Unlocking the secrets of LRRK2 function with selective kinase inhibitors

Discovery of potent azaindazole leucine-rich repeat kinase 2 (LRRK2) inhibitors possessing a key intramolecular hydrogen bond - Part 2

The discovery of disease-modifying therapies for Parkinson's Disease (PD) represents a critical need in neurodegenerative medicine. Genetic mutations in LRRK2 are risk factors for the development of PD, and some of these mutations have been linked to increased LRRK2 kinase activity and neuronal toxicity in cellular and animal models. As such, research towards brain-permeable kinase inhibitors of LRRK2 has received much attention. In the course of a program to identify structurally diverse inhibitors of LRRK2 kinase activity, a 5-azaindazole series was optimized for potency, metabolic stability and brain penetration. A key design element involved the incorporation of an intramolecular hydrogen bond to increase permeability and potency against LRRK2. This communication will outline the structure-activity relationships of this matched pair series including the challenge of obtaining a desirable balance between metabolic stability and brain penetration.

Chemical Biology of Leucine-Rich Repeat Kinase 2 (LRRK2) Inhibitors

There is an urgent need for the development of Parkinson's disease (PD) treatments that can slow disease progression. The leucine-rich repeat kinase 2 (LRRK2) protein has been genetically and functionally linked to PD, and modulation of LRRK2 enzymatic activity has been proposed as a novel therapeutic strategy. In this review, we describe the bioactivity of selected small molecules that have been used to inhibit LRRK2 kinase activity in vitro or in vivo. These compounds are important tools for understanding the cellular biology of LRRK2 and for evaluating the potential of LRRK2 inhibitors as disease-modifying PD therapies.

Parkinson's disease-implicated kinases in the brain; insights into disease pathogenesis

Substantial evidence implicates abnormal protein kinase function in various aspects of Parkinson’s disease (PD) etiology. Elevated phosphorylation of the PD-defining pathological protein, α-synuclein, correlates with its aggregation and toxic accumulation in neurons, whilst genetic missense mutations in the kinases PTEN-induced putative kinase 1 and leucine-rich repeat kinase 2, increase susceptibility to PD. Experimental evidence also links kinases of the phosphoinositide 3-kinase and mitogen-activated protein kinase signaling pathways, amongst others, to PD. Understanding how the levels or activities of these enzymes or their substrates change in brain tissue in relation to pathological states can provide insight into disease pathogenesis. Moreover, understanding when and where kinase dysfunction occurs is important as modulation of some of these signaling pathways can potentially lead to PD therapeutics. This review will summarize what is currently known in regard to the expression of these PD-implicated kinases in pathological human postmortem brain tissue.