Cluster 6 containing proteins that were sharply decreased in the condition with most pathology, AD APOE4 BA41/42, similarly showed decreases in pathways involved in synaptic function including CREB signalling and GABA receptor signalling, along with decreases in pathways implicated in mitochondrial function including oxidative phosphorylation (Fig. 5). Here, CREB1 is linked to Alzheimer disease.