To confirm these predictions, we performed an in vitro phosphorylation reaction of GST-MARCKS with candidate MAPKs, including JNK, which has been implicated in Alzheimer’s disease, and performed mass spectrometry to examine whether these kinases could actually phosphorylate MARCKS at Ser46 (Supplementary Figure 8b). Here, MARCKS is linked to early-onset autosomal dominant Alzheimer disease.