TY - JOUR

T1 - Herp regulates Hrd1-mediated ubiquitylation in a ubiquitin-like domain-dependent manner

AU - Kny, Melanie

AU - Standera, Sybille

AU - Hartmann-Petersen, Rasmus

AU - Kloetzel, Peter-Michael

AU - Seeger, Michael

PY - 2011

Y1 - 2011

N2 - Accumulation of aberrant proteins in the endoplasmic reticulum (ER) triggers the unfolded protein response pathway that helps the cell to survive under these stress conditions. Herp is a mammalian ubiquitin domain protein, which is strongly induced by the unfolded protein response. It is involved in ER-associated protein degradation (ERAD) and interacts directly with the ubiquitin ligase Hrd1, which is found in high molecular mass complexes of the ER membrane. Here we present the first evidence that Herp regulates Hrd1-mediated ubiquitylation in a ubiquitin-like (UBL) domain-dependent manner. We found that upon exposure of cells to ER stress, elevation of Herp steady state levels is accompanied by an enhanced association of Herp with pre-existing Hrd1. Hrd1-associated Herp is rapidly degraded and substituted by de novo synthesized Herp, suggesting a continuous turnover of the protein at Hrd1 complexes. Further analysis revealed the presence of multiple Hrd1 copies in a single complex enabling binding of a variable number of Herp molecules. Efficient ubiquitylation of the Hrd1-specific ERAD substrate a1-antitrypsin null Hong Kong (NHK) required the presence of the Herp UBL domain, which was also necessary for NHK degradation. In summary, we propose that binding of Herp to Hrd1-containing ERAD complexes positively regulates the ubiquitylation activity of these complexes, thus permitting survival of the cell during ER stress.

AB - Accumulation of aberrant proteins in the endoplasmic reticulum (ER) triggers the unfolded protein response pathway that helps the cell to survive under these stress conditions. Herp is a mammalian ubiquitin domain protein, which is strongly induced by the unfolded protein response. It is involved in ER-associated protein degradation (ERAD) and interacts directly with the ubiquitin ligase Hrd1, which is found in high molecular mass complexes of the ER membrane. Here we present the first evidence that Herp regulates Hrd1-mediated ubiquitylation in a ubiquitin-like (UBL) domain-dependent manner. We found that upon exposure of cells to ER stress, elevation of Herp steady state levels is accompanied by an enhanced association of Herp with pre-existing Hrd1. Hrd1-associated Herp is rapidly degraded and substituted by de novo synthesized Herp, suggesting a continuous turnover of the protein at Hrd1 complexes. Further analysis revealed the presence of multiple Hrd1 copies in a single complex enabling binding of a variable number of Herp molecules. Efficient ubiquitylation of the Hrd1-specific ERAD substrate a1-antitrypsin null Hong Kong (NHK) required the presence of the Herp UBL domain, which was also necessary for NHK degradation. In summary, we propose that binding of Herp to Hrd1-containing ERAD complexes positively regulates the ubiquitylation activity of these complexes, thus permitting survival of the cell during ER stress.

KW - Cell Survival

KW - Endoplasmic Reticulum

KW - Hela Cells

KW - Humans

KW - Membrane Proteins

KW - Protein Binding

KW - Protein Structure, Tertiary

KW - Ubiquitin

KW - Ubiquitin-Protein Ligases

KW - Ubiquitination

KW - Unfolded Protein Response

U2 - 10.1074/jbc.M110.134551

DO - 10.1074/jbc.M110.134551

M3 - Journal article

C2 - 21149444

VL - 286

SP - 5151

EP - 5156

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 7

ER -