Membrane Domain Localization and Interaction of the Prion-Family Proteins, Prion and Shadoo with Calnexin

Abstract

The cellular prion protein (PrPC) is renowned for its infectious conformational isoform PrPSc, capable of templating subsequent conversions of healthy PrPCs and thus triggering the group of incurable diseases known as transmissible spongiform encephalopathies. Besides this mechanism not being fully uncovered, the protein’s physiological role is also elusive. PrPC and its newest, less understood paralog Shadoo are glycosylphosphatidylinositol-anchored proteins highly expressed in the central nervous system. While they share some attributes and neuroprotective actions, opposing roles have also been reported for the two; however, the amount of data about their exact functions is lacking. Protein–protein interactions and membrane microdomain localizations are key determinants of protein function. Accurate identification of these functions for a membrane protein, however, can become biased due to interactions occurring during sample processing. To avoid such artifacts, we apply a non-detergent-based membrane-fractionation approach to study the prion protein and Shadoo. We show that the two proteins occupy similarly raft and non-raft membrane fractions when expressed in N2a cells and that both proteins pull down the chaperone calnexin in both rafts and non-rafts. These indicate their possible binding to calnexin in both types of membrane domains, which might be a necessary requisite to aid the inherently unstable native conformation during their lifetime.

Novel Polymorphisms and Genetic Characteristics of the Shadow of Prion Protein Gene (SPRN) in Cats, Hosts of Feline Spongiform Encephalopathy

“…We analyzed the omega-site and signal sequences of the GPl anchor among humans, mice, cattle, sheep, goats, red deer, dogs, horses and cats ( Table 5 ). The murine Sho has been reported to have a GPI signal sequence of 123–147 aa [ 23 , 25 ], and the prediction results (116–147 aa) of the present study showed a slight difference from the previous study. Mice and cattle had the longest signal sequences of the GPI anchor of the Sho protein (32 aa).…”