The levels of ryanodine receptors (RyRs) are usually increased in the brains of human Alzheimer disease (AD) and AD animal models. To evaluate the underlying alteration of brain RyRs in prion disease, scrapie infected cell line SMB-S15 and its infected mice were tested. RyR2 specific Western blots revealed markedly decreased RyR2 levels both in the cells and in the brains of infected mice. Assays of the brain samples of other scrapie (agents 139A and ME7) infected mice collected at different time-points during incubation period showed time-dependent decreases of RyR2. Immunofluorescent assays (IFA) verified that the expression of RyR2 locates predominantly in cytoplasm of SMB cells and overlapped with the neurons in the brain slices of mice. Furthermore, significant down-regulation of RyR2 was also detected in the postmortem cortical brains of the patients of various types of human prion diseases, including sporadic Creutzfeldt-Jakob disease (sCJD), fatal familial insomnia (FFI) and G114V-genetic CJD. Our data here propose the evidences of remarkably decreased brain RyR2 at terminal stages of both human prion diseases and prion infected rodent models. It also highlights that the therapeutic strategy with antagonist of RyRs in AD may not be suitable for prion disease.
Keywords: brain; neuron loss; prion disease; ryanodine receptors.