LRRK2 and Parkinson disease: The linked activity of the catalytic domains is important, as three missense mutations in the GTPase domain (R1441C, R1441G, R1441H) and two in kinase domain (G2019S and I2020T) are pathogenic for PD, and all lead to an increase in LRRK2 kinase activity (Sheng et al., 2012; Steger et al., 2016).