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Leucine-rich repeat kinase 2 interacts with p21-activated kinase 6 to control neurite complexity in mammalian brain.

ABSTRACT: Leucine-rich repeat kinase 2 (LRRK2) is a causative gene for Parkinson's disease, but the physiological function and the mechanism(s) by which the cellular activity of LRRK2 is regulated are poorly understood. Here, we identified p21-activated kinase 6 (PAK6) as a novel interactor of the GTPase/ROC domain of LRRK2. p21-activated kinases are serine-threonine kinases that serve as targets for the small GTP binding proteins Cdc42 and Rac1 and have been implicated in different morphogenetic processes through remodeling of the actin cytoskeleton such as synapse formation and neuritogenesis. Using an in vivo neuromorphology assay, we show that PAK6 is a positive regulator of neurite outgrowth and that LRRK2 is required for this function. Analyses of post-mortem brain tissue from idiopathic and LRRK2 G2019S carriers reveal an increase in PAK6 activation state, whereas knock-out LRRK2 mice display reduced PAK6 activation and phosphorylation of PAK6 substrates. Taken together, these results support a critical role of LRRK2 GTPase domain in cytoskeletal dynamics in vivo through the novel interactor PAK6, and provide a valuable platform to unravel the mechanism underlying LRRK2-mediated pathophysiology. We propose p21-activated kinase 6 (PAK6) as a novel interactor of leucine-rich repeat kinase 2 (LRRK2), a kinase involved in Parkinson's disease (PD). In health, PAK6 regulates neurite complexity in the brain and LRRK2 is required for its function, (a) whereas PAK6 is aberrantly activated in LRRK2-linked PD brain (b) suggesting that LRRK2 toxicity is mediated by PAK6.

SUBMITTER: Civiero L

PROVIDER: S-EPMC4715492 | biostudies-literature |

REPOSITORIES: biostudies-literature

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

Project description: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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Leucine Rich Repeat Kinase 2 and Innate Immunity.

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Project description:Numerous leucine-rich repeat kinase 2 mutations identified throughout the protein are associated with Parkinson disease, however the activating G2019S kinase domain mutation is currently regarded as the most common cause of familial and sporadic forms of this disorder. Despite studies demonstrating the prominent role that its kinase activity plays in the pathobiology of leucine-rich repeat kinase 2, few substrates have been identified and only a subset of these have been linked to disease. Therefore, we utilized protein microarrays to screen over 9,000 human proteins in an unbiased radiometric assay for potential targets of the kinase. ProtoArrayM-bM-^DM-" Human Protein Microarrays v5.0 (Invitrogen, Carlsbad, CA, USA) were used following the manufactureM-bM-^@M-^Ys protocol (ProtoArray Kinase Substrate Identification Kit). Briefly, slides were equilibrated at 4C for 15 min before blocking in 1% BSA in PBS for 1 h at 4oC with gentle shaking. Recombinant G2019S or D1994A glutathione-S-transferase (GST)-LRRK2 (970-2527) (Invitrogen) was diluted to 50nM in 20mM Tris (pH 7.5), 10mM MgCl2, 1mM EGTA, 1mM Na3VO4, 5mM beta-glycerophosphate, 2mM DTT, 0.02% polysorbate 20, and 10 mCi /mL of [gamma- 33P]ATP (33 nM final concentration) in a total volume of 120uL. Slides were overlayed with buffer alone, or buffer containing G2019S or D1994A LRRK2, then covered with a coverslip and placed in a 50 mL conical tube for 1 h at 30oC. Afterwards, slides were washed with 0.5% SDS buffer and water followed by centrifugation. Dried slides were exposed to a PhosphorImager plate (Amersham Biosciences, Piscataway, NJ, USA), and scanned on a Storm 840 (Molecular Dynamics, Inc., Sunnyvale, CA, USA) at 50 microns.

2012-07-13 | E-GEOD-30496 | biostudies-arrayexpress

Role of tropomodulin's leucine rich repeat domain in the formation of neurite-like processes.

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Substrate phosphorylation of protein microarray by leucine-rich repeat kinase 2

2012-07-14 | GSE30496 | GEO

Parkinson's disease-associated mutations in leucine-rich repeat kinase 2 augment kinase activity.

Project description:Mutations in the leucine-rich repeat kinase 2 gene (LRRK2) cause late-onset Parkinson's disease (PD) with a clinical appearance indistinguishable from idiopathic PD. Initial studies suggest that LRRK2 mutations are the most common yet identified determinant of PD susceptibility, transmitted in an autosomal-dominant mode of inheritance. Herein, we characterize the LRRK2 gene and transcript in human brain and subclone the predominant ORF. Exogenously expressed LRRK2 protein migrates at approximately 280 kDa and is present largely in the cytoplasm but also associates with the mitochondrial outer membrane. Familial-linked mutations G2019S or R1441C do not have an obvious effect on protein steady-state levels, turnover, or localization. However, in vitro kinase assays using full-length recombinant LRRK2 reveal an increase in activity caused by familial-linked mutations in both autophosphorylation and the phosphorylation of a generic substrate. These results suggest a gain-of-function mechanism for LRRK2-linked disease with a central role for kinase activity in the development of PD.

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Project description:Mutation in leucine-rich repeat kinase-2 (LRRK2) is the most common cause of late-onset Parkinson's disease (PD). Although most cases of PD are sporadic, some are inherited, including those caused by LRRK2 mutations. Because these mutations may be associated with a toxic gain of function, controlling the expression of LRRK2 may decrease its cytotoxicity. Here we show that the carboxyl terminus of HSP70-interacting protein (CHIP) binds, ubiquitinates, and promotes the ubiquitin proteasomal degradation of LRRK2. Overexpression of CHIP protects against and knockdown of CHIP exacerbates toxicity mediated by mutant LRRK2. Moreover, HSP90 forms a complex with LRRK2, and inhibition of HSP90 chaperone activity by 17AAG leads to proteasomal degradation of LRRK2, resulting in increased cell viability. Thus, increasing CHIP E3 ligase activity and blocking HSP90 chaperone activity can prevent the deleterious effects of LRRK2. These findings point to potential treatment options for LRRK2-associated PD.

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Project description:Abcission, the natural shedding of leaves, flowers and fruits, is a fundamental component of plant development. Abscission is a highly regulated process that occurs at distinct zones of cells that undergo enlargement and subsequent separation. Although some components of abscission, including accumulation of the hormone ethylene and cell wall-degrading enzymes, have been described, the regulatory pathways remain largely unknown. In this paper we describe a critical component required for floral organ abscission in Arabidopsis thaliana, the receptor-like protein kinase HAESA. Histochemical analysis of transgenic plants harboring a HAESA promoter:: beta-glucuronidase reporter gene and in situ RNA hybridization experiments show HAESA expression in the abscission zones where the sepals, petals, and stamens attach to the receptacle, at the base of pedicels, and at the base of petioles where leaves attach to the stem. Immunodetection, immunoprecipitation, and protein kinase activity assays reveal HAESA is a plasma membrane serine/threonine protein kinase. The reduction of function of HAESA in transgenic plants harboring an antisense construct results in delayed abscission of floral organs, and the severity of the phenotype is directly correlated with the level of HAESA protein. These results demonstrate that HAESA functions in developmentally regulated floral organ abscission.

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