GO:0160063 multi-pass transmembrane protein insertion into ER membrane: Protein Biogenesis Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0160063 describes the insertion of multi-pass transmembrane proteins into the endoplasmic reticulum (ER) membrane, a process mediated by the multi-pass translocon complex following initial insertion of the first transmembrane segments by the SEC61 complex.
• The multi-pass translocon complex, which includes the ER membrane protein complex (EMC), is essential for the biogenesis of multi-pass membrane proteins that cannot be inserted by the SEC61 complex alone.
• The EMC is a transmembrane-domain insertase that facilitates the insertion of transmembrane domains of multi-pass proteins into the ER membrane.
• Defects in multi-pass transmembrane protein insertion can lead to protein misfolding and are implicated in various diseases, including cancer and neurological disorders, though direct links require further investigation.
• Key genes involved include EMC1, EMC2, EMC3, EMC4, EMC5, EMC6, EMC7, EMC8, EMC9, EMC10, SEC61A1, SEC61B, SEC61G, and others that form the multi-pass translocon complex.
• Research methods to study this process include CRISPR knockout screens, structural biology (cryo-EM), proteomics, and fluorescence microscopy, often using ER membrane models.
Description
The endoplasmic reticulum (ER) is the site of synthesis and folding of secretory and membrane proteins. Multi-pass transmembrane proteins, which span the membrane multiple times, are inserted into the ER membrane through a specialized process termed multi-pass transmembrane protein insertion into ER membrane (GO:0160063). This process is mediated by the multi-pass translocon complex and occurs after the SEC61 complex inserts the first few transmembrane segments, facilitating the insertion of subsequent transmembrane regions. Understanding this process is crucial because multi-pass membrane proteins include receptors, channels, and transporters that are essential for cellular communication and homeostasis. Defects in their biogenesis can lead to a range of diseases, making this pathway a target for therapeutic intervention.
multi-pass transmembrane protein insertion into ER membrane At A Glance
| GO ID | GO:0160063 |
|---|---|
| GO term | multi-pass transmembrane protein insertion into ER membrane |
| Ontology | biological_process |
| Synonym | None |
| Major function | Insertion of multi-pass transmembrane proteins into the ER membrane |
| Complex involved | Multi-pass translocon complex, including the ER membrane protein complex (EMC) |
| Preceding step | Initial insertion of first transmembrane segments by the SEC61 complex |
| Cellular location | Endoplasmic reticulum membrane |
What Is GO:0160063?
GO:0160063, multi-pass transmembrane protein insertion into ER membrane, is a biological process defined as the insertion of multi-pass membrane proteins into the ER membrane. This insertion is mediated by the multi-pass translocon complex and takes place following the membrane insertion of the first few transmembrane segments of proteins by the SEC61 complex, which promotes the insertion of subsequent transmembrane regions.
Why Is multi-pass transmembrane protein insertion into ER membrane Important in Cell Biology?
Multi-pass transmembrane protein insertion into the ER membrane is essential for the biogenesis of a large class of membrane proteins that function in cell signaling, transport, and adhesion. Disruption of this process can lead to protein misfolding, ER stress, and disease. The multi-pass translocon complex, particularly the EMC, is critical for the stability and function of many multi-pass proteins, and mutations in its components have been linked to developmental disorders and cancer.
• Enables the proper folding and function of multi-pass membrane proteins, which constitute about 25% of the proteome.
• The EMC is required for the biogenesis of numerous multi-pass proteins, including G protein-coupled receptors and ion channels.
• Dysregulation of ER membrane protein insertion can contribute to cancer progression through altered cell surface receptor expression.
• Mutations in EMC subunits are associated with neurological disorders such as intellectual disability and epilepsy.
• The process is a potential target for antiviral therapies, as some viruses exploit ER membrane insertion for their envelope proteins.
• Understanding this pathway aids in the design of biologics and membrane protein-based drugs.
• It is critical for immune surveillance, as MHC class I molecules are multi-pass membrane proteins.
• Defects in this process can trigger the unfolded protein response (UPR), linking it to metabolic diseases.
• The multi-pass translocon complex is conserved from yeast to humans, facilitating genetic studies.
• Research on this process informs synthetic biology efforts to engineer membrane proteins.
What Happens During multi-pass transmembrane protein insertion into ER membrane?
Initial Insertion by the SEC61 Complex
In simple terms: The first step is like threading the first few loops of a string through a hole; the SEC61 complex helps the first parts of the protein enter the ER membrane.
The SEC61 complex, a conserved heterotrimeric channel, mediates the insertion of the first transmembrane segments of multi-pass membrane proteins into the ER membrane. This initial insertion is co-translational and requires the ribosome and the Sec61 channel. The SEC61 complex recognizes hydrophobic signal sequences and transmembrane domains, facilitating their lateral transfer into the lipid bilayer.
Recruitment of the Multi-pass Translocon Complex
In simple terms: After the first segments are in, a specialized machine called the multi-pass translocon complex takes over to insert the remaining parts.
Following the initial insertion, the multi-pass translocon complex is recruited to the SEC61 complex. This complex includes the ER membrane protein complex (EMC) and other accessory factors. The EMC is a transmembrane-domain insertase that interacts with the SEC61 complex and the ribosome to promote the insertion of subsequent transmembrane regions of multi-pass proteins.
Insertion of Subsequent Transmembrane Segments
In simple terms: The multi-pass translocon complex helps the rest of the protein's transmembrane segments slide into the membrane one by one.
The multi-pass translocon complex facilitates the insertion of additional transmembrane segments by providing a hydrophilic environment for the transmembrane domains to partition into the lipid bilayer. The EMC subunit EMC3 forms a hydrophilic vestibule that guides the transmembrane domains, while other subunits such as EMC6 and EMC7 contribute to complex stability and function.
Folding and Quality Control
In simple terms: Once inserted, the protein folds into its proper shape, and quality control systems check for errors.
After insertion, multi-pass membrane proteins fold into their native conformations, often assisted by chaperones. Misfolded proteins are recognized by ER quality control mechanisms and targeted for degradation via the ER-associated degradation (ERAD) pathway. The EMC has been implicated in quality control of multi-pass proteins, ensuring only properly folded proteins proceed to the Golgi.
Key Genes Involved in GO:0160063 multi-pass transmembrane protein insertion into ER membrane
The following genes encode components of the multi-pass translocon complex and associated factors that are critical for multi-pass transmembrane protein insertion into the ER membrane.
| Gene | Major Role | Research Relevance |
|---|---|---|
| EMC1 | Core component of the ER membrane protein complex (EMC) | Mutations linked to neurodevelopmental disorders; knockout leads to multi-pass protein instability |
| EMC2 | EMC subunit, involved in transmembrane domain insertion | Essential for EMC stability; knockdown affects GPCR biogenesis |
| EMC3 | Hydrophilic vestibule for transmembrane domain insertion | Key insertase subunit; structural studies reveal mechanism |
| EMC4 | EMC subunit, regulates complex assembly | Knockout causes ER stress and reduced multi-pass protein levels |
| EMC5 | EMC subunit, may assist in substrate recognition | Implicated in cancer cell proliferation |
| EMC6 | EMC subunit, involved in complex stability | Autophagy-related; links to membrane protein quality control |
| EMC7 | EMC subunit, interacts with SEC61 | Required for efficient insertion of multi-pass proteins |
| EMC8 | EMC subunit, potential regulatory role | Knockdown affects ER morphology |
| EMC9 | EMC subunit, less characterized | May have tissue-specific functions |
| EMC10 | EMC subunit, secreted form exists | Involved in metabolic regulation |
| SEC61A1 | Main channel of the SEC61 complex | Mutations cause tubulointerstitial kidney disease |
| SEC61B | SEC61 complex subunit | Regulates channel gating |
| SEC61G | SEC61 complex subunit | Amplified in cancers; target for therapy |
| RPN1 | Oligosaccharyltransferase subunit, interacts with EMC | Links glycosylation to insertion |
| RPN2 | Oligosaccharyltransferase subunit | Required for multi-pass protein N-glycosylation |
| DERL1 | ERAD component, quality control | Degrades misfolded multi-pass proteins |
| DERL2 | ERAD component | Cooperates with DERL1 in quality control |
How Is multi-pass transmembrane protein insertion into ER membrane Regulated?
The process of multi-pass transmembrane protein insertion into the ER membrane is regulated at multiple levels. The expression of EMC subunits can be induced by ER stress through the unfolded protein response (UPR), which upregulates genes involved in protein folding and degradation. Additionally, the EMC interacts with the SEC61 complex dynamically, and its activity may be modulated by post-translational modifications such as phosphorylation. However, specific regulatory mechanisms remain an active area of research.
multi-pass transmembrane protein insertion into ER membrane and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| EMC1 | Neurodevelopmental disorder with epilepsy | Knockout mouse or patient-derived iPSCs |
| EMC6 | Glioblastoma | Knockout glioma cell lines |
| SEC61G | Breast cancer | Overexpression in MCF-7 cells |
| EMC10 | Obesity and type 2 diabetes | Knockout mouse models |
| SEC61A1 | Tubulointerstitial kidney disease | Knock-in mouse with patient mutation |
Cancer
Altered expression of EMC subunits has been observed in various cancers. For example, EMC6 is downregulated in glioblastoma, and its overexpression inhibits cell proliferation. SEC61G is amplified in breast cancer and promotes tumor growth. These findings suggest that dysregulation of multi-pass transmembrane protein insertion contributes to cancer pathogenesis.
Neurological Disorders
Mutations in EMC1 cause a neurodevelopmental disorder characterized by intellectual disability, epilepsy, and cerebellar atrophy. EMC1 is essential for the insertion of multi-pass proteins in neurons, and its loss leads to ER stress and neuronal death.
Metabolic Diseases
EMC10 is involved in energy homeostasis, and its genetic variants are associated with obesity and type 2 diabetes. The EMC complex is required for the biogenesis of multi-pass proteins that regulate lipid metabolism.
From multi-pass transmembrane protein insertion into ER membrane-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of EMC1 in neuronal survival? | EMC1 knockout mouse |
| How does EMC3 mutation affect GPCR insertion? | Point mutation knock-in in HEK293 cells |
| Does EMC6 overexpression inhibit tumor growth? | Overexpression in glioblastoma cell lines |
| What is the interactome of the EMC complex? | Tagged knock-in of EMC subunits followed by mass spectrometry |
| How does SEC61G amplification drive breast cancer? | Knockout of SEC61G in breast cancer cells |
| Can EMC10 variants cause metabolic syndrome? | Knock-in mouse models with human variants |
How to Study the multi-pass transmembrane protein insertion into ER membrane Process
| Method | What It Measures | Typical Application |
|---|---|---|
| CRISPR knockout screen | Gene essentiality for multi-pass protein insertion | Identify novel regulators |
| Cryo-EM | 3D structure of translocon complexes | Mechanistic studies |
| Co-immunoprecipitation | Protein-protein interactions | Map the multi-pass translocon interactome |
| Ribo-seq | Translation efficiency and ribosome stalling | Assess co-translational insertion |
| Proteomics | Global protein expression changes | Quantify multi-pass protein levels |
| Fluorescence microscopy | Subcellular localization | Monitor ER retention and trafficking |
| Flow cytometry | Cell surface expression of multi-pass proteins | Measure insertion efficiency |
| RNA-seq | Transcriptional changes upon EMC perturbation | Identify UPR activation |
CRISPR-Cas9 Knockout Screens
Genome-wide CRISPR knockout screens can identify genes required for multi-pass transmembrane protein insertion. For example, a screen for regulators of a multi-pass reporter protein identified EMC subunits as essential factors. This method allows unbiased discovery of novel components.
Structural Biology (Cryo-EM)
Cryo-electron microscopy has been used to determine the structure of the EMC complex, revealing how it interacts with the SEC61 complex and facilitates transmembrane domain insertion. High-resolution structures provide mechanistic insights.
Proteomics and Interactomics
Affinity purification coupled with mass spectrometry can identify proteins that interact with the multi-pass translocon complex. Tagged knock-in of EMC subunits followed by immunoprecipitation has revealed stable interactions with SEC61 and ribosomes.
Fluorescence Microscopy
Live-cell imaging of fluorescently tagged multi-pass proteins can monitor their insertion and trafficking. This approach has shown that EMC depletion causes retention of multi-pass proteins in the ER.
How CRISPR Can Be Used to Study GO:0160063 multi-pass transmembrane protein insertion into ER membrane
Knockout
CRISPR knockout of EMC subunits in cell lines leads to reduced levels of multi-pass membrane proteins and activation of ER stress, providing a model to study the consequences of impaired insertion.
Point Mutation
Introducing patient-derived point mutations in EMC1 (e.g., p.Leu656Pro) using CRISPR knock-in recapitulates neurodevelopmental phenotypes in cellular models, allowing functional analysis.
Knock-in
Tagged knock-in of EMC3 with a fluorescent protein enables live-cell imaging of the multi-pass translocon complex and its dynamics during insertion.
Overexpression
Overexpression of EMC6 in glioblastoma cells inhibits proliferation, suggesting a tumor-suppressive role and providing a model for therapeutic targeting.
How EDITGENE Supports multi-pass transmembrane protein insertion into ER membrane Research
Researchers studying multi-pass transmembrane protein insertion into ER membrane-related genes often need to determine whether a candidate gene is causally involved in the process or in associated diseases. This requires precise genetic manipulation, which can be achieved through CRISPR-based models.
Contact EDITGENE today to design your custom CRISPR model for multi-pass transmembrane protein insertion into ER membrane research.
Frequently Asked Questions About multi-pass transmembrane protein insertion into ER membrane
What is GO:0160063?
GO:0160063 is a Gene Ontology term for the biological process of multi-pass transmembrane protein insertion into the ER membrane, mediated by the multi-pass translocon complex.
What genes are involved in multi-pass transmembrane protein insertion into ER membrane?
Key genes include EMC1-10, SEC61A1, SEC61B, SEC61G, and accessory factors like RPN1 and RPN2.
What is the multi-pass translocon complex?
It is a protein complex, including the ER membrane protein complex (EMC), that facilitates the insertion of multi-pass transmembrane proteins into the ER membrane after initial insertion by SEC61.
How does the EMC complex function?
The EMC acts as a transmembrane-domain insertase, guiding hydrophobic transmembrane segments into the lipid bilayer.
What diseases are associated with defects in this process?
Mutations in EMC1 cause neurodevelopmental disorders, while EMC6 and SEC61G are implicated in cancer.
What methods are used to study multi-pass transmembrane protein insertion?
CRISPR screens, cryo-EM, proteomics, and fluorescence microscopy are commonly used.
Can CRISPR be used to model diseases related to this process?
Yes, CRISPR knockout or knock-in of EMC genes can recapitulate disease phenotypes in cell and animal models.
What is the role of SEC61 in multi-pass protein insertion?
SEC61 inserts the first transmembrane segments, then hands off to the multi-pass translocon complex for subsequent segments.
How is the multi-pass translocon complex regulated?
It is regulated by ER stress via the UPR and potentially by post-translational modifications.
What cell models are available for studying this process?
Knockout, point mutation, knock-in, and overexpression models in cell lines such as HEK293 and cancer cells are available.
Conclusion
Multi-pass transmembrane protein insertion into the ER membrane (GO:0160063) is a vital cellular process mediated by the multi-pass translocon complex, including the EMC. It ensures the proper biogenesis of multi-pass membrane proteins, which are critical for numerous physiological functions. Dysregulation of this process is linked to cancer, neurological disorders, and metabolic diseases. Continued research using CRISPR models and advanced structural techniques will further elucidate its mechanisms and therapeutic potential.
References
- 1. McGilvray PT et al.. 2020. An ER translocon for multi-pass membrane protein biogenesis.. Elife 9 PMID: 32820719
- 2. Bai L et al.. 2020. Structure of the ER membrane complex, a transmembrane-domain insertase.. Nature 584(7821):475-478 PMID: 32494008
