The Novel Chaperone Activity of p47 Modulates Force-Mediated Retrotranslocation from the Endoplasmic Reticulum to the Cytosol

Protein quality control in the endoplasmic reticulum (ER) maintains cellular proteostasis by regulating protein folding, assembly, and degradation. While protein translocation from the cytosol into the ER is well-studied, the reverse process, known as retrotranslocation, which exports proteins from the ER lumen or membrane into the cytosol, is less understood.

In this study, we investigate the role of p47, a cofactor of the ATPase p97, in retrotranslocation and its chaperone-like activity on the model substrate talin using single-molecule magnetic tweezers. We find that p47 enhances the mechanical stability of talin, by increasing its folding probabilities by 8 pN, which generate a maximum work output of up to ∼199.5 zJ to facilitate the extraction of the protein from the ER lumen. These findings suggest that p47 interacts with substrates emerging from the ER, generating pulling forces that aid retrotranslocation, which uncovers a novel mechanistic role for p47 in ER-associated degradation, advancing the understanding of retrotranslocation.