wiley Periodicals, Inc.     

Changes in matrix metalloprotease activity and progranulin levels may contribute to the pathophysiological function of mutant leucine‐rich repeat kinase 2

Increasing evidence suggests that Parkinson's disease (PD)‐linked Leucine‐rich repeat kinase 2 (LRRK2) has a role in peripheral and brain‐resident immune cells. Furthermore, dysregulation of the anti‐inflammatory, neurotrophic protein progranulin (PGRN) has been demonstrated in several chronic neurodegenerative diseases. Here we show that PGRN levels are significantly reduced in conditioned medium of LRRK2(R1441G) mutant mouse fibroblasts, leukocytes, and microglia, whereas levels of proinflammatory factors, like interleukin‐1β and keratinocyte‐derived chemokine, were significantly increased. Decreased PGRN levels were also detected in supernatants of cultured human fibroblasts isolated from presymptomatic LRRK2(G2019S) mutation carriers, while mitochondrial function was unaffected. Furthermore, medium levels of matrix metalloprotease (MMP) 2 increased, whereas MMP 9 decreased in LRRK2(R1441G) mutant microglia. Increased proteolytic cleavage of the MMP substrates ICAM‐5 and α‐synuclein in synaptoneurosomes from LRRK2(R1441G) mutant mouse brain indicates increased net synaptic MMP activity. PGRN levels were decreased in the cerebrospinal fluid of presymptomatic LRRK2 mutant mice, whereas PGRN levels were increased in aged symptomatic mutant mice. Notably, PGRN levels were also increased in the cerebrospinal fluid of PD patients carrying LRRK2 mutations, but not in idiopathic PD patients and in healthy control donors. Our data suggest that proinflammatory activity of peripheral and brain‐resident immune cells may particularly contribute to the early stages of Parkinson's disease caused by LRRK2 mutations. GLIA 2014;62:1075–1092     

Identification of blood serum micro‐RNAs associated with idiopathic and LRRK2 Parkinson's disease

Blood‐cell‐free circulating micro‐RNAs (miRNAs) have been proposed as potential accessible biomarkers for neurodegenerative diseases such as Parkinson's disease (PD). Here we analyzed the serum levels of 377 miRNAs in a discovery set of 10 idiopathic Parkinson's disease (IPD) patients, 10 PD patients carriers of the LRRK2 G2019S mutation (LRRK2 PD), and 10 controls by using real‐time quantitative PCR‐based TaqMan MicroRNA arrays. We detected candidate differentially expressed miRNAs, which were further tested in a first validation set consisting of 20 IPD, 20 LRRK2 PD, and 20 control samples. We found four statistically significant miRNAs that were downregulated in either LRRK2 or IPD (miR‐29a, miR‐29c, miR‐19a, and miR‐19b). Subsequently, we validated these findings in a third set of samples consisting of 65 IPD and 65 controls and confirmed the association of downregulated levels of miR‐29c, miR‐29a, and miR‐19b in IPD. Differentially expressed miRNAs are predicted to target genes belonging to pathways related to ECM–receptor interaction, focal adhesion, MAPK, Wnt, mTOR, adipocytokine, and neuron projection. Results from our exploratory study indicate that downregulated levels of specific circulating serum miRNAs are associated with PD and suggest their potential use as noninvasive biomarkers for PD. Future studies should further confirm the association of these miRNAs with PD. © 2014 Wiley Periodicals, Inc.     

Leucine‐rich repeat kinase 2 (LRRK2): A key player in the pathogenesis of Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, with a prevalence of more than 1% after the age of 65 years. Mutations in the gene encoding leucine‐rich repeat kinase‐2 (LRRK2) have recently been linked to autosomal dominant, late‐onset PD that is clinically indistinguishable from typical, idiopathic disease. LRRK2 is a multidomain protein containing several protein interaction motifs as well as dual enzymatic domains of GTPase and protein kinase activities. Disease‐associated mutations are found throughout the multidomain structure of the protein. LRRK2, however, is unique among the PD‐causing genes, because a missense mutation, G2019S, is a frequent determinant of not only familial but also sporadic PD. Thus, LRRK2 has emerged as a promising therapeutic target for combating PD. In this Mini‐Review, we look at the current state of knowledge regarding the domain structure, amino acid substitutions, and potential functional roles of LRRK2. © 2008 Wiley‐Liss, Inc.     

Review: Induced pluripotent stem cell models of frontotemporal dementia

The increasing prevalence of dementia in the ageing population combined with the lack of treatments and the burden on national health care systems globally make dementia a public health priority. Despite the plethora of important research findings published over the past two decades, the mechanisms underlying dementia are still poorly understood and the progress in pharmacological interventions is limited. Recent advances in cellular reprogramming and genome engineering technologies offer an unprecedented new paradigm in disease modeling. Induced pluripotent stem cells (iPSCs) have enabled the study of patient‐derived neurons in vitro, a significant progress in the field of dementia research. The first studies using iPSCs to model dementia have recently emerged, holding promise for elucidating disease pathogenic mechanisms and accelerating drug discovery. In this review, we summarize the major findings of iPSC‐based studies in frontotemporal dementia (FTD) and FTD overlapping with amyotrophic lateral sclerosis (FTD/ALS). We also discuss some of the main challenges in the use of iPSCs to model complex, late‐onset neurodegenerative diseases such as dementias.     

LRRK2干扰对MPP+诱导PD细胞模型线粒体功能的影响

目的 探讨富亮氨酸重复激酶2(LRRK2)干扰对1-甲基-4-苯基吡啶离子(MPP+)诱导的帕金森病(PD)细胞模型线粒体功能及CaMKK-β/AMPK通路的影响.方法 采用MPP+诱导传代培养的SH-SY5Y细胞构建PD细胞模型.将造模的SH-SY5Y细胞随机分PD模型组、空载转染组(空载转染PD模型细胞)和siRN...     

Evidence that the LRRK2 ROC domain Parkinson's disease‐associated mutants A1442P and R1441C exhibit increased intracellular degradation

Mutations in the leucine‐rich repeat kinase 2 (lrrk2) gene are the leading genetic cause of Parkinson's disease (PD). In characterizing the novel ROC domain mutant A1442P, we compared its steady‐state protein levels, propensity to aggregate, and toxicity with the pathogenic R1441C mutant and wild‐type (WT) LRRK2. Mutant (R1441C and A1442P) and WT LRRK2 fused to green fluorescent protein (GFP) and FLAG were transiently expressed in HEK293 cells using plasmid constructs. Western analysis and fluorescence microscopy consistently demonstrated lower mutant LRRK2 protein levels compared with WT. A time‐course expression study using flow cytometry showed that WT LRRK2 expression increased initially but then plateaued by 72 hr. Conversely, R1441C and A1442P mutant expression attained 85% and 74% of WT levels at 24 hr but fell to 68% and 55% of WT levels by 72 hr, respectively. We found that proteasome inhibition markedly increased mutant LRRK2 to levels approaching those of WT. Taken together, our findings reveal increased intracellular degradation for both mutants. Furthermore, the impact of mutant and WT LRRK2 expression on HEK293 cell viability was assessed under normative and oxidative (hydrogen peroxide) conditions and found not to differ. Expression of WT and mutant LRRK2 protein gave rise to intracellular aggregates of similar appearance and cellular localization. In summary, we provide evidence that the novel A1442P mutant and the previously investigated R1441C pathogenic mutant exhibit increased intracellular degradation, a property reportedly demonstrated for the pathogenic LRRK2 kinase domain mutant I2020T. © 2013 Wiley Periodicals, Inc.     

Molecular biology changes associated with LRRK2 mutations in Parkinson's disease

Parkinson's disease (PD) is characterized by progressive dopaminergic neuronal loss in the substantia nigra. The recent discovery of leucine-rich-repeat kinase 2 gene (LRRK2) mutations in PD is significant because these mutations are the most common cause of autosomal dominant PD. Furthermore, a common recurrent mutation (G2019S) is associated with a significant proportion of nonfamilial PD, and a polymorphic variant (G2385R) has been found to increase the risk in the Asian race. The large LRRK2 protein of 280 kD contains three protein-protein interaction domains and two enzymatic domains, the Ras-related GTPase and the kinase. Mutations in these domains have been described in PD patients. Preliminary evidence suggests that some types of LRRK2 mutations increase the kinase activity, and this is associated with significantly higher apoptotic cell death in dopaminergic cell lines and primary neurons; abolishing the kinase function ameliorates this cellular toxicity. It also appears that its GTPase domain can be activated independently, whereas the kinase activity strictly requires the GTPase activation. Mutations in the LRRK2 have displayed notable pleomorphic pathologies that might indicate an upstream role of LRRK2 in cellular signaling pathways. The identification of physiological substrates (likely to be involved in signaling and apoptotic pathways) of LRRK2 remains an important step in our understanding of the role of LRRK2 in the disease process. Further in vitro and in vivo studies will unravel the role of LRRK2 in cell signaling and its impact on proliferation, differentiation, and survival of neurons.     

The genetic background of Parkinson's disease: current progress and future prospects

Almost two decades of genetic research in Parkinson's disease (PD) have remarkably increased our knowledge regarding the genetic basis of PD with numerous genes and genetic loci having been found to cause familial PD or affect the risk for PD. Approximately 5–10% of PD patients have monogenic forms of the disease, exhibiting a classical Mendelian type of inheritance, however, the majority PD cases are sporadic, probably caused by a combination of genetic and environmental risk factors. Nowadays, six genes, alpha synuclein, LRRK2, VPS35, Parkin, PINK1 and DJ‐1, have definitely been associated with an autosomal dominant or recessive PD mode of inheritance. The advent of genome‐wide association studies (GWAS) and the implementation of new technologies, like next generation sequencing (NGS) and exome sequencing has undoubtedly greatly aided the identification on novel risk variants for sporadic PD. In this review, we will summarize the current progress and future prospects in the field of PD genetics.     

LRRK2 Parkinson's disease: from animal models to cellular mechanisms

Mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) play a major role in the development of Parkinson's disease. The most frequently defined mutations of LRRK2 are located in the central catalytic region of the LRRK2 protein, suggesting that dysregulations of its enzymatic activities contribute to PD pathogenesis. Herein, we review recent progress in research concerning how LRRK2 mutations affect cellular pathways and lead to neuronal degeneration. We also summarize recent evidence revealing the endogenous function of LRRK2 protein within cells. These concepts can be used to further understand disease pathophysiology and serve as a platform to develop therapeutic strategies for the treatment of Parkinson's disease.     

LRRK2 R1628P variant is a risk factor of Parkinson's disease among Han‐Chinese from mainland China

Mutations in LRRK2, the gene that encodes leucine‐rich repeat kinase 2 (LRRK2), are associated with autosomal dominant and sporadic forms of Parkinson's disease (PD) and are the most common genetic causes of PD. Recently, a R1628P variant has been reported as a risk factor for PD in Taiwan and Singapore. To determine the association of this variant and PD in the Han‐Chinese population from mainland China, we analyzed its frequency in a cohort of 600 patients and 459 unrelated healthy controls. Forty (6.7%) patients were heterozygous and 3 (0.5%) homozygous for the R1628P variant, which was significantly more frequent than in the controls [2.4% heterozygous and 0.0% homozygous, Odds ratio = 3.14, 95%CI: 1.60–6.17, P < 0.01]. Considering the age at onset, this difference was found only in late‐onset PD (older than 50) [Odds ratio = 3.76, 95% CI: 1.90–7.45, P < 0.01]. Our data confirms that the LRRK2 R1628P variant is associated with an increased risk to develop late onset PD in the ethnic Han‐Chinese population. © 2009 Movement Disorder Society     

The unlikely partnership between LRRK2 and α‐synuclein in Parkinson's disease

Our understanding of the mechanisms underlying Parkinson's disease, the once archetypical nongenetic neurogenerative disorder, has dramatically increased with the identification of α‐synuclein and LRRK2 pathogenic mutations. While α‐synuclein protein composes the aggregates that can spread through much of the brain in disease, LRRK2 encodes a multidomain dual‐enzyme distinct from any other protein linked to neurodegeneration. In this review, we discuss emergent datasets from multiple model systems that suggest these unlikely partners do interact in important ways in disease, both within cells that express both LRRK2 and α‐synuclein as well as through more indirect pathways that might involve neuroinflammation. Although the link between LRRK2 and disease can be understood in part through LRRK2 kinase activity (phosphotransferase activity), α‐synuclein toxicity is multilayered and plausibly interacts with LRRK2 kinase activity in several ways. We discuss common protein interactors like 14‐3‐3s that may regulate α‐synuclein and LRRK2 in disease. Finally, we examine cellular pathways and outcomes common to both mutant α‐synuclein expression and LRRK2 activity and points of intersection. Understanding the interplay between these two unlikely partners in disease may provide new therapeutic avenues for PD.     

Genetic mouse models for understanding LRRK2 biology, pathology and pre-clinical application

Missense mutations in Leucine-Rich Repeat kinase 2 (LRRK2) are the most common cause of inherited Parkinson's disease (PD). Elucidation of LRRK2 biology and pathophysiology is central to the development of therapeutic intervention. Our group and others have developed a number of genetic mouse models of LRRK2 utilizing different genetic approaches. These models exhibit certain PD-related pathologies (e.g. impaired dopamine transmission and tauopathies) and abnormal motor functions, providing valuable insight into potential LRRK2-mediated pathogenesis of PD. However, not surprisingly they lack of substantial neuropathology and clinical syndromes of PD. Ongoing investigation of these models has begun to shed light on LRRK2 cellular functions and pathogenic pathways and is expected to assist the identification and validation of PD drug targets. This report summarizes the recent findings in our genetic LRRK2 models and discusses their utility in understanding much needed knowledge regarding early stage (pre-symptomatic) disease progression, drug target identification, and potential application in chemical screening focused on inhibitors of kinase activity of LRRK2.     

Kinases as targets for Parkinson's disease: from genetics to therapy

Intense research efforts are currently directed at elucidating the etiology of Parkinson's disease (PD). One approach that has begun to shed light on the PD pathogenic pathways is the identification of disease genes through genetic linkage or association studies. These studies have revealed that several kinases may be involved in PD, as some PD genes encode kinases themselves while other PD genes are found in the same cellular pathways as kinases. Two of these kinases stand out as potential drug targets for novel PD therapy, namely leucine rich repeat kinase 2 (LRRK2) and the alpha-synuclein (α-syn) phosphorylating polo-like kinase 2 (PLK2). Indeed, both α- syn and LRRK2 show genetic linkage as well as genetic association with PD, indicating their relevance to a large number of PD cases. Also, due to the dominant mode of α-syn and LRRK2 inheritance and based on current knowledge of LRRK2 and α-syn phosphorylation by PLK2, inhibition of LRRK2 and PLK2 may constitute a potential therapy for PD. Here we discuss the function of these kinases as well as progress in their validation as drug targets for the treatment of PD.     

LRRK2 expression in idiopathic and G2019S positive Parkinson's disease subjects: a morphological and quantitative study

S. Sharma, R. Bandopadhyay, T. Lashley, A. E. M. Renton, A. E. Kingsbury, R. Kumaran, C. Kallis, C. Vilariño‐Güell, S. S. O'Sullivan, A. J. Lees, T. Revesz, N. W. Wood and J. L. Holton (2011) Neuropathology and Applied Neurobiology 37, 777–790 LRRK2 expression in idiopathic and G2019S positive Parkinson's disease subjects: a morphological and quantitative study Aims: Mutations in the gene encoding leucine‐rich repeat kinase‐2 (LRRK2) have been established as a common genetic cause of Parkinson's disease (PD). The distribution of LRRK2 mRNA and protein in the human brain has previously been described, although it has not been reported in PD cases with the common LRRK2 G2019S mutation. Methods: To further elucidate the role of LRRK2 in PD, we determined the localization of LRRK2 mRNA and protein in post‐mortem brain tissue from control, idiopathic PD (IPD) and G2019S positive PD cases. Results: Widespread neuronal expression of LRRK2 mRNA and protein was recorded and no difference was observed in the morphological localization of LRRK2 mRNA or protein between control, IPD and G2019S positive PD cases. Using quantitative real‐time polymerase chain reaction, we demonstrated that there is no regional variation in LRRK2 mRNA in normal human brain, but we have identified differential expression of LRRK2 mRNA with significant reductions recorded in limbic and neocortical regions of IPD cases compared with controls. Semi‐quantitative analysis of LRRK2 immunohistochemical staining demonstrated regional variation in staining intensity, with weak LRRK2 immunoreactivity consistently recorded in the striatum and substantia nigra. No clear differences were identified in LRRK2 immunoreactivity between control, IPD and G2019S positive PD cases. LRRK2 protein was identified in a small proportion of Lewy bodies. Conclusions: Our data suggest that widespread dysregulation of LRRK2 mRNA expression may contribute to the pathogenesis of IPD.     

Structural Biology of LRRK2 and its Interaction with Microtubules

Mutations in leucine rich repeat kinase 2 (LRRK2) are a major cause of familial Parkinson's disease (PD) and a risk factor for its sporadic form. LRRK2 hyperactivity has also been reported in sporadic PD, making LRRK2 an appealing target for PD small-molecule therapeutics. At a cellular level, increasing evidence suggests that LRRK2 regulates membrane trafficking. Under some conditions LRRK2 also associates with microtubules, the cellular tracks used by dynein and kinesin motors to move membranes. At a structural level, however, relatively little was known about LRRK2. An important step toward bridging this gap took place last year with the publication of structures of LRRK2's cytosolic and microtubule-bound forms. Here, we review the main findings from these studies and discuss what we see as the major challenges going forward with a focus on areas that will require structural information. We also introduce the structural techniques—cryo-electron microscopy and cryo-electron tomography—that were instrumental to solving the structures of LRRK2. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society     

Precision Neurology for Parkinson’s Disease: Coupling Miro1-Based Diagnosis With Drug Discovery

Parkinson’s disease (PD) is a debilitating movement disorder, significantly afflicting the aging population. Efforts to develop an effective treatment have been challenged by the lack of understanding of the pathological mechanisms underlying neurodegeneration. We have shown that Miro1, an outer mitochondrial membrane protein, situates at the intersection of the complex genetic and functional network of PD. Removing Miro1 from the surface of damaged mitochondria is a prerequisite for mitochondrial clearance via mitophagy. Parkinson’s proteins PINK1, Parkin, and LRRK2 are the molecular helpers to remove Miro1 from dysfunctional mitochondria destined for mitophagy. We have found a delay in clearing Miro1 and initiating mitophagy in postmortem brains and induced pluripotent stem cell–derived neurons from PD patients harboring mutations in LRRK2, PINK1, or Parkin, or from sporadic PD patients with no known mutations. In addition, we have shown that reducing Miro1 by both genetic and pharmacological approaches can correct this Miro1 phenotype and rescue Parkinson’s-relevant phenotypes in human neurons and fly PD models. These results suggest that the Miro1 defect may be a common denominator for PD, and compounds that reduce Miro1 promise a new class of drugs to battle PD. We propose to couple this Miro1 phenotype with Miro1-based drug discovery in future therapeutic studies, which could significantly improve the success of clinical trials. © 2020 International Parkinson and Movement Disorder Society