LRRK2 stimulates MKK phosphorylation. A. Recombinant MKK3, 6 or 7 (Flag-tagged) was incubated ± LRRK2 (WT, G2019S or KD, GST-tagged), in the presence of kinase buffer and 32P-ATP. B. Coomassie gel showing the purity of the recombinant MKK3, 6 and 7. C & D. Quantification of MKK phosphorylation (C) and LRRK2 autophosphorylation (D) by densitometry. Error bars show the SEM from three independent experiments.