Homeodomain interacting protein kinase 2: a target for Alzheimer's beta amyloid leading to misfolded p53 and inappropriate cell survival

Background: Homeodomain interacting protein kinase 2 (HIPK2) is an evolutionary conserved serine/threonine kinasewhose activity is fundamental in maintaining wild-type p53 function, thereby controlling the destiny of cells when exposedto DNA damaging agents. We recently reported an altered conformational state of p53 in tissues from patients withAlzheimer’s Disease (AD) that led to an impaired and dysfunctional response to stressors.Methodology/Principal Findings: Here we examined the molecular mechanisms underlying the impairment of p53 activityin two cellular models, HEK-293 cells overexpressing the amyloid precursor protein and fibroblasts from AD patients,starting from recent findings showing that p53 conformation may be regulated by HIPK2. We demonstrated that betaamyloid1–40 induces HIPK2 degradation and alters HIPK2 binding activity to DNA, in turn regulating the p53conformational state and vulnerability to a noxious stimulus. Expression of HIPK2 was analysed by western blotexperiments, whereas HIPK2 DNA binding was examined by chromatin immunoprecipitation analysis. In particular, weevaluated the recruitment of HIPK2 onto some target promoters, including hypoxia inducible factor-1a and metallothionein2A.Conclusions/Significance: These results support the existence of a novel amyloid-based pathogenetic mechanism in ADpotentially leading to the survival of injured dysfunctional cells.