ABSTRACT
The role of p53 in neurodegenerative diseases is essentially associated with neuronal death. Recently an alternative point of view is emerging, as altered p53 conformation and impaired protein function have been found in fibroblasts and blood cells derived from Alzheimer's disease patients. Here, using stable transfected SH-SY5Y cells overexpressing APP751wt (SY5Y-APP) we demonstrated that the expression of an unfolded p53 conformation compromised neuronal functionality. In particular, these cells showed (i) augmented expression of amyloid precursor protein (APP) and its metabolites, including the C-terminal fragments C99 and C83 and ß-amyloid peptide (ii) high levels of oxidative markers, such as 4-hydroxy-2-nonenal Michael-adducts and 3-nitro-tyrosine and (iii) altered p53 conformation, mainly due to nitration of its tyrosine residues. The consequences of high-unfolded p53 expression resulted in loss of p53 pro-apoptotic activity, and reduction of growth-associated protein 43 (GAP-43) mRNA and protein levels. The role of unfolded p53 in cell death resistance and lack of GAP-43 transcription was demonstrated by ZnCl(2) treatment. Zinc supplementation reverted p53 wild-type tertiary structure, increased cells sensitivity to acute cytotoxic injury and GAP-43 levels in SY5Y-APP clone.
Subject(s)
GAP-43 Protein/metabolism , Neurons/metabolism , Tumor Suppressor Protein p53/chemistry , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/metabolism , Cell Line, Tumor , Cell Survival/drug effects , Chlorides/pharmacology , GAP-43 Protein/genetics , Humans , Hydrogen Peroxide/toxicity , Oxidative Stress , Protein Structure, Tertiary , Protein Unfolding , RNA, Messenger/metabolism , Transcription, Genetic/drug effects , Tumor Suppressor Protein p53/metabolism , Tyrosine/analogs & derivatives , Tyrosine/chemistry , Zinc Compounds/pharmacologyABSTRACT
In this study, we demonstrated for the first time an increased CD44 gene expression in lymphocytes derived from Alzheimer's disease (AD) patients in comparison with healthy subjects. CD44 is a surface antigen expressed by cells of the immune and central nervous system as well as in a variety of other tissues. Functioning as adhesion molecule, CD44 is furthermore involved in driving immune response into infected tissues, including the CNS. We also found that lymphocytes of the same patients expressed significant levels of unfolded p53 isoform, confirming what we already demonstrated in fibroblasts and lymphocytes derived from other cohorts of AD patients. A correlation between p53 and CD44 expression has been well demonstrated in cancer cells, suggesting that CD44 could be a target gene of mutant p53, or either mutant p53 could lack its ability to negatively regulate CD44 expression. The contemporaneous increased expression of unfolded p53 and CD44 in AD lymphocytes may suggest that these two molecules cross-talk together participating in peripheral immune response during the development of the disease.
