Amyloid plaques and neurofibrillary tangles are the major pathological hallmarks of Alzheimer's disease. Neurofibrillary tangles are composed of filaments and paired helical filaments containing polymerized hyperphosphorylated tau protein. Derlin proteins are a family of proteins that are conserved in all eukaryotes, in which they function in endoplasmic reticulum-associated degradation. Protein disulfide isomerase (PDI) is a member of the thioredoxin superfamily and is believed to accelerate the folding of disulfide-bonded proteins in the luminal space of the endoplasmic reticulum. In this study, we found that derlin-1 and PDI were colocalized in neurofibrillary tangles in the brain of patients with Alzheimer's disease. Derlin-1 and PDI may work as partners to avoid the accumulation of unfolded proteins in Alzheimer's disease. Furthermore, we found that derlin-1 was immunopositive for neurofibrillary tangles and upregulated in Alzheimer's disease and that derlin-1 may play an important role in endoplasmic reticulum-associated degradation during the pathogenesis of Alzheimer's disease. We hypothesize that derlin-1 was upregulated to avoid the aggregation of unfolded proteins. Despite the upregulation of derlin-1, the functions of chaperone proteins and Alzheimer tau protein were lost and these proteins were also accumulated. Finally, they were involved in neurofibrillary tangles. These results suggest that derlin-1 may be associated with endoplasmic reticulum stress in neuronal cells in Alzheimer's disease.
aDepartment of Pharmacoepidemiology, Graduate School of Medicine and Public Health
bDepartment of Neurology, Facility of Medicine, Kyoto University, Koyoto
cDepartment of Neurology and Neuroscience, Osaka City University Medical School, Osaka
dDepartment of Neurology and Psychiatry, Osaka City Kosaiin Hospital, Osaka, Japan
Correspondence to Koji Kawakami, MD, PhD, Department of Pharmacoepidemiology, Graduate School of Medicine and Public Health, Kyoto University, Yoshida Konoecho, Sakyoku, Kyoto 606-8501, Japan Tel: +81 75 753 4459; fax: +81 75 753 4469; e-mail: firstname.lastname@example.org
Received March 24, 2012
accepted April 23, 2012