Capturing Differences in the Regulation of LRRK2 Dynamics and Conformational States by Small Molecule Kinase Inhibitors

Decoding Inhibitor Egression from Wild-Type and G2019S Mutant LRRK2 Kinase: Insights into Unbinding Mechanisms for Precision Drug Design in Parkinson's Disease

Leucine-rich repeat kinase 2 (LRRK2) remains a viable target for drug development since the discovery of the association of its mutations with Parkinson's disease (PD). G2019S (in the kinase domain) is the most common mutation for LRRK2-based PD. Though various types of inhibitors have been developed for the kinase domain to reduce the effect of the mutation, understanding the working of these inhibitors at the molecular level is still ongoing. This study focused on the exploration of the dissociation mechanism (pathways) of inhibitors from (WT and G2019S) LRRK2 kinase (using homology model CHK1 kinase), which is one of the crucial aspects in drug discovery. Here, two ATP-competitive type I inhibitors, PF-06447475 and MLi-2 (Comp1 and Comp2 ), and one non-ATP-competitive type II inhibitor, rebastinib (Comp3), were considered for this investigation. To study the unbinding process, random accelerated molecular dynamics simulations were performed. The binding free energies of the three inhibitors for different egression paths were determined using umbrella sampling. This work found four major egression pathways that were adopted by the inhibitors Comp1 (path1, path2, and path3), Comp2 (path1, path2 and path3), and Comp3 (path3 and path4). Also, the mechanism of unbinding for each path and key residues involved in unbinding were explored. Mutation was not observed to impact the preference of the particular egression pathways for both LRRK2-Comp1 and -Comp2 systems. However, the findings suggested that the size of the inhibitor molecules might have an effect on the preference of the egression pathways. The binding energy and residence time of the inhibitors followed a similar trend to experimental observations. The findings of this work might provide insight into designing more potent inhibitors for the G2019S LRRK2 kinase.

Practical Three-Component Regioselective Synthesis of Drug-Like 3-Aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnolines as Potential Non-Covalent Multi-Targeting Inhibitors To Combat Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are one of the prominent health challenges facing contemporary society, and many efforts have been made to overcome and (or) control it. In this research paper, we described a practical one-pot two-step three-component reaction between 3,4-dihydronaphthalen-1(2H)-one (1), aryl(or heteroaryl)glyoxal monohydrates (2a-h), and hydrazine monohydrate (NH2NH2•H2O) for the regioselective preparation of some 3-aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnoline derivatives (3a-h). After synthesis and characterization of the mentioned cinnolines (3a-h), the in silico multi-targeting inhibitory properties of these heterocyclic scaffolds have been investigated upon various Homo sapiens-type enzymes, including hMAO-A, hMAO-B, hAChE, hBChE, hBACE-1, hBACE-2, hNQO-1, hNQO-2, hnNOS, hiNOS, hPARP-1, hPARP-2, hLRRK-2(G2019S), hGSK-3β, hp38α MAPK, hJNK-3, hOGA, hNMDA receptor, hnSMase-2, hIDO-1, hCOMT, hLIMK-1, hLIMK-2, hRIPK-1, hUCH-L1, hPARK-7, and hDHODH, which have confirmed their functions and roles in the neurodegenerative diseases (NDs), based on molecular docking studies, and the obtained results were compared with a wide range of approved drugs and well-known (with IC50, EC50, etc.) compounds. In addition, in silico ADMET prediction analysis was performed to examine the prospective drug properties of the synthesized heterocyclic compounds (3a-h). The obtained results from the molecular docking studies and ADMET-related data demonstrated that these series of 3-aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnolines (3a-h), especially hit ones, can really be turned into the potent core of new drugs for the treatment of neurodegenerative diseases (NDs), and/or due to the having some reactionable locations, they are able to have further organic reactions (such as cross-coupling reactions), and expansion of these compounds (for example, with using other types of aryl(or heteroaryl)glyoxal monohydrates) makes a new avenue for designing novel and efficient drugs for this purpose.

RedOx regulation of LRRK2 kinase activity by active site cysteines

Mutations of the human leucine-rich repeat kinase 2 (LRRK2) have been associated with both, idiopathic and familial Parkinson's disease (PD). Most of these pathogenic mutations are located in the kinase domain (KD) or GTPase domain of LRRK2. In this study we describe a mechanism in which protein kinase activity can be modulated by reversible oxidation or reduction, involving a unique pair of adjacent cysteines, the "CC" motif. Among all human protein kinases, only LRRK2 contains this "CC" motif (C2024 and C2025) in the Activation Segment (AS) of the kinase domain. In an approach combining site-directed mutagenesis, biochemical analyses, cell-based assays, and Gaussian accelerated Molecular Dynamics (GaMD) simulations we could attribute a role for each of those cysteines. We employed reducing and oxidizing agents with potential clinical relevance to investigate effects on kinase activity and microtubule docking. We find that each cysteine gives a distinct contribution: the first cysteine, C2024, is essential for LRRK2 protein kinase activity, while the adjacent cysteine, C2025, contributes significantly to redox sensitivity. Implementing thiolates (R-S-) in GaMD simulations allowed us to analyse how each of the cysteines in the "CC" motif interacts with its surrounding residues depending on its oxidation state. From our studies we conclude that oxidizing agents can downregulate kinase activity of hyperactive LRRK2 PD mutations and may provide promising tools for therapeutic strategies.

Role of the leucine-rich repeat protein kinase 2 C-terminal tail in domain cross-talk

Leucine-rich repeat protein kinase 2 (LRRK2) is a multi-domain protein encompassing two of biology's most critical molecular switches, a kinase and a GTPase, and mutations in LRRK2 are key players in the pathogenesis of Parkinson's disease (PD). The availability of multiple structures (full-length and truncated) has opened doors to explore intra-domain cross-talk in LRRK2. A helix extending from the WD40 domain and stably docking onto the kinase domain is common in all available structures. This C-terminal (Ct) helix is a hub of phosphorylation and organelle-localization motifs and thus serves as a multi-functional protein : protein interaction module. To examine its intra-domain interactions, we have recombinantly expressed a stable Ct motif (residues 2480-2527) and used peptide arrays to identify specific binding sites. We have identified a potential interaction site between the Ct helix and a loop in the CORB domain (CORB loop) using a combination of Gaussian accelerated molecular dynamics simulations and peptide arrays. This Ct-Motif contains two auto-phosphorylation sites (T2483 and T2524), and T2524 is a 14-3-3 binding site. The Ct helix, CORB loop, and the CORB-kinase linker together form a part of a dynamic 'CAP' that regulates the N-lobe of the kinase domain. We hypothesize that in inactive, full-length LRRK2, the Ct-helix will also mediate interactions with the N-terminal armadillo, ankyrin, and LRR domains (NTDs) and that binding of Rab substrates, PD mutations, or kinase inhibitors will unleash the NTDs.

Pharmacology of LRRK2 with type I and II kinase inhibitors revealed by cryo-EM

LRRK2 is one of the most promising drug targets for Parkinson's disease. Though type I kinase inhibitors of LRRK2 are under clinical trials, alternative strategies like type II inhibitors are being actively pursued due to the potential undesired effects of type I inhibitors. Currently, a robust method for LRRK2-inhibitor structure determination to guide structure-based drug discovery is lacking, and inhibition mechanisms of available compounds are also unclear. Here we present near-atomic-resolution structures of LRRK2 with type I (LRRK2-IN-1 and GNE-7915) and type II (rebastinib, ponatinib, and GZD-824) inhibitors, uncovering the structural basis of LRRK2 inhibition and conformational plasticity of the kinase domain with molecular dynamics (MD) simulations. Type I and II inhibitors bind to LRRK2 in active-like and inactive conformations, so LRRK2-inhibitor complexes further reveal general structural features associated with LRRK2 activation. Our study provides atomic details of LRRK2-inhibitor interactions and a framework for understanding LRRK2 activation and for rational drug design.

Rab29-dependent asymmetrical activation of leucine-rich repeat kinase 2

Gain-of-function mutations in LRRK2, which encodes the leucine-rich repeat kinase 2 (LRRK2), are the most common genetic cause of late-onset Parkinson's disease. LRRK2 is recruited to membrane organelles and activated by Rab29, a Rab guanosine triphosphatase encoded in the PARK16 locus. We present cryo-electron microscopy structures of Rab29-LRRK2 complexes in three oligomeric states, providing key snapshots during LRRK2 recruitment and activation. Rab29 induces an unexpected tetrameric assembly of LRRK2, formed by two kinase-active central protomers and two kinase-inactive peripheral protomers. The central protomers resemble the active-like state trapped by the type I kinase inhibitor DNL201, a compound that underwent a phase 1 clinical trial. Our work reveals the structural mechanism of LRRK2 spatial regulation and provides insights into LRRK2 inhibitor design for Parkinson's disease treatment.

Inhibition of Parkinson's disease-related LRRK2 by type I and type II kinase inhibitors: Activity and structures

Mutations in leucine-rich repeat kinase 2 (LRRK2) are a common cause of familial Parkinson's disease (PD) and a risk factor for the sporadic form. Increased kinase activity was shown in patients with both familial and sporadic PD, making LRRK2 kinase inhibitors a major focus of drug development efforts. Although much progress has been made in understanding the structural biology of LRRK2, there are no available structures of LRRK2 inhibitor complexes. To this end, we solved cryo-electron microscopy structures of LRRK2, wild-type and PD-linked mutants, bound to the LRRK2-specific type I inhibitor MLi-2 and the broad-spectrum type II inhibitor GZD-824. Our structures revealed an active-like LRRK2 kinase in the type I inhibitor complex, and an inactive DYG-out in the type II inhibitor complex. Our structural analysis also showed how inhibitor-induced conformational changes in LRRK2 are affected by its autoinhibitory N-terminal repeats. The structures provide a template for the rational development of LRRK2 kinase inhibitors covering both canonical inhibitor binding modes.

Small molecule activates citrullination through targeting PAD2

Citrullination is a post-translational modification catalysed by peptidyl arginine deiminase (PAD) enzymes, and dysregulation of protein citrullination is involved in various pathological disorders. During the past decade, a panel of citrullination inhibitors has been developed, while small molecules activating citrullination have rarely been reported so far. In this study, we screened citrullination activator using an antibody against citrullinated histone H3 (cit-H3), and a natural compound demethoxycurcumin (DMC) significantly activated citrullination. The requirement of PAD2 for DMC-activated citrullination was confirmed by a loss of function assay. Notably, DMC directly engaged with PAD2, and showed binding selectivity among PAD family enzymes. Point mutation assay indicated that residue E352 is essential for DMC targeting PAD2. Consistently, DMC induced typical phenotypes of cells with dysregulation of PAD2 activity, including citrullination-associated cell apoptosis and DNA damage. Overall, our study not only presents a strategy for rationally screening citrullination activators, but also provides a chemical approach for activating protein citrullination. This article is part of the Theo Murphy meeting issue 'The virtues and vices of protein citrullination'.

Unveiling the Selectivity Mechanism of Type-I LRRK2 Inhibitors by Computational Methods: Insights from Binding Thermodynamics and Kinetics Simulation

Understanding the selectivity mechanisms of inhibitors toward highly similar proteins is very important in new drug discovery. Developing highly selective targeting of leucine-rich repeat kinase 2 (LRRK2) kinases for the treatment of Parkinson's disease (PD) is challenging because of the similarity of the kinase ATP binding pocket. During the development of LRRK2 inhibitors, off-target effects on other kinases, especially TTK and JAK2 kinases, have been observed. As a result, significant time and resources have been devoted to improving the selectivity for the LRRK2 target. DNL201 is an LRRK2 kinase inhibitor entering phase I clinical studies. The experiments have shown that DNL201 significantly inhibits LRRK2 kinase activity, with >167-fold selectivity over JAK2 and TTK kinases. However, the potential mechanisms of inhibitor preferential binding to LRRK2 kinase are still not well elucidated. In this work, to reveal the underlying general selectivity mechanism, we carried out several computational methods and comprehensive analyses from both the binding thermodynamics and kinetics on two representative LRRK2 inhibitors (DNL201 and GNE7915) to LRRK2. Our results suggest that the structural and kinetic differences between the proteins may play a key role in determining the activity of the selective small-molecule inhibitor. The selectivity mechanisms proposed in this work could be helpful for the rational design of novel selective LRRK2 kinase inhibitors against PD.

Synthesis of 1-Methylcyclopropyl Aryl Ethers from Phenols Using an Alkenylation-Cyclopropanation Sequence

1-Methylcyclopropyl aryl ethers (McPAEs) can be viewed as cyclized derivatives of their O-tert-butyl counterparts. Although these compounds can find use in medicinal chemistry, they are much less represented in the literature than their aryl cyclopropyl ether analogues. McPAEs are generally prepared via an SNAr reaction using 1-methylcyclopropanol. However, this method works exclusively with highly deactivated arenes. We report herein a two-step sequence to access McPAEs consisting of the 1-methylvinylation of phenols followed by cyclopropanation of the corresponding 1-methylvinyl aryl ethers. Isomeric mono- and dimethyl analogues were also prepared using this sequence.

Capturing the domain crosstalk in full length LRRK2 and LRRK2RCKW

LRRK2 is a multi-domain protein with three catalytically inert N-terminal domains (NtDs) and four C-terminal domains, including a kinase and a GTPase domain. LRRK2 mutations are linked to Parkinson's Disease. Recent structures of LRRK2RCKW and a full-length inactive LRRK2 (fl-LRRK2INACT) monomer revealed that the kinase domain drives LRRK2 activation. The LRR domain and also an ordered LRR- COR linker, wrap around the C-lobe of the kinase domain and sterically block the substrate binding surface in fl-LRRK2INACT. Here we focus on the crosstalk between domains. Our biochemical studies of GTPase and kinase activities of fl-LRRK2 and LRRK2RCKW reveal how mutations influence this crosstalk differently depending on the domain borders investigated. Furthermore, we demonstrate that removing the NtDs leads to altered intramolecular regulation. To further investigate the crosstalk, we used Hydrogen-Deuterium exchange Mass Spectrometry (HDX-MS) to characterize the conformation of LRRK2RCKW   and Gaussian Accelerated Molecular Dynamics (GaMD) to create dynamic portraits of fl-LRRK2 and LRRK2RCKW. These models allowed us to investigate the dynamic changes in wild type and mutant LRRK2s. Our data show that the a3ROC helix, the Switch II motif in the ROC domain, and the LRR-ROC linker play crucial roles in mediating local and global conformational changes. We demonstrate how these regions are affected by other domains in fl-LRRK2 and LRRK2RCKW and show how unleashing of the NtDs as well as PD mutations lead to changes in conformation and dynamics of the ROC and kinase domains which ultimately impact kinase and GTPase activities. These allosteric sites are potential therapeutic targets.