Neurobiology of Aging 27 (2006) 1193–1201 Identification of a mutant-like conformation of p53 in fibroblasts from sporadic Alzheimer’s disease patients Daniela Uberti a,∗ , Cristina Lanni b , Teresina Carsana a , Simona Francisconi a , Cristina Missale a , Marco Racchi b , Stefano Govoni b , Maurizio Memo a a Department of Biomedical Sciences and Biotechnologies, University of Brescia, Viale Europa 11, 25124 Brescia, Italy b Department of Experimental and Applied Pharmacology, University of Pavia, Pavia, Italy Received 29 July 2004; received in revised form 29 April 2005; accepted 21 June 2005 Available online 13 September 2005 Abstract Here we show that fibroblasts from sporadic Alzheimer’s disease (AD) patients specifically express an anomalous and detectable confor- mational state of p53 that makes these cells distinct from fibroblasts of age-matched non-AD subjects. In particular, we found that, in contrast to non-AD fibroblasts, p53 in AD fibroblasts is expressed at higher levels in resting condition, and presents a significant impairment of its DNA binding and transcriptional activity. All together, these findings figured out the presence of a mutant-like p53 phenotype. However, gene sequencing of the entire p53 gene from either AD or non-AD did not unravel point mutations. Based on immunoprecipitation studies with conformation-specific p53 antibodies (PAb1620 and PAb240), which discriminated folded versus unfolded p53 tertiary structure, we found that a significant amount of p53 assumed an unfolded tertiary structure in fibroblasts from AD patients. This conformational mutant-like p53 form was virtually undetectable in fibroblasts from non-AD patients. These data, independently from their relevance in understanding the etiopathogenesis of AD, might be useful for supporting AD diagnosis. © 2005 Elsevier Inc. All rights reserved. Keywords: Protein tertiary structure; Human; Cell cycle; Reactive oxygen species; p21; EMSA 1. Introduction Alzheimer disease (AD) is a progressive neurodegener- ative disorder characterized by the presence in the brain of senile plaques and neurofibrillary tangles. To date, recog- nition and quantification of these neuropathological lesions remains the only valid criteria for an unequivocal diagnosis of AD. Neurologists, taking advantage to validated clinical criteria, can diagnose probable or possible AD, if the demen- tia is atypical in onset and progression, with an accuracy of nearly 90% and 50%, respectively [32]. For these reasons, the identification of biological markers of AD, in addition to increasing our understanding of the pathogenesis of the dis- ease, can be extremely useful to improve diagnostic accuracy and/or to monitor the efficacy of putative therapies. In this ∗ Corresponding author. Tel.: +39 030 3717509; fax: +39 030 3717409. E-mail address: uberti@med.unibs.it (D. Uberti). regard, peripheral cells may be of great importance, because of their easy accessibility. Among extra-neuronal tissue, cultured skin fibroblasts derived from AD patients (AD-fibroblasts) have gained par- ticular attention since they show a number of abnormalities in metabolic and biochemical processes, with some of them mirroring events that occur in the AD brain [9,15]. For exam- ple, in AD fibroblasts, changes have found to occur in signal transduction systems, including ion channels, cyclic AMP and phosphatidylinositide cascade, as well as in -amyloid (A) protein regulation [11,26,27]. Dysfunction in mitogen- activated protein kinases signalling cascade was also found in fibroblasts from both familiar and sporadic AD, but not in age-matched controls [37]. Abnormalities in ERK1/2 phos- phorylation were also specifically found in AD fibroblasts since they were not present in fibroblasts from Huntington’s disease patients with dementia [37]. Furthermore, reduced and abnormal glyceraldehyde-3-phosphate dehydrogenase 0197-4580/$ – see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.neurobiolaging.2005.06.013