GO:1990877 FNIP-folliculin RagC/D GAP: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990877 describes the FNIP-folliculin RagC/D GAP, a heterodimeric GTPase-activating protein complex that acts on Rag family GTPases.
• In budding yeast the complex is formed by Lst4 and Lst7, which together function as a GAP for the Rag GTPase Gtr2.
• The mammalian orthologous complex contains folliculin (FLCN) paired with either FNIP1 or FNIP2.
• This complex is a key upstream regulator of TORC1/mTORC1 signaling in response to amino acid availability.
• Loss of GAP activity leads to constitutive Rag GTPase signaling and is linked to diseases such as Birt-Hogg-Dubé syndrome and cancer.
• Studying this complex requires integrated approaches including CRISPR knockout, biochemical GAP assays, and structural modeling.
Description
The FNIP-folliculin RagC/D GAP (GO:1990877) is a cellular component defined as a heterodimeric complex that functions as a GTPase-activating protein (GAP) for Rag family GTPases. This complex is conserved from yeast to humans and serves as a critical node linking amino acid availability to the master growth regulator TORC1 (target of rapamycin complex 1). In budding yeast, the complex comprises Lst4 and Lst7, which act on the Rag GTPase Gtr2. In mammals, the orthologous complex consists of folliculin (FLCN) and either follicular interacting protein 1 (FNIP1) or FNIP2, targeting the RagC/D GTPases. Understanding this complex is essential because it provides a direct mechanistic link between nutrient sensing and cell growth control, with profound implications for cancer, metabolic disorders, and lysosomal signaling.
FNIP-folliculin RagC/D GAP At A Glance
| GO ID | GO:1990877 |
|---|---|
| GO term | FNIP-folliculin RagC/D GAP |
| Ontology | cellular_component |
| Synonym | BFC complex, FLCN-FNIP1 complex, FLCN-FNIP2 complex, FNIP-Folliculin RagC/D GAP complex, Lst4-Lst7 complex |
| Major function | GTPase-activating protein (GAP) complex for Rag family GTPases |
| Yeast components | Lst4 and Lst7 |
| Mammalian components | FLCN with FNIP1 or FNIP2 |
| Target GTPases | RagC/D in mammals; Gtr2 in yeast |
| Pathway | TORC1/mTORC1 signaling |
What Is GO:1990877?
According to the Gene Ontology, GO:1990877 (FNIP-folliculin RagC/D GAP) is a heterodimeric complex that functions as a GTPase-activating protein (GAP) complex for members of the Rag family of GTPases. In budding yeast, this complex contains Lst4 and Lst7, while the orthologous mammalian complex contains folliculin (FLCN) and either follicular interacting protein 1 (FNIP1) or FNIP2. The complex is also known by synonyms such as BFC complex, FLCN-FNIP1 complex, FLCN-FNIP2 complex, FNIP-Folliculin RagC/D GAP complex, and Lst4-Lst7 complex.
Why Is FNIP-folliculin RagC/D GAP Important in Cell Biology?
The FNIP-folliculin RagC/D GAP complex is critically important because it directly controls the activation state of Rag GTPases, which in turn determine whether TORC1/mTORC1 is switched on or off in response to amino acids. This places the complex at the heart of nutrient sensing and cell growth regulation, processes that are frequently deregulated in cancer and metabolic diseases. Mutations in FLCN cause Birt-Hogg-Dubé syndrome, a inherited disorder characterized by skin lesions and increased risk of kidney cancer, underscoring the clinical relevance of this complex. Moreover, the yeast Lst4-Lst7 complex provides a genetically tractable model to dissect the molecular mechanism of GAP activity toward Rag GTPases.
• Central regulator of TORC1/mTORC1 signaling in response to amino acid availability.
• Directly controls Rag GTPase nucleotide state through GAP activity.
• Mutations in FLCN, a component of the complex, cause Birt-Hogg-Dubé syndrome and predispose to kidney cancer.
• Provides a conserved mechanism from yeast to humans for nutrient-dependent growth control.
• Potential therapeutic target for cancers with hyperactive mTORC1 signaling.
• Key to understanding lysosomal nutrient sensing and Rag GTPase cycles.
• Yeast Lst4-Lst7 serves as a powerful genetic model for studying GAP function.
• Links amino acid signaling to cell growth, autophagy, and metabolism.
• Involved in cellular responses to stress and energy status.
• Offers opportunities for CRISPR-based disease modeling and drug discovery.
What Happens During FNIP-folliculin RagC/D GAP?
Amino Acid Sensing and Complex Recruitment
In simple terms: When amino acids are available, the cell recruits the GAP complex to the lysosome to turn on growth signals.
In budding yeast, amino acids stimulate TORC1 through the Lst4-Lst7 complex, which acts as a GAP for the Rag family GTPase Gtr2. The complex is recruited to the lysosomal/vacuolar membrane in response to amino acid availability, where it engages its substrate GTPase. This recruitment is a prerequisite for subsequent GAP activity and TORC1 activation.
GAP Activity and Rag GTPase Inactivation
In simple terms: The complex acts like a switch that turns off the Rag GTPase by accelerating its GTP hydrolysis.
The Lst4-Lst7 complex functions as a GTPase-activating protein (GAP) for Gtr2, promoting the hydrolysis of GTP to GDP on the Rag GTPase. This inactivation of the Rag GTPase is a critical step in the signaling cascade that leads to TORC1 activation. In mammals, the FLCN-FNIP complex similarly acts as a GAP for RagC/D, facilitating the conversion to the GDP-bound state.
TORC1 Activation and Downstream Signaling
In simple terms: Once the Rag GTPase is switched off, the growth controller TORC1 is switched on.
GAP-mediated inactivation of the Rag GTPase allows TORC1 to become active, leading to phosphorylation of downstream effectors that promote cell growth and proliferation. This signaling axis is conserved from yeast to mammals, highlighting the fundamental importance of the FNIP-folliculin RagC/D GAP complex in nutrient sensing.
Key Genes Involved in GO:1990877 FNIP-folliculin RagC/D GAP
The following genes and proteins are core components or direct regulators of the FNIP-folliculin RagC/D GAP complex.
| Gene | Major Role | Research Relevance |
|---|---|---|
| LST4 | Yeast component of the Lst4-Lst7 GAP complex | Genetic model for GAP function and TORC1 signaling |
| LST7 | Yeast component of the Lst4-Lst7 GAP complex | Essential partner for Lst4 stability and GAP activity |
| GTR2 | Yeast Rag GTPase targeted by the GAP complex | Substrate for GAP assays and TORC1 regulation |
| FLCN | Mammalian folliculin, component of the FLCN-FNIP complex | Tumor suppressor mutated in Birt-Hogg-Dubé syndrome |
| FNIP1 | Folliculin interacting protein 1, alternative partner of FLCN | Modulates FLCN function and mTORC1 signaling |
| FNIP2 | Folliculin interacting protein 2, alternative partner of FLCN | Modulates FLCN function and mTORC1 signaling |
| RRAGC | Mammalian RagC GTPase, substrate of the GAP complex | Direct target of GAP activity; mutations in cancer |
| RRAGD | Mammalian RagD GTPase, substrate of the GAP complex | Direct target of GAP activity; mutations in cancer |
| MTOR | mTOR kinase, catalytic subunit of TORC1 | Downstream effector of Rag GTPase signaling |
| RPTOR | Raptor, regulatory subunit of TORC1 | Scaffold for TORC1 assembly and substrate recruitment |
| MLST8 | mLST8, component of TORC1 | Stabilizes TORC1 complex |
| DEPTOR | DEP domain-containing mTOR-interacting protein | Negative regulator of mTORC1 |
| TSC1 | Tuberous sclerosis 1, component of TSC complex | Cross-talk with Rag GTPase signaling |
| TSC2 | Tuberous sclerosis 2, component of TSC complex | Cross-talk with Rag GTPase signaling |
| RHEB | Ras homolog enriched in brain, mTORC1 activator | Integrates signals from Rag GTPases |
| SLC38A9 | Lysosomal amino acid transporter | Upstream sensor for arginine and leucine |
| LAMTOR1 | Late endosomal/lysosomal adaptor, component of Ragulator | Scaffold for Rag GTPase recruitment |
How Is FNIP-folliculin RagC/D GAP Regulated?
The FNIP-folliculin RagC/D GAP complex is regulated by amino acid availability, which controls its recruitment to the lysosomal membrane and its interaction with Rag GTPases. In budding yeast, amino acids stimulate TORC1 through Lst4-Lst7, indicating that the complex is a direct downstream responder to nutrient signals. Additionally, the complex may be subject to post-translational modifications and protein-protein interactions that modulate its GAP activity, although the precise mechanisms require further investigation.
FNIP-folliculin RagC/D GAP and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| FLCN | Birt-Hogg-Dubé syndrome, kidney cancer | FLCN knockout cell lines and mouse models |
| FNIP1 | Cancer predisposition, metabolic defects | FNIP1 knockout and knock-in models |
| FNIP2 | Cancer predisposition, metabolic defects | FNIP2 knockout and knock-in models |
| RRAGC | Sporadic cancers, mTORC1 hyperactivation | RRAGC point-mutation knock-in models |
| RRAGD | Sporadic cancers, mTORC1 hyperactivation | RRAGD point-mutation knock-in models |
Birt-Hogg-Dubé Syndrome and Kidney Cancer
Mutations in FLCN, a core component of the FNIP-folliculin RagC/D GAP complex, cause Birt-Hogg-Dubé syndrome, an inherited disorder characterized by fibrofolliculomas, lung cysts, and a markedly increased risk of renal cell carcinoma. Loss of FLCN function impairs GAP activity toward RagC/D, leading to constitutive mTORC1 signaling and tumorigenesis.
Sporadic Cancers with mTORC1 Dysregulation
Dysregulation of the Rag GTPase-TORC1 axis, in which the FNIP-folliculin RagC/D GAP complex plays a central role, is observed in various sporadic cancers. Activating mutations in Rag GTPases or loss of GAP components can drive aberrant cell growth and proliferation, making this complex a potential therapeutic target.
Metabolic and Lysosomal Storage Disorders
Given its role in amino acid sensing and lysosomal signaling, the FNIP-folliculin RagC/D GAP complex may contribute to metabolic disorders and lysosomal storage diseases, although direct evidence is still emerging. The yeast Lst4-Lst7 model provides a valuable system to study these connections.
From FNIP-folliculin RagC/D GAP-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of FLCN loss on mTORC1 signaling? | FLCN knockout cell lines |
| How does the Lst4-Lst7 complex regulate Gtr2? | Yeast LST4/LST7 deletion strains |
| What is the structural basis of GAP activity? | Recombinant FLCN-FNIP complex for cryo-EM |
| Can point mutations in Rag GTPases mimic disease? | RRAGC/RRAGD knock-in mutations |
| How does amino acid availability affect complex localization? | Tagged knock-in of FLCN or Lst4 with fluorescent tags |
| What are the downstream transcriptional changes? | Overexpression of FLCN or FNIP1/2 followed by RNA-seq |
How to Study the FNIP-folliculin RagC/D GAP Process
| Method | What It Measures | Typical Application |
|---|---|---|
| GTP hydrolysis assay | GAP activity | In vitro validation of complex function |
| CRISPR knockout screening | Gene essentiality and modifiers | Identification of pathway components |
| AP-MS | Protein-protein interactions | Mapping the interactome |
| BioID proximity labeling | Transient interactions | Capturing dynamic complexes |
| Fluorescence microscopy | Subcellular localization | Nutrient-dependent recruitment |
| RNA-seq | Transcriptional changes | Downstream effects of GAP loss |
| Phosphoproteomics | mTORC1 substrate phosphorylation | Signaling output measurement |
Biochemical GAP Assays
GTPase-activating protein activity of the FNIP-folliculin complex can be measured using in vitro GTP hydrolysis assays with recombinant Rag GTPases. These assays typically employ fluorescently labeled GTP or radioactive GTP to monitor the rate of hydrolysis in the presence or absence of the complex.
CRISPR-Based Genetic Screens
Genome-wide CRISPR knockout or activation screens can identify modifiers of the FNIP-folliculin RagC/D GAP pathway. Such screens are powerful for uncovering synthetic lethal interactions and resistance mechanisms relevant to cancer therapy.
Proteomics and Interactomics
Affinity purification coupled with mass spectrometry (AP-MS) can define the interactome of the FNIP-folliculin complex and its dynamic association with Rag GTPases. Proximity labeling approaches such as BioID can capture transient interactions in living cells.
Imaging and Localization Studies
Fluorescence microscopy of tagged components (e.g., GFP-FLCN, mCherry-Lst4) allows visualization of complex recruitment to lysosomes or vacuoles under different nutrient conditions. Live-cell imaging can reveal the spatiotemporal dynamics of GAP activity.
How CRISPR Can Be Used to Study GO:1990877 FNIP-folliculin RagC/D GAP
Knockout
CRISPR knockout of FLCN, FNIP1, FNIP2, or yeast LST4/LST7 can abolish GAP complex function, leading to constitutive Rag GTPase signaling and mTORC1 activation. These models are essential for studying loss-of-function phenotypes and testing targeted therapies.
Point Mutation
Introducing disease-associated point mutations into FLCN or Rag GTPases (e.g., RRAGC) via CRISPR base editing or HDR can mimic patient-specific alterations and reveal their impact on GAP activity and downstream signaling.
Knock-in
Knock-in of epitope tags (e.g., HA, GFP) or luciferase into endogenous FLCN or FNIP loci enables real-time tracking of complex localization, interaction, and stability without overexpression artifacts.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of FLCN, FNIP1, or FNIP2 can amplify GAP complex levels to study gain-of-function effects on mTORC1 suppression and cell growth.
How EDITGENE Supports FNIP-folliculin RagC/D GAP Research
Researchers studying FNIP-folliculin RagC/D GAP-related genes often need to determine whether a candidate gene is causally involved in nutrient sensing, mTORC1 signaling, or disease pathogenesis. EDITGENE provides end-to-end CRISPR solutions to generate precisely engineered cell models that answer these questions.
Contact EDITGENE today to design your custom CRISPR model for FNIP-folliculin RagC/D GAP research.
Frequently Asked Questions About FNIP-folliculin RagC/D GAP
What is GO:1990877?
GO:1990877 is the Gene Ontology identifier for the FNIP-folliculin RagC/D GAP, a heterodimeric GTPase-activating protein complex that acts on Rag family GTPases.
What genes are involved in FNIP-folliculin RagC/D GAP?
In yeast, the complex contains Lst4 and Lst7; in mammals, it contains folliculin (FLCN) and either FNIP1 or FNIP2.
What does the FNIP-folliculin RagC/D GAP complex do?
It functions as a GTPase-activating protein (GAP) for Rag GTPases, promoting GTP hydrolysis and thereby regulating TORC1/mTORC1 signaling in response to amino acids.
How is the FNIP-folliculin RagC/D GAP complex regulated?
It is regulated by amino acid availability, which controls its recruitment to the lysosomal membrane and its interaction with Rag GTPases.
What diseases are associated with FNIP-folliculin RagC/D GAP?
Mutations in FLCN cause Birt-Hogg-Dubé syndrome, and dysregulation of the complex is linked to various cancers and metabolic disorders.
What is the yeast ortholog of the FNIP-folliculin RagC/D GAP?
The yeast ortholog is the Lst4-Lst7 complex, which acts as a GAP for the Rag GTPase Gtr2.
How can I study the FNIP-folliculin RagC/D GAP complex?
Common methods include CRISPR knockout, biochemical GAP assays, proteomics, and imaging of tagged components.
What are the synonyms for GO:1990877?
Synonyms include BFC complex, FLCN-FNIP1 complex, FLCN-FNIP2 complex, FNIP-Folliculin RagC/D GAP complex, and Lst4-Lst7 complex.
Why is the FNIP-folliculin RagC/D GAP complex important for cancer research?
Because it controls mTORC1 signaling, and its dysfunction leads to constitutive growth signals that drive tumorigenesis.
Can CRISPR be used to model FNIP-folliculin RagC/D GAP-related diseases?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to study the complex and its role in disease.
Conclusion
The FNIP-folliculin RagC/D GAP (GO:1990877) is a conserved heterodimeric complex that serves as a critical GAP for Rag GTPases, linking amino acid sensing to TORC1/mTORC1 activation. Its central role in nutrient signaling and its association with diseases such as Birt-Hogg-Dubé syndrome and cancer make it a high-priority research target. Advanced CRISPR-based models and biochemical assays will continue to unravel its mechanism and therapeutic potential.
References
- 1. Péli-Gulli MP et al.. 2015. Amino Acids Stimulate TORC1 through Lst4-Lst7, a GTPase-Activating Protein Complex for the Rag Family GTPase Gtr2.. Cell Rep 13(1):1-7 PMID: 26387955
