Misfolded GPI-anchored proteins are escorted through the secretory pathway by ER-derived factors
Abstract
We have used misfolded prion protein (PrP*) as a model to investigate how mammalian cells recognize and degrade misfolded GPI-anchored proteins. While most misfolded membrane proteins are degraded by proteasomes, misfolded GPI-anchored proteins are primarily degraded in lysosomes. Quantitative flow cytometry analysis showed that at least 85% of PrP* molecules transiently access the plasma membrane en route to lysosomes. Unexpectedly, time-resolved quantitative proteomics revealed a remarkably invariant PrP* interactome during its trafficking from the ER to lysosomes. Hence, PrP* arrives at the plasma membrane in complex with ER-derived chaperones and cargo receptors. These interaction partners were critical for rapid endocytosis because a GPI-anchored protein induced to misfold at the cell surface was not recognized effectively for degradation. Thus, resident ER factors have post-ER itineraries that not only shield misfolded GPI-anchored proteins during their trafficking, but also provide a quality control cue at the cell surface for endocytic routing to lysosomes.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files. Source data for Fig. 5E has been provided as a figure supplement.
Article and author information
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Funding
Medical Research Council (MC_UP_A022_1007)
- Ramanujan S Hegde
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Zavodszky & Hegde
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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