In-cell cryo-electron tomography reveals differential effects of type I and type II kinase inhibitors on LRRK2 filament formation and microtubule association

A recent study has unveiled the differential impacts of type I and type II kinase inhibitors on LRRK2 filament formation and microtubule association. LRRK2 mutations are a major driver of both familial and sporadic Parkinson's disease (PD). These mutations generally boost kinase activity, resulting in heightened phosphorylation of Rab GTPases, which messes with vesicular transport, cytoskeletal dynamics, and autophagy.

Typically, normal LRRK2 resides in the cellular cytosol. Yet, artificially introduced LRRK2 can develop microtubule-associated filaments that hamper molecular transport along microtubules in a lab setting. However, the actual relevance of this microtubule binding in the body remains unclear. Several ongoing inhibitors, both in development and testing phases, have been found to either encourage or hinder LRRK2 filament formation.

In this study, researchers scrutinized the localization and resultant molecular organization of hyperactive LRRK2-I2020T, a prevalent PD mutation, in HEK 293FT cells that had been exposed to type I (MLi-2) or type II (GZD-824) kinase inhibitors. Cells treated with a type I inhibitor exhibited extensive LRRK2-I2020T sticking to microtubules and microtubule bundling.

By stabilizing these LRRK2-I2020T filaments through type I inhibitor treatment, researchers managed to construct a full-length closed-kinase model of LRRK2-I2020T within its cellular context. In contrast, cells treated with a type II inhibitor showed minimal microtubule sticking by LRRK2-I2020T compared to those treated with the type I inhibitor.

This research provides a structural framework for comprehending how type I and type II kinase inhibitors differently influence LRRK2 filament formation. The study reveals that type I inhibitor treatment fosters a unique filament architecture, while such assemblies are not observed with type II inhibitors.