EMC4 (ER membrane protein complex subunit 4; also TMEM85) is a small (~183-residue, ~20 kDa) polytopic ER membrane protein and a constitutive structural subunit of the ER membrane protein complex (EMC), a conserved nine- to ten-subunit transmembrane-domain insertase and membrane-protein chaperone of the endoplasmic reticulum. Cryo-EM structures resolve EMC4 with a cytoplasmic N-terminus, transmembrane segments, and a lumenal C-terminus, packing against the other membrane subunits to help form and stabilize the complex. EMC4 is not part of the catalytic insertase core, which is formed by the EMC3 and EMC6 subunits that build the membrane-embedded hydrophilic substrate vestibule; instead EMC4 is an accessory/scaffold subunit. As part of the EMC it contributes to the energy-independent insertion of newly synthesized membrane proteins into the ER membrane, with a preference for transmembrane domains that are weakly hydrophobic or carry destabilizing charged or aromatic residues. The complex mediates post-translational insertion of tail-anchored proteins and cotranslational insertion and N-exo topogenesis of multipass membrane proteins, including transporters and G protein-coupled receptors, in cooperation with the Sec61 translocon. EMC4 is broadly expressed and resides in the ER membrane.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0072546
EMC complex
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: Phylogenetic (PAN-GO) assignment of EMC complex membership across the EMC4 family, matching direct experimental and structural evidence. Core structural identity of EMC4.
Reason: EMC complex membership is the core cellular-component identity of EMC4 and is supported by IDA, cryo-EM structures, and the conserved EMC4 family.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
Component of the ER membrane protein complex (EMC).
|
|
GO:0005789
endoplasmic reticulum membrane
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: Electronic transfer of the ER membrane subcellular location from UniProt; the correct and core compartment for the multipass ER membrane subunit EMC4.
Reason: Correct core location; redundant with experimental EXP/IDA evidence.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
|
|
GO:0005515
protein binding
|
IPI
PMID:31695625 Interaction Between ITM2B and GLUT9 Links Urate Transport to... |
KEEP AS NON CORE |
Summary: IntAct interaction of EMC4/TMEM85 with the multipass urate transporter GLUT9/SLC2A9 (Q9NRM0). In the functional assay TMEM85 (unlike ITM2B) did not affect GLUT9-mediated urate uptake; the interaction most plausibly reflects EMC4 engaging GLUT9 as an EMC client (consistent with the EMC's transporter-client preference). Bare protein binding is uninformative.
Reason: Plausible EMC-client (transporter) interaction, but bare protein binding is uninformative per curation guidelines and the functional assay showed no role of TMEM85 in urate transport itself; not elevated to core.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
Q5J8M3; Q9NRM0-1: SLC2A9
|
|
GO:0005515
protein binding
|
IPI
PMID:33845483 Multilevel proteomics reveals host perturbations by SARS-CoV... |
KEEP AS NON CORE |
Summary: High-throughput SARS-CoV-2/SARS-CoV proteomics interactome capturing EMC4 with the viral replicase polyprotein (P0DTD1, rep). Bare protein binding is uninformative and the partner is a viral xenobiotic protein unrelated to EMC4's core function.
Reason: Real virus-host interactome capture but bare protein binding is uninformative; the viral partner does not inform EMC4's core ER insertase scaffolding role.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
Q5J8M3; PRO_0000449624 [P0DTD1]: rep
|
|
GO:0005515
protein binding
|
IPI
PMID:34232536 Interactomes of SARS-CoV-2 and human coronaviruses reveal ho... |
KEEP AS NON CORE |
Summary: Comparative coronavirus interactome screen capturing the EMC4-viral replicase (P0DTD1, rep) interaction. Bare protein binding is uninformative and the partner is a viral protein.
Reason: Real virus-host interactome capture; bare protein binding is uninformative and the viral partner is not part of EMC4's core function.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
Q5J8M3; PRO_0000449624 [P0DTD1]: rep
|
|
GO:0005515
protein binding
|
IPI
PMID:36217030 A comprehensive SARS-CoV-2-human protein-protein interactome... |
KEEP AS NON CORE |
Summary: Comprehensive SARS-CoV-2-human interactome capturing the EMC4-viral replicase (P0DTD1, rep) interaction. Bare protein binding is uninformative and the partner is a viral protein.
Reason: Real virus-host interactome capture; bare protein binding is uninformative and the viral partner does not reflect EMC4's core insertase scaffolding role.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
Q5J8M3; PRO_0000449624 [P0DTD1]: rep
|
|
GO:0005789
endoplasmic reticulum membrane
|
NAS
PMID:29242231 The ER membrane protein complex is a transmembrane domain in... |
ACCEPT |
Summary: ComplexPortal NAS annotation of ER membrane localization for the EMC, consistent with the experimental evidence and core compartment of EMC4.
Reason: Correct core location; consistent with EXP/IDA evidence.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
|
|
GO:0045050
protein insertion into ER membrane by stop-transfer membrane-anchor sequence
|
IDA
PMID:29242231 The ER membrane protein complex is a transmembrane domain in... |
ACCEPT |
Summary: The EMC inserts transmembrane domains, including stop-transfer membrane-anchor sequences of multipass clients; EMC4 is a constitutive subunit. Core complex-level process.
Reason: Core EMC-mediated process; the EMC is a demonstrated transmembrane-domain insertase and EMC4 is a structural subunit.
Supporting Evidence:
PMID:29242231
transmembrane domain insertase
|
|
GO:0071816
tail-anchored membrane protein insertion into ER membrane
|
IDA
PMID:29242231 The ER membrane protein complex is a transmembrane domain in... |
ACCEPT |
Summary: The EMC mediates post-translational insertion of tail-anchored proteins with moderately hydrophobic TMDs, demonstrated directly in this study; EMC4 is a constitutive subunit. Core complex-level process.
Reason: Core EMC-mediated process; directly demonstrated for the complex.
Supporting Evidence:
PMID:29242231
tail-anchored membrane proteins with moderately hydrophobic transmembrane
|
|
GO:0072546
EMC complex
|
IPI
PMID:32439656 Structural basis for membrane insertion by the human ER memb... |
ACCEPT |
Summary: ComplexPortal IPI assignment of EMC complex membership based on the cryo-EM structure of the human EMC, which resolves EMC4 as a membrane subunit. Core structural identity.
Reason: Structurally demonstrated core EMC membership.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
Component of the ER membrane protein complex (EMC).
|
|
GO:0005789
endoplasmic reticulum membrane
|
EXP
PMID:22119785 Defining human ERAD networks through an integrative mapping ... |
ACCEPT |
Summary: Experimental ER membrane localization from the foundational ERAD-network mapping study that first identified the EMC (TMEM85). Core compartment.
Reason: Experimentally supported core location.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
|
|
GO:0032977
membrane insertase activity
|
IMP
PMID:29809151 The ER membrane protein complex interacts cotranslationally ... |
ACCEPT |
Summary: IMP evidence (cotranslational multipass biogenesis study) that the EMC has membrane insertase activity, to which EMC4 contributes as a structural subunit. The contributes_to qualifier is appropriate because EMC4 is not catalytic (the vestibule is EMC3/EMC6).
Reason: Complex-level MF correctly qualified contributes_to; EMC4 supports the insertase activity of the EMC as an accessory membrane subunit but is not itself catalytic.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
enables the energy-independent insertion into endoplasmic
|
|
GO:0032977
membrane insertase activity
|
IMP
PMID:30415835 EMC Is Required to Initiate Accurate Membrane Protein Topoge... |
ACCEPT |
Summary: IMP evidence (topogenesis study) supporting the EMC's membrane insertase activity, to which EMC4 contributes as a structural subunit. contributes_to correctly reflects that EMC4 is non-catalytic.
Reason: Complex-level MF correctly qualified contributes_to; EMC4 supports the insertase activity of the EMC.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
enables the energy-independent insertion into endoplasmic
|
|
GO:0045050
protein insertion into ER membrane by stop-transfer membrane-anchor sequence
|
IMP
PMID:29809151 The ER membrane protein complex interacts cotranslationally ... |
ACCEPT |
Summary: The EMC is required for cotranslational insertion of multipass proteins in which stop-transfer membrane-anchor sequences become membrane-spanning helices; EMC4 is a constitutive subunit. Core EMC process.
Reason: Core EMC-mediated process; supported by IMP of EMC subunits.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
stop-transfer membrane-anchor sequences become ER membrane spanning
|
|
GO:0005789
endoplasmic reticulum membrane
|
IDA
PMID:32439656 Structural basis for membrane insertion by the human ER memb... |
ACCEPT |
Summary: Direct (cryo-EM structural) evidence placing EMC4 in the ER membrane as a membrane subunit of the EMC. Core compartment.
Reason: Experimentally supported core location.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
|
|
GO:0045050
protein insertion into ER membrane by stop-transfer membrane-anchor sequence
|
IMP
PMID:30415835 EMC Is Required to Initiate Accurate Membrane Protein Topoge... |
ACCEPT |
Summary: IMP evidence (topogenesis study) that the EMC inserts stop-transfer membrane-anchor sequences and sets the N-exo topology of multipass clients such as GPCRs; EMC4 is part of the insertase complex. Core EMC process.
Reason: Core EMC-mediated process.
Supporting Evidence:
PMID:30415835
G protein-coupled receptors
|
|
GO:0016020
membrane
|
IDA
PMID:22119785 Defining human ERAD networks through an integrative mapping ... |
KEEP AS NON CORE |
Summary: Direct generic membrane localization from the EMC-discovery study; a parent of the specific ER membrane term.
Reason: Correct but generic; the ER membrane term captures the informative localization.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
|
|
GO:0072546
EMC complex
|
IDA
PMID:22119785 Defining human ERAD networks through an integrative mapping ... |
ACCEPT |
Summary: Direct experimental identification of EMC4/TMEM85 in the EMC by the foundational ERAD-network mapping study. Core structural identity.
Reason: Core EMC membership; directly demonstrated.
Supporting Evidence:
file:human/EMC4/EMC4-uniprot.txt
Component of the ER membrane protein complex (EMC).
|
Q: What specific structural role does EMC4 play in EMC assembly and stability, and does loss of EMC4 selectively impair insertion of particular client classes (e.g. multipass transporters)?
Q: Does the EMC4-GLUT9 interaction represent a productive client-engagement event during GLUT9 biogenesis, and is GLUT9 surface expression EMC4-dependent?
Experiment: Knock out EMC4 in human cells and perform quantitative membrane proteomics with rescue to define the EMC4-dependent client repertoire and distinguish it from clients tolerant of EMC4 loss.
Experiment: Test EMC4 dependence of GLUT9 and other candidate transporter clients by measuring their folding, ER export and plasma-membrane levels in EMC4-depleted versus rescued cells.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The literature and database evidence retrieved here consistently match the UniProt-provided identity: human EMC4 = βER membrane protein complex subunit 4β, encoded by EMC4 (Ensembl ENSG00000128463), and functioning as a subunit of the ER membrane protein complex (EMC). This aligns with UniProt Q5J8M3 (ER membrane protein complex subunit 4; TMEM85/ PIG17) and with Open Targets target metadata. (OpenTargets Search: -EMC4)
The endoplasmic reticulum membrane protein complex (EMC) is an ER-localized, multi-subunit membrane protein biogenesis factor that acts as a co- and post-translational insertase for certain transmembrane helices (TMDs). Structural and biochemical evidence supports a model in which EMC provides a hydrophilic vestibule within the bilayer to reduce the energetic barrier for insertion of challenging TMDs (e.g., weakly hydrophobic tail-anchors), while also supporting later steps of folding/assembly for complex multipass clients. (pleiner2020structuralbasisfor pages 7-11, pleiner2020structuralbasisfor pages 1-3, odonnell2020thearchitectureof pages 1-2)
A central mechanistic concept is that EMC contains intramembrane cavities/surfaces that engage substrate TMDs and provide an βenergy-independentβ insertion route without nucleotide-binding domains. (odonnell2020thearchitectureof pages 1-2, odonnell2020thearchitectureof pages 2-4)
EMC4 is a membrane-embedded EMC subunit that (i) contributes to the architecture enclosing the insertase vestibule and (ii) participates in EMCβs client-facing surfaces.
A major update from 2023 is that improved cryo-EM maps unambiguously assign three transmembrane domains (TMDs) in human EMC4; EMC4, together with the single TMDs of EMC7 and EMC10, helps enclose the insertase vestibule. (pleiner2023aselectivityfilter pages 4-6)
Mechanistically, EMC4 is not merely a passive scaffold: EMC4 is found at the client-interaction environment (vestibule side) and can be crosslinked to substrates, consistent with a direct role in substrate handling. (pleiner2023aselectivityfilter pages 2-4, pleiner2023aselectivityfilter pages 19-23)
EMC (including EMC4) is localized to the endoplasmic reticulum membrane. This is directly supported by multiple human EMC structural studies performed on purified/reconstituted complexes and by functional assays in cells where EMC supports ER membrane insertion events. (pleiner2020structuralbasisfor pages 7-11, pleiner2020structuralbasisfor pages 1-3, odonnell2020thearchitectureof pages 1-2)
High-resolution cryo-EM defines the EMC as a tripartite assembly with cytosolic, membrane, and lumenal domains. In one foundational structure, the human EMC map was reported at ~3.4 Γ overall resolution, with a prominent intramembrane hydrophilic vestibule formed by the conserved insertase core (EMC3/EMC6). (pleiner2020structuralbasisfor pages 1-3)
EMC4 is positioned adjacent to this insertase core and contributes to the vestibule enclosure:
* Pleiner et al. (J Cell Biol, 2023-05) show that the hydrophilic vestibule is partially enclosed by dynamic TMDs from EMC4/7/10, and that three EMC4 TMDs can be assigned in an improved reconstruction. (pleiner2023aselectivityfilter pages 4-6)
* Li et al. (Aging, 2024-03) likewise describe EMC4 as an ordered three-TMH bundle adjacent to EMC3/EMC6 that forms part of the sidewall of the hydrophilic vestibule, reinforcing EMC4βs direct role in shaping the substrate-binding/insertion environment. (li2024structuralinsightsinto pages 1-3)
The EMC insertase is centered on the EMC3/EMC6 module that provides a hydrophilic vestibule for insertion. (pleiner2020structuralbasisfor pages 1-3, pleiner2023aselectivityfilter pages 4-6)
EMC4 contributes in three experimentally supported ways:
1. Vestibule enclosure and geometry: the vestibule is βpartially enclosedβ by EMC4/7/10 TMDs; EMC4 loss can impair incorporation of EMC7 and EMC10 into EMC, consistent with EMC4βs architectural role. (pleiner2023aselectivityfilter pages 4-6)
2. Direct substrate proximity: in substrate mapping, site-specific photocrosslinking and disulfide crosslinking detect substrate contacts not only with EMC3 but also with EMC4, consistent with EMC4 forming part of the client-facing surface of the vestibule. (pleiner2023aselectivityfilter pages 2-4, pleiner2023aselectivityfilter pages 19-23)
3. Functional requirement for tail-anchored biogenesis: EMC4 is required for biogenesis/insertion of the tail-anchored substrate squalene synthase (SQS/FDFT1) in the Pleiner et al. reporter systems. (pleiner2023aselectivityfilter pages 19-23, pleiner2023aselectivityfilter pages 23-26)
Pleiner et al. (J Cell Biol, 2023-05) propose that the EMC hydrophilic vestibule acts as a selectivity filter that limits misinsertion/mislocalization by using charge-based discrimination.
Key points supported by experiments:
* The vestibule is positively charged and can repel substrates with positively charged soluble domains, helping enforce correct topology (βpositive-insideβ considerations) and preventing inappropriate ER insertion of mitochondrial tail-anchored proteins. (pleiner2023aselectivityfilter pages 6-8, pleiner2023aselectivityfilter pages 8-10)
* This work includes a sequence-scale analysis of 709 human GPCR sequences, and shows that even one added positive charge to an SQS reporter C-terminus can markedly reduce ER integration in cells and in vitro. (pleiner2023aselectivityfilter pages 6-8)
EMC4βs role here is primarily structural (enclosing the vestibule and contributing substrate-facing surfaces), whereas the most explicitly tested selectivity residues in text are on EMC3 (e.g., R31/R180). (pleiner2023aselectivityfilter pages 4-6, pleiner2023aselectivityfilter pages 8-10)
The 2023 J Cell Biol study improved assignment of EMC4 TMDs and provides multiple crosslinking modalities showing substrates can contact EMC4 at the vestibule side. (pleiner2023aselectivityfilter pages 4-6, pleiner2023aselectivityfilter pages 2-4, pleiner2023aselectivityfilter pages 19-23)
Chen et al. (Nature, 2023-05-) determined cryo-EM structures of an EMC-bound assembly intermediate for voltage-gated calcium channel CaV1.2, concluding that EMC functions as a holdase/chaperone during assembly. The EMCβCaV1.2(ΞC)βCaVΞ²3 complex is reported as ~0.6 MDa and solved at 3.4 Γ and 3.3 Γ overall. (chen2023emcchaperoneβcavstructure pages 3-4, chen2023emcchaperoneβcavstructure pages 1-3)
EMC4 is part of EMCβs client-engaging architecture in this system:
* The cytoplasmic chaperone module that engages CaV includes EMC2, EMC3, EMC4, EMC5 and EMC8. (chen2023emcchaperoneβcavstructure pages 3-4)
* A lumenal subassembly comprising EMC1/EMC4/EMC7/EMC10 is implicated in supporting a transmembrane docking region during channel assembly. (chen2023emcchaperoneβcavstructure pages 11-13)
Li et al. (Aging, 2024-03) report cryo-EM structures of human EMC and a VDAC-bound state, suggesting EMC can engage VDAC proteins at mitochondriaβER contact sites and that a βgating plugβ inside the vestibule changes conformation between apo and VDAC-bound conditions. In that analysis, EMC4 forms part of the ordered three-TMH bundle shaping the vestibule sidewall. (li2024structuralinsightsinto pages 1-3)
Li et al. (PNAS, 2024-04) propose that lipid scrambling is a general feature of protein insertases, and report coarse-grained MD evidence localizing EMC scrambling activity specifically to Emc3 and Emc4. They tested >150 proteins/complexes in silico and quantified lipid scrambling with an angular criterion (>125Β° for upper-leaflet lipids; <55Β° for lower-leaflet lipids). (li2024lipidscramblingis pages 3-5, li2024lipidscramblingis pages 7-8)
While this is not yet a definitive demonstration of human EMC4 scramblase activity in cells, it is a mechanistically coherent proposal because the same hydrophilic pathway used for protein insertion could allow lipid flip-flop. (li2024lipidscramblingis pages 3-5)
The best-supported βprimaryβ function for EMC4 is as a structural and mechanistic subunit of the EMC insertase/chaperone machinery that promotes membrane protein biogenesis in the ER by:
* shaping/enclosing the hydrophilic vestibule used for insertion, and
* participating in client engagement surfaces (crosslinking evidence), and
* enabling downstream folding/assembly steps for complex multipass clients (e.g., CaV channels). (pleiner2023aselectivityfilter pages 4-6, pleiner2023aselectivityfilter pages 2-4, chen2023emcchaperoneβcavstructure pages 3-4)
EMC4 is not an enzyme with a known catalytic reaction; rather, it is a membrane biogenesis factor contributing to a proteinaceous insertion/chaperone environment.
Across the retrieved sources, EMC clients include:
* Tail-anchored proteins with weakly hydrophobic TMDs, including SQS/FDFT1 (a canonical EMC-dependent TA in multiple studies). (pleiner2020structuralbasisfor pages 7-11, pleiner2023aselectivityfilter pages 19-23)
* Multipass membrane proteins, enriched for transporters in proteomic datasets, and including ion channels. (shurtleff2018theermembrane pages 8-10, chen2023emcchaperoneβcavstructure pages 3-4)
* Voltage-gated calcium channels: EMC binds an assembly intermediate and supports maturation/functional expression. (chen2023emcchaperoneβcavstructure pages 3-4)
Quantitative proteomics in mammalian cells reported 11 proteins decreased β₯2-fold upon both EMC2 and EMC4 depletion (10/11 with at least one TMD), consistent with an effect on a subset of membrane proteins rather than global translation changes. (shurtleff2018theermembrane pages 8-10)
Multiple viruses exploit ER biogenesis machinery. EMC4 is experimentally validated as a proviral host factor for several viruses:
Flaviviruses (dengue, yellow fever, Zika)
* EMC4 knockout/targeting reduces infectivity and virus production, with effects reported as ~5β20-fold reductions in infectivity (YFV imaging assays) and up to 3 log10 reduced extracellular YFV titers at 33.5 h post infection; for DENV2/DENV4, virus output fell below detection in EMC4 KO lines in the described assays. (barrows2019dualrolesfor pages 3-5)
* EMC4 depletion in a ZIKV replicon context reduced replicon RNA by ~54β55% and EMC4 protein levels by 73% or 94% (two siRNAs), with downstream reductions in multiple viral proteins. (barrows2019dualrolesfor pages 9-10)
* Biochemically, EMC4 is used for co-immunoprecipitation assays in which EMC associates with flavivirus non-structural multipass proteins such as NS4B, consistent with a direct role in viral membrane-protein biogenesis. (lin2019theermembrane pages 13-14)
Polyomavirus SV40 entry
EMC4 and EMC7 promote late endosome-to-ER targeting of SV40 during entry. EMC4 engages Rab7 (late endosome) and syntaxin18 (ER fusion machinery) and is proposed to act as a tether stabilizing LEβER contacts that facilitate viral transport; EMC4-FLAG rescue experiments support specificity. (bagchi2020selectiveemcsubunits pages 1-2)
These findings create a plausible translational directionβtargeting host insertion/trafficking dependenciesβalthough the retrieved evidence does not yet provide a clinically validated EMC4-specific inhibitor or trial.
Structural mechanistic definition of EMC (including EMC4βs vestibule enclosure and CaV chaperone role) informs biotechnological strategies aimed at improving expression/assembly of difficult multipass proteins (e.g., channels and GPCRs) in cell systems by modulating EMC function. (pleiner2023aselectivityfilter pages 4-6, chen2023emcchaperoneβcavstructure pages 3-4)
A recurring expert view is that EMC is built around a deeply conserved insertase core and has additional roles in folding/assembly that extend beyond insertion alone. Structural and mechanistic studies emphasize that distinct EMC regions contribute to different client classes (tail-anchored vs multipass), consistent with EMC being a multifunctional membrane biogenesis machine. (millervedam2020structuralandmechanistic pages 7-10, pleiner2020structuralbasisfor pages 7-11, millervedam2020structuralandmechanistic pages 18-21)
In this context, EMC4 is best interpreted as a βperipheral-but-mechanistically-relevantβ subunit: depletion of EMC4 may leave other EMC subunits largely stable (suggesting it is not the sole assembly scaffold), yet it is required for specific biogenesis functions and contributes to the vestibule/client interface. (shurtleff2018theermembrane pages 8-10, pleiner2023aselectivityfilter pages 4-6)
Direct, well-established monogenic human diseases caused by EMC4 variants were not identified in the retrieved full-text evidence. However, aggregated evidence in Open Targets links EMC4 to multiple disease categories (including neurodegenerative diseases and dengue disease) with modest scores and evidence size = 5 for each shown association; this should be interpreted as hypothesis-generating and often driven by functional genomics screens rather than causal human genetics. (OpenTargets Search: -EMC4)
The following retrieved figure crops from Pleiner et al. (J Cell Biol, 2023) visually support the claim that EMC4βs 3 TMDs enclose the EMC3/6 insertase core hydrophilic vestibule and that EMC10 contributes additional enclosure density. (pleiner2023aselectivityfilter media 2fbee94e, pleiner2023aselectivityfilter media bf0f9cf4, pleiner2023aselectivityfilter media ac5195ae)
| Topic | Key findings | Key quantitative/statistical details | Key sources with publication year and URL | Citation IDs |
|---|---|---|---|---|
| Identity / localization | Human EMC4 is ER membrane protein complex subunit 4, encoded by EMC4 (ENSG00000128463), matching UniProt Q5J8M3. EMC is an ER-localized multi-subunit insertase/chaperone complex required for membrane protein biogenesis. | Human EMC described as 9-subunit; complex dimensions reported at ~200 Γ 70 Γ 100 Γ in one cryo-EM study. | Open Targets EMC4 target entry; Pleiner et al., 2020, Science, https://doi.org/10.1126/science.abb5008; O'Donnell et al., 2020, eLife, https://doi.org/10.7554/elife.57887 | (OpenTargets Search: -EMC4, pleiner2020structuralbasisfor pages 1-3, odonnell2020thearchitectureof pages 1-2) |
| Structure / topology of EMC4 | EMC4 is a membrane subunit adjacent to the EMC3/EMC6 insertase core. Improved human cryo-EM maps assigned 3 EMC4 transmembrane helices, and EMC4 also contributes a C-terminal Ξ²-strand that completes an EMC1 membrane-proximal Ξ²-propeller, indicating structural roles in both the membrane and lumenal domains. | 3 TMDs assigned to EMC4 in 2023 human structure; vestibule partly enclosed by 5 dynamic TMDs from EMC4/7/10. | Pleiner et al., 2023, J Cell Biol, https://doi.org/10.1083/jcb.202212007; Li et al., 2024, Aging (Albany NY), https://doi.org/10.18632/aging.205660; Pleiner et al., 2020, Science, https://doi.org/10.1126/science.abb5008 | (pleiner2023aselectivityfilter pages 4-6, pleiner2023aselectivityfilter pages 2-4, pleiner2023aselectivityfilter pages 19-23, li2024structuralinsightsinto pages 1-3, pleiner2020structuralbasisfor pages 1-3) |
| Insertase mechanism | EMC acts as a co- and post-translational insertase for transmembrane helices, especially weakly hydrophobic tail-anchored TMDs and some multipass membrane proteins. Mechanistically, EMC3/EMC6 form a hydrophilic vestibule that lowers the energetic barrier to membrane insertion, while EMC4 helps shape/enclose this insertion environment. | Cryo-EM resolutions reported at 3.4 Γ overall for human EMC; vestibule includes conserved positive charges and a methionine-rich capture loop; membrane proteins comprise ~20β25% of eukaryotic/human genes according to review/background. | Pleiner et al., 2020, Science, https://doi.org/10.1126/science.abb5008; O'Donnell et al., 2020, eLife, https://doi.org/10.7554/elife.57887; Bai et al., 2020, Nature, https://doi.org/10.1038/s41586-020-2389-3; Hegde, 2022, Annu Rev Biochem, https://doi.org/10.1146/annurev-biochem-032620-104553 | (pleiner2020structuralbasisfor pages 7-11, pleiner2020structuralbasisfor pages 1-3, bai2020structureofthe pages 1-2, odonnell2020thearchitectureof pages 1-2) |
| EMC4 role in vestibule architecture / substrate contacts | EMC4 partially encloses only the hydrophilic vestibule side of EMC, and substrate photocrosslinking/disulfide-crosslinking showed contacts with EMC4 as well as EMC3. EMC4 loss also impairs incorporation of EMC7 and EMC10, indicating EMC4 helps assemble the vestibule-enclosing module. | Disulfide formation interpreted at ~3β5 Γ proximity; crosslinking detected for EMC3 and EMC4; complete EMC4 loss impaired EMC7/EMC10 assembly. | Pleiner et al., 2023, J Cell Biol, https://doi.org/10.1083/jcb.202212007 | (pleiner2023aselectivityfilter pages 4-6, pleiner2023aselectivityfilter pages 2-4, pleiner2023aselectivityfilter pages 19-23) |
| Selectivity filter / topology control | EMC contains a positively charged hydrophilic vestibule that acts as a selectivity filter, repelling substrates with positively charged soluble domains and limiting misinsertion of mitochondrial TA proteins while helping enforce correct topology of multipass substrates. EMC4 contributes the sidewall/enclosure of this vestibule rather than the key charged residues themselves. | Analysis included 709 human GPCR sequences; even a single added positive charge to an SQS reporter strongly reduced ER insertion; electrostatic potential mapped from β3 to +3 kT/e; EMC3 R31/R180 mutants altered selectivity. | Pleiner et al., 2023, J Cell Biol, https://doi.org/10.1083/jcb.202212007 | (pleiner2023aselectivityfilter pages 4-6, pleiner2023aselectivityfilter pages 6-8, pleiner2023aselectivityfilter pages 8-10) |
| Chaperone / assembly role for multipass proteins | Beyond insertase activity, EMC also functions as a holdase/chaperone for complex multipass clients. In the CaV1.2 assembly intermediate, EMC4 participates in the EMC client-binding/chaperone architecture and in the lumenal EMC1/4/7/10 module that supports a transmembrane docking site during channel assembly. | EMCβCaV1.2(ΞC)βCaVΞ²3 complex mass ~0.6 MDa; cryo-EM maps at 3.4 Γ and 3.3 Γ ; Cyto dock ~1,500 Γ Β² with EMC8 site 962 Γ Β² and EMC2 site 550 Γ Β². | Chen et al., 2023, Nature, https://doi.org/10.1038/s41586-023-06175-5; Miller-Vedam et al., 2020, eLife, https://doi.org/10.1101/2020.09.02.280008 | (chen2023emcchaperoneβcavstructure pages 11-13, chen2023emcchaperoneβcavstructure pages 3-4, chen2023emcchaperoneβcavstructure pages 1-3, millervedam2020structuralandmechanistic pages 18-21) |
| Peripheral versus structural-essential subunit behavior | EMC4 is not as globally assembly-critical as EMC2, but it is not merely dispensable: EMC4 depletion leaves many other EMC subunits stable, yet phenocopies client defects and contributes directly to insertion/chaperone functions. Reviews and knockdown studies therefore place EMC4 among more peripheral subunits with specific mechanistic importance. | In one proteomic study, 11 proteins decreased β₯2-fold in both EMC2- and EMC4-depleted cells, and 10/11 had at least one TMD; EMC4 knockdown had no effect on abundance of other EMC members in that dataset. | Shurtleff et al., 2018, eLife, https://doi.org/10.7554/elife.37018; Chitwood & Hegde, 2019, Trends Cell Biol, https://doi.org/10.1016/j.tcb.2019.01.007 | (shurtleff2018theermembrane pages 8-10, chitwood2019theroleof pages 2-4) |
| Client/substrate classes and pathways | EMC/EMC4 support biogenesis of tail-anchored proteins (e.g., SQS/FDFT1), sterol-related enzymes, GPCRs, ion channels, and diverse multipass transporters/secretory membrane proteins. EMC-dependent biology therefore connects EMC4 to membrane protein proteostasis, sterol/cholesterol homeostasis, and ER quality-control pathways. | Yeast TMT proteomics identified 38 likely EMC clients; mammalian depletion studies found 11 proteins reduced β₯2-fold in both EMC2 and EMC4 knockdown backgrounds. | Bai et al., 2020, Nature, https://doi.org/10.1038/s41586-020-2389-3; Volkmar et al., 2019, J Cell Sci, https://doi.org/10.1242/jcs.223453; Shurtleff et al., 2018, eLife, https://doi.org/10.7554/elife.37018 | (bai2020structureofthe pages 1-2, shurtleff2018theermembrane pages 8-10) |
| Lipid scrambling hypothesis | Recent computational/biophysical work suggests lipid scrambling may be a general property of insertases and localizes EMC scrambling activity specifically to Emc3 and Emc4 in silico. This supports a model in which EMC4 helps create a hydrophilic pathway used for both protein insertion and lipid flip-flop. | >150 proteins/complexes tested in silico; scrambling criterion used lipid angle >125Β° (upper leaflet) or <55Β° (lower leaflet); BSA back-extraction assay typically reduced NBD fluorescence by ~50% (practically 35β45%). | Li et al., 2024, PNAS, https://doi.org/10.1073/pnas.2319476121 | (li2024lipidscramblingis pages 3-5, li2024lipidscramblingis pages 7-8, li2024lipidscramblingis pages 2-3) |
| Viral host-factor role: flaviviruses | EMC4 is a validated proviral host factor for dengue, yellow fever, and Zika viruses. EMC4 supports infection at least at two stages: an early step at or before uncoating and a later step in viral membrane-protein biogenesis, including NS4B-associated processes. | EMC4-targeting sgRNAs reduced YFV infectivity ~5β20-fold; EMC4 KO caused up to 3 log10 lower YFV titers by 33.5 hpi; DENV2/DENV4 production fell below detection; anti-EMC4 siRNAs reduced ZIKV replicon RNA by ~54β55% with 73% or 94% EMC4 knockdown. | Barrows et al., 2019, Sci Rep, https://doi.org/10.1038/s41598-019-45910-9; Lin et al., 2019, Cell Reports, https://doi.org/10.1016/j.celrep.2019.04.051; Verhaegen & Vermeire, 2024, npj Viruses, https://doi.org/10.1038/s44298-024-00031-7 | (barrows2019dualrolesfor pages 3-5, lin2019theermembrane pages 13-14, barrows2019dualrolesfor pages 1-2, barrows2019dualrolesfor pages 9-10) |
| Viral host-factor role: SV40 / organelle tethering | EMC4 also has a more selective EMC-independent or EMC-submodule-like role in SV40 entry, where EMC4 and EMC7 promote late endosome-to-ER transport. EMC4 engages Rab7 and syntaxin18 and was proposed to act as a molecular tether stabilizing LEβER contacts needed for viral trafficking. | EMC4 knockdown blocked SV40 infection; siRNA-resistant EMC4-FLAG fully rescued infection in the reported assays. | Bagchi et al., 2020, Nat Commun, https://doi.org/10.1038/s41467-020-14967-w | (bagchi2020selectiveemcsubunits pages 1-2) |
| Disease / phenotype associations | Direct monogenic human disease attribution for EMC4 itself remains limited in the retrieved evidence, but EMC4 is linked through EMC biology to neurodegeneration-related screening signals, lysosomal storage disease, Alzheimer disease, Parkinson disease, and dengue disease in Open Targets evidence aggregation. Expert reviews emphasize broader EMC involvement in membrane-protein folding diseases and cholesterol-homeostasis phenotypes rather than EMC4-specific clinical syndromes. | Open Targets evidence sizes shown as 5 for the listed EMC4 disease associations; no clinical trials were retrieved. | Open Targets EMC4 associations; Hegde, 2022, Annu Rev Biochem, https://doi.org/10.1146/annurev-biochem-032620-104553; Volkmar et al., 2019, J Cell Sci, https://doi.org/10.1242/jcs.223453 | (OpenTargets Search: -EMC4, chitwood2019theroleof pages 2-4) |
Table: This table summarizes the main experimentally supported roles of human EMC4 within the ER membrane protein complex, including structure, mechanism, client classes, and disease-relevant phenotypes. It is useful as a compact evidence map linking EMC4-specific findings to broader EMC biology.
References
(OpenTargets Search: -EMC4): Open Targets Query (-EMC4, 5 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(pleiner2020structuralbasisfor pages 7-11): Tino Pleiner, Giovani Pinton Tomaleri, Kurt Januszyk, Alison J. Inglis, Masami Hazu, and Rebecca M. Voorhees. Structural basis for membrane insertion by the human er membrane protein complex. Jul 2020. URL: https://doi.org/10.1126/science.abb5008, doi:10.1126/science.abb5008. This article has 192 citations and is from a highest quality peer-reviewed journal.
(pleiner2020structuralbasisfor pages 1-3): Tino Pleiner, Giovani Pinton Tomaleri, Kurt Januszyk, Alison J. Inglis, Masami Hazu, and Rebecca M. Voorhees. Structural basis for membrane insertion by the human er membrane protein complex. Jul 2020. URL: https://doi.org/10.1126/science.abb5008, doi:10.1126/science.abb5008. This article has 192 citations and is from a highest quality peer-reviewed journal.
(odonnell2020thearchitectureof pages 1-2): John P O'Donnell, Ben P Phillips, Yuichi Yagita, Szymon Juszkiewicz, Armin Wagner, Duccio Malinverni, Robert J Keenan, Elizabeth A Miller, and Ramanujan S Hegde. The architecture of emc reveals a path for membrane protein insertion. May 2020. URL: https://doi.org/10.7554/elife.57887, doi:10.7554/elife.57887. This article has 121 citations and is from a domain leading peer-reviewed journal.
(odonnell2020thearchitectureof pages 2-4): John P O'Donnell, Ben P Phillips, Yuichi Yagita, Szymon Juszkiewicz, Armin Wagner, Duccio Malinverni, Robert J Keenan, Elizabeth A Miller, and Ramanujan S Hegde. The architecture of emc reveals a path for membrane protein insertion. May 2020. URL: https://doi.org/10.7554/elife.57887, doi:10.7554/elife.57887. This article has 121 citations and is from a domain leading peer-reviewed journal.
(pleiner2023aselectivityfilter pages 4-6): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(pleiner2023aselectivityfilter pages 2-4): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(pleiner2023aselectivityfilter pages 19-23): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(li2024structuralinsightsinto pages 1-3): Mingyue Li, Chunli Zhang, Yuntao Xu, Shaobai Li, Chenhui Huang, Jian Wu, and Ming Lei. Structural insights into human emc and its interaction with vdac. Aging (Albany NY), 16:5501-5525, Mar 2024. URL: https://doi.org/10.18632/aging.205660, doi:10.18632/aging.205660. This article has 6 citations.
(pleiner2023aselectivityfilter pages 23-26): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(pleiner2023aselectivityfilter pages 6-8): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(pleiner2023aselectivityfilter pages 8-10): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(chen2023emcchaperoneβcavstructure pages 3-4): Zhou Chen, Abhisek Mondal, Fayal Abderemane-Ali, Seil Jang, Sangeeta Niranjan, JosΓ© L. MontaΓ±o, Balyn W. Zaro, and Daniel L. Minor. Emc chaperoneβcav structure reveals an ion channel assembly intermediate. Nature, 619:410-419, May 2023. URL: https://doi.org/10.1038/s41586-023-06175-5, doi:10.1038/s41586-023-06175-5. This article has 77 citations and is from a highest quality peer-reviewed journal.
(chen2023emcchaperoneβcavstructure pages 1-3): Zhou Chen, Abhisek Mondal, Fayal Abderemane-Ali, Seil Jang, Sangeeta Niranjan, JosΓ© L. MontaΓ±o, Balyn W. Zaro, and Daniel L. Minor. Emc chaperoneβcav structure reveals an ion channel assembly intermediate. Nature, 619:410-419, May 2023. URL: https://doi.org/10.1038/s41586-023-06175-5, doi:10.1038/s41586-023-06175-5. This article has 77 citations and is from a highest quality peer-reviewed journal.
(chen2023emcchaperoneβcavstructure pages 11-13): Zhou Chen, Abhisek Mondal, Fayal Abderemane-Ali, Seil Jang, Sangeeta Niranjan, JosΓ© L. MontaΓ±o, Balyn W. Zaro, and Daniel L. Minor. Emc chaperoneβcav structure reveals an ion channel assembly intermediate. Nature, 619:410-419, May 2023. URL: https://doi.org/10.1038/s41586-023-06175-5, doi:10.1038/s41586-023-06175-5. This article has 77 citations and is from a highest quality peer-reviewed journal.
(li2024lipidscramblingis pages 3-5): Dazhi Li, Cristian Rocha-Roa, Matthew A. Schilling, Karin M. Reinisch, and Stefano Vanni. Lipid scrambling is a general feature of protein insertases. Proceedings of the National Academy of Sciences of the United States of America, Apr 2024. URL: https://doi.org/10.1073/pnas.2319476121, doi:10.1073/pnas.2319476121. This article has 70 citations and is from a highest quality peer-reviewed journal.
(li2024lipidscramblingis pages 7-8): Dazhi Li, Cristian Rocha-Roa, Matthew A. Schilling, Karin M. Reinisch, and Stefano Vanni. Lipid scrambling is a general feature of protein insertases. Proceedings of the National Academy of Sciences of the United States of America, Apr 2024. URL: https://doi.org/10.1073/pnas.2319476121, doi:10.1073/pnas.2319476121. This article has 70 citations and is from a highest quality peer-reviewed journal.
(shurtleff2018theermembrane pages 8-10): Matthew J Shurtleff, Daniel N Itzhak, Jeffrey A Hussmann, Nicole T Schirle Oakdale, Elizabeth A Costa, Martin Jonikas, Jimena Weibezahn, Katerina D Popova, Calvin H Jan, Pavel Sinitcyn, Shruthi S Vembar, Hilda Hernandez, JΓΌrgen Cox, Alma L Burlingame, Jeffrey L Brodsky, Adam Frost, Georg HH Borner, and Jonathan S Weissman. The er membrane protein complex interacts cotranslationally to enable biogenesis of multipass membrane proteins. eLife, May 2018. URL: https://doi.org/10.7554/elife.37018, doi:10.7554/elife.37018. This article has 257 citations and is from a domain leading peer-reviewed journal.
(barrows2019dualrolesfor pages 3-5): Nicholas J. Barrows, Yesseinia Anglero-Rodriguez, Byungil Kim, Sharon F. Jamison, Caroline Le Sommer, Charles E. McGee, James L. Pearson, George Dimopoulos, Manuel Ascano, Shelton S. Bradrick, and Mariano A. Garcia-Blanco. Dual roles for the er membrane protein complex in flavivirus infection: viral entry and protein biogenesis. Scientific Reports, Jul 2019. URL: https://doi.org/10.1038/s41598-019-45910-9, doi:10.1038/s41598-019-45910-9. This article has 62 citations and is from a peer-reviewed journal.
(barrows2019dualrolesfor pages 9-10): Nicholas J. Barrows, Yesseinia Anglero-Rodriguez, Byungil Kim, Sharon F. Jamison, Caroline Le Sommer, Charles E. McGee, James L. Pearson, George Dimopoulos, Manuel Ascano, Shelton S. Bradrick, and Mariano A. Garcia-Blanco. Dual roles for the er membrane protein complex in flavivirus infection: viral entry and protein biogenesis. Scientific Reports, Jul 2019. URL: https://doi.org/10.1038/s41598-019-45910-9, doi:10.1038/s41598-019-45910-9. This article has 62 citations and is from a peer-reviewed journal.
(lin2019theermembrane pages 13-14): David L. Lin, Takamasa Inoue, Yu-Jie Chen, Aaron Chang, Billy Tsai, and Andrew W. Tai. The er membrane protein complex promotes biogenesis of dengue and zika virus non-structural multi-pass transmembrane proteins to support infection. Cell reports, 27:1666-1674.e4, May 2019. URL: https://doi.org/10.1016/j.celrep.2019.04.051, doi:10.1016/j.celrep.2019.04.051. This article has 115 citations and is from a highest quality peer-reviewed journal.
(bagchi2020selectiveemcsubunits pages 1-2): Parikshit Bagchi, Mauricio Torres, Ling Qi, and Billy Tsai. Selective emc subunits act as molecular tethers of intracellular organelles exploited during viral entry. Nature Communications, Feb 2020. URL: https://doi.org/10.1038/s41467-020-14967-w, doi:10.1038/s41467-020-14967-w. This article has 31 citations and is from a highest quality peer-reviewed journal.
(millervedam2020structuralandmechanistic pages 7-10): Lakshmi E. Miller-Vedam, Bastian BrΓ€uning, Katerina D. Popova, Nicole T. Schirle Oakdale, Jessica L. Bonnar, Jesuraj Rajan Prabu, Elizabeth A. Boydston, Natalia Sevillano, Matthew J. Shurtleff, Robert M. Stroud, Charles S. Craik, Brenda A. Schulman, Adam Frost, and Jonathan S. Weissman. Structural and mechanistic basis of the emc-dependent biogenesis of distinct transmembrane clients. eLife, Sep 2020. URL: https://doi.org/10.1101/2020.09.02.280008, doi:10.1101/2020.09.02.280008. This article has 102 citations and is from a domain leading peer-reviewed journal.
(millervedam2020structuralandmechanistic pages 18-21): Lakshmi E. Miller-Vedam, Bastian BrΓ€uning, Katerina D. Popova, Nicole T. Schirle Oakdale, Jessica L. Bonnar, Jesuraj Rajan Prabu, Elizabeth A. Boydston, Natalia Sevillano, Matthew J. Shurtleff, Robert M. Stroud, Charles S. Craik, Brenda A. Schulman, Adam Frost, and Jonathan S. Weissman. Structural and mechanistic basis of the emc-dependent biogenesis of distinct transmembrane clients. eLife, Sep 2020. URL: https://doi.org/10.1101/2020.09.02.280008, doi:10.1101/2020.09.02.280008. This article has 102 citations and is from a domain leading peer-reviewed journal.
(pleiner2023aselectivityfilter media 2fbee94e): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(pleiner2023aselectivityfilter media bf0f9cf4): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(pleiner2023aselectivityfilter media ac5195ae): Tino Pleiner, Masami Hazu, Giovani Pinton Tomaleri, Vy N. Nguyen, Kurt Januszyk, and Rebecca M. Voorhees. A selectivity filter in the er membrane protein complex limits protein misinsertion at the er. The Journal of Cell Biology, May 2023. URL: https://doi.org/10.1083/jcb.202212007, doi:10.1083/jcb.202212007. This article has 28 citations.
(bai2020structureofthe pages 1-2): Lin Bai, Qinglong You, Xiang Feng, Amanda Kovach, and Huilin Li. Structure of the er membrane complex, a transmembrane-domain insertase. Jun 2020. URL: https://doi.org/10.1038/s41586-020-2389-3, doi:10.1038/s41586-020-2389-3. This article has 164 citations and is from a highest quality peer-reviewed journal.
(chitwood2019theroleof pages 2-4): Patrick J. Chitwood and Ramanujan S. Hegde. The role of emc during membrane protein biogenesis. Trends in cell biology, 29 5:371-384, May 2019. URL: https://doi.org/10.1016/j.tcb.2019.01.007, doi:10.1016/j.tcb.2019.01.007. This article has 97 citations and is from a domain leading peer-reviewed journal.
(li2024lipidscramblingis pages 2-3): Dazhi Li, Cristian Rocha-Roa, Matthew A. Schilling, Karin M. Reinisch, and Stefano Vanni. Lipid scrambling is a general feature of protein insertases. Proceedings of the National Academy of Sciences of the United States of America, Apr 2024. URL: https://doi.org/10.1073/pnas.2319476121, doi:10.1073/pnas.2319476121. This article has 70 citations and is from a highest quality peer-reviewed journal.
(barrows2019dualrolesfor pages 1-2): Nicholas J. Barrows, Yesseinia Anglero-Rodriguez, Byungil Kim, Sharon F. Jamison, Caroline Le Sommer, Charles E. McGee, James L. Pearson, George Dimopoulos, Manuel Ascano, Shelton S. Bradrick, and Mariano A. Garcia-Blanco. Dual roles for the er membrane protein complex in flavivirus infection: viral entry and protein biogenesis. Scientific Reports, Jul 2019. URL: https://doi.org/10.1038/s41598-019-45910-9, doi:10.1038/s41598-019-45910-9. This article has 62 citations and is from a peer-reviewed journal.
UniProt: Q5J8M3 (EMC4_HUMAN). 183 aa. Synonyms TMEM85, PIG17, HSPC184. Gene on chr15.
contributes_to qualifier (it contributes to complex insertase activity, not standalone).contributes_to: ACCEPT (complex-level catalytic contribution, scaffold framing), not standalone core MF for EMC4.New EMC4-relevant references verified against PubMed and added to the review (all additive; no action changes):
ER proteostasis | Protein transport | Transmembrane protein import | EMC complex component; PN-node mapping: type=mapped/ok_for_propagation β GO:0072546 EMC complex (already_in_goa_exact); groupβGO:0044743, classβGO:0015031 (new_to_goa); branch=no_mapping.This file is generated from the current PROTEOSTASIS phase-1 dossier and local gene-review artifacts. Edit the source review, PN mapping, or dossier rather than this generated note when correcting the underlying curation.
id: Q5J8M3
gene_symbol: EMC4
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: EMC4 (ER membrane protein complex subunit 4; also TMEM85) is a small (~183-residue, ~20 kDa) polytopic ER membrane protein and a constitutive structural subunit of the ER membrane protein complex (EMC), a conserved nine- to ten-subunit transmembrane-domain insertase and membrane-protein chaperone of the endoplasmic reticulum. Cryo-EM structures resolve EMC4 with a cytoplasmic N-terminus, transmembrane segments, and a lumenal C-terminus, packing against the other membrane subunits to help form and stabilize the complex. EMC4 is not part of the catalytic insertase core, which is formed by the EMC3 and EMC6 subunits that build the membrane-embedded hydrophilic substrate vestibule; instead EMC4 is an accessory/scaffold subunit. As part of the EMC it contributes to the energy-independent insertion of newly synthesized membrane proteins into the ER membrane, with a preference for transmembrane domains that are weakly hydrophobic or carry destabilizing charged or aromatic residues. The complex mediates post-translational insertion of tail-anchored proteins and cotranslational insertion and N-exo topogenesis of multipass membrane proteins, including transporters and G protein-coupled receptors, in cooperation with the Sec61 translocon. EMC4 is broadly expressed and resides in the ER membrane.
alternative_products:
- name: 1 (TMEM85v1)
id: Q5J8M3-1
- name: 2 (TMEM85v2)
id: Q5J8M3-2
sequence_note: VSP_020798, VSP_020799
- name: '3'
id: Q5J8M3-3
sequence_note: VSP_037374, VSP_037375
existing_annotations:
- term:
id: GO:0072546
label: EMC complex
evidence_type: IBA
original_reference_id: GO_REF:0000033
qualifier: part_of
review:
summary: Phylogenetic (PAN-GO) assignment of EMC complex membership across the EMC4 family, matching direct experimental and structural evidence. Core structural identity of EMC4.
action: ACCEPT
reason: EMC complex membership is the core cellular-component identity of EMC4 and is supported by IDA, cryo-EM structures, and the conserved EMC4 family.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: Component of the ER membrane protein complex (EMC).
- term:
id: GO:0005789
label: endoplasmic reticulum membrane
evidence_type: IEA
original_reference_id: GO_REF:0000044
qualifier: located_in
review:
summary: Electronic transfer of the ER membrane subcellular location from UniProt; the correct and core compartment for the multipass ER membrane subunit EMC4.
action: ACCEPT
reason: Correct core location; redundant with experimental EXP/IDA evidence.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:31695625
qualifier: enables
review:
summary: IntAct interaction of EMC4/TMEM85 with the multipass urate transporter GLUT9/SLC2A9 (Q9NRM0). In the functional assay TMEM85 (unlike ITM2B) did not affect GLUT9-mediated urate uptake; the interaction most plausibly reflects EMC4 engaging GLUT9 as an EMC client (consistent with the EMC's transporter-client preference). Bare protein binding is uninformative.
action: KEEP_AS_NON_CORE
reason: Plausible EMC-client (transporter) interaction, but bare protein binding is uninformative per curation guidelines and the functional assay showed no role of TMEM85 in urate transport itself; not elevated to core.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'Q5J8M3; Q9NRM0-1: SLC2A9'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:33845483
qualifier: enables
review:
summary: High-throughput SARS-CoV-2/SARS-CoV proteomics interactome capturing EMC4 with the viral replicase polyprotein (P0DTD1, rep). Bare protein binding is uninformative and the partner is a viral xenobiotic protein unrelated to EMC4's core function.
action: KEEP_AS_NON_CORE
reason: Real virus-host interactome capture but bare protein binding is uninformative; the viral partner does not inform EMC4's core ER insertase scaffolding role.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'Q5J8M3; PRO_0000449624 [P0DTD1]: rep'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:34232536
qualifier: enables
review:
summary: Comparative coronavirus interactome screen capturing the EMC4-viral replicase (P0DTD1, rep) interaction. Bare protein binding is uninformative and the partner is a viral protein.
action: KEEP_AS_NON_CORE
reason: Real virus-host interactome capture; bare protein binding is uninformative and the viral partner is not part of EMC4's core function.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'Q5J8M3; PRO_0000449624 [P0DTD1]: rep'
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:36217030
qualifier: enables
review:
summary: Comprehensive SARS-CoV-2-human interactome capturing the EMC4-viral replicase (P0DTD1, rep) interaction. Bare protein binding is uninformative and the partner is a viral protein.
action: KEEP_AS_NON_CORE
reason: Real virus-host interactome capture; bare protein binding is uninformative and the viral partner does not reflect EMC4's core insertase scaffolding role.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'Q5J8M3; PRO_0000449624 [P0DTD1]: rep'
- term:
id: GO:0005789
label: endoplasmic reticulum membrane
evidence_type: NAS
original_reference_id: PMID:29242231
qualifier: located_in
review:
summary: ComplexPortal NAS annotation of ER membrane localization for the EMC, consistent with the experimental evidence and core compartment of EMC4.
action: ACCEPT
reason: Correct core location; consistent with EXP/IDA evidence.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
id: GO:0045050
label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
evidence_type: IDA
original_reference_id: PMID:29242231
qualifier: involved_in
review:
summary: The EMC inserts transmembrane domains, including stop-transfer membrane-anchor sequences of multipass clients; EMC4 is a constitutive subunit. Core complex-level process.
action: ACCEPT
reason: Core EMC-mediated process; the EMC is a demonstrated transmembrane-domain insertase and EMC4 is a structural subunit.
supported_by:
- reference_id: PMID:29242231
supporting_text: transmembrane domain insertase
- term:
id: GO:0071816
label: tail-anchored membrane protein insertion into ER membrane
evidence_type: IDA
original_reference_id: PMID:29242231
qualifier: involved_in
review:
summary: The EMC mediates post-translational insertion of tail-anchored proteins with moderately hydrophobic TMDs, demonstrated directly in this study; EMC4 is a constitutive subunit. Core complex-level process.
action: ACCEPT
reason: Core EMC-mediated process; directly demonstrated for the complex.
supported_by:
- reference_id: PMID:29242231
supporting_text: tail-anchored membrane proteins with moderately hydrophobic transmembrane
- term:
id: GO:0072546
label: EMC complex
evidence_type: IPI
original_reference_id: PMID:32439656
qualifier: part_of
review:
summary: ComplexPortal IPI assignment of EMC complex membership based on the cryo-EM structure of the human EMC, which resolves EMC4 as a membrane subunit. Core structural identity.
action: ACCEPT
reason: Structurally demonstrated core EMC membership.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: Component of the ER membrane protein complex (EMC).
- term:
id: GO:0005789
label: endoplasmic reticulum membrane
evidence_type: EXP
original_reference_id: PMID:22119785
qualifier: located_in
review:
summary: Experimental ER membrane localization from the foundational ERAD-network mapping study that first identified the EMC (TMEM85). Core compartment.
action: ACCEPT
reason: Experimentally supported core location.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
id: GO:0032977
label: membrane insertase activity
evidence_type: IMP
original_reference_id: PMID:29809151
qualifier: contributes_to
review:
summary: IMP evidence (cotranslational multipass biogenesis study) that the EMC has membrane insertase activity, to which EMC4 contributes as a structural subunit. The contributes_to qualifier is appropriate because EMC4 is not catalytic (the vestibule is EMC3/EMC6).
action: ACCEPT
reason: Complex-level MF correctly qualified contributes_to; EMC4 supports the insertase activity of the EMC as an accessory membrane subunit but is not itself catalytic.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: enables the energy-independent insertion into endoplasmic
- term:
id: GO:0032977
label: membrane insertase activity
evidence_type: IMP
original_reference_id: PMID:30415835
qualifier: contributes_to
review:
summary: IMP evidence (topogenesis study) supporting the EMC's membrane insertase activity, to which EMC4 contributes as a structural subunit. contributes_to correctly reflects that EMC4 is non-catalytic.
action: ACCEPT
reason: Complex-level MF correctly qualified contributes_to; EMC4 supports the insertase activity of the EMC.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: enables the energy-independent insertion into endoplasmic
- term:
id: GO:0045050
label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
evidence_type: IMP
original_reference_id: PMID:29809151
qualifier: involved_in
review:
summary: The EMC is required for cotranslational insertion of multipass proteins in which stop-transfer membrane-anchor sequences become membrane-spanning helices; EMC4 is a constitutive subunit. Core EMC process.
action: ACCEPT
reason: Core EMC-mediated process; supported by IMP of EMC subunits.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: stop-transfer membrane-anchor sequences become ER membrane spanning
- term:
id: GO:0005789
label: endoplasmic reticulum membrane
evidence_type: IDA
original_reference_id: PMID:32439656
qualifier: located_in
review:
summary: Direct (cryo-EM structural) evidence placing EMC4 in the ER membrane as a membrane subunit of the EMC. Core compartment.
action: ACCEPT
reason: Experimentally supported core location.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
id: GO:0045050
label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
evidence_type: IMP
original_reference_id: PMID:30415835
qualifier: involved_in
review:
summary: IMP evidence (topogenesis study) that the EMC inserts stop-transfer membrane-anchor sequences and sets the N-exo topology of multipass clients such as GPCRs; EMC4 is part of the insertase complex. Core EMC process.
action: ACCEPT
reason: Core EMC-mediated process.
supported_by:
- reference_id: PMID:30415835
supporting_text: G protein-coupled receptors
- term:
id: GO:0016020
label: membrane
evidence_type: IDA
original_reference_id: PMID:22119785
qualifier: located_in
review:
summary: Direct generic membrane localization from the EMC-discovery study; a parent of the specific ER membrane term.
action: KEEP_AS_NON_CORE
reason: Correct but generic; the ER membrane term captures the informative localization.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
id: GO:0072546
label: EMC complex
evidence_type: IDA
original_reference_id: PMID:22119785
qualifier: part_of
review:
summary: Direct experimental identification of EMC4/TMEM85 in the EMC by the foundational ERAD-network mapping study. Core structural identity.
action: ACCEPT
reason: Core EMC membership; directly demonstrated.
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: Component of the ER membrane protein complex (EMC).
core_functions:
- description: Constitutive accessory/structural membrane subunit of the ER membrane protein complex (EMC); packs against the other membrane subunits to help form and stabilize the complex and contributes to its energy-independent membrane insertase activity, while the catalytic vestibule is formed by EMC3 and EMC6.
molecular_function:
id: GO:0032977
label: membrane insertase activity
in_complex:
id: GO:0072546
label: EMC complex
locations:
- id: GO:0005789
label: endoplasmic reticulum membrane
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: Component of the ER membrane protein complex (EMC).
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: enables the energy-independent insertion into endoplasmic
- reference_id: PMID:37199759
supporting_text: EMC4 is resolved as a three-TMD subunit that, with EMC7/EMC10, partially encloses the hydrophilic insertase vestibule and contacts substrates at the client-facing surface.
full_text_unavailable: true
- reference_id: PMID:38517390
supporting_text: EMC4 forms an ordered three-TMH bundle adjacent to the EMC3/EMC6 core, constituting a sidewall of the hydrophilic vestibule.
full_text_unavailable: true
- description: As part of the EMC, contributes to post-translational insertion of tail-anchored proteins and cotranslational insertion and N-exo topogenesis of multipass membrane proteins (including transporters and GPCRs) at the ER membrane.
molecular_function:
id: GO:0032977
label: membrane insertase activity
locations:
- id: GO:0005789
label: endoplasmic reticulum membrane
supported_by:
- reference_id: file:human/EMC4/EMC4-uniprot.txt
supporting_text: post-translational insertion of tail-anchored/TA proteins in
- reference_id: PMID:37196677
supporting_text: EMC4 participates in the client-engaging cytoplasmic chaperone module and lumenal EMC1/EMC4/EMC7/EMC10 subassembly during assembly of the multipass CaV1.2 channel.
full_text_unavailable: true
directly_involved_in:
- id: GO:0071816
label: tail-anchored membrane protein insertion into ER membrane
- id: GO:0045050
label: protein insertion into ER membrane by stop-transfer membrane-anchor sequence
proposed_new_terms: []
references:
- id: PMID:32459176
title: The architecture of EMC reveals a path for membrane protein insertion.
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: 'O''Donnell et al. 2020 (eLife). Cryo-EM architecture of the human EMC,
establishing the overall complex organization and subunit topology relevant to
EMC4 as a constitutive EMC subunit.'
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
findings: []
- id: PMID:22119785
title: Defining human ERAD networks through an integrative mapping strategy.
findings:
- statement: Affinity-MS ERAD-network mapping that first identified the EMC (including TMEM85/EMC4) in human cells and localized it to the ER membrane.
reference_section_type: ABSTRACT
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: Foundational identification of the human EMC; source of EMC complex membership and ER membrane localization for EMC4.
- id: PMID:29242231
title: The ER membrane protein complex is a transmembrane domain insertase.
findings:
- statement: EMC is a transmembrane domain insertase that post-translationally inserts tail-anchored membrane proteins with moderately hydrophobic TMDs.
reference_section_type: ABSTRACT
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: Establishes the insertase function of the EMC; basis for the insertion BP/MF annotations.
- id: PMID:29809151
title: The ER membrane protein complex interacts cotranslationally to enable biogenesis of multipass membrane proteins.
findings:
- statement: The EMC engages multipass membrane protein clients cotranslationally, with a particular enrichment for transporters, to enable their biogenesis.
reference_section_type: ABSTRACT
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: Cotranslational multipass biogenesis role of the EMC (transporter clients); basis for the IMP MF/BP annotations.
- id: PMID:30415835
title: EMC Is Required to Initiate Accurate Membrane Protein Topogenesis.
findings:
- statement: The EMC sets the N-exo topology of the first TMD of GPCRs and other multipass proteins, initiating accurate topogenesis in cooperation with Sec61.
reference_section_type: ABSTRACT
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: Topogenesis/orientation role of the EMC; GPCR clients; basis for IMP MF/BP annotations.
- id: PMID:31695625
title: Interaction Between ITM2B and GLUT9 Links Urate Transport to Neurodegenerative Disorders.
findings:
- statement: TMEM85/EMC4 interacts with GLUT9/SLC2A9, but ITM2B (not TMEM85) inhibited GLUT9-mediated urate uptake.
reference_section_type: ABSTRACT
reference_review:
relevance: LOW
correctness: VERIFIED
review_notes: Source of the EMC4-GLUT9 IPI; the GLUT9 interaction most plausibly reflects EMC4 engaging a multipass transporter client, but TMEM85 itself did not affect urate transport.
- id: PMID:32439656
title: Structural basis for membrane insertion by the human ER membrane protein complex.
findings:
- statement: Cryo-EM structure of the human EMC; substrate insertion occurs via an enclosed hydrophilic vestibule formed by EMC3 and EMC6, with EMC4 resolved as a membrane subunit of the complex.
reference_section_type: ABSTRACT
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: Structural basis for the EMC; confirms EMC4 as a (non-catalytic) membrane subunit. Abstract-only in cache.
- id: PMID:33845483
title: Multilevel proteomics reveals host perturbations by SARS-CoV-2 and SARS-CoV.
findings: []
reference_review:
relevance: LOW
correctness: VERIFIED
review_notes: High-throughput virus-host proteomics; source of an IPI protein-binding annotation with the viral replicase (P0DTD1).
- id: PMID:34232536
title: Interactomes of SARS-CoV-2 and human coronaviruses reveal host factors potentially affecting pathogenesis.
findings: []
reference_review:
relevance: LOW
correctness: VERIFIED
review_notes: Comparative coronavirus interactome; source of an IPI protein-binding annotation with the viral replicase (P0DTD1).
- id: PMID:36217030
title: A comprehensive SARS-CoV-2-human protein-protein interactome reveals COVID-19 pathobiology and potential host therapeutic targets.
findings: []
reference_review:
relevance: LOW
correctness: VERIFIED
review_notes: Comprehensive SARS-CoV-2-human interactome; source of an IPI protein-binding annotation with the viral replicase (P0DTD1).
- id: PMID:37199759
title: A selectivity filter in the ER membrane protein complex limits protein misinsertion at the ER.
findings:
- statement: Improved cryo-EM model of human EMC assigns three transmembrane domains to EMC4; EMC4/EMC7/EMC10 TMDs partially enclose the hydrophilic insertase vestibule, and substrate photocrosslinking/disulfide crosslinking detects contacts with EMC4 as well as EMC3.
reference_section_type: RESULTS
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: PubMed-verified (J Cell Biol 2023). Recent structural/mechanistic study that resolves EMC4 as a three-TMD vestibule-enclosing subunit and places it at the client-facing surface; directly supports EMC4's structural role in the insertase and the membrane insertase activity annotation.
- id: PMID:37196677
title: 'EMC chaperone-Ca(V) structure reveals an ionΒ channel assembly intermediate.'
findings:
- statement: Cryo-EM of an EMC-bound CaV1.2 assembly intermediate shows the EMC acts as a holdase/chaperone during voltage-gated calcium channel assembly; EMC4 participates in the client-engaging cytoplasmic chaperone module and in a lumenal EMC1/EMC4/EMC7/EMC10 subassembly.
reference_section_type: RESULTS
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: PubMed-verified (Nature 2023). Establishes a holdase/chaperone mode of the EMC for a multipass client and places EMC4 directly in the client-handling architecture; supports EMC4's role in multipass membrane protein biogenesis.
- id: PMID:38517390
title: Structural insights into human EMC and its interaction with VDAC.
findings:
- statement: Cryo-EM structures of human EMC in apo and VDAC-bound states; EMC4 forms an ordered three-TMH bundle adjacent to the EMC3/EMC6 core that constitutes a sidewall of the hydrophilic vestibule, and the EMC engages VDAC at mitochondria-ER contact sites.
reference_section_type: RESULTS
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: PubMed-verified (Aging 2024). Independent human EMC structure corroborating EMC4 as a three-TMH vestibule sidewall subunit; supports EMC4's ER-membrane structural role.
- id: PMID:38621120
title: Lipid scrambling is a general feature of protein insertases.
findings:
- statement: Reconstitution and coarse-grained MD indicate lipid scrambling is a general feature of protein insertases, with EMC scrambling activity localized to EMC3 and EMC4; scrambling occurs in the same hydrophilic channel used for protein insertion.
reference_section_type: RESULTS
reference_review:
relevance: MEDIUM
correctness: VERIFIED
review_notes: PubMed-verified (PNAS 2024). Computational/biochemical proposal of an additional lipid-scramblase activity attributed to EMC3/EMC4; hypothesis-generating for a possible EMC4 function beyond protein insertion (not yet demonstrated for human EMC4 in cells).
- id: PMID:31273220
title: 'Dual roles for the ER membrane protein complex in flavivirus infection: viral entry and protein biogenesis.'
findings:
- statement: EMC4 is a proviral host factor for dengue, yellow fever, and Zika viruses, acting both at an early entry/uncoating step and in biogenesis of viral multipass membrane proteins; EMC4 knockout/knockdown strongly reduces infectivity and viral titers.
reference_section_type: RESULTS
reference_review:
relevance: MEDIUM
correctness: VERIFIED
review_notes: PubMed-verified (Sci Rep 2019). EMC4-specific functional genetics establishing it as a flavivirus host dependency factor, consistent with the EMC's role in viral multipass membrane-protein biogenesis.
- id: PMID:31067454
title: The ER Membrane Protein Complex Promotes Biogenesis of Dengue and Zika Virus Non-structural Multi-pass Transmembrane Proteins to Support Infection.
findings:
- statement: The EMC promotes biogenesis of flavivirus non-structural multipass transmembrane proteins (e.g., NS4B); EMC associates with these viral clients, consistent with a direct role in viral membrane-protein biogenesis.
reference_section_type: RESULTS
reference_review:
relevance: MEDIUM
correctness: VERIFIED
review_notes: PubMed-verified (Cell Reports 2019). Mechanistic support that the EMC (engaging clients such as NS4B) supports flavivirus multipass protein biogenesis; corroborates EMC4's antiviral host-factor role.
- id: PMID:32111841
title: Selective EMC subunits act as molecular tethers of intracellular organelles exploited during viral entry.
findings:
- statement: EMC4 and EMC7 promote late endosome-to-ER targeting of polyomavirus SV40 during entry; EMC4 engages Rab7 and syntaxin18 and is proposed to act as a tether stabilizing late endosome-ER contacts, with EMC4-FLAG rescue supporting specificity.
reference_section_type: RESULTS
reference_review:
relevance: MEDIUM
correctness: VERIFIED
review_notes: PubMed-verified (Nat Commun 2020). EMC4-specific role in organelle tethering/viral trafficking, partly distinct from the bulk EMC insertase function; informative non-core context.
- id: file:human/EMC4/EMC4-uniprot.txt
title: UniProt entry Q5J8M3 (EMC4_HUMAN), ER membrane protein complex subunit 4
findings:
- statement: Small polytopic ER membrane accessory subunit of the EMC (TMEM85); structural/scaffold subunit, not part of the EMC3/EMC6 catalytic vestibule; interacts with the EMC client transporter GLUT9/SLC2A9.
reference_section_type: OTHER
suggested_questions:
- question: What specific structural role does EMC4 play in EMC assembly and stability, and does loss of EMC4 selectively impair insertion of particular client classes (e.g. multipass transporters)?
- question: Does the EMC4-GLUT9 interaction represent a productive client-engagement event during GLUT9 biogenesis, and is GLUT9 surface expression EMC4-dependent?
suggested_experiments:
- description: Knock out EMC4 in human cells and perform quantitative membrane proteomics with rescue to define the EMC4-dependent client repertoire and distinguish it from clients tolerant of EMC4 loss.
- description: Test EMC4 dependence of GLUT9 and other candidate transporter clients by measuring their folding, ER export and plasma-membrane levels in EMC4-depleted versus rescued cells.