Degradation of Endoplasmic Reticulum (ER) Quality Control Substrates Requires Transport between the ER and Golgi

Sabrina R Caldwell,Kathryn J Hill,Antony A Cooper

doi:10.1074/jbc.m102962200

Sabrina R Caldwell, Kathryn J Hill + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m102962200

Copy DOI

Abstract

Endoplasmic reticulum (ER) quality control (ERQC) components retain and degrade misfolded proteins, and our results have found that the degradation of the soluble ERQC substrates CPY* and PrA* but not membrane spanning ERQC substrates requires transport between the ER and Golgi. Stabilization of these misfolded soluble proteins was seen in cells lacking Erv29p, a probable Golgi localized protein that cycles through the ER by means of a di-lysine ER retrieval motif (KKKIY). Cells lacking Erv29p also displayed severely retarded ER exit kinetics for a subset of correctly folded proteins. We suggest that Erv29p is likely involved in cargo loading of a subset of proteins, including soluble misfolded proteins, into vesicles for ER exit. The stabilization of soluble ERQC substrates in both erv29Delta cells and sec mutants blocked in either ER exit (sec12) or vesicle delivery to the Golgi (sec18) suggests that ER-Golgi transport is required for ERQC and reveals a new aspect of the degradative mechanism.

Highlights

Proteins entering the secretory pathway are first translocated into the endoplasmic reticulum (ER)1 where they undergo folding and maturation involving either N- or O-glycosylation, oligomerization, disulfide bond formation, or subunit assembly
We examined recent microarray data of ERstressed S. cerevisiae and identified a number of uncharacterized candidate genes (Table II) based on up-regulation following Endoplasmic reticulum (ER) stress induced by both expression of an ER by the quality control (ERQC) substrate [12] and the compounds DTT and tunicamycin, which inhibit protein folding in the ER [13]
As an internal control we included a strain that was disrupted in HRD1/DER3 as Hrd1p is required for efficient degradation of CPY* [6]

Summary

TABLE I Yeast strains used in this study

MATa ade101 ura leu112 his3-⌬200 trp901 suc2-⌬9 vph1⌬ϻLEU2 in SEY6211 erv29⌬ϻKAN in KHY30 erv14⌬ϻKAN in KHY30 pep4⌬ϻTRP1 in KHY30 erv29⌬ϻKAN in KHY275 erv14⌬ϻKAN in KHY275 MATa vph1⌬ϻLEU2 prc trp901 leu112 ura ade101 his3-⌬200 suc2-⌬9 erv29⌬ϻKAN in KHY163 erv46⌬ϻKAN in KHY163 erv14⌬ϻKAN in KHY163 erv25⌬ϻKAN in KHY163 emp24⌬ϻKAN in KHY163 erv41⌬ϻKAN in KHY163 erv14⌬ϻKAN in KHY275 MATa ura leu112 trp289 his his suc2-⌬9 MATa sec ura leu112 trp289 his his gal MATa leu112 ura his3-⌬200 MATa sec leu112 ura Ade1⁄7 met trp1E MET14 in CJRY21–3B␣. Ref. 30 This work This work This work This work This work This work This work This work This work This work This work This work This work This work Ref. 43 Ref. 43 Ref. 54 Ref. 54 This work. The ER and Golgi, indicating that ER-Golgi transport is necessary for soluble ERQC substrate degradation

EXPERIMENTAL PROCEDURES

RESULTS

Wild type

DISCUSSION