Our results shown that fibroblasts from AD patients had increased expression of the autophagy markers LC3II, LAMP2 and Cathepsin D, a significant increase in total GSK3, phosphorylated ERK1/2 (Thr202/Tyr204) and phosphorylated tau (Thr231, Ser396, and Ser404), but no difference in the phosphorylation of Akt (Ser473) or the α (Ser21) and β (Ser9) GSK3 isoforms, highlighting the relevant role of abnormal protein post-translational modifications in age-related neurodegenerative diseases, such as AD. Here, CTSD is linked to Alzheimer disease.