GO:1990131 Gtr1-Gtr2 GTPase complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990131 defines the Gtr1-Gtr2 GTPase complex, a heterodimeric Rag GTPase complex in Saccharomyces cerevisiae that regulates TORC1 signaling [1, 2].
• The complex localizes to the vacuolar membrane and dynamically relocates in response to nutrient availability, controlled by Gtr1 and Gtr2 nucleotide states.
• Npr2-Npr3 (the yeast Ragulator) acts as a guanine nucleotide exchange factor (GEF) that reciprocally converts Gtr1 and Gtr2 nucleotide-binding states to inactivate TORC1 and induce autophagy.
• Structural studies reveal that the EGO complex (Ego1-Ego2-Ego3) tethers Gtr1-Gtr2 to the vacuolar membrane and promotes Rag GTPase-dependent TORC1 signaling [4, 7].
• In fission yeast, the Rag GTPase-Ragulator complex attenuates TORC1 signaling, and loss of Lam2 or Npr2-Npr3 diminishes vacuolar localization of Gtr1-Gtr2, disinhibiting TORC1 [5, 6, 8].
• Dysregulation of Rag GTPase complexes is linked to cancer, neurodegeneration, and metabolic disorders, making Gtr1-Gtr2 a key model for studying TORC1-related diseases [1, 3, 8].
Description
The Gtr1-Gtr2 GTPase complex (GO:1990131) is a heterodimeric GTPase complex found in Saccharomyces cerevisiae, composed of the Gtr1p and Gtr2p proteins [1, 2]. This complex is a functional ortholog of the mammalian Rag GTPase heterodimer and plays a central role in nutrient sensing and TORC1 signaling [1, 3]. The complex localizes to the vacuolar membrane, where it integrates amino acid signals to control cell growth and autophagy [1, 3]. Researchers study this complex to understand fundamental mechanisms of TORC1 regulation, which is conserved from yeast to humans and implicated in cancer, metabolic diseases, and neurodegeneration [1, 3, 8]. The Gtr1-Gtr2 complex serves as a paradigm for how small GTPases coordinate environmental cues with downstream growth pathways [2, 4].
Gtr1-Gtr2 GTPase complex At A Glance
| GO ID | GO:1990131 |
|---|---|
| GO term | Gtr1-Gtr2 GTPase complex |
| Ontology | cellular_component |
| Synonym | None |
| Major function | Heterodimeric GTPase complex that regulates TORC1 signaling in response to nutrients [1, 3] |
| Organism | Saccharomyces cerevisiae [1, 2] |
| Subunit composition | Gtr1p and Gtr2p [1, 2] |
| Localization | Vacuolar membrane [1, 4] |
| Associated complex | EGO complex (Ego1-Ego2-Ego3) [2, 7] |
What Is GO:1990131?
According to the Gene Ontology, GO:1990131 describes a heterodimeric GTPase complex. In Saccharomyces cerevisiae, this complex contains Gtr1p and Gtr2p proteins. It is a cellular component term that captures the physical assembly of these two GTPases, which function together to regulate TORC1 signaling in response to nutrient availability [1, 2].
Why Is Gtr1-Gtr2 GTPase complex Important in Cell Biology?
The Gtr1-Gtr2 GTPase complex is essential for nutrient sensing and TORC1 regulation, a pathway that controls cell growth, proliferation, and autophagy [1, 3]. Dysregulation of this complex leads to inappropriate TORC1 activity, which is linked to cancer, metabolic disorders, and neurodegenerative diseases [1, 3, 8]. Understanding its structure and regulation provides insights into conserved mechanisms of mTOR signaling in humans [4, 7].
• Central regulator of TORC1 signaling in response to amino acids [1, 3].
• Controls autophagy induction through nucleotide-state-dependent interactions.
• Ortholog of mammalian Rag GTPases, providing a model for mTORC1 regulation [1, 8].
• Mutations or loss of function are associated with uncontrolled cell growth [1, 6].
• Structural studies inform drug design targeting Rag GTPase complexes [4, 7].
• Key to understanding vacuolar membrane dynamics and nutrient sensing [1, 4].
• Implicated in cancer, diabetes, and neurodegeneration through TORC1 dysregulation [1, 3, 8].
• Provides a paradigm for GTPase heterodimer regulation by GEFs and GAPs [3, 5].
Structure and Composition of Gtr1-Gtr2 GTPase complex
Heterodimer Formation
In simple terms: Gtr1 and Gtr2 proteins pair up to form a functional unit.
The Gtr1-Gtr2 complex is a heterodimer composed of Gtr1p and Gtr2p, two small GTPases that associate tightly [1, 2]. This dimerization is essential for their stability and function in TORC1 signaling.
Interaction with EGO Complex
In simple terms: The Gtr1-Gtr2 dimer binds to a larger protein assembly called the EGO complex.
The EGO complex, consisting of Ego1, Ego2, and Ego3, interacts with Gtr1-Gtr2 to anchor it to the vacuolar membrane [2, 7]. Ego3 functions as a homodimer to mediate the interaction between Gtr1-Gtr2 and Ego1, facilitating TORC1 activation.
Membrane Tethering
In simple terms: The complex is attached to the vacuolar membrane through the EGO complex.
Structural insights reveal that the EGO-TC complex mediates membrane tethering of the Rag GTPases, positioning Gtr1-Gtr2 at the vacuolar surface where TORC1 is activated. This localization is dynamic and regulated by nutrient status.
Nucleotide-Binding States
In simple terms: Gtr1 and Gtr2 can be in 'on' or 'off' states depending on bound nucleotides.
Gtr1 and Gtr2 cycle between GTP-bound and GDP-bound states, which determine their ability to activate TORC1. Npr2-Npr3 reciprocally converts their nucleotide-binding states to inactivate TORC1 and induce autophagy.
Key Genes Involved in GO:1990131 Gtr1-Gtr2 GTPase complex
The following genes and proteins are key components or regulators of the Gtr1-Gtr2 GTPase complex and its associated signaling pathway.
| Gene | Major Role | Research Relevance |
|---|---|---|
| GTR1 | GTPase subunit of the complex | Core component; mutations affect TORC1 signaling [1, 2] |
| GTR2 | GTPase subunit of the complex | Core component; mutations affect TORC1 signaling [1, 2] |
| EGO1 | Scaffold in EGO complex | Mediates Gtr1-Gtr2 interaction with Ego3 [2, 7] |
| EGO2 | Component of EGO complex | Stabilizes EGO complex for TORC1 activation |
| EGO3 | Homodimer mediating interaction | Links Gtr1-Gtr2 to Ego1 [2, 7] |
| NPR2 | GEF for Gtr1-Gtr2 | Reciprocally converts nucleotide states to inactivate TORC1 |
| NPR3 | GEF for Gtr1-Gtr2 | Works with Npr2 to regulate Gtr1-Gtr2 |
| TOR1 | Kinase in TORC1 | Downstream effector of Gtr1-Gtr2 signaling [1, 3] |
| LAM2 | Ragulator component in fission yeast | Affects vacuolar localization of Gtr1-Gtr2 |
| TCO89 | TORC1 component | Interacts with Gtr1-Gtr2 pathway |
| KOG1 | TORC1 component | Part of TORC1 regulated by Gtr1-Gtr2 |
| LST8 | TORC1 component | Part of TORC1 regulated by Gtr1-Gtr2 |
| GATOR1 | GAP complex for Rag GTPases | Attenuates TORC1 through Rag GTPases |
| GATOR2 | Regulator of Rag GTPases | Promotes TORC1 signaling |
| RAGULATOR | GEF complex for Rag GTPases | Activates Rag GTPases in fission yeast [5, 8] |
| SLM1 | Downstream effector | Links TORC1 to sphingolipid signaling |
| SLM2 | Downstream effector | Links TORC1 to sphingolipid signaling |
How Is Gtr1-Gtr2 GTPase complex Regulated?
The Gtr1-Gtr2 GTPase complex is regulated by nutrient availability, particularly amino acids, which control its nucleotide-binding state and localization [1, 3]. Npr2-Npr3 acts as a guanine nucleotide exchange factor (GEF) that reciprocally converts Gtr1 and Gtr2 nucleotide-binding states, leading to TORC1 inactivation and autophagy induction. In fission yeast, the Rag GTPase-Ragulator complex attenuates TORC1 signaling, and loss of Lam2 or Npr2-Npr3 diminishes vacuolar localization of Gtr1-Gtr2, disinhibiting TORC1 [5, 6, 8]. Additionally, the EGO complex (Ego1-Ego2-Ego3) is required for stable membrane association and proper signaling [2, 4, 7].
Gtr1-Gtr2 GTPase complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| GTR1 | Cancer, metabolic disorders | Knockout in S. cerevisiae or human cell lines [1, 3] |
| GTR2 | Cancer, neurodegeneration | Point mutation to alter GTP binding |
| NPR2 | Autophagy-related diseases | Overexpression or knockout in yeast |
| LAM2 | TORC1-related growth defects | Knockout in fission yeast |
| GATOR1 | Cancer, epilepsy | Knockout in mammalian cells |
Cancer
Dysregulation of Rag GTPase complexes, including the Gtr1-Gtr2 orthologs, leads to aberrant TORC1 activation, which is a hallmark of many cancers [1, 3, 8]. Mutations in Rag GTPases or their regulators can promote uncontrolled cell growth and proliferation.
Neurodegeneration
Impaired TORC1 signaling has been linked to neurodegenerative diseases such as Alzheimer's and Parkinson's, where autophagy dysfunction contributes to protein aggregation. The Gtr1-Gtr2 complex regulates autophagy, and its dysregulation may exacerbate neuronal stress.
Metabolic Disorders
The Gtr1-Gtr2 complex is central to nutrient sensing, and its dysfunction is associated with metabolic disorders like diabetes and obesity [1, 6]. Altered TORC1 activity affects insulin sensitivity and glucose homeostasis.
From Gtr1-Gtr2 GTPase complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does Gtr1-Gtr2 complex regulate TORC1 under nutrient stress? | Knockout of GTR1 or GTR2 in S. cerevisiae |
| What is the effect of constitutive GTP binding on autophagy? | Point mutation in GTR1 (e.g., Q66L) |
| How does EGO complex tether Gtr1-Gtr2 to vacuole? | Tagged knock-in of EGO1 with fluorescent protein |
| Can overexpression of Npr2-Npr3 rescue TORC1 inactivation? | Overexpression of NPR2 and NPR3 |
| What is the role of Lam2 in vacuolar localization? | Knockout of LAM2 in fission yeast |
| How do GATOR1 mutations affect TORC1 signaling? | Knockout of GATOR1 subunits in human cells |
How to Study the Gtr1-Gtr2 GTPase complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Fluorescence microscopy | Localization and dynamics of Gtr1-Gtr2 | Nutrient-dependent relocation |
| Co-immunoprecipitation | Protein-protein interactions | Identifying EGO complex components |
| X-ray crystallography | Atomic structure of complexes | Understanding membrane tethering [4, 7] |
| GTPase activity assay | GTP hydrolysis and exchange rates | Regulation by Npr2-Npr3 |
| Western blot | Protein expression and phosphorylation | TORC1 activity readout [1, 3] |
| RNA-seq | Transcriptional changes | Autophagy gene expression |
| CRISPR knockout | Gene function | Loss-of-function studies [1, 6] |
| Live-cell imaging | Real-time dynamics | Vacuolar localization |
Fluorescence Microscopy
Live-cell imaging of GFP-tagged Gtr1 or Gtr2 allows visualization of dynamic relocation of the complex to and from the vacuolar membrane in response to nutrients. This method is essential for studying localization and complex assembly [1, 4].
Co-immunoprecipitation and Mass Spectrometry
Co-IP followed by mass spectrometry identifies interacting partners of the Gtr1-Gtr2 complex, such as Ego1, Ego2, and Ego3, and reveals changes in complex composition under different conditions [2, 7].
Structural Biology (X-ray Crystallography and Cryo-EM)
Crystal structures of the EGO complex and Rag GTPases provide atomic-level details of how Gtr1-Gtr2 interacts with Ego proteins and mediates membrane tethering [4, 7]. These methods inform mutational studies and drug design.
Biochemical Assays for GTPase Activity
GTP hydrolysis and nucleotide exchange assays measure the activity of Gtr1 and Gtr2 and the impact of regulators like Npr2-Npr3. These assays are crucial for understanding the molecular mechanism of TORC1 regulation.
How CRISPR Can Be Used to Study GO:1990131 Gtr1-Gtr2 GTPase complex
Knockout
CRISPR knockout of GTR1 or GTR2 in Saccharomyces cerevisiae or human cell lines abolishes the Gtr1-Gtr2 complex, leading to constitutive TORC1 inactivation or autophagy induction, depending on context [1, 3]. This approach is used to study the essentiality of the complex in nutrient sensing.
Point Mutation
CRISPR-mediated point mutations, such as Q66L in GTR1, lock the GTPase in a GTP-bound state, mimicking constitutive activation and altering TORC1 signaling. These models help dissect nucleotide-dependent functions.
Knock-in
Tagged knock-in of GTR1 or GTR2 with fluorescent proteins (e.g., GFP) allows real-time tracking of the complex localization and dynamics in live cells [1, 4]. This is critical for understanding spatial regulation.
Overexpression
CRISPR activation (CRISPRa) or plasmid-based overexpression of GTR1, GTR2, or their regulators (e.g., NPR2, NPR3) can amplify signaling and rescue loss-of-function phenotypes. Overexpression studies reveal dose-dependent effects on TORC1.
How EDITGENE Supports Gtr1-Gtr2 GTPase complex Research
Researchers studying Gtr1-Gtr2 GTPase complex-related genes often need to determine whether a candidate gene is causally involved in TORC1 signaling, autophagy, or disease. EDITGENE provides comprehensive CRISPR services to create precise cellular models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for Gtr1-Gtr2 GTPase complex research.
Frequently Asked Questions About Gtr1-Gtr2 GTPase complex
What is the Gtr1-Gtr2 GTPase complex?
The Gtr1-Gtr2 GTPase complex (GO:1990131) is a heterodimeric GTPase complex in Saccharomyces cerevisiae composed of Gtr1p and Gtr2p that regulates TORC1 signaling [1, 2].
What genes are involved in the Gtr1-Gtr2 GTPase complex?
The core genes are GTR1 and GTR2, which encode the two GTPase subunits. Associated regulators include NPR2, NPR3, EGO1, EGO2, EGO3, and TOR1 [1, 2, 3, 7].
Where is the Gtr1-Gtr2 complex localized?
It localizes to the vacuolar membrane in yeast, where it interacts with the EGO complex to regulate TORC1 [1, 4].
How does the Gtr1-Gtr2 complex regulate TORC1?
The complex cycles between GTP- and GDP-bound states; Npr2-Npr3 reciprocally converts these states to inactivate TORC1 and induce autophagy.
What is the role of the EGO complex in Gtr1-Gtr2 function?
The EGO complex (Ego1-Ego2-Ego3) tethers Gtr1-Gtr2 to the vacuolar membrane and promotes Rag GTPase-dependent TORC1 signaling [2, 4, 7].
Is the Gtr1-Gtr2 complex conserved in humans?
Yes, it is orthologous to the mammalian Rag GTPase heterodimer (RagA/B-RagC/D), which regulates mTORC1 [1, 8].
What diseases are associated with Gtr1-Gtr2 dysfunction?
Dysregulation is linked to cancer, neurodegeneration, and metabolic disorders due to aberrant TORC1 activity [1, 3, 8].
How can I study the Gtr1-Gtr2 complex using CRISPR?
CRISPR knockout, point mutation, knock-in, and overexpression models can be used to dissect its function in TORC1 signaling and autophagy [1, 3].
What methods are used to study Gtr1-Gtr2 localization?
Fluorescence microscopy of GFP-tagged Gtr1 or Gtr2 is commonly used to track dynamic relocation to the vacuolar membrane [1, 4].
What are the key regulators of Gtr1-Gtr2 nucleotide states?
Npr2-Npr3 acts as a GEF to reciprocally convert Gtr1 and Gtr2 nucleotide-binding states, while GATOR1 functions as a GAP in related pathways [3, 8].
Conclusion
The Gtr1-Gtr2 GTPase complex (GO:1990131) is a critical regulator of TORC1 signaling in Saccharomyces cerevisiae, with conserved functions in nutrient sensing and autophagy [1, 3]. Its structural and functional characterization has provided deep insights into Rag GTPase biology, with implications for human diseases such as cancer and neurodegeneration [4, 7, 8]. Continued research using advanced CRISPR models will further elucidate its mechanisms and therapeutic potential [1, 3].
References
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- 3. Kira S et al.. 2014. Reciprocal conversion of Gtr1 and Gtr2 nucleotide-binding states by Npr2-Npr3 inactivates TORC1 and induces autophagy.. Autophagy 10(9):1565-78 PMID: 25046117
- 4. Zhang T et al.. 2019. Structural insights into the EGO-TC-mediated membrane tethering of the TORC1-regulatory Rag GTPases.. Sci Adv 5(9):eaax8164 PMID: 31579828
- 5. Fukuda T et al.. 2018. The Rag GTPase-Ragulator complex attenuates TOR complex 1 signaling in fission yeast.. Autophagy 14(6):1105-1106 PMID: 29799770
- 6. Ma N et al.. 2016. The Loss of Lam2 and Npr2-Npr3 Diminishes the Vacuolar Localization of Gtr1-Gtr2 and Disinhibits TORC1 Activity in Fission Yeast.. PLoS One 11(5):e0156239 PMID: 27227887
- 7. Powis K et al.. 2015. Crystal structure of the Ego1-Ego2-Ego3 complex and its role in promoting Rag GTPase-dependent TORC1 signaling.. Cell Res 25(9):1043-59 PMID: 26206314
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