scholarly journals The ER membrane protein complex interacts cotranslationally to enable biogenesis of multipass membrane proteins

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Matthew J Shurtleff ◽  
Daniel N Itzhak ◽  
Jeffrey A Hussmann ◽  
Nicole T Schirle Oakdale ◽  
Elizabeth A Costa ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Protein Complex ◽  
Transmembrane Domain ◽  
Transmembrane Proteins ◽  
Ribosome Profiling ◽  
Membrane Insertion ◽  
Membrane Protein Complex ◽  
Trade Off ◽  
Charged Residues ◽  
Er Membrane

The endoplasmic reticulum (ER) supports biosynthesis of proteins with diverse transmembrane domain (TMD) lengths and hydrophobicity. Features in transmembrane domains such as charged residues in ion channels are often functionally important, but could pose a challenge during cotranslational membrane insertion and folding. Our systematic proteomic approaches in both yeast and human cells revealed that the ER membrane protein complex (EMC) binds to and promotes the biogenesis of a range of multipass transmembrane proteins, with a particular enrichment for transporters. Proximity-specific ribosome profiling demonstrates that the EMC engages clients cotranslationally and immediately following clusters of TMDs enriched for charged residues. The EMC can remain associated after completion of translation, which both protects clients from premature degradation and allows recruitment of substrate-specific and general chaperones. Thus, the EMC broadly enables the biogenesis of multipass transmembrane proteins containing destabilizing features, thereby mitigating the trade-off between function and stability.

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

Cell Reports ◽  
2019 ◽  
Vol 27 (6) ◽  
pp. 1666-1674.e4 ◽  
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

scholarly journals Structural basis for membrane insertion by the human ER membrane protein complex

Science ◽  
2020 ◽  
pp. eabb5008 ◽  
Author(s):  
Tino Pleiner ◽  
Giovani Pinton Tomaleri ◽  
Kurt Januszyk ◽  
Alison J. Inglis ◽  
Masami Hazu ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Protein Complex ◽  
Structural Basis ◽  
Membrane Insertion ◽  
Transmembrane Helices ◽  
Membrane Protein Complex ◽  
Cryo Electron Microscopy ◽  
Membrane Thinning ◽  
Positively Charged ◽  
Er Membrane

A defining step in the biogenesis of a membrane protein is the insertion of its hydrophobic transmembrane helices into the lipid bilayer. The nine-subunit ER membrane protein complex (EMC) is a conserved co- and post-translational insertase at the endoplasmic reticulum. We determined the structure of the human EMC in a lipid nanodisc to an overall resolution of 3.4 Å by cryo-electron microscopy, permitting building of a nearly complete atomic model. We used structure-guided mutagenesis to demonstrate that substrate insertion requires a methionine-rich cytosolic loop and occurs via an enclosed hydrophilic vestibule within the membrane formed by the subunits EMC3 and EMC6. We propose that the EMC uses local membrane thinning and a positively charged patch to decrease the energetic barrier for insertion into the bilayer.

scholarly journals The ER membrane protein complex is a transmembrane domain insertase

Science ◽  
2017 ◽  
Vol 359 (6374) ◽  
pp. 470-473 ◽  
Author(s):  
Alina Guna ◽  
Norbert Volkmar ◽  
John C. Christianson ◽  
Ramanujan S. Hegde
Keyword(s):  
Membrane Protein ◽  
Protein Complex ◽  
Transmembrane Domain ◽  
Membrane Protein Complex ◽  
Er Membrane

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

eLife ◽  
2019 ◽  
Vol 8 ◽  
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.

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

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.

scholarly journals ER membrane protein complex is required for the insertions of late-synthesized transmembrane helices of Rh1 in Drosophila photoreceptors

2019 ◽  
Vol 30 (23) ◽  
pp. 2890-2900 ◽  
Author(s):  
Naoki Hiramatsu ◽  
Tatsuya Tago ◽  
Takunori Satoh ◽  
Akiko K. Satoh
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Protein Complex ◽  
Model System ◽  
Membrane Insertion ◽  
Transmembrane Helices ◽  
Membrane Protein Complex ◽  
C Terminus ◽  
Wide Range ◽  
Er Membrane

Most membrane proteins are synthesized on and inserted into the membrane of the endoplasmic reticulum (ER), in eukaryote. The widely conserved ER membrane protein complex (EMC) facilitates the biogenesis of a wide range of membrane proteins. In this study, we investigated the EMC function using Drosophila photoreceptor as a model system. We found that the EMC was necessary only for the biogenesis of a subset of multipass membrane proteins such as rhodopsin (Rh1), TRP, TRPL, Csat, Cni, SERCA, and Na+K+ATPase α, but not for that of secretory or single-pass membrane proteins. Additionally, in EMC-deficient cells, Rh1 was translated to its C terminus but degraded independently from ER-associated degradation. Thus, EMC exerted its effect after translation but before or during the membrane integration of transmembrane domains (TMDs). Finally, we found that EMC was not required for the stable expression of the first three TMDs of Rh1 but was required for that of the fourth and fifth TMDs. Our results suggested that EMC is required for the ER membrane insertion of succeeding TMDs of multipass membrane proteins.

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