Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

LRRK2 is a 250 kDa multidomain protein, mutations in which cause familial Parkinson's disease. Previously, we have demonstrated that the R1441C mutation in the ROC domain decreases GTPase activity. Here we show that the R1441C alters the folding properties of the ROC domain, lowering its thermodynamic stability. Similar to small GTPases, binding of different guanosine nucleotides alters the stability of the ROC domain, suggesting that there is an alteration in conformation dependent on GDP or GTP occupying the active site. GTP/GDP bound state also alters the self-interaction of the ROC domain, accentuating the impact of the R1441C mutation on this property. These data suggest a mechanism whereby the R1441C mutation can reduce the GTPase activity of LRRK2, and highlights the possibility of targeting the stability of the ROC domain as a therapeutic avenue in LRRK2 disease.
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PMID:The R1441C mutation alters the folding properties of the ROC domain of LRRK2. 1978 41

Leucine-rich repeat kinase 2 (LRRK2) is a large, complex, multidomain protein containing kinase and GTPase enzymatic activities and multiple protein-protein interaction domains. Mutations linked to autosomal dominant forms of Parkinson's disease result in amino acid changes throughout the protein and alterations in both its enzymatic properties and interactions. The best characterized mutation to date, G2019S, leads to increased kinase activity, and mutations in the GTPase domain, such as R1441C and R1441G, have also been reported to influence kinase activity. Therefore, an examination of LRRK2's properties as a kinase is important for understanding the mechanisms underlying the disorder and has the potential to lead to therapeutics. These findings also suggest that there may be complex interplay between the functional domains of LRRK2. Here, we review LRRK2's biochemical functions based on structural and kinetic studies of the enzymatic domains, its potential substrates and the role of its interactions. Despite the field's embryonic understanding of the true relevance of these substrates and interactions, initial studies are providing clues with respect to its pathophysiological functions. Together, these findings should increase our understanding of mechanisms underlying Parkinson's disease and place LRRK2 as a unique molecular target for effective therapeutic development.
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PMID:LRRK2 in Parkinson's disease: biochemical functions. 1980 16

Dominant missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common known genetic cause of Parkinson disease. LRRK2 encodes a serine/threonine protein kinase, and pathogenic mutations may increase kinase activity. Intrinsic GTP binding in the GTPase domain may govern kinase activity through an internal signal transduction cascade. As with many protein kinases, LRRK2 self-interacts through mechanisms that may regulate enzymatic activity. We find that the disruption of either GTPase or kinase activity enhances the formation of high molecular weight oligomers and prevents the formation of LRRK2 dimer structures. In addition, brief application of the broad spectrum kinase inhibitor staurosporine ablates LRRK2 dimers and promotes LRRK2 high molecular weight oligomers. LRRK2 interactions with other proteins in cell lines are kinase-independent and include chaperones and cell cytoskeleton components, suggesting that LRRK2 self-assembly principally dictates complex size. To further explore the mechanics of kinase activation, we separate soluble LRRK2 protein that encodes the pathogenic G2019S mutation into high molecular weight oligomers, dimers, and monomers and find that kinase activity resides with dimeric LRRK2. Some PD-associated mutations that increase kinase activity in vitro significantly increase the proportion of dimer structures relative to total LRRK2 protein, providing additional insight into how pathogenic mutations may alter normal enzymatic regulation. Targeting and tracking LRRK2 dimerization may provide a clear way to observe LRRK2 kinase activity in living cells, and disruption of dimeric LRRK2 through kinase inhibition or other means may attenuate pathogenic increases in LRRK2 enzymatic output.
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PMID:Dependence of leucine-rich repeat kinase 2 (LRRK2) kinase activity on dimerization. 1982 9

In Parkinson's disease (PD), dopaminergic (DA) neurons in the substantia nigra (SN, A9) are particularly vulnerable, compared to adjacent DA neurons within the ventral tegmental area (VTA, A10). Here, we show that in rat and human, one RAB3 isoform, RAB3B, has higher expression levels in A10 compared to A9 neurons. RAB3 is a monomeric GTPase protein that is highly enriched in synaptic vesicles and is involved in synaptic vesicle trafficking and synaptic transmission, disturbances of which have been implicated in several neurodegenerative diseases, including PD. These findings prompted us to further investigate the biology and neuroprotective capacity of RAB3B both in vitro and in vivo. RAB3B overexpression in human dopaminergic BE (2)-M17 cells increased neurotransmitter content, [(3)H] dopamine uptake, and levels of presynaptic proteins. AAV-mediated RAB3B overexpression in A9 DA neurons of the rat SN increased striatal dopamine content, number and size of synaptic vesicles, and levels of the presynaptic proteins, confirming in vitro findings. Measurement of extracellular DOPAC, a dopamine metabolite, following l-DOPA injection supported a role for RAB3B in enhancing the dopamine storage capacity of synaptic terminals. RAB3B overexpression in BE (2)-M17 cells was protective against toxins that simulate aspects of PD in vitro, including an oxidative stressor 6-hydroxydopamine (6-OHDA) and a proteasome inhibitor MG-132. Furthermore, RAB3B overexpression in rat SN both protected A9 DA neurons and resulted in behavioral improvement in a 6-OHDA retrograde lesion model of PD. These results suggest that RAB3B improves dopamine handling and storage capacity at presynaptic terminals, and confers protection to vulnerable DA neurons.
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PMID:Functional enhancement and protection of dopaminergic terminals by RAB3B overexpression. 2000 72

Mutations in leucine-rich repeat kinase 2 (LRRK2) that increase its kinase activity associate with familial forms of Parkinson disease (PD). As phosphorylation determines the functional state of most protein kinases, we systematically mapped LRRK2 phosphorylation sites by mass spectrometry. Our analysis revealed a high degree of constitutive phosphorylation in a narrow serine-rich region preceding the LRR-domain. Allowing de novo autophosphorylation of purified LRRK2 in an in vitro autokinase assay prior to mass spectrometric analysis, we discovered multiple sites of autophosphorylation. Solely serine and threonine residues were found phosphorylated suggesting LRRK2 as a true serine threonine kinase. Autophosphorylation mainly targets the ROC GTPase domain and its clustering around the GTP binding pocket of ROC suggests cross-regulatory activity between kinase and Roc domain. In conclusion, the phosphoprotein LRRK2 functions as an autocatalytically active serine threonine kinase. Clustering of phosphosites within two discrete domains suggest that phosphorylation may regulate its biological functions in a yet unknown fashion.
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PMID:Phosphopeptide analysis reveals two discrete clusters of phosphorylation in the N-terminus and the Roc domain of the Parkinson-disease associated protein kinase LRRK2. 2010 44

Parkinson's disease (PD) is generally sporadic but a number of genetic diseases have parkinsonism as a clinical feature. Two dominant genes, alpha-synuclein (SNCA) and leucine-rich repeat kinase 2 (LRRK2), are important for understanding inherited and sporadic PD. SNCA is a major component of pathologic inclusions termed Lewy bodies found in PD. LRRK2 is found in a significant proportion of PD cases. These two proteins may be linked as most LRRK2 PD cases have SNCA-positive Lewy bodies. Mutations in both proteins are associated with toxic effects in model systems although mechanisms are unclear. LRRK2 is an intracellular signaling protein possessing both GTPase and kinase activities that may contribute to pathogenicity. A third protein, tau, is implicated as a risk factor for PD. We discuss the potential relationship between these genes and suggest a model for PD pathogenesis where LRRK2 is upstream of pathogenic effects through SNCA, tau, or both proteins.
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PMID:Mechanisms in dominant parkinsonism: The toxic triangle of LRRK2, alpha-synuclein, and tau. 2012 2

Recent studies have identified mutations in the leucine-rich repeat kinase2 gene (LRRK2) in the most common familial forms and some sporadic forms of Parkinson's disease (PD). LRRK2 is a large and complex protein that possesses kinase and GTPase activities. Some LRRK2 mutants enhance kinase activity and possibly contribute to PD through a toxic gain-of-function mechanism. Given the role of LRRK2 in the pathogenesis of PD, understanding the kinetic mechanism of its two enzymatic properties is critical for the discovery of inhibitors of LRRK2 kinase that would be therapeutically useful in treating PD. In this report, by using LRRK2 protein purified from murine brain, first we characterize kinetic mechanisms for the LRRK2-catalyzed phosphorylation of two peptide substrates: PLK-derived peptide (PLK-peptide) and LRRKtide. We found that LRRK2 follows a rapid equilibrium random mechanism for the phosphorylation of PLK-peptide with either ATP or PLK-peptide being the first substrate binding to the enzyme, as evidenced by initial velocity and inhibition mechanism studies with nucleotide analogues AMP and AMP-PNP, product ADP, and an analogue of the peptide substrate. The binding of the first substrate has no effect on the binding affinity of the second substrate. Identical mechanistic conclusions were drawn when LRRKtide was the phosphoryl acceptor. Next, we characterize the GTPase activity of LRRK2 with a k(cat) of 0.2 +/- 0.02 s(-1) and a K(m) of 210 +/- 29 microM. A SKIE of 0.97 +/- 0.04 was measured on k(cat) for the GTPase activity of LRRK2 in a D(2)O molar fraction of 0.86 and suggested that the product dissociation step is rate-limiting, of the steps governed by k(cat) in the LRRK2-catalyzed GTP hydrolysis. Surprisingly, binding of GTP, GDP, or GMP has no effect on kinase activity, although GMP and GDP inhibit the GTPase activity. Finally, we have identified compound LDN-73794 through screen of LRRK2 kinase inhibitors. Our study revealed that this compound is a competitive inhibitor of the binding of ATP and inhibits the kinase activity without affecting the GTPase activity.
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PMID:Kinetic mechanistic studies of wild-type leucine-rich repeat kinase 2: characterization of the kinase and GTPase activities. 2014 35

Septins are highly conserved filamentous proteins first characterized in budding yeast and subsequently identified in must eukaryotes. Septins can bind and hydrolyze GTP, which is intrinsically related to their formation of septin hexamers and functional protein interactions. The human septin family is composed of 14 loci, SEPT1-SEPT14, which encode dozens of different septin proteins. Their central GTPase and polybasic domain regions are highly conserved but they diverge in their N-terminus and/or C-terminus. The mechanism by which the different isoforms are generated is not yet well understood, but one can hypothesize that the use of different promoters and/or alternative splicing could give rise to these variants. Septins perform diverse cellular functions according to tissue expression and their interacting partners. Functions identified to date include cell division, chromosome segregation, protein scaffolding, cellular polarity, motility, membrane dynamics, vesicle trafficking, exocytosis, apoptosis, and DNA damage response. Their expression is tightly regulated to maintain proper filament assembly and normal cellular functions. Alterations of these proteins, by mutation or expression changes, have been associated with a variety of cancers and neurological diseases. The association of septins with cancer results from alterations of expression in solid tumors or translocations in leukemias [mixed lineage leukemia (MLL)]. Expression changes in septins have also been associated with neurological conditions such as Alzheimer's and Parkinson's disease, as well as retinopathies, hepatitis C, spermatogenesis and Listeria infection. Pathogenic mutations of SEPT9 were identified in the autosomal dominant neurological disorder hereditary neuralgic amyotrophy (HNA). Human septin research over the past decade has established their importance in cell biology and human disease. Further functional characterization of septins is crucial to our understanding of their possible diagnostic, prognostic, and therapeutic applications.
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PMID:Conquering the complex world of human septins: implications for health and disease. 2023 26

Mutations in LRRK2 are thus far the most frequent known cause of autosomal dominant and idiopathic Parkinson's disease (PD) with prevalent mutations being found within the GTPase (R1441C/G) and kinase (G2019S) domains. Previous in vitro studies have revealed that R1441C and G2019S mutations are associated with increased kinase activity. To better understand LRRK2-linked PD pathogenesis in vivo, we have generated transgenic C. elegans overexpressing human LRRK2 wild type, R1441C and G2019S in dopaminergic (DA) neurons. Overexpression of these LRRK2 proteins causes age-dependent DA neurodegeneration, behavioral deficits, and locomotor dysfunction that are accompanied by a reduction of dopamine levels in vivo. In comparison, R1441C and G2019S mutants cause more severe phenotypes than the wild type protein. Interestingly, treatment with exogenous dopamine rescues the LRRK2-induced behavioral and locomotor phenotypes. In contrast, expression of the GTP binding defective mutant, K1347A, or knockout of the C. elegans LRRK2 homolog, LRK-1, prevents the LRRK2-induced neurodegeneration and behavioral abnormalities. Hence, our transgenic LRRK2 C. elegans models recapitulate key features of PD including progressive neurodegeneration, impairment of dopamine-dependent behavior and locomotor function, and reduction in dopamine levels. Furthermore, our findings provide strong support for the critical role of GTPase/kinase activity in LRRK2-linked pathologies. These invertebrate models will be useful for studying pathogenesis of PD and for development of potential therapeutics for the disease.
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PMID:LRRK2-mediated neurodegeneration and dysfunction of dopaminergic neurons in a Caenorhabditis elegans model of Parkinson's disease. 2038 24

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with late-onset, autosomal-dominant, familial Parkinson's disease (PD) and also contribute to sporadic disease. The LRRK2 gene encodes a large protein with multiple domains, including functional Roc GTPase and protein kinase domains. Mutations in LRRK2 most likely cause disease through a toxic gain-of-function mechanism. The expression of human LRRK2 variants in cultured primary neurons induces toxicity that is dependent on intact GTP binding or kinase activities. However, the mechanism(s) underlying LRRK2-induced neuronal toxicity is poorly understood, and the contribution of GTPase and/or kinase activity to LRRK2 pathobiology is not well defined. To explore the pathobiology of LRRK2, we have developed a model of LRRK2 cytotoxicity in the baker's yeast Saccharomyces cerevisiae. Protein domain analysis in this model reveals that expression of GTPase domain-containing fragments of human LRRK2 are toxic. LRRK2 toxicity in yeast can be modulated by altering GTPase activity and is closely associated with defects in endocytic vesicular trafficking and autophagy. These truncated LRRK2 variants induce similar toxicity in both yeast and primary neuronal models and cause similar vesicular defects in yeast as full-length LRRK2 causes in primary neurons. The toxicity induced by truncated LRRK2 variants in yeast acts through a mechanism distinct from toxicity induced by human alpha-synuclein. A genome-wide genetic screen identified modifiers of LRRK2-induced toxicity in yeast including components of vesicular trafficking pathways, which can also modulate the trafficking defects caused by expression of truncated LRRK2 variants. Our results provide insight into the basic pathobiology of LRRK2 and suggest that the GTPase domain may contribute to the toxicity of LRRK2. These findings may guide future therapeutic strategies aimed at attenuating LRRK2-mediated neurodegeneration.
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PMID:GTPase activity plays a key role in the pathobiology of LRRK2. 2038 43


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