PrP ^c Does Not Mediate Internalization of PrP ^Sc but Is Required at an Early Stage for De Novo Prion Infection of Rov Cells

Cell models of prion infection

“…A similar observation was reported for PrP Sc from brain homogenate in CHO cells [55]. Finally, Paquet et al demonstrated an efficient entry of abnormal PrP in permissive Rov cells by mechanisms that apparently did not rely on cellular heparan sulphates [98]. Collectively, these studies suggest that abnormal PrP can enter the cells by different routes.…”

“…A number of studies are consistent with the involvement of heparan sulphates in the biogenesis of prions. A variety of sulphated glycans, including pentosan polysulphate [13,28], dextran sulphate 500 [8,12,28], heparin [49], and various heparan mimicking molecules [1,126] are potent inhibitors of PrP Sc accumulation in several cell lines infected with murine prions and in Rov cells infected with a sheep scrapie agent [98], presumably by competitive inhibition of cellular heparan sulphates for the binding to PrP C [49]. More direct evidence for a role of cellular heparan sulphates in the formation of abnormal PrP was obtained by showing that treatment of infected N2a cells with heparinase III resulted in a marked reduction of PrP res [11].…”

“…Other studies used infected brain tissues homogenised in physiological buffers, arguing that PK-digested, highly aggregated forms have poor biological relevance. Despite varying experimental conditions which may hinder comparisons among them, all of these studies have shown that PrP Sc is internalised by a process that does not require the presence of PrP C at the cell surface [55,81,98]. The identification of putative cellular receptors for PrP Sc led to a different outcome.…”

“…Early pulse-chase experiments with infected N2a and HaB cells have revealed that conversion of PrP C to the protease-resistant state is a late post-translational event that takes place after PrP C has been delivered to the plasma membrane [15,25]. More recently, it was shown that transmission of infection requires the presence of cellular heparan sulphates and the presence of PrP C during exposure to the inoculum [58,98]. While this suggests that molecular complexes between PrP Sc , PrP C , and cellular heparan sulphates are required at the plasma membrane, it remains unclear whether conversion can proceed further at the cell surface or if the putative complexes are driven to intracellular compartments for initiation of conversion.…”

The role of the prion protein membrane anchor in prion infection

“…Lacking of an antibody that can specifically distinguish PrP-res from PrP-sen in live cells and by the difficulty of detecting the input PrP-res from the PrP-res made de novo by the cell. Recently, however, several groups have been able to study PrP-res uptake using input PrP-res that was either fluorescently labeled [18][19][20] or tagged with the epitope to the monoclonal antibody 3F4, 21 or cell lines that express little or no PrP-sen. 19,[21][22][23] The data show that PrP-res uptake is independent of scrapie strain or cell type but is influenced by the PrPres microenvironment as well as PrP-res aggregate size. 21 Importantly, these studies demonstrated that PrP-sen expression was not required.…”