Cargo selection into COPII vesicles is driven by the Sec24p subunit.

Elizabeth Miller; Bruno Antonny; Susan Hamamoto; Randy Schekman

doi:10.1093/emboj/cdf605

Home/Archive/PubMed

PubMed · 12426382

Cargo selection into COPII vesicles is driven by the Sec24p subunit.

Elizabeth Miller·Bruno Antonny·Susan Hamamoto·Randy Schekman

View original source ↗Export metadata ↓

Abstract

Transport of secretory proteins out of the endoplasmic reticulum (ER) is mediated by vesicles generated by the COPII coat complex. In order to understand how cargo molecules are selected by this cytoplasmic coat, we investigated the functional role of the Sec24p homolog, Lst1p. We show that Lst1p can function as a COPII subunit independently of Sec24p on native ER membranes and on synthetic liposomes. However, vesicles generated with Lst1p in the absence of Sec24p are deficient in a distinct subset of cargo molecules, including the SNAREs, Bet1p, Bos1p and Sec22p. Consistent with the absence of any SNAREs, these vesicles are unable to fuse with Golgi membranes. Furthermore, unlike Sec24p, Lst1p fails to bind to Bet1p in vitro, indicating a direct correlation between cargo binding and recruitment into vesicles. Our data suggest that the principle role of Sec24p is to discriminate cargo molecules for incorporation into COPII vesicles.

Explore related subjects

COP-Coated Vesicles Liposomes Membrane Fusion Membrane Proteins Membrane Transport Proteins Monomeric GTP-Binding Proteins Protein Subunits Protein Transport Qc-SNARE Proteins SNARE Proteins Saccharomyces cerevisiae Saccharomyces cerevisiae Proteins Structure-Activity Relationship Vesicular Transport Proteins Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Elizabeth Miller, Bruno Antonny, Susan Hamamoto, Randy Schekman. 2002-11-15. Cargo selection into COPII vesicles is driven by the Sec24p subunit.. https://doi.org/10.1093/emboj%2Fcdf605

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2006

Genetic and molecular interactions of the Erv41p-Erv46p complex involved in transport between the endoplasmic reticulum and Golgi complex.

Erv41p and Erv46p are integral membrane proteins conserved across species. They were originally identified as abundant constituents of COPII-coated vesicles, and form a complex which cycles between the endoplasmic reticulum and Golgi complex. Yeast strains lacking these proteins are viable but display subtle secretory phenotypes. In order to obtain information about possible biological roles of this protein complex in endoplasmic reticulum to Golgi transport, we employed the Synthetic Genetic Array approach to screen for synthetic genetic interactions with the erv46 null mutation. We identified synthetic interactions with vma12, vma21, vma22 and vps1 deletion mutations. The vma21Delta mutation exacerbates transport defects caused by the erv46Delta mutation. Unexpectedly, yeast strains lacking Vma21p fail to sort the endoplasmic reticulum to Golgi v-SNARE, Bos1p, efficiently into COPII vesicles, yet these vesicles are fully fusion competent. In addition, we set out to identify, by a biochemical approach, proteins interacting with the Erv41p-Erv46p complex. We report a strong interaction between the Erv41p-Erv46p complex and endoplasmic reticulum glucosidase II. Strains lacking a cycling Erv41p-Erv46p complex display a mild glycoprotein processing defect.

COP-Coated Vesicles↗

PubMed2006

ER-associated degradation of membrane proteins in yeast.

Proteins destined for the secretory pathway are translocated into the endoplasmic reticulum (ER), where they are subjected to a variety of post-translational modifications before they reach their final destination. Newly synthesized proteins that have defect in polypeptide folding or subunit assembly are recognized by quality control systems and eliminated by the 26S proteasome, a cytosolic ATP-dependent proteolytic machinery. Delivery of non-native ER proteins to the proteasome requires retrograde transport across the ER membrane and depends on a protein-unfolding machine consisting of Cdc48p, Ufd1p, and Npl4p. Recent studies in yeast have highlighted the possible function of the Sar1p/COPII machinery in ER-associated degradation of some lumenal and membrane proteins.

COP-Coated Vesicles↗

PubMed2006

Sterols regulate ER-export dynamics of secretory cargo protein ts-O45-G.

Alterations in endoplasmic reticulum (ER) cholesterol are fundamental for a variety of cellular processes such as the regulation of lipid homeostasis or efficient protein degradation. We show that reduced levels of cellular sterols cause a delayed ER-to-Golgi transport of the secretory cargo membrane protein ts-O45-G and a relocation to the ER of an endogenous protein cycling between the ER and the Golgi complex. Transport inhibition is characterized by a delay in the accumulation of ts-O45-G in ER-exit sites (ERES) and correlates with a reduced mobility of ts-O45-G within ER membranes. A simple mathematical model describing the kinetics of ER-exit predicts that reduced cargo loading to ERES and not the reduced mobility of ts-O45-G accounts for the delayed ER-exit and arrival at the Golgi. Consistent with this, membrane turnover of the COPII component Sec23p is delayed in sterol-depleted cells. Altogether, our results demonstrate the importance of sterol levels in COPII mediated ER-export.

COP-Coated Vesicles↗