The Parkinson disease-linked LRRK2 protein mutation I2020T stabilizes an active state conformation leading to...

Area of Science:

• Biochemistry
• Molecular Biology
• Enzyme Kinetics

Background:

• The role of leucine-rich repeat kinase 2 (LRRK2) mutations in disease pathogenesis is under intense investigation.
• The specific impact of the LRRK2 I2020T mutation on kinase activity remains debated, with conflicting reports.
• Understanding LRRK2 kinase kinetics is crucial for developing targeted therapies.

Purpose of the Study:

• To elucidate the precise effect of the LRRK2 I2020T mutation on kinase activity using detailed kinetic analyses.
• To investigate the mechanism by which the I2020T mutation influences substrate phosphorylation and inhibitor binding.
• To explore the structural implications of the I2020T mutation on LRRK2 conformation and activity.

Main Methods:

• Steady-state and pre-steady-state kinetic studies using LRRKtide and LRRKtide(S) as substrates.
• Enzyme kinetics assays to determine kinetic parameters (e.g., kcat, Km, KATP).
• Molecular modeling and metadynamic simulations to analyze protein conformation and inhibitor interactions.

Main Results:

• The I2020T mutation differentially affects LRRK2 activity based on the rate-limiting step of phosphorylation.
• The mutant exhibits increased activity with LRRKtide(S) (rate-limiting phosphoryl transfer) but decreased activity with LRRKtide (rate-limiting product release).
• I2020T LRRK2 shows reduced stability, a low KATP, resistance to ATP-competitive inhibitors, and an altered binding mechanism for type II inhibitors.

Conclusions:

• The LRRK2 I2020T mutation's effect on kinase activity is substrate-dependent due to altered rate-limiting steps.
• The mutation impacts enzyme stability and inhibitor sensitivity, suggesting complex allosteric effects.
• Structural insights reveal the mutant stabilizes an active conformation and forms an unusual allosteric pocket influencing inhibitor binding.