These results suggest that effective therapeutic intervention may require more subtle allosteric modulation of LRRK2 kinase activity, and highlight the critical importance of understanding the regulation and function of this enzyme. In addition, LRRK2 knockout rodent models display severe kidney phenotypes ( 17, 18). However, the value of this therapeutic approach has been challenged by the observation that treatment with LRRK2 kinase inhibitors results in significant lung toxicity in primates ( 16). These results have prompted the development of highly potent and specific kinase inhibitors with K i values in the low nanomolar range ( 15).
In addition, LRRK2 mutations within the Roc domain have been associated with decreased LRRK2 GTPase activity ( 13, 14). Various PD-associated mutations in LRRK2 have been shown to augment kinase activity ( 6, 7, 11, 12) and increase the phosphorylation of Rab proteins, recently identified as likely physiological substrates ( 12). These domains include the N-terminal ankyrin, armadillo, and namesake leucine-rich repeat (LRR) domains, along with a C-terminal WD40 domain. Besides the enzymatic core region, LRRK2 contains four predicted solenoid domains commonly involved in protein–protein interactions ( 10). Members of this family have a Ras of complex proteins (Roc) G-domain and an adjacent conserved C-terminal of Roc (COR) dimerization domain in common ( 8, 9). LRRK2 is a multidomain, 286-kDa protein exhibiting both GTPase and kinase activities ( 5– 7) that belongs to the recently identified Roco protein family of G proteins. Unfortunately, the biological function of LRRK2 and the mechanism by which it contributes to PD pathogenesis are not well understood. Mutations in the LRRK2 gene are found in 5–15% of families with autosomal dominant PD, making them the most common cause of Mendelian PD identified so far ( 4). Overall, our studies provide, to our knowledge, the first structural framework for understanding the role of the different domains of full-length LRRK2 in the pathogenesis of PD. Close contacts between the N-terminal ankyrin and C-terminal WD40 domains, and their proximity-together with the LRR domain-to the kinase domain suggest an intramolecular mechanism for LRRK2 kinase activity regulation. Our model reveals dimeric LRRK2 has a compact overall architecture with a tight, multidomain organization.
Here, we have modeled the 3D structure of dimeric, full-length LRRK2 by combining domain-based homology models with multiple experimental constraints provided by chemical cross-linking combined with mass spectrometry, negative-stain EM, and small-angle X-ray scattering. Despite the role of LRRK2 in the pathogenesis of PD, little is known about its overall architecture and how PD-linked mutations alter its function and enzymatic activities. Several of these mutations have been linked to increased kinase activity. Mutations associated with familial and sporadic Parkinson’s disease (PD) have been identified in both catalytic domains, as well as in several of its multiple putative regulatory domains. Leucine-rich repeat kinase 2 (LRRK2) is a large, multidomain protein containing two catalytic domains: a Ras of complex proteins (Roc) G-domain and a kinase domain.
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