PD-causing LRRK2 mutations represent a gain of function through the direct activation of kinase activity; mutations in the kinase domain lead to an elevation in kinase activity, while mutations in the Roc domain leave LRRK2 in a GTP-bound kinase-active form by disrupting GTP hydrolysis, thus prolonging kinase activity [10,11]. Here, LRRK2 is linked to Parkinson disease.