Mutant prion protein-mediated aggregation of normal prion protein in the endoplasmic reticulum: implications for prion propagation and neurotoxicity.
Familial prion disorders are believed to result from spontaneous conversion of mutant prion protein (PrPM) to the pathogenic isoform (PrPSc). While most familial cases are heterozygous and thus express the normal (PrPC) and mutant alleles of PrP, the role of PrPC in the pathogenic process is unclear. Plaques from affected cases reveal a heterogeneous picture; in some cases only PrPM is detected, whereas in others both PrPC and PrPM are transformed to PrPSc. To understand if the coaggregation of PrPC is governed by PrP mutations or is a consequence of the cellular compartment of PrPM aggregation, we coexpressed PrPM and PrPC in neuroblastoma cells, the latter tagged with green fluorescent protein (PrPC-GFP) for differentiation. Two PrPM forms (PrP231T, PrP217R/231T) that aggregate spontaneously in the endoplasmic reticulum (ER) were generated for this analysis. We report that PrPC-GFP aggregates when coexpressed with PrP231T or PrP217R/231T, regardless of sequence homology between the interacting forms. Furthermore, intracellular aggregates of PrP231T induce the accumulation of a C-terminal fragment of PrP, most likely derived from a potentially neurotoxic transmembrane form of PrP (CtmPrP) in the ER. These findings have implications for prion pathogenesis in familial prion disorders, especially in cases where transport of PrPM from the ER is blocked by the cellular quality control.
Gu
Yaping
Y
Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Verghese
Susamma
S
Mishra
Ravi Shankar
RS
Xu
Xeumin
X
Shi
Yongchang
Y
Singh
Neena
N
D003902:Detergents; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008164:Luminescent Proteins; D009154:Mutation / Q000502:physiology*; D010446:Peptide Fragments / Q000378:metabolism; D017096:Prion Diseases / Q000235:genetics; D011328:Prions / Q000737:chemistry / Q000502:physiology*; D012016:Reference Values; D012995:Solubility; D014407:Tumor Cells, Cultured
D003902:Detergents; D008164:Luminescent Proteins; D010446:Peptide Fragments; D011328:Prions; D049452:Green Fluorescent Proteins