G2385R and I2020T Mutations Increase LRRK2 GTPase Activity

Area of Science:

• Neuroscience
• Genetics
• Biochemistry

Background:

• Leucine-Rich Repeat Kinase 2 (LRRK2) mutations are key genetic factors in familial Parkinson's disease (PD).
• While LRRK2 possesses both GTPase and kinase functions altered by mutations, research has predominantly focused on kinase activity, particularly the G2019S mutation.
• The G2019S mutation is infrequent in Asian populations, where the G2385R mutation is a significant PD risk factor, yet studies on G2385R also primarily examine kinase activity.

Purpose of the Study:

• To investigate the GTPase activities of LRRK2 mutations, including G2385R and G2019S, R1441C, and I2020T, in comparison to wild-type (WT) LRRK2.
• To determine if LRRK2 mutations prevalent in Asian populations, such as G2385R, impact GTPase function.

Main Methods:

• Comparative analysis of GTPase activities across various LRRK2 mutants (G2019S, G2385R, R1441C, I2020T) and WT.
• Enzyme kinetics assays using commercial recombinant LRRK2 proteins to assess both GTPase and kinase activities.

Main Results:

• The LRRK2 mutants I2020T and G2385R exhibited enhanced GTPase activities compared to WT.
• Kinase assays indicated that I2020T displayed stronger kinase activity, while G2385R showed weaker activity than WT.
• This study provides the first report on the GTPase activities of LRRK2 I2020T and G2385R mutations.

Conclusions:

• Most pathogenic or risk-associated LRRK2 mutations appear to alter either kinase or GTPase enzymatic activity.
• The observed alterations in enzyme activity are likely the underlying cause of the physiological consequences leading to Parkinson's disease.
• Investigating both GTPase and kinase functions is crucial for understanding the full spectrum of LRRK2 mutation effects in PD pathogenesis.