Explore the vast range of titles available.

Parkinson’s disease (PD) is a major and progressive neurodegenerative disorder, yet the biological mechanisms involved in its aetiology are poorly understood. Evidence links this disorder with mitochondrial dysfunction and/or impaired lysosomal degradation – key features of the autophagy of mitochondria, known as mitophagy. Here, we investigated the role of LRRK2, a protein kinase frequently mutated in PD, in this process in vivo. Using mitophagy and autophagy reporter mice, bearing either knockout of LRRK2 or expressing the pathogenic kinase-activating G2019S LRRK2 mutation, we found that basal mitophagy was specifically altered in clinically relevant cells and tissues. Our data show that basal mitophagy inversely correlates with LRRK2 kinase activity in vivo. In support of this, use of distinct LRRK2 kinase inhibitors in cells increased basal mitophagy, and a CNS penetrant LRRK2 kinase inhibitor, GSK3357679A, rescued the mitophagy defects observed in LRRK2 G2019S mice. This study provides the first in vivo evidence that pathogenic LRRK2 directly impairs basal mitophagy, a process with strong links to idiopathic Parkinson’s disease, and demonstrates that pharmacological inhibition of LRRK2 is a rational mitophagy-rescue approach and potential PD therapy.

Mutations in Park8, encoding for the multidomain Leucine-rich repeat kinase 2 (LRRK2) protein, comprise the predominant genetic cause of Parkinson's disease (PD). G2019S, the most common amino acid substitution activates the kinase two- to threefold. This has motivated the development of LRRK2 kinase inhibitors; however, poor consensus on physiological LRRK2 substrates has hampered clinical development of such therapeutics. We employ a combination of phosphoproteomics, genetics, and pharmacology to unambiguously identify a subset of Rab GTPases as key LRRK2 substrates. LRRK2 directly phosphorylates these both in vivo and in vitro on an evolutionary conserved residue in the switch II domain. Pathogenic LRRK2 variants mapping to different functional domains increase phosphorylation of Rabs and this strongly decreases their affinity to regulatory proteins including Rab GDP dissociation inhibitors (GDIs). Our findings uncover a key class of bona-fide LRRK2 substrates and a novel regulatory mechanism of Rabs that connects them to PD. Parkinson’s disease is a degenerative disorder of the nervous system that affects approximately 1% of the elderly population. Mutations in the gene that encodes an enzyme known as LRRK2 are the most common causes of the inherited form of the disease. Such mutations generally increase the activity of LRRK2 and so drug companies have developed drugs that inhibit LRRK2 to prevent or delay the progression of Parkinson’s disease. However, it was not known what role LRRK2 plays in cells, and why its over-activation is harmful. Steger et al. used a 'proteomics' approach to find other proteins that are regulated by LRRK2. The experiments tested a set of newly developed LRRK2 inhibitors in cells and brain tissue from mice. The mice had mutations in the gene encoding LRRK2 that are often found in human patients with Parkinson’s disease. The experiments show that LRRK2 targets some proteins belonging to the Rab GTPase family, which are involved in transporting molecules and other 'cargoes' around cells. Several Rab GTPases are less active in the mutant mice, which interferes with the ability of these proteins to correctly direct the movement of cargo around the cell. Steger et al.’s findings will help to advance the development of new therapies for Parkinson’s disease. The next challenges are to identify how altering the activity of Rab GTPases leads to degeneration of the nervous system and how LRRK2 inhibitors may slow down these processes.

Identifying effective therapeutic targets for Parkinson’s disease (PD) is challenging, with no current disease-modifying therapies available. To address this, The Michael J. Fox Foundation for Parkinson’s Research launched the Targets to Therapies (T2T) initiative, uniting experts to prioritize and validate promising targets. T2T aims to develop validation strategies, create comprehensive target data profiles, and build tools to support drug development, ultimately accelerating the discovery of new therapies for PD patients.

Receptor tyrosine kinases of the Eph family are upregulated in several different types of cancer. One family member in particular, the EphA2 receptor, has been linked to breast, prostate, lung and colon cancer, as well as melanoma. However, mechanisms by which EphA2 contributes to tumor progression are far from clear. In certain tumor cell lines, EphA2 receptor is underphosphorylated, raising the question of whether ligand-induced receptor phosphorylation and its kinase activity play a role in oncogenesis. To test directly the role of EphA2 receptor phosphorylation/kinase activity in tumor progression, we generated EphA2 receptor variants that were either lacking the cytoplasmic domain or carrying a point mutation that inhibits its kinase activity. Expression of these EphA2 mutants in breast cancer cells resulted in decreased tumor volume and increased tumor apoptosis in primary tumors. In addition, the numbers of lung metastases were significantly reduced in both experimental and spontaneous metastasis models. Reduced tumor volume and metastasis are not due to defects in tumor angiogenesis, as there is no significant difference in tumor vessel density between wild-type tumors and tumors expressing EphA2-signaling-defective mutants. In contrast, tumor cells expressing the EphA2 mutants are defective in RhoA GTPase activation and cell migration. Taken together, these results suggest that receptor phosphorylation and kinase activity of the EphA2 receptor, at least in part, contribute to tumor malignancy.

Abstract Parkinson’s disease (PD) is a major and progressive neurodegenerative disorder, yet the biological mechanisms involved in its aetiology are poorly understood. Evidence links this disorder with mitochondrial dysfunction and/or impaired lysosomal degradation – key features of the autophagy of mitochondria, known as mitophagy. Here we investigated the role of LRRK2, a protein kinase frequently mutated in PD, on this process in vivo. Using mitophagy and autophagy reporter mice, bearing either knockout of LRRK2 or expressing the pathogenic kinase-activating G2019S LRRK2 mutation, we found that basal mitophagy was specifically altered in clinically relevant cells and tissues. Our data show that basal mitophagy inversely correlates with LRRK2 kinase activity in vivo. In support of this, use of distinct LRRK2 kinase inhibitors in cells increased basal mitophagy, and a CNS penetrant LRRK2 kinase inhibitor, GSK3357679A, rescued the mitophagy defects observed in LRRK2 G2019S mice. This study provides the first in vivo evidence that pathogenic LRRK2 directly impairs basal mitophagy, a process with strong links to idiopathic Parkinson’s disease, and demonstrates that pharmacological inhibition of LRRK2 is a rational mitophagy-rescue approach and potential PD therapy. Competing Interest Statement The authors have declared no competing interest.

Much effort has been devoted to the development of selective inhibitors of the LRRK2 as a potential treatment for LRRK2 driven Parkinson's disease. In this study we first compare the properties of Type I (GSK3357679A and MLi-2) and Type II (GZD-824, Rebastinib and Ponatinib) kinase inhibitors that bind to the closed or open conformations of the LRRK2 kinase domain, respectively. We show that Type I and Type II inhibitors suppress phosphorylation of Rab10 and Rab12, key physiological substrates of LRRK2 and also promote mitophagy, a process suppressed by LRRK2. Type II inhibitors also display higher potency towards wild type LRRK2 compared to pathogenic mutants. Unexpectedly, we find that Type II inhibitors, in contrast to Type I compounds, fail to induce dephosphorylation of a set of well-studied LRRK2 biomarker phosphorylation sites at the N-terminal region of LRRK2, including Ser935. These findings emphasize that the biomarker phosphorylation sites on LRRK2 are likely reporting on the open vs closed conformation of LRRK2 kinase and that only inhibitors which stabilize the closed conformation induce dephosphorylation of these biomarker sites. Finally, we demonstrate that the LRRK2[A2016T] mutant which is resistant to MLi-2 Type 1 inhibitor, also induces resistance to GZD-824 and Rebastinib suggesting this mutation could be exploited to distinguish off target effects of Type II inhibitors. Our observations provide a framework of knowledge to aide with the development of more selective Type II LRRK2 inhibitors. Competing Interest Statement The authors have declared no competing interest. Footnotes * This version of the manuscript contains additional new data in Table 1, Figures 1, 5, and SFig 1B * https://www.ppu.mrc.ac.uk/

Background Despite recent developments in amyloid‐clearing therapies for Alzheimer's Disease (AD), there remains a need for more effective, safe treatments. Funded by the UK National Institute of Health and Care Research, our aim was to establish a robust, systematic, and unbiased drug prioritisation pipeline to identify repurposed drugs with the greatest potential for sustained clinical effect in clinical 'real‐world' AD (MMSE >17). These would then be considered for inclusion in a planned multi‐arm UK platform trial. Method We invited the wider AD community to propose compounds by summarising their rationale and evidence in a prespecified drug proposal form. Fourteen proposals were received, and the drug proposers were invited to the first panel meeting. They presented a pre‐clinical data focused rationale for each compound to an international expert panel comprised of AD clinicians, scientists, industry professionals, as well as both charity and patient/public representatives. In the context of a platform trial using prespecified primary outcome of cognition (ADAS‐Cog, with neuropsychiatric symptoms and everyday activities as secondary outcomes), the panel ranked their top three compounds based on efficacy, biological plausibility, and safety in AD. Ten compounds were taken forward with two subsequently excluded due to lack of data in humans. We compiled extended drug curriculum vitae (CV) for the eight shortlisted compounds. This incorporated practical clinically relevant information and was supplemented by systematic clinical literature review using Repurposing Living Systematic Review (ReLiSyR), a machine learning tool that searches databases and screens studies to identify relevant publications. Result Drug CVs were reviewed in a second panel meeting. Compound rankings were repeated with previous considerations and also practical clinical factors. The highest ranked compounds were atomoxetine (1st), metformin (2nd), isosorbide mononitrate and levetiracetam (joint 3rd). The pivotal determining factors across the top ranked compounds included scientific evidence of plausible mechanistic pathways in AD as well as evidence of substantial clinical data on safety and tolerability. Conclusion We present a practical approach to prioritising repurposed drugs to evaluate in the context of clinical AD. We would like to thank our patient and public contributors and the wider investigator team.

Despite recent developments in amyloid-clearing therapies for Alzheimer's Disease (AD), there remains a need for more effective, safe treatments. Funded by the UK National Institute of Health and Care Research, our aim was to establish a robust, systematic, and unbiased drug prioritisation pipeline to identify repurposed drugs with the greatest potential for sustained clinical effect in clinical 'real-world' AD (MMSE >17). These would then be considered for inclusion in a planned multi-arm UK platform trial. We invited the wider AD community to propose compounds by summarising their rationale and evidence in a prespecified drug proposal form. Fourteen proposals were received, and the drug proposers were invited to the first panel meeting. They presented a pre-clinical data focused rationale for each compound to an international expert panel comprised of AD clinicians, scientists, industry professionals, as well as both charity and patient/public representatives. In the context of a platform trial using prespecified primary outcome of cognition (ADAS-Cog, with neuropsychiatric symptoms and everyday activities as secondary outcomes), the panel ranked their top three compounds based on efficacy, biological plausibility, and safety in AD. Ten compounds were taken forward with two subsequently excluded due to lack of data in humans. We compiled extended drug curriculum vitae (CV) for the eight shortlisted compounds. This incorporated practical clinically relevant information and was supplemented by systematic clinical literature review using Repurposing Living Systematic Review (ReLiSyR), a machine learning tool that searches databases and screens studies to identify relevant publications. Drug CVs were reviewed in a second panel meeting. Compound rankings were repeated with previous considerations and also practical clinical factors. The highest ranked compounds were atomoxetine (1 ), metformin (2 ), isosorbide mononitrate and levetiracetam (joint 3 ). The pivotal determining factors across the top ranked compounds included scientific evidence of plausible mechanistic pathways in AD as well as evidence of substantial clinical data on safety and tolerability. We present a practical approach to prioritising repurposed drugs to evaluate in the context of clinical AD. We would like to thank our patient and public contributors and the wider investigator team.

Extracellular release and cellular uptake of pathogenic forms of the microtubule-associated protein tau contribute to the pathogenesis of several neurodegenerative diseases, including Alzheimer's disease. Defining the cellular mechanisms and pathways for tau entry to human neurons is essential to understanding tauopathy pathogenesis and the rational design of disease-modifying therapeutics. Whole genome CRISPR loss-of-function screens in human iPSC-derived excitatory neurons, the major neuronal cell type affected in these diseases, enabled the delineation of the different cellular pathways for uptake of extracellular monomeric and fibrillar tau. Monomeric and fibrillar tau are both taken up by human neurons by receptor-mediated endocytosis, but involve different routes of entry at the neuronal surface: the low-density lipoprotein LRP1 is the primary receptor for monomeric tau, but contributes less to fibrillar tau entry. Similarly, endocytosis of monomeric tau is dependent on the familial Parkinson's disease gene LRRK2, but not required for endocytosis of fibrillar tau. These findings implicate LRP1 and LRRK2 in the pathogenesis of tauopathies and Parkinson's disease and identify LRRK2 as a potential therapeutic target for altering progression of these diseases.Competing Interest StatementOpen Targets is a public-private partnership between non-profit research institutions and the pharmaceutical industry.Footnotes* The paper has been substantially expanded from the previous version, including: - Data confirming a set of hits from the primary screen (Figure 2) - Analysis of the effect of LRRK2 loss and gain of function mutations on neuronal uptake of different cargoes, including tau, alpha-synuclein and Abeta42 (Figure 6)