Regulated assembly of the ER membrane protein complex

SummaryThe assembly of nascent proteins into multi-subunit complexes is tightly regulated to maintain cellular homeostasis. The ER membrane protein complex (EMC) is an essential insertase that requires seven membrane-spanning and two soluble subunits for function. Here we show that the kinase With no lysine 1 (WNK1), known for its role in hypertension and neuropathy, is required for assembly of the human EMC. WNK1 uses a conserved amphipathic helix to stabilize the soluble subunit, EMC2, by binding to the EMC2-8 interface. Shielding this hydrophobic surface prevents promiscuous interactions of unassembled EMC2 and precludes binding of ubiquitin ligases, permitting assembly. Using biochemical reconstitution, we show that after EMC2 reaches the membrane, its interaction partners within the EMC displace WNK1, and similarly shield its exposed hydrophobic surfaces. This work describes an unexpected role for WNK1 in protein biogenesis, and defines the general requirements of an assembly factor that will apply across the proteome.

Download Full-text

WNK1 is an assembly factor for the human ER membrane protein complex

Molecular Cell ◽

10.1016/j.molcel.2021.04.013 ◽

2021 ◽

Author(s):

Tino Pleiner ◽

Masami Hazu ◽

Giovani Pinton Tomaleri ◽

Kurt Januszyk ◽

Robert S. Oania ◽

...

Keyword(s):

Membrane Protein ◽

Protein Complex ◽

Membrane Protein Complex ◽

Assembly Factor ◽

Er Membrane

Download Full-text

The ER membrane protein complex is required to ensure correct topology and stable expression of flavivirus polyproteins

eLife ◽

10.7554/elife.48469 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 13

Author(s):

Ashley M Ngo ◽

Matthew J Shurtleff ◽

Katerina D Popova ◽

Jessie Kulsuptrakul ◽

Jonathan S Weissman ◽

...

Keyword(s):

Membrane Protein ◽

Protein Complex ◽

Transmembrane Protein ◽

Point Mutations ◽

Transmembrane Proteins ◽

Physical Interaction ◽

Translation Efficiency ◽

Membrane Protein Complex ◽

Protein Biogenesis ◽

Er Membrane

Flaviviruses translate their genomes as multi-pass transmembrane proteins at the endoplasmic reticulum (ER) membrane. Here, we show that the ER membrane protein complex (EMC) is indispensable for the expression of viral polyproteins. We demonstrated that EMC was essential for accurate folding and post-translational stability rather than translation efficiency. Specifically, we revealed degradation of NS4A-NS4B, a region rich in transmembrane domains, in absence of EMC. Orthogonally, by serial passaging of virus on EMC-deficient cells, we identified two non-synonymous point mutations in NS4A and NS4B, which rescued viral replication. Finally, we showed a physical interaction between EMC and viral NS4B and that the NS4A-4B region adopts an aberrant topology in the absence of the EMC leading to degradation. Together, our data highlight how flaviviruses hijack the EMC for transmembrane protein biogenesis to achieve optimal expression of their polyproteins, which reinforces a role for the EMC in stabilizing challenging transmembrane proteins during synthesis.

Download Full-text

Dual roles for the ER membrane protein complex in flavivirus infection: viral entry and protein biogenesis

Scientific Reports ◽

10.1038/s41598-019-45910-9 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 16

Author(s):

Nicholas J. Barrows ◽

Yesseinia Anglero-Rodriguez ◽

Byungil Kim ◽

Sharon F. Jamison ◽

Caroline Le Sommer ◽

...

Keyword(s):

Membrane Protein ◽

Viral Entry ◽

Protein Complex ◽

Dual Roles ◽

Membrane Protein Complex ◽

Protein Biogenesis ◽

Flavivirus Infection ◽

Er Membrane

Download Full-text

The ER membrane protein complex is required to ensure correct topology and stable expression of flavivirus polyproteins

10.1101/572602 ◽

2019 ◽

Author(s):

Ashley M Ngo ◽

Matthew J Shurtleff ◽

Katerina D Popova ◽

Jessie Kulsuptrakul ◽

Jonathan S Weissman ◽

...

Keyword(s):

Membrane Protein ◽

Protein Complex ◽

Transmembrane Protein ◽

Point Mutations ◽

Transmembrane Proteins ◽

Physical Interaction ◽

Translation Efficiency ◽

Membrane Protein Complex ◽

Protein Biogenesis ◽

Er Membrane

AbstractFlaviviruses translate their genomes as multi-pass transmembrane proteins at the endoplasmic reticulum (ER) membrane. Here, we show that the ER membrane protein complex (EMC) is indispensable for the expression of viral polyproteins. We demonstrated that EMC was essential for accurate folding and post-translational stability rather than translation efficiency. Specifically, we revealed degradation of NS4A-NS4B, a region rich in transmembrane domains, in absence of EMC. Orthogonally, by serial passaging of virus on EMC-deficient cells, we identified two non-synonymous point mutations in NS4A and NS4B, which rescued viral replication. Finally, we showed a physical interaction between EMC and viral NS4B and that the NS4A-4B region adopts an aberrant topology in the absence of the EMC leading to degradation. Together, our data highlight how flaviviruses hijack the EMC for transmembrane protein biogenesis to achieve optimal expression of their polyproteins, which reinforces a role for the EMC in stabilizing challenging transmembrane proteins during synthesis.

Download Full-text

Faculty Opinions recommendation of Structural basis for membrane insertion by the human ER membrane protein complex.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.737989329.793574938 ◽

2020 ◽

Author(s):

Karin Romisch

Keyword(s):

Membrane Protein ◽

Protein Complex ◽

Structural Basis ◽

Membrane Insertion ◽

Membrane Protein Complex ◽

Er Membrane

Download Full-text

The ER membrane protein complex promotes biogenesis of sterol-related enzymes maintaining cholesterol homeostasis

Journal of Cell Science ◽

10.1242/jcs.223453 ◽

2018 ◽

Vol 132 (2) ◽

pp. jcs223453 ◽

Cited By ~ 25

Author(s):

Norbert Volkmar ◽

Maria-Laetitia Thezenas ◽

Sharon M. Louie ◽

Szymon Juszkiewicz ◽

Daniel K. Nomura ◽

...

Keyword(s):

Membrane Protein ◽

Protein Complex ◽

Cholesterol Homeostasis ◽

Membrane Protein Complex ◽

Er Membrane

Download Full-text

The ER Membrane Protein Complex Promotes Biogenesis of Dengue and Zika Virus Non-structural Multi-pass Transmembrane Proteins to Support Infection

Cell Reports ◽

10.1016/j.celrep.2019.04.051 ◽

2019 ◽

Vol 27 (6) ◽

pp. 1666-1674.e4 ◽

Cited By ~ 22

Author(s):

David L. Lin ◽

Takamasa Inoue ◽

Yu-Jie Chen ◽

Aaron Chang ◽

Billy Tsai ◽

...

Keyword(s):

Membrane Protein ◽

Zika Virus ◽

Protein Complex ◽

Transmembrane Proteins ◽

Membrane Protein Complex ◽

Er Membrane

Download Full-text

The ubiquitous and ancient ER membrane protein complex (EMC): tether or not?

F1000Research ◽

10.12688/f1000research.6944.2 ◽

2015 ◽

Vol 4 ◽

pp. 624 ◽

Cited By ~ 8

Author(s):

Jeremy G. Wideman

Keyword(s):

Membrane Protein ◽

Protein Complex ◽

Common Ancestor ◽

Eukaryotic Cells ◽

Eukaryotic Lineage ◽

Membrane Protein Complex ◽

Outer Membranes ◽

Homology Searching ◽

Eukaryote Evolution ◽

Er Membrane

The recently discovered endoplasmic reticulum (ER) membrane protein complex (EMC) has been implicated in ER-associated degradation (ERAD), lipid transport and tethering between the ER and mitochondrial outer membranes, and assembly of multipass ER-membrane proteins. The EMC has been studied in both animals and fungi but its presence outside the Opisthokont clade (animals + fungi + related protists) has not been demonstrated. Here, using homology-searching algorithms, I show that the EMC is truly an ancient and conserved protein complex, present in every major eukaryotic lineage. Very few organisms have completely lost the EMC, and most, even over 2 billion years of eukaryote evolution, have retained a majority of the complex members. I identify Sop4 and YDR056C in Saccharomyces cerevisiae as Emc7 and Emc10, respectively, subunits previously thought to be specific to animals. This study demonstrates that the EMC was present in the last eukaryote common ancestor (LECA) and is an extremely important component of eukaryotic cells even though its primary function remains elusive.

Download Full-text