Cell-Specific Metabolism and Pathogenesis of Transmembrane Prion Protein

Abstract

The C-transmembrane form of prion protein (^CtmPrP) has been implicated in prion disease pathogenesis, but the factors underlying its biogenesis and cyotoxic potential remain unclear. Here we show that ^CtmPrP interferes with cytokinesis in cell lines where it is transported to the plasma membrane. These cells fail to separate following cell division, assume a variety of shapes and sizes, and contain multiple nuclei, some of which are pyknotic. Furthermore, the synthesis and transport of ^CtmPrP to the plasma membrane are modulated through a complex interaction between cis- and trans-acting factors and the endoplasmic reticulum translocation machinery. Thus, insertion of eight amino acids before or within the N region of the N signal peptide (N-SP) of PrP results in the exclusive synthesis of ^CtmPrP regardless of the charge conferred to the N region. Subsequent processing and transport of ^CtmPrP are modulated by specific amino acids in the N region of the N-SP and by the cell line of expression. Although the trigger for ^CtmPrP upregulation in naturally occurring prion disorders remains elusive, these data highlight the underlying mechanisms of ^CtmPrP biogenesis and neurotoxicity and reinforce the idea that ^CtmPrP may serve as the proximate cause of neuronal death in certain prion disorders.

We thank Pierluigi Gambetti, Man-Sun Sy, and Ruliang Li for anti-PrP antibodies 8B4 and 8H4 and Anil Kumar for helping with the PrP^N3F4 and PrP^NFlag constructs.

This study was supported by NIH grants NS39089 and NS35962 to N.S.