Faculty Opinions recommendation of Different redox sensitivity of endoplasmic reticulum associated degradation clients suggests a novel role for disulphide bonds in secretory proteins.

To maintain proteostasis in the endoplasmic reticulum (ER), terminally misfolded secretory proteins must be recognized, partially unfolded, and dislocated to the cytosol for proteasomal destruction, in a complex process called ER-associated degradation (ERAD). Dislocation implies reduction of inter-chain disulphide bonds. When in its reduced form, protein disulphide isomerase (PDI) can act not only as a reductase but also as an unfoldase, preparing substrates for dislocation. PDI oxidation by Ero1 favours substrate release and transport across the ER membrane. Here we addressed the redox dependency of ERAD and found that DTT stimulates the dislocation of proteins with DTT-resistant disulphide bonds (i.e., orphan Ig-μ chains) but stabilizes a ribophorin mutant (Ri332) devoid of them. DTT promotes the association of Ri332, but not of Ig-µ, with PDI. This discrepancy may suggest that disulphide bonds in cargo proteins can be utilized to oxidize PDI, hence facilitating substrate detachment and degradation also in the absence of Ero1. Accordingly, Ero1 silencing retards Ri332 degradation, but has little if any effect on Ig-µ. Thus, some disulphides can increase the stability and simultaneously favour quality control of secretory proteins.

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Oxidative protein folding in the mammalian endoplasmic reticulum

Biochemical Society Transactions ◽

10.1042/bst0320655 ◽

2004 ◽

Vol 32 (5) ◽

pp. 655-658 ◽

Cited By ~ 51

Author(s):

C.E. Jessop ◽

S. Chakravarthi ◽

R.H. Watkins ◽

N.J. Bulleid

Keyword(s):

Endoplasmic Reticulum ◽

Mammalian Cells ◽

Redox State ◽

Structure And Function ◽

Reduced Form ◽

Secretory Proteins ◽

Oxidative Protein Folding ◽

Disulphide Bonds ◽

And Function ◽

Substrate Proteins

Native disulphide bonds are essential for the structure and function of many membrane and secretory proteins. Disulphide bonds are formed, reduced and isomerized in the endoplasmic reticulum of mammalian cells by a family of oxidoreductases, which includes protein disulphide isomerase (PDI), ERp57, ERp72, P5 and PDIR. This review will discuss how these enzymes are maintained in either an oxidized redox state that allows them to form disulphide bonds in substrate proteins or a reduced form that allows them to perform isomerization and reduction reactions, how these opposing pathways may co-exist within the same compartment and why so many oxidoreductases exist when PDI alone can perform all three of these functions.

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Efect of Sec61 interaction with Mpd1 on Endoplasmic Reticulum- Associated Degradation

10.1101/411173 ◽

2018 ◽

Author(s):

Fábio Pereira ◽

Mandy Rettel ◽

Frank Stein ◽

Mikhail M. Savitski ◽

Ian Collinson ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Protein Import ◽

Retrograde Transport ◽

Secretory Proteins ◽

Chemical Crosslinking ◽

Endoplasmic Reticulum Associated Degradation ◽

Channel Opening ◽

Interaction Partners ◽

Sec61 Channel

AbstractProteins that misfold in the endoplasmic reticulum (ER) are transported back to the cytosol for ER-associated degradation (ERAD). The Sec61 channel is one of the candidates for the retrograde transport conduit. Channel opening from the ER lumen must be triggered by ERAD factors and substrates. Here we identified new lumenal interaction partners of Sec61 by chemical crosslinking and mass spectrometry. In addition to known Sec61 interactors we detected ERAD factors including Cue1, Ubc6, Ubc7, Asi3, and Mpd1. We show that the CPY* ERAD factor Mpd1 binds to the lumenal Sec61 hinge region. Deletion of the Mpd1 binding site reduced the interaction between both proteins and caused an ERAD defect specific for CPY* without affecting protein import into the ER or ERAD of other substrates. Our data suggest that Mpd1 binding to Sec61 is a prerequisite for CPY* ERAD and confirm a role of Sec61 in ERAD of misfolded secretory proteins.

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Degradation of integral membrane proteins modified with the photosensitive degron module requires the cytosolic endoplasmic reticulum–associated degradation pathway

Molecular Biology of the Cell ◽

10.1091/mbc.e18-12-0754 ◽

2019 ◽

Vol 30 (20) ◽

pp. 2558-2570 ◽

Cited By ~ 2

Author(s):

Johannes Scheffer ◽

Sophia Hasenjäger ◽

Christof Taxis

Keyword(s):

Endoplasmic Reticulum ◽

Membrane Proteins ◽

Protein Quality ◽

Degradation Pathway ◽

Integral Membrane Proteins ◽

Secretory Proteins ◽

Ubiquitin Protein Ligase ◽

Aaa Atpase ◽

Endoplasmic Reticulum Associated Degradation ◽

Ubiquitin Conjugating Enzymes

Protein quality mechanisms are fundamental for proteostasis of eukaryotic cells. Endoplasmic reticulum–associated degradation (ERAD) is a well-studied pathway that ensures quality control of secretory and endoplasmic reticulum (ER)–resident proteins. Different branches of ERAD are involved in degradation of malfolded secretory proteins, depending on the localization of the misfolded part, the ER lumen (ERAD-L), the ER membrane (ERAD-M), and the cytosol (ERAD-C). Here we report that modification of several ER transmembrane proteins with the photosensitive degron (psd) module resulted in light-dependent degradation of the membrane proteins via the ERAD-C pathway. We found dependency on the ubiquitylation machinery including the ubiquitin-activating enzyme Uba1, the ubiquitin-conjugating enzymes Ubc6 and Ubc7, and the ubiquitin–protein ligase Doa10. Moreover, we found involvement of the Cdc48 AAA-ATPase complex members Ufd1 and Npl4, as well as the proteasome, in degradation of Sec62-myc-psd. Thus, our work shows that ERAD-C substrates can be systematically generated via synthetic degron constructs, which facilitates future investigations of the ERAD-C pathway.

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