Affinage

EMC9

ER membrane protein complex subunit 9 · UniProt Q9Y3B6

Round 2 corrected
Length
208 aa
Mass
23.1 kDa
Annotated
2026-04-28
33 papers in source corpus 7 papers cited in narrative 7 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

EMC9 is an alternative subunit (interchangeable with EMC8) of the nine-subunit ER membrane protein complex (EMC), a conserved co- and post-translational insertase that mediates the correct topological insertion of transmembrane domains into the ER lipid bilayer (PMID:30415835, PMID:29242231). The EMC inserts tail-anchored proteins with moderately hydrophobic TMDs and ensures correct orientation of the first TMD of multipass clients such as GPCRs, using a hydrophilic vestibule formed by EMC3 and EMC6 whose mechanism was resolved by cryo-EM at 3.4 Å (PMID:32439656, PMID:30415835). The complex engages substrates cotranslationally at ribosomes, shielding charged-TMD segments from premature degradation, and participates in ER-associated degradation and ER quality control networks (PMID:29809151, PMID:22119785). In Xenopus, emc9 depletion causes neural crest and craniofacial cartilage defects, demonstrating a developmental requirement for EMC-dependent transmembrane protein biogenesis (PMID:37318954).

Mechanistic history

Synthesis pass · year-by-year structured walk · 6 steps
  1. 2011 Medium

    Establishing that the EMC, including EMC9, operates within the mammalian ER-associated degradation network answered whether this complex participates in ER protein quality control beyond simple chaperoning.

    Evidence Integrative proteomics, RNAi functional genomics, and transcriptional profiling of ER stress in mammalian cells

    PMID:22119785

    Open questions at the time
    • EMC9 was not individually validated; complex membership inferred from co-purification
    • Direct enzymatic or insertase activity of the complex was not yet demonstrated
    • Relationship between ERAD function and transmembrane insertion was unclear
  2. 2016 Medium

    Identification of the EMC as a host dependency factor for dengue and Zika virus replication revealed that EMC-mediated transmembrane protein processing has physiological consequences beyond housekeeping ER functions.

    Evidence Genome-wide RNAi and CRISPR/Cas9 screens for flavivirus host factors with EMC subunit validation

    PMID:27342126

    Open questions at the time
    • EMC9-specific contribution not resolved from the whole complex
    • Viral substrate(s) requiring EMC insertion not identified
    • Whether EMC acts on viral structural or non-structural transmembrane proteins was unknown
  3. 2017 High

    Reconstitution of EMC-dependent insertion in synthetic liposomes established that the complex is a bona fide transmembrane domain insertase for tail-anchored proteins with moderately hydrophobic TMDs, resolving the fundamental biochemical activity of the complex.

    Evidence In vitro liposome reconstitution with purified EMC; calmodulin-substrate shielding assays; EMC loss-of-function in cells

    PMID:29242231

    Open questions at the time
    • Whether EMC also acts cotranslationally on multipass substrates was unresolved
    • Structural basis of the insertion mechanism was unknown
    • Role of individual subunits including EMC9 in the insertion reaction was not defined
  4. 2018 High

    Demonstrating that the EMC functions cotranslationally to orient the first TMD of GPCRs—and that EMC8/EMC9 are alternative subunits—resolved both the topogenesis mechanism and the subunit architecture of the complex.

    Evidence In vitro reconstitution of β1-adrenergic receptor biogenesis with purified EMC and SRP receptor; EMC-knockout cells; topology rescue with signal peptides; subunit composition analysis

    PMID:29809151 PMID:30415835

    Open questions at the time
    • Functional distinction between EMC8-containing and EMC9-containing complexes was not determined
    • Structural basis of the insertion vestibule was still unknown
    • Substrate selectivity rules for cotranslational versus post-translational clients were unclear
  5. 2020 High

    The 3.4 Å cryo-EM structure of the human EMC revealed the hydrophilic vestibule formed by EMC3/EMC6 through which substrates traverse the membrane, and mutagenesis validated key catalytic residues, providing an atomic-level mechanism for the insertase activity.

    Evidence Cryo-EM in lipid nanodiscs at 3.4 Å resolution; structure-guided mutagenesis; functional insertion assays

    PMID:32439656

    Open questions at the time
    • EMC9 position in the structure and its specific contribution to substrate engagement or complex stability were not individually resolved
    • No substrate-bound structure to show TMD handoff mechanism
    • Structural basis for EMC8/EMC9 interchangeability not elucidated
  6. 2023 Medium

    Loss of emc9 in Xenopus produced neural crest and craniofacial defects, demonstrating that EMC9 is non-redundant in vivo for developmental transmembrane protein biogenesis in a vertebrate model.

    Evidence Morpholino knockdown in Xenopus tropicalis; neural crest marker assays; craniofacial cartilage staining

    PMID:37318954

    Open questions at the time
    • Specific EMC substrates whose misfolding causes the neural crest phenotype are unknown
    • Whether mammalian EMC9 loss produces equivalent craniofacial defects has not been tested
    • Rescue experiments with EMC8 were not performed to test subunit interchangeability in vivo

Open questions

Synthesis pass · forward-looking unresolved questions
  • The functional distinction between EMC8-containing and EMC9-containing complexes remains unresolved: it is unknown whether they differ in substrate selectivity, tissue expression, or efficiency of insertion, and no substrate-bound structural model exists to reveal how EMC9 participates in the insertion cycle.
  • No EMC9-specific biochemical activity or binding partner has been identified independently of the complex
  • No substrate-engaged EMC structure is available
  • Tissue-specific expression patterns of EMC8 vs EMC9 and their phenotypic consequences in mammals are uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3
Localization
GO:0005783 endoplasmic reticulum 5
Pathway
R-HSA-392499 Metabolism of proteins 4 R-HSA-9609507 Protein localization 3
Partners
EMC1EMC10EMC2EMC3EMC4EMC5EMC6EMC7EMC8
Complex memberships
ER membrane protein complex (EMC)

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2018 The ER membrane protein complex (EMC) contains either EMC8 or EMC9 as alternative subunits (together with EMC1-7 and EMC10), and functions as a co-translational insertase required for correct topogenesis of the first transmembrane domain (TMD1) of GPCRs such as β1-adrenergic receptor; without EMC, TMD1 inserts in an inverted orientation or fails to insert, and enforcing correct TMD1 topology with an N-terminal signal peptide bypasses the EMC requirement. Reconstitution of β1AR biogenesis in vitro with purified EMC and SRP receptor; EMC-knockout cell lines; topology assays; identification of EMC subunit composition including EMC8/EMC9 as alternative members Cell High 30415835
2017 The EMC complex (of which EMC9 is a subunit) functions as a transmembrane domain insertase for tail-anchored membrane proteins with moderately hydrophobic TMDs; these substrates are shielded in the cytosol by calmodulin, dynamically released to sample the ER, and then inserted by the EMC in a reconstituted liposome system. In vitro reconstitution of EMC-dependent insertion in synthetic liposomes with purified EMC; calmodulin-substrate interaction assays; EMC loss-of-function in cells Science High 29242231
2018 The EMC (containing EMC9 as a subunit) engages multipass transmembrane protein clients cotranslationally, particularly those with charged residues in TMDs, protecting them from premature degradation and recruiting chaperones; proximity-specific ribosome profiling showed EMC associates with ribosomes immediately following clusters of charged-TMD-enriched segments. Proximity-specific ribosome profiling in yeast and human cells; systematic proteomics; EMC depletion with defined substrate stabilization/degradation readouts eLife High 29809151
2020 Cryo-EM structure of the human nine-subunit EMC (which includes EMC9 as a subunit) in a lipid nanodisc resolved to 3.4 Å; structure-guided mutagenesis demonstrated that substrate insertion requires a methionine-rich cytosolic loop and occurs via an enclosed hydrophilic vestibule within the membrane formed by EMC3 and EMC6; local membrane thinning and a positively charged patch decrease the energetic barrier for insertion. Cryo-electron microscopy in lipid nanodiscs (3.4 Å resolution); structure-guided mutagenesis of insertion pathway residues; functional insertion assays Science High 32439656
2016 The EMC complex (of which EMC9 is a subunit) is required for early stages of both dengue virus (DENV) and Zika virus (ZIKV) infection, identified by orthologous RNAi and CRISPR/Cas9 functional genomic screens as a host dependency factor involved in transmembrane protein processing and maturation. Genome-wide RNAi and CRISPR/Cas9 screens; validation of EMC requirement for flavivirus replication Cell reports Medium 27342126
2011 The EMC complex (including EMC9 as a subunit) was identified as part of the mammalian ERAD network through integrative proteomics, functional genomics, and transcriptional response to ER stress, linking it to the recognition, ubiquitylation, and dislocation of misfolded ER substrates. Integrative proteomics, functional genomics (RNAi), and transcriptional profiling of ER stress response Nature cell biology Medium 22119785
2023 EMC9 (together with EMC10) is specifically required for neural crest development and craniofacial structure formation in Xenopus tropicalis; morpholino depletion of emc9 produced neural crest and craniofacial cartilage defects similar to emc1 loss of function, consistent with a shared mechanism of dysfunction in transmembrane protein topogenesis. Morpholino knockdown in Xenopus tropicalis; neural crest assays; craniofacial cartilage staining; neuromuscular function assays Genesis Medium 37318954

Source papers

Stage 0 corpus · 33 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Towards a proteome-scale map of the human protein-protein interaction network. Nature 2090 16189514
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
2015 The BioPlex Network: A Systematic Exploration of the Human Interactome. Cell 1118 26186194
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2014 A proteome-scale map of the human interactome network. Cell 977 25416956
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2018 High-Density Proximity Mapping Reveals the Subcellular Organization of mRNA-Associated Granules and Bodies. Molecular cell 580 29395067
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2022 OpenCell: Endogenous tagging for the cartography of human cellular organization. Science (New York, N.Y.) 432 35271311
2011 Defining human ERAD networks through an integrative mapping strategy. Nature cell biology 427 22119785
2000 Identification of novel human genes evolutionarily conserved in Caenorhabditis elegans by comparative proteomics. Genome research 392 10810093
2016 Identification of Zika Virus and Dengue Virus Dependency Factors using Functional Genomics. Cell reports 306 27342126
2013 Loci associated with N-glycosylation of human immunoglobulin G show pleiotropy with autoimmune diseases and haematological cancers. PLoS genetics 292 23382691
2017 The ER membrane protein complex is a transmembrane domain insertase. Science (New York, N.Y.) 233 29242231
2018 EMC Is Required to Initiate Accurate Membrane Protein Topogenesis. Cell 190 30415835
2018 The ER membrane protein complex interacts cotranslationally to enable biogenesis of multipass membrane proteins. eLife 170 29809151
2020 Structural basis for membrane insertion by the human ER membrane protein complex. Science (New York, N.Y.) 137 32439656
2021 SARS-CoV-2-host proteome interactions for antiviral drug discovery. Molecular systems biology 86 34709727
2021 Comprehensive interactome profiling of the human Hsp70 network highlights functional differentiation of J domains. Molecular cell 64 33957083
2023 Evolutionarily conserved regulators of tau identify targets for new therapies. Neuron 39 36610398
2022 ESCPE-1 mediates retrograde endosomal sorting of the SARS-CoV-2 host factor Neuropilin-1. Proceedings of the National Academy of Sciences of the United States of America 22 35696571
2023 Sequential genome-wide CRISPR-Cas9 screens identify genes regulating cell-surface expression of tetraspanins. Cell reports 20 36724073
2021 Circular RNA circ-FAM158A promotes retinoblastoma progression by regulating miR-138-5p/SLC7A5 axis. Experimental eye research 20 34102206
2023 ESYT1 tethers the ER to mitochondria and is required for mitochondrial lipid and calcium homeostasis. Life science alliance 18 37931956
2019 FAM105A/OTULINL Is a Pseudodeubiquitinase of the OTU-Class that Localizes to the ER Membrane. Structure (London, England : 1993) 11 31056421
2022 Role of circular RNAs in retinoblastoma. Functional & integrative genomics 10 36547723
2018 Transcriptomics-genomics data integration and expression quantitative trait loci analyses in oocyte donors and embryo recipients for improving invitro production of dairy cattle embryos. Reproduction, fertility, and development 10 32188542
2025 The solute carrier superfamily interactome. Molecular systems biology 9 40355756
2024 The comprehensive SARS-CoV-2 'hijackome' knowledge base. Cell discovery 7 39653747
2023 The impact of non-coding RNAs in the pathobiology of eye disorders. International journal of biological macromolecules 7 37001772
2023 Expanding EMC foldopathies: Topogenesis deficits alter the neural crest. Genesis (New York, N.Y. : 2000) 3 37318954