DLG4 and Alzheimer disease: However, the expression levels of synapse-related proteins, such as synaptophysin, PSD-95, p-CaMKII, and p-CREB, are significantly decreased in the cortex and hippocampus of AD patients and of an AD mouse model (Gylys et al., 2004; Almeida et al., 2005; Zeng et al., 2015).