Conformational conversion of the normal cellular isoform of prion protein, PrP
C, a glycoprotein anchored to the cell membrane by a glycosylphosphatidylinositol moiety, into the abnormally folded, amyloidogenic prion protein, PrP
Sc, plays a pivotal role in the pathogenesis of prion diseases. It has been suggested that PrP
C might be functionally disturbed by constitutive conversion to PrP
Sc due to either the resulting depletion of PrP
C or the dominant negative effects of PrP
Sc on PrP
C or both. Consistent with this, we and others showed that mice devoid of PrP
C (PrP-/-) spontaneously developed abnormal phenotypes very similar to the neurological abnormalities of prion diseases, supporting the concept that functional loss of PrP
C might at least be partly involved in the pathogenesis of the diseases. However, no neuronal cell death could be detected in PrP-/- mice, indicating that the functional loss of PrP
C alone might not be enough to induce neuronal cell death, one of major pathological hallmarks of prion diseases. Interestingly, it was recently shown that the first identified PrP-like protein, termed PrPLP/Doppel (Dpl), is neurotoxic in the absence of PrP
C, causing Purkinje cell degeneration in the cerebellum of mice. Although it is not understood if PrP
Sc could have a neurotoxic potential similar to PrPLP/Dpl, it is very interesting to speculate that accumulation of PrP
Sc and the functional disturbance of PrP
C, both of which are caused by constitutive conversion, might be required for the neurodegeneration in prion diseases. J. Med. Invest. 54: 211-223, August, 2007
View full abstract