Overexpression of PrP^Cby Adenovirus-Mediated Gene Targeting Reduces Ischemic Injury in a Stroke Rat Model

Abstract

Prion diseases are induced by pathologically misfolded prion protein (PrPSc ), which recruit normal sialoglycoprotein PrP C by a templatedirected process. In this study, we investigated the expression of PrP C in a rat model of cerebral ischemia to more fully understand its physiological role. Immunohistochemical analysis demonstrated that PrP C -immunoreactive cells increased significantly in the penumbra of ischemic rat brain compared with the untreated brain. Western blot analysis showed that PrP C protein expression increased in ischemic brain tissue in a time-dependent manner. In addition, PrP C protein expression was seen to colocalize with neuron, glial, and vascular endothelial cells in the penumbric region of the ischemic brain. Overexpression of PrP C by injection of rAd (replication-defective recombinant adenoviral)-PGK (phosphoglycerate kinase)-PrP C -Flag into ischemic rat brain improved neurological behavior and reduced the volume of cerebral infarction, which is supportive of a role for PrP C in the neuroprotective adaptive cellular response to ischemic lesions. Concomitant upregulation of PrP C and activated extracellular signal-regulated kinase (ERK1/2) under hypoxia-reoxygenation in primary cortical cultures was shown to be dependent on ERK1/2 phosphorylation. During hypoxia-reoxygenation, mouse neuroblastoma cell line N18 cells transfected with luciferase rat PrP C promoter reporter constructs, containing the heat shock element (HSE), expressed higher luciferase activities (3-to 10-fold) than those cells transfected with constructs not containing HSE. We propose that HSTF-1 (hypoxia-activated transcription factor), phosphorylated by ERK1/2, may in turn interact with HSE in the promoter of PrP C resulting in gene expression of the prion gene. In summary, we conclude that upregulation of PrP C expression after cerebral ischemia and hypoxia exerts a neuroprotective effect on injured neural tissue. This study suggests that PrP C has physiological relevance to cerebral ischemic injury and could be useful as a therapeutic target for the treatment of cerebral ischemia.

Absence of the Cellular Prion Protein Exacerbates and Prolongs Neuroinflammation in Experimental Autoimmune Encephalomyelitis

“…15 In contrast, adenovirus-mediated PrP C overexpression reduced CNS damage in a rat model of cerebral ischemia. 16 While the mechanism(s) underlying these phenomena remain unclear, such in vivo findings have lent strong support to the idea that PrP C may have a neuroprotective function.…”

Disease-associated Mutations in the Prion Protein Impair Laminin-induced Process Outgrowth and Survival

“…In the last decade a diverse range of functions has been attributed to the native PrP C protein, such as neuroprotection against cellular and systemic insults, neuritogenesis, neuronal plasticity and excitability, and memory formation and consolidation (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). Noteworthy, PrP C mutations associated to CJD, fatal familial insomnia, and Gerstmann-Straussler-Scheinker disease decrease or abolish the anti-bax function in primary human neurons and breast cancer cell lines promoting programmed cell death (34).…”

Prion protein (PrP c ) positively regulates neural precursor proliferation during developmental and adult mammalian neurogenesis

“…Recent work has shown that PrP c induces polarization in synapse development as well as in neuritogenesis in embryonic hippocampal neuron cultures (5,6). PrP c is also up-regulated after focal cerebral ischemia (7), and PrP c overexpression reduces the extent of neuronal loss after ischemic insult, suggesting that PrP c might confer a neuroprotective effect in certain contexts (8). Recent studies have also shown that PrP c is expressed on the surface of long-term repopulating hematopoietic stem cells and that PrP c -null mice have limited hematopoietic stem cell self-renewal (9).…”