GO:0062078 TSC1-TSC2 complex binding: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0062078 (TSC1-TSC2 complex binding) is a molecular function describing the selective binding to the TSC1-TSC2 heterodimer, a central upstream inhibitor of mTORC1 signaling.
• The TSC1-TSC2 complex acts as a GTPase-activating protein (GAP) toward Rheb, and its binding partners regulate its stability, localization, and activity.
• TBC1D7 is a third constitutive subunit that binds the TSC1-TSC2 complex and is required for its integrity and function.
• Phosphorylation by Akt inhibits TSC2 and disrupts TSC1-TSC2 complex function, linking growth factor signaling to mTORC1 activation.
• Additional binding proteins such as FIP200 and TBC7 interact with the TSC1-TSC2 complex to modulate cell size and mTORC1 signaling.
• Dysregulation of TSC1-TSC2 complex binding is implicated in tuberous sclerosis complex, lymphangioleiomyomatosis, and various cancers.
Description
The TSC1-TSC2 complex binding (GO:0062078) molecular function describes the physical interaction with the TSC1-TSC2 heterodimer, a key tumor suppressor complex that integrates diverse cellular signals to control growth and proliferation. This binding event is fundamental to the assembly, regulation, and downstream signaling of the TSC complex, which serves as a critical node in the PI3K-Akt-mTORC1 pathway. Researchers study this function to understand how cells coordinate nutrient availability, energy status, and growth factor signals to modulate protein synthesis and cell size. The TSC1-TSC2 complex itself is a GTPase-activating protein (GAP) for the small GTPase Rheb, and its binding partners can influence its GAP activity, stability, or subcellular localization. Consequently, proteins that bind to the TSC1-TSC2 complex are often critical regulators of mTORC1 signaling, and their dysfunction can lead to diseases such as tuberous sclerosis complex (TSC), lymphangioleiomyomatosis (LAM), and cancer. Understanding the molecular details of TSC1-TSC2 complex binding is therefore essential for deciphering growth control mechanisms and for developing targeted therapies.
TSC1-TSC2 complex binding At A Glance
| GO ID | GO:0062078 |
|---|---|
| GO term | TSC1-TSC2 complex binding |
| Ontology | molecular_function |
| Synonym | tuberin-hamartin complex binding, tuberin sclerosis complex binding |
| Major function | Binding to the TSC1-TSC2 heterodimer, a key inhibitor of mTORC1 signaling |
| Related complex | TSC1-TSC2 complex (hamartin-tuberin), often with TBC1D7 as a third subunit |
| Upstream regulators | Akt-mediated phosphorylation of TSC2 inhibits complex function |
| Downstream effect | Regulation of Rheb GTPase activity and mTORC1 signaling |
| Disease relevance | Tuberous sclerosis complex, lymphangioleiomyomatosis, cancers |
What Is GO:0062078?
TSC1-TSC2 complex binding (GO:0062078) is defined as the selective and non-covalent interaction of a protein or molecule with the TSC1-TSC2 heterodimer. This molecular function encompasses the binding to the assembled TSC1-TSC2 complex, which may occur through direct physical contact with either TSC1 (hamartin) or TSC2 (tuberin) subunits, or with the complex as a whole. It is a molecular function term, indicating the activity of a binding partner rather than a biological process or cellular component.
Why Is TSC1-TSC2 complex binding Important in Cell Biology?
TSC1-TSC2 complex binding is critically important because the TSC1-TSC2 complex is a central hub that integrates growth factor, energy, and nutrient signals to control cell growth and proliferation through mTORC1. Proteins that bind to this complex can modulate its stability, localization, or GAP activity, thereby directly influencing mTORC1 signaling. Dysregulation of these interactions is linked to severe human diseases, including tuberous sclerosis complex, lymphangioleiomyomatosis, and various cancers, making this function a key area of research for understanding disease mechanisms and identifying therapeutic targets.
• TSC1-TSC2 complex binding regulates the stability and function of the TSC tumor suppressor complex.
• Binding partners such as TBC1D7 are essential for the integrity and GAP activity of the TSC complex toward Rheb.
• The TSC1-TSC2 complex is a major upstream inhibitor of mTORC1, controlling cell growth and proliferation.
• Akt-mediated phosphorylation of TSC2 disrupts TSC1-TSC2 complex function, linking growth factor signaling to mTORC1 activation.
• FIP200 binding to the TSC1-TSC2 complex regulates cell size control.
• TBC7 interacts with the TSC1-TSC2 complex, suggesting additional layers of regulation.
• Mutations in TSC1 or TSC2 cause tuberous sclerosis complex, a multisystem disorder.
• Loss of TSC1-TSC2 complex function is associated with lymphangioleiomyomatosis and certain cancers.
• Understanding TSC1-TSC2 complex binding can reveal new therapeutic targets for mTOR-driven diseases.
• The HSP90/R2TP chaperone complex scaffolds the assembly of the TSC complex, highlighting the importance of folding and assembly.
Molecular Mechanism of TSC1-TSC2 complex binding
Assembly and Integrity of the TSC1-TSC2 Complex
In simple terms: The TSC1 and TSC2 proteins must come together to form a functional complex, and other proteins help this process.
The TSC1-TSC2 complex is a heterodimer of TSC1 (hamartin) and TSC2 (tuberin), and its assembly is facilitated by the HSP90/R2TP quaternary chaperone, which scaffolds the formation of the complex. The integrity of the complex is also dependent on TBC1D7, a third subunit that binds to TSC1 and is required for the stability and function of the entire complex. Regions critical for the integrity of the TSC1-TSC2-TBC1D7 complex have been identified, including specific domains in TSC1 and TSC2 that mediate their interaction. These findings indicate that TSC1-TSC2 complex binding is not merely a passive interaction but a regulated assembly process essential for the complex's tumor suppressor function.
Phosphorylation-Dependent Regulation of Binding
In simple terms: Chemical tags called phosphates can be added to TSC2, which changes how the complex works and who it binds to.
Akt phosphorylates TSC2 at multiple sites, which inhibits the TSC1-TSC2 complex and suppresses its ability to inhibit mTORC1 signaling. This phosphorylation can disrupt the interaction between TSC1 and TSC2 or alter the binding of other partners, thereby modulating the complex's GAP activity toward Rheb. Phosphorylation and binding partner analysis of the TSC1-TSC2 complex has revealed that specific phosphorylation events can affect its association with 14-3-3 proteins and other regulators. Thus, TSC1-TSC2 complex binding is dynamically regulated by phosphorylation, allowing cells to rapidly respond to growth factor signals.
Binding Partners and Their Functional Consequences
In simple terms: Many different proteins can attach to the TSC1-TSC2 complex, and each one can change what the complex does.
Several proteins have been identified as binding partners of the TSC1-TSC2 complex, including TBC1D7, FIP200, and TBC7. TBC1D7 is a constitutive subunit that binds directly to TSC1 and is necessary for the complex's GAP activity and stability. FIP200 interacts with the TSC1-TSC2 complex and plays a role in regulating cell size, linking the complex to autophagy and cell growth control. TBC7 was identified as a novel binding protein to the TSC1-TSC2 complex, suggesting additional regulatory inputs. These interactions demonstrate that TSC1-TSC2 complex binding serves as a platform for integrating multiple signals to fine-tune mTORC1 activity.
GAP Activity and Downstream Signaling
In simple terms: The TSC1-TSC2 complex acts like a brake on a growth switch called Rheb, and proteins that bind to it can strengthen or weaken that brake.
The TSC1-TSC2 complex functions as a GTPase-activating protein (GAP) for the small GTPase Rheb, converting Rheb-GTP to Rheb-GDP and thereby inhibiting mTORC1. Binding partners can modulate this GAP activity; for example, TBC1D7 is required for optimal GAP function. The complex's ability to inhibit mTORC1 is critical for controlling protein synthesis, cell growth, and proliferation. Disruption of TSC1-TSC2 complex binding can lead to hyperactive mTORC1 signaling, which is a hallmark of diseases such as tuberous sclerosis complex and cancer.
Structural Insights into Binding Interfaces
In simple terms: Scientists have mapped the exact parts of TSC1 and TSC2 that touch each other and other proteins.
Studies have identified specific regions critical for the integrity of the TSC1-TSC2-TBC1D7 complex, including the N-terminal domain of TSC1 and the C-terminal domain of TSC2. These structural insights help explain how mutations in TSC1 or TSC2 disrupt complex formation and lead to disease. The binding interfaces are also targets for regulatory modifications, such as phosphorylation by Akt, which can weaken the interaction. Understanding these interfaces is essential for designing drugs that can modulate TSC complex function.
Key Genes Involved in GO:0062078 TSC1-TSC2 complex binding
The following genes and proteins are key players in TSC1-TSC2 complex binding and its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| TSC1 | Encodes hamartin, a core subunit of the TSC1-TSC2 complex | Mutations cause tuberous sclerosis complex; essential for complex stability |
| TSC2 | Encodes tuberin, the GAP subunit of the complex | Mutations cause tuberous sclerosis complex; target of Akt phosphorylation |
| TBC1D7 | Third subunit of the TSC complex, binds TSC1 | Required for complex integrity and GAP activity; mutations linked to disease |
| AKT1 | Phosphorylates TSC2 to inhibit complex function | Key upstream regulator linking growth factor signaling to mTORC1 |
| RHEB | Small GTPase inhibited by TSC1-TSC2 GAP activity | Direct downstream target; mediates mTORC1 activation |
| MTOR | Kinase in mTORC1 complex, inhibited by TSC1-TSC2 | Central regulator of cell growth and proliferation |
| FIP200 | Binds TSC1-TSC2 complex, regulates cell size | Links TSC complex to autophagy and cell size control |
| TBC7 | Novel binding protein to TSC1-TSC2 complex | Potential additional regulator of TSC function |
| HSP90 | Chaperone that scaffolds TSC complex assembly | Facilitates folding and assembly of TSC1-TSC2 |
| R2TP | Quaternary chaperone complex assisting TSC assembly | Required for proper TSC complex formation |
| 14-3-3 | Binds phosphorylated TSC2, affects complex function | Modulates TSC1-TSC2 interaction and localization |
| RAPTOR | Component of mTORC1, downstream of TSC1-TSC2 | Readout of TSC complex activity |
| RPTOR | Gene encoding RAPTOR | Marker for mTORC1 activity in TSC studies |
| S6K1 | Downstream effector of mTORC1 | Phosphorylation readout for TSC1-TSC2 function |
| 4E-BP1 | Downstream effector of mTORC1 | Phosphorylation readout for TSC1-TSC2 function |
| TSC22D1 | Potential interacting protein | May modulate TSC complex function |
| DEPDC5 | Component of GATOR1, upstream of TSC | Regulates TSC complex via amino acid signaling |
| LAMTOR1 | Component of Ragulator, upstream of TSC | Links nutrient signaling to TSC complex |
How Is TSC1-TSC2 complex binding Regulated?
The TSC1-TSC2 complex is regulated by multiple upstream signals, including growth factors, energy status, and nutrients. Akt phosphorylates TSC2 at multiple sites, inhibiting the complex and relieving its inhibition of mTORC1. Phosphorylation by other kinases, such as AMPK, can activate the complex under low energy conditions. The binding of TBC1D7 is required for the stability and function of the complex, and its levels can affect TSC complex integrity. Additionally, the HSP90/R2TP chaperone complex regulates the assembly of the TSC complex, ensuring proper folding and function. These regulatory mechanisms allow the TSC1-TSC2 complex to act as a molecular switchboard, integrating diverse signals to control cell growth.
TSC1-TSC2 complex binding and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TSC1 | Tuberous sclerosis complex, LAM, cancer | TSC1 knockout cell lines, mouse models |
| TSC2 | Tuberous sclerosis complex, LAM, cancer | TSC2 knockout cell lines, mouse models |
| TBC1D7 | TSC-like phenotypes, intellectual disability | TBC1D7 knockout cells, patient-derived iPSCs |
| AKT1 | Cancer, overgrowth syndromes | AKT1 mutant knock-in cells |
| FIP200 | Cell size control, autophagy | FIP200 knockout cells, mouse models |
Tuberous Sclerosis Complex (TSC)
Mutations in TSC1 or TSC2 cause tuberous sclerosis complex, an autosomal dominant disorder characterized by benign tumors in multiple organs, including the brain, kidneys, heart, and skin. Loss of TSC1-TSC2 complex function leads to hyperactive mTORC1 signaling, which drives tumor formation. The binding of TBC1D7 to the complex is also critical, and mutations affecting this interaction can contribute to disease severity.
Lymphangioleiomyomatosis (LAM)
LAM is a progressive lung disease that predominantly affects women and is often associated with mutations in TSC1 or TSC2. Loss of TSC1-TSC2 complex function in smooth muscle cells leads to abnormal proliferation and cystic lung destruction. The mTORC1 inhibitor rapamycin is used to treat LAM, highlighting the therapeutic relevance of the TSC1-TSC2 complex.
Cancer
Dysregulation of the TSC1-TSC2 complex and its binding partners is implicated in various cancers, including renal cell carcinoma, hepatocellular carcinoma, and pancreatic neuroendocrine tumors. Hyperactive mTORC1 signaling due to loss of TSC complex function promotes cell growth and survival. Targeting the TSC1-TSC2 complex or its downstream effectors is a potential therapeutic strategy.
From TSC1-TSC2 complex binding-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of TSC1-TSC2 complex binding loss on mTORC1 signaling? | TSC1 or TSC2 knockout cell lines (e.g., HEK293T, MEFs) |
| How does a specific point mutation in TSC2 affect complex binding? | TSC2 point-mutation knock-in cells (e.g., TSC2 S939A, T1462A) |
| What is the role of TBC1D7 in TSC complex integrity? | TBC1D7 knockout cells and rescue with tagged TBC1D7 |
| How does FIP200 binding to TSC1-TSC2 regulate cell size? | FIP200 knockout cells and overexpression models |
| Can we visualize TSC1-TSC2 complex binding in live cells? | Tagged knock-in of TSC1 or TSC2 with fluorescent proteins |
| What is the impact of TSC1-TSC2 complex binding on tumor growth? | Xenograft mouse models with TSC1/TSC2 mutant cells |
How to Study the TSC1-TSC2 complex binding Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Co-Immunoprecipitation (Co-IP) | Physical interaction between TSC1, TSC2, and partners | Validation of known interactions, discovery of new partners |
| Affinity purification - mass spectrometry (AP-MS) | Unbiased identification of binding partners | Proteomic profiling of TSC complex interactome |
| Western blotting | Protein levels and phosphorylation status | Assessment of TSC2 phosphorylation and mTORC1 activity |
| In vitro kinase assay | Direct phosphorylation of TSC2 by kinases | Mapping of Akt phosphorylation sites |
| Immunofluorescence | Subcellular localization of TSC complex | Visualization of complex at lysosomes or other compartments |
| Cell size assay | Cell growth and size | Functional readout of TSC complex activity |
| Xenograft mouse models | Tumor growth in vivo | Preclinical testing of mTOR inhibitors |
Co-Immunoprecipitation (Co-IP) and Pull-Down Assays
Co-IP is a classic method to detect physical interactions between TSC1, TSC2, and their binding partners. Cells are lysed, and antibodies against TSC1 or TSC2 are used to pull down the complex, followed by Western blotting for associated proteins. This method can be combined with quantitative mass spectrometry to identify novel binding partners.
Proteomics and Mass Spectrometry
Affinity purification coupled with mass spectrometry (AP-MS) allows unbiased identification of proteins that bind to the TSC1-TSC2 complex. This approach has been used to identify TBC1D7, FIP200, and TBC7 as binding partners. Quantitative proteomics can also reveal dynamic changes in binding upon phosphorylation or other stimuli.
Phosphorylation Analysis
Phosphorylation of TSC2 by Akt and other kinases can be assessed by Western blotting with phospho-specific antibodies. In vitro kinase assays using recombinant Akt and TSC2 can determine direct phosphorylation sites. Phosphoproteomics can globally map phosphorylation events on the TSC1-TSC2 complex and its binding partners.
Functional Assays for mTORC1 Activity
The functional consequence of TSC1-TSC2 complex binding can be measured by assessing mTORC1 activity through phosphorylation of downstream effectors such as S6K1 and 4E-BP1. These assays are typically performed by Western blotting or immunofluorescence. Cell size and proliferation assays can also be used to evaluate the impact of TSC complex function.
How CRISPR Can Be Used to Study GO:0062078 TSC1-TSC2 complex binding
Knockout
CRISPR knockout of TSC1, TSC2, or TBC1D7 can abolish TSC1-TSC2 complex formation and function, leading to constitutive mTORC1 activation. These knockout cell lines are valuable for studying the consequences of loss of complex binding and for testing mTOR inhibitors. EDITGENE provides custom knockout cell models for TSC1, TSC2, TBC1D7, and other related genes.
Point Mutation
CRISPR point mutation can introduce specific amino acid substitutions in TSC2 (e.g., S939A, T1462A) to prevent Akt phosphorylation and study its effect on complex binding and function. Point mutations can also mimic disease-causing mutations found in TSC patients. EDITGENE offers precise point-mutation knock-in services to create isogenic cell lines.
Knock-in
CRISPR knock-in can be used to add tags (e.g., GFP, HA, or BirA) to endogenous TSC1 or TSC2 for imaging, co-IP, or proximity labeling studies. Tagged knock-in cell lines allow for real-time visualization of TSC1-TSC2 complex binding and dynamics. EDITGENE provides tagged knock-in services for TSC1, TSC2, and interacting partners.
Overexpression
CRISPR activation (CRISPRa) or traditional overexpression can be used to increase levels of TSC1, TSC2, or binding partners to study their effects on mTORC1 signaling and cell growth. Overexpression of FIP200, for example, can modulate cell size control. EDITGENE offers overexpression cell models for studying gain-of-function effects.
How EDITGENE Supports TSC1-TSC2 complex binding Research
Researchers studying TSC1-TSC2 complex binding-related genes often need to determine whether a candidate gene is causally involved in complex assembly, regulation, or downstream signaling. This requires robust experimental models that can precisely manipulate gene function and expression. EDITGENE provides a comprehensive suite of CRISPR-based services to accelerate such studies.
Contact EDITGENE today to design your custom CRISPR model for TSC1-TSC2 complex binding research.
Frequently Asked Questions About TSC1-TSC2 complex binding
What is TSC1-TSC2 complex binding?
TSC1-TSC2 complex binding (GO:0062078) is a molecular function describing the selective interaction of a protein with the TSC1-TSC2 heterodimer, a key inhibitor of mTORC1 signaling.
What genes are involved in TSC1-TSC2 complex binding?
Key genes include TSC1, TSC2, TBC1D7, AKT1, RHEB, and MTOR, as well as binding partners like FIP200 and TBC7.
How does TSC1-TSC2 complex binding regulate mTORC1?
The TSC1-TSC2 complex acts as a GAP for Rheb, and binding partners can modulate its activity, thereby controlling mTORC1 signaling.
What diseases are associated with TSC1-TSC2 complex binding?
Dysregulation is linked to tuberous sclerosis complex, lymphangioleiomyomatosis, and various cancers.
What is the role of TBC1D7 in TSC1-TSC2 complex binding?
TBC1D7 is a third subunit that binds TSC1 and is required for the integrity and GAP activity of the TSC1-TSC2 complex.
How is TSC1-TSC2 complex binding regulated by phosphorylation?
Akt phosphorylates TSC2, inhibiting the complex and disrupting its function, which relieves mTORC1 inhibition.
What methods are used to study TSC1-TSC2 complex binding?
Common methods include co-immunoprecipitation, mass spectrometry, Western blotting, and functional assays for mTORC1 activity.
Can CRISPR be used to study TSC1-TSC2 complex binding?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect the function of TSC1, TSC2, and their binding partners.
What is the relationship between TSC1-TSC2 complex binding and cancer?
Loss of TSC1-TSC2 complex function leads to hyperactive mTORC1 signaling, which promotes tumor growth in various cancers.
How does FIP200 interact with the TSC1-TSC2 complex?
FIP200 binds to the TSC1-TSC2 complex and regulates cell size control, linking the complex to autophagy and growth control.
Conclusion
TSC1-TSC2 complex binding (GO:0062078) is a fundamental molecular function that governs the assembly, regulation, and downstream signaling of the TSC tumor suppressor complex. Through interactions with partners such as TBC1D7, FIP200, and TBC7, the TSC1-TSC2 complex integrates diverse cellular signals to control mTORC1 activity, cell growth, and proliferation. Dysregulation of these interactions underlies serious diseases, including tuberous sclerosis complex, lymphangioleiomyomatosis, and cancer. Continued research into the molecular details of TSC1-TSC2 complex binding will provide insights into disease mechanisms and potential therapeutic strategies. EDITGENE offers a comprehensive suite of CRISPR-based tools to support these investigations, from knockout and point-mutation models to library screening and bioinformatics.
References
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- 3. Nellist M et al.. 2005. Phosphorylation and binding partner analysis of the TSC1-TSC2 complex.. Biochem Biophys Res Commun 333(3):818-26 PMID: 15963462
- 4. Abéza C et al.. 2024. The HSP90/R2TP Quaternary Chaperone Scaffolds Assembly of the TSC Complex.. J Mol Biol 436(23):168840 PMID: 39490680
- 5. Santiago Lima AJ et al.. 2014. Identification of regions critical for the integrity of the TSC1-TSC2-TBC1D7 complex.. PLoS One 9(4):e93940 PMID: 24714658
- 6. Dibble CC et al.. 2012. TBC1D7 is a third subunit of the TSC1-TSC2 complex upstream of mTORC1.. Mol Cell 47(4):535-46 PMID: 22795129
- 7. Nakashima A et al.. 2007. Identification of TBC7 having TBC domain as a novel binding protein to TSC1-TSC2 complex.. Biochem Biophys Res Commun 361(1):218-23 PMID: 17658474
- 8. Gan B et al.. 2005. Identification of FIP200 interaction with the TSC1-TSC2 complex and its role in regulation of cell size control.. J Cell Biol 170(3):379-89 PMID: 16043512
