Development of a high-throughput AlphaScreen assay measuring full-length LRRK2(G2019S) kinase activity using moesin protein substrate

Recent advances in targeting leucine-rich repeat kinase 2 as a potential strategy for the treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease. Several single gene mutations involved in PD have been identified such as leucine-rich repeat kinase 2 (LRRK2), the most common cause of sporadic and familial PD. Its mutations have attracted much attention to therapeutically targeting this kinase. To date, many compounds including small chemical molecules with diverse scaffolds and RNA agents have been developed with significant amelioration in preclinical PD models. Currently, five candidates, DNL201, DNL151, WXWH0226, NEU-723 and BIIB094, have advanced to clinical trials for PD treatment. In this review, we describe the structure, pathogenic mutations and the mechanism of LRRK2, and summarize the development of LRRK2 inhibitors in preclinical and clinical studies, trying to provide an insight into targeting LRRK2 for PD intervention in future.

High-Content C. elegans Screen Identifies Natural Compounds Impacting Mitochondria-Lipid Homeostasis and Promoting Healthspan

The aging process is concurrently shaped by genetic and extrinsic factors. In this work, we screened a small library of natural compounds, many of marine origin, to identify novel possible anti-aging interventions in Caenorhabditis elegans, a powerful model organism for aging studies. To this aim, we exploited a high-content microscopy platform to search for interventions able to induce phenotypes associated with mild mitochondrial stress, which is known to promote animal's health- and lifespan. Worms were initially exposed to three different concentrations of the drugs in liquid culture, in search of those affecting animal size and expression of mitochondrial stress response genes. This was followed by a validation step with nine compounds on solid media to refine compounds concentration, which led to the identification of four compounds (namely isobavachalcone, manzamine A, kahalalide F and lutein) consistently affecting development, fertility, size and lipid content of the nematodes. Treatment of Drosophila cells with the four hits confirmed their effects on mitochondria activity and lipid content. Out of these four, two were specifically chosen for analysis of age-related parameters, kahalalide F and lutein, which conferred increased resistance to heat and oxidative stress and extended animals' healthspan. We also found that, out of different mitochondrial stress response genes, only the C. elegans ortholog of the synaptic regulatory proteins neuroligins, nlg-1, was consistently induced by the two compounds and mediated lutein healthspan effects.

A homogeneous immunoassay for detection of the interaction between two tumor biomarkers of IGF1R-β and SOCS1

The current protein interaction method is time consuming and cumbersome or the instrument is expensive. A new method that is convenient, fast, and high throughput needs to be studied urgently. The purpose of this study was to establish a homogeneous immunoassay to detect the interaction between insulin-like growth factor-1 receptor-β (IGF1R-β) and suppressor of cytokine signaling 1 (SOCS1). The recombinant vectors IGF1R-β/pENTER and SOCS1/pENTER were constructed and transfected into 293T cells. Based on homogeneous immunoassay technology, we established a suitable method. The signal intensity in the 293T lysate that overexpressed IGF1R-β and SOCS1, respectively, was compared with the signal intensity in the simultaneous expression of IGF1R-β and SOCS1. The interaction between IGF1R-β and SOCS1 was verified in vitro. The detection system for the interaction between IGF1R-β and SOCS1 was established. Compared with other methods, homogeneous immunoassay has the advantages of being rapid and sensitive, having higher sensitivity, and easy to operate. The interaction between IGF1R-β and SOCS1 was tested to verify the feasibility of this method and prove its practicability and sensitivity. This new method can be used as a high-throughput platform for protein-protein interaction, with the advantages of trace detection, short detective time, and high detective sensitivity.

Screening for chemical modulators for LRRK2

After the discovery of leucine-rich repeat kinase 2 (LRRK2) as a risk factor for sporadic Parkinson's disease (PD) and mutations in LRRK2 as a cause of some forms of familial PD, there has been substantial interest in finding chemical modulators of LRRK2 function. Most of the pathogenic mutations in LRRK2 are within the enzymatic cores of the protein; therefore, many screens have focused on finding chemical modulators of this enzymatic activity. There are alternative screening approaches that could be taken to investigate compounds that modulate LRRK2 cellular functions. These screens are more often phenotypic screens. The preparation for a screen has to be rigorous and enable high-throughput accurate assessment of a compound's activity. The pipeline to beginning a drug screen and some LRRK2 inhibitor and phenotypic screens will be discussed.

High-throughput platforms for the screening of new therapeutic targets for neurodegenerative diseases

Despite the recent progress in the understanding of neurodegenerative disorders, a lack of solid fundamental knowledge on the etiology of many of the major neurodegenerative diseases has made it difficult to obtain effective therapies to treat these conditions. Scientists have been looking to carry out more-human-relevant studies, with strong statistical power, to overcome the limitations of preclinical animal models that have contributed to the failure of numerous therapeutics in clinical trials. Here, we identify currently existing platforms to mimic central nervous system tissues, healthy and diseased, mainly focusing on cell-based platforms and discussing their strengths and limitations in the context of the high-throughput screening of new therapeutic targets and drugs.

A High-Throughput Screen to Identify LRRK2 Kinase Inhibitors for the Treatment of Parkinson’s Disease Using RapidFire Mass Spectrometry

LRRK2 is a large multidomain protein containing two functional enzymatic domains: a GTPase domain and a protein kinase domain. Dominant coding mutations in the LRRK2 protein are associated with Parkinson’s disease (PD). Among such pathogenic mutations, Gly2019Ser mutation in the LRRK2 kinase domain is the most frequent cause of familial PD in Caucasians and is also found in some apparently sporadic PD cases. This mutation results in 2- to 3-fold elevated LRRK2 kinase activity compared with wild type, providing a clear clinical hypothesis for the application of kinase inhibitors in the treatment of this disease. To date, reported screening assays for LRRK2 have been based on detection of labeled adenosine triphosphate and adenosine diphosphate or on antibody-based detection of phosphorylation events. While these assays do offer a high-throughput method of monitoring LRRK2 kinase activity, they are prone to interference from autofluorescent compounds and nonspecific events. Here we describe a label-free assay for LRRK2 kinase activity using the RapidFire mass spectrometry system. This assay format was found to be highly robust and enabled a screen of 100,000 lead-like small molecules. The assay successfully identified a number of known LRRK2 chemotypes that met stringent physicochemical criteria.

LRRK2 Kinase Inhibitors as New Drugs for Parkinson’s Disease?

It is a rare event in drug discovery that mutations in a gene associated with the autosomal dominant forms of a disease, for which there is a large unmet medical need, affect a protein that belongs to a major class of drug targets. As a consequence, in recent years leucine‐rich repeat kinase 2 (LRRK2) has emerged as a major target candidate for therapies of Parkinson’s disease, and selective inhibitors of this kinase are being evaluated as possible new drugs for this detrimental disease. In this chapter, we review recent advances in the design of potent and selective LRRK2 inhibitors as well as the availability of models for their pharmacological evaluation. We also touch upon the challenges ahead – for further improvement of small molecule inhibitors and for in vivo pharmacological target validation.

Pharmacological inhibition of LRRK2 cellular phosphorylation sites provides insight into LRRK2 biology

Mutations in LRRK2 (leucine-rich repeat kinase 2) have been linked to inherited forms of PD (Parkinson's disease). Substantial pre-clinical research and drug discovery efforts have focused on LRRK2 with the hope that small-molecule inhibitors of the enzyme may be valuable for the treatment or prevention of the onset of PD. The pathway to develop therapeutic or neuroprotective agents based on LRRK2 function (i.e. kinase activity) has been facilitated by the development of both biochemical and cell-based assays for LRRK2. LRRK2 is phosphorylated on Ser910, Ser935, Ser955 and Ser973 in the N-terminal domain of the enzyme, and these sites of phosphorylation are likely to be regulated by upstream enzymes in an LRRK2 kinase-activity-dependent manner. Knowledge of these phosphorylation sites and their regulation can be adapted to high-throughput-screening-amenable platforms. The present review describes the utilization of LRRK2 phosphorylation as indicators of enzyme inhibition, as well as how such assays can be used to deconvolute the pathways in which LRRK2 plays a role.

Current understanding of LRRK2 in Parkinson's disease: biochemical and structural features and inhibitor design

Since leucine-rich repeat kinase 2 (LRRK2) was linked to Parkinson's disease in 2004, kinase activity of LRRK2 has been believed to play a critical role in the pathogenesis of Parkinson's disease. As a result, identification of LRRK2 inhibitors has been a focus for drug discovery. However, most LRRK2 mutations do not simply increase kinase activity. In this review we summarize the potential mechanisms that regulate the kinase activity of LRRK2. We outline some currently available kinase inhibitors, including the identification of a DFG-out (type-II) inhibitor. Finally, we discuss the relationship of LRRK2 with tau and α-synuclein. The fact that all three proteins are autophapgy-related provides a future strategy for the identification of LRRK2 physiological substrate(s).

A novel angiogenesis inhibitor impairs lovo cell survival via targeting against human VEGFR and its signaling pathway of phosphorylation

Colorectal cancer represents the fourth commonest malignancy, and constitutes a major cause of significant morbidity and mortality among other diseases. However, the chemical therapy is still under development. Angiogenesis plays an important role in colon cancer development. We developed HMQ18–22 (a novel analog of taspine) with the aim to target angiogenesis. We found that HMQ18–22 significantly reduced angiogenesis of chicken chorioallantoic membrane (CAM) and mouse colon tissue, and inhibited cell migration and tube formation as well. Then, we verified the interaction between HMQ18–22 and VEGFR2 by AlphaScreen P-VEGFR assay, screened the targets on angiogenesis by VEGF Phospho Antibody Array, validated the target by western blot and RNAi in lovo cells. We found HMQ18–22 could decrease phosphorylation of VEGFR2(Tyr¹²¹⁴), VEGFR1(Tyr¹³³³), Akt(Tyr³²⁶), protein kinase Cα (PKCα) (Tyr⁶⁵⁷) and phospholipase-Cγ-1 (PLCγ-1) (Tyr⁷⁷¹). Most importantly, HMQ18–22 inhibited proliferation of lovo cell and tumor growth in a human colon tumor xenografted model of athymic mice. Compared with normal lovo cells proliferation, the inhibition on proliferation of knockdown cells (VEGFR2, VEGFR1, Akt, PKCα and PLCγ-1) by HMQ18–22 decreased. These results suggested that HMQ18–22 is a novel angiogenesis inhibitor and can be a useful therapeutic candidate for colon cancer intervention.

Leucine-rich repeat kinase 2 (LRRK2) as a potential therapeutic target in Parkinson's disease

Parkinson's disease (PD) is caused by the progressive degeneration of dopaminergic neurons in the substantia nigra. Although the etiology for most PD remains elusive, the identification of specific genetic defects in familial cases of PD and the signaling pathways governed by these genes has provided tremendous insight into PD pathogenesis. Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are frequently found in familial and sporadic PD. Although current knowledge regarding the regulatory mechanisms of LRRK2 activation is limited, it is becoming increasingly evident that aberrant kinase activity of the pathologic mutants of LRRK2 is associated with neurodegeneration, suggesting that the kinase activity of LRRK2 is a potential therapeutic target. In addition, LRRK2 inhibitors might provide valuable tools to understand the pathophysiological and physiological roles of LRRK2 as well as the etiology of PD. We discuss here the potential and feasibility of targeting LRRK2 as a therapeutic strategy for PD.

Small molecule kinase inhibitors for LRRK2 and their application to Parkinson's disease models

Parkinson's disease (PD) is the second most common neurodegenerative disorder. Several single gene mutations have been linked to this disease. Mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) indicate LRRK2 as promising therapeutic target for the treatment of PD. LRRK2 mutations were observed in sporadic as well as familial PD patients and have been investigated intensively. LRRK2 is a large and complex protein, with multiple enzymatic and protein-interaction domains, each of which is effected by mutations. The most common mutation in PD patients is G2019S. Several LRRK2 inhibitors have been reported already, although the crystal structure of LRRK2 has not yet been determined. This review provides a summary of known LRRK2 inhibitors and will discuss recent in vitro and in vivo results of these inhibitors.

Development of homogeneous nonradioactive methyltransferase and demethylase assays targeting histone H3 lysine 4

Histone posttranslational modifications are among the epigenetic mechanisms that modulate chromatin structure and gene transcription. Histone methylation and demethylation are dynamic processes controlled respectively by histone methyltransferases (HMTs) and demethylases (HDMs). Several HMTs and HDMs have been implicated in cancer, inflammation, and diabetes, making them attractive targets for drug therapy. Hence, the discovery of small-molecule modulators for these two enzyme classes has drawn significant attention from the pharmaceutical industry. Herein, the authors describe the development and optimization of homogeneous LANCE Ultra and AlphaLISA antibody-based assays for measuring the catalytic activity of two epigenetic enzymes acting on lysine 4 of histone H3: SET7/9 methyltransferase and LSD1 demethylase. Both the SET7/9 and LSD1 assays were designed as signal-increase assays using biotinylated peptides derived from the N-terminus of histone H3. In addition, the SET7/9 assay was demonstrated using full-length histone H3 protein as substrate in the AlphaLISA format. Optimized assays in 384-well plates are robust (Z' factors ≥0.7) and sensitive, requiring only nanomolar concentrations of enzyme and substrate. All assays allowed profiling of known SET7/9 and LSD1 inhibitors. The results demonstrate that the optimized LANCE Ultra and AlphaLISA assay formats provide a relevant biochemical screening approach toward the identification of small-molecule inhibitors of HMTs and HDMs that could lead to novel epigenetic therapies.

Inhibitors of LRRK2 kinase attenuate neurodegeneration and Parkinson-like phenotypes in Caenorhabditis elegans and Drosophila Parkinson's disease models

Mutations in leucine-rich repeat kinase 2 (LRRK2) have been identified as a genetic cause of familial Parkinson's disease (PD) and have also been found in the more common sporadic form of PD, thus positioning LRRK2 as important in the pathogenesis of PD. Biochemical studies of the disease-causing mutants of LRRK2 implicates an enhancement of kinase activity as the basis of neuronal toxicity and thus possibly the pathogenesis of PD due to LRRK2 mutations. Previously, a chemical library screen identified inhibitors of LRRK2 kinase activity. Here, two of these inhibitors, GW5074 and sorafenib, are shown to protect against G2019S LRRK2-induced neurodegeneration in vivo in Caenorhabditis elegans and in Drosophila. These findings indicate that increased kinase activity of LRRK2 is neurotoxic and that inhibition of LRRK2 activity can have a disease-modifying effect. This suggests that inhibition of LRRK2 holds promise as a treatment for PD.

Identification of chemicals to inhibit the kinase activity of leucine-rich repeat kinase 2 (LRRK2), a Parkinson's disease-associated protein

Parkinson's disease (PD) is a late-onset neurodegenerative disease which occurs at more than 1% in populations aging 65-years and over. Recently, leucine-rich repeat kinase 2 (LRRK2) has been identified as a causative gene for autosomal dominantly inherited familial PD cases. LRRK2 G2019S which is a prevalent mutant found in familial PD patients with LRRK2 mutations, exhibited kinase activity stronger than that of the wild type, suggesting the LRRK2 kinase inhibitor as a potential PD therapeutics. To develop such therapeutics, we initially screened a small chemical library and selected compound 1, whose IC(50) is about 13.2 μM. To develop better inhibitors, we tested five of the compound 1 derivatives and found a slightly better inhibitor, compound 4, whose IC(50) is 4.1 μM. The cell-based assay showed that these two chemicals inhibited oxidative stress-induced neurotoxicity caused by over-expression of a PD-specific LRRK2 mutant, G2019S. In addition, the structural analysis of compound 4 suggested hydrogen bond interactions between compound 4 and Ala 1950 residue in the backbone of the ATP binding pocket of LRRK2 kinas domain. Therefore, compound 4 may be a promising lead compound to further develop a PD therapeutics based on LRRK2 kinase inhibition.