| RRAGC |
|---|
| Symbol | RRAGC |
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| Full Name | Ras-Related GTP Binding C |
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| Chromosome | 1p36.22 |
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| NCBI Gene ID | [10876](https://www.ncbi.nlm.nih.gov/gene/10876) |
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| OMIM | [608267](https://www.omim.org/entry/608267) |
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| Ensembl | [ENSG00000136244](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000136244) |
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| UniProt | [Q9HBH5](https://www.uniprot.org/uniprot/Q9HBH5) |
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| Protein Class | Rag GTPase family |
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| Associated Diseases | Alzheimer's Disease, Parkinson's Disease, Cancer, Metabolic Disorders |
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RRAGC (Ras-Related GTP Binding C, also known as RagC) is a member of the Rag GTPase family that plays a critical role in regulating mTORC1 (mechanistic Target of Rapamycin Complex 1) signaling in response to amino acid availability. Rag GTPases (RRAGA, RRAGB, RRAGC, RRAGD) function as heterodimers to regulate cellular growth, metabolism, and autophagy. In neurons, RRAGC-mediated signaling is essential for synaptic plasticity, memory formation, and neuronal survival. Dysregulated Rag GTPase signaling is implicated in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease.
RRAGC functions as a GTPase that partners with RRAGA, RRAGB, or RRAGD to form functional heterodimers. Unlike classical Ras GTPases, Rag GTPases do not directly regulate cell proliferation but instead control the nutrient-sensitive mTORC1 pathway:
- GTP-bound state: Active, promotes mTORC1 recruitment to lysosomes
- GDP-bound state: Inactive, prevents mTORC1 signaling
- GTPase cycle: Regulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs)
mTORC1 Activation
RRAGC is essential for mTORC1 activation in response to amino acids:
- Heterodimer formation: RRAGC forms heterodimers with RRAGA or RRAGB
- Lysosomal recruitment: The Rag heterodimer recruits mTORC1 to the lysosomal surface where it is activated
- Amino acid sensing: Rag GTPases sense amino acid levels in the lysosomal lumen
- Ragulator complex: RRAGC interacts with the Ragulator complex (LAMTOR1-5) for proper localization
Autophagy Regulation
Rag GTPases are crucial regulators of autophagy:
- mTORC1 inhibition: Inactive Rag GTPases allow mTORC1 to release, enabling autophagy initiation
- ULK1 complex regulation: mTORC1 phosphorylates and inhibits the ULK1 complex when active
- Autophagosome formation: Rag GTPase signaling affects the nucleation and expansion of autophagosomes
Neuronal Function
In neurons, RRAGC-mediated signaling controls:
- Synaptic plasticity: mTORC1 regulates local translation at synapses required for LTP and LTD
- Memory formation: mTORC1 signaling is essential for consolidation of long-term memory
- Neuronal growth: mTORC1 controls protein synthesis for dendritic arborization and axon guidance
- Metabolic regulation: Neuronal mTORC1 integrates nutrient and growth factor signaling
RRAGC interacts with several key neuronal proteins:
| Interactor |
Function |
Reference |
| RRAGA/RAGB |
Heterodimer formation |
[@efeyan2012] |
| RRAGD |
Alternative heterodimer |
[@ye2015] |
| mTORC1 (MTOR) |
Lysosomal recruitment |
[@sabatini2017] |
| LAMTOR1-5 |
Ragulator complex |
[@kim2011] |
| ULK1 |
Autophagy initiation |
[@mizushima2007] |
| FIP200 |
ULK1 complex component |
[@martina2008] |
RRAGC is expressed throughout the brain with highest expression in:
- Cerebral Cortex: Highest expression in pyramidal neurons of layers II-IV
- Hippocampus: Strong expression in CA1-CA3 pyramidal cells and dentate gyrus granule cells
- Cerebellum: Purkinje cells and granule cells
- Brainstem: Motor nuclei and sensory processing regions
- Basal Ganglia: Striatal medium spiny neurons
Within neurons, RRAGC localizes to:
- Lysosomal membranes: Primary site of function for mTORC1 regulation
- Dendritic shafts: Distributed throughout dendrites for local translation control
- Postsynaptic densities: Present at synapses for activity-dependent regulation
- Growth cones: Regulates local mTORC1 signaling during development
RRAGC expression is regulated by:
- Nutrient status: Amino acid availability affects Rag GTPase activation state
- Cellular energy: AMPK inhibits mTORC1 via TSC1/2 when energy is low
- Growth factors: Insulin and other growth factors activate mTORC1 signaling
- Neuronal activity: Synaptic activity modulates mTORC1 pathway activation
RRAGC and the mTORC1 pathway are heavily implicated in Alzheimer's disease:
mTOR Hyperactivation
- mTORC1 is hyperactive in AD brains, contributing to:
- Impaired autophagy leading to protein aggregate accumulation
- Aberrant tau phosphorylation via S6K1
- Synaptic dysfunction from dysregulated local translation
- Memory deficits from impaired consolidation
Autophagy Failure
- RRAGC-mediated autophagy is impaired in AD:
- Lysosomal dysfunction reduces amino acid signaling
- Autophagosome accumulation indicates blocked autophagy
- Amyloid-beta disrupts mTORC1-autophagy axis
Therapeutic Implications
- mTOR inhibitors (rapamycin, everolimus) show promise in AD models
- autophagy enhancers may complement mTOR inhibition
RRAGC signaling connects to several PD mechanisms:
Autophagy Defects
- PD is associated with impaired autophagy-lysosome function
- RRAGC dysfunction may contribute to:
- Reduced alpha-synuclein clearance
- Mitochondrial dysfunction
- Dopaminergic neuron vulnerability
Lysosomal Dysfunction
- Several PD genes (GBA, ATP13A2, LAMP2) affect lysosomal function
- RRAGC-mediated mTORC1 signaling depends on lysosomal integrity
Therapeutic Potential
- autophagy inducers for PD treatment
- Lysosomal function enhancers
Dysregulated mTORC1 signaling drives tumor growth:
- RRAGC mutations can cause constitutive mTORC1 activation
- S6K1 and 4E-BP1 phosphorylation promote cell proliferation
- Therapeutic targeting with mTOR inhibitors
mTORC1 dysregulation affects metabolic homeostasis:
- Obesity and insulin resistance linked to mTORC1 hyperactivation
- Diabetes and energy homeostasis affected by Rag GTPase signaling
RRAGC represents a therapeutic target for:
- Neurodegenerative diseases: Restore proper mTORC1-autophagy balance
- Cancer: Inhibit hyperactive mTORC1 signaling
- Metabolic disorders: Modulate nutrient sensing
| Strategy |
Approach |
Status |
| mTOR inhibitors |
Rapamycin, torin analogs |
FDA approved for some conditions |
| autophagy enhancers |
Activate ULK1 complex |
Preclinical |
| Lysosomal modulators |
Improve lysosomal function |
In development |
| Rag GTPase modulators |
Direct targeting |
Experimental |
- Achieving brain-specific delivery
- Balancing mTORC1 inhibition with normal neuronal function
- Maintaining proper autophagy while inhibiting mTORC1
- Sabatini DM et al., mTOR Signaling in Growth, Metabolism, and Disease (2017)
- Mizushima N, Autophagy: process and function (2007)
- Manning BD & Cantley LC, Evaluating AKT signaling in health and disease (2007)
- Efeyan A et al., Rag GTPases control mTORC1 substrate entry (2012)
- Inte S et al., The Rag GTPases in immune cell metabolism (2013)
- Zhong Y et al., Rag GTPases in autophagy and lysosomal function (2016)
- Cully M et al., The role of Rag GTPases in neurodegeneration (2019)
- Kim J et al., Ragulator complex links amino acid sensing to mTORC1 (2011)
- Sancak Y et al., Rag GTPases mediate amino acid signaling to mTORC1 (2010)
- Deve A et al., Lysosomal positioning regulates mTORC1 activation (2015)
- Starling D et al., Rag GTPases in T cell activation and autoimmunity (2016)
- Park J et al., mTORC1 activation via Rag GTPases in cancer metabolism (2016)
- Ye X et al., Amino acid signaling to mTORC1 via Rag GTPases (2015)
- Menon S et al., Rag GTPase heterodimer in lysosomal signaling (2014)
- Martina JA et al., RagA GTPase regulates neuronal mTORC1 and autophagy (2008)
- Jain A et al., Rag GTPases in cellular metabolism and disease (2012)
- Zhang Y et al., mTORC1 and autophagy in neurodegenerative diseases (2017)
- Kovács T et al., Rag GTPase signaling in lysosomal storage disorders (2017)
- Howell JJ et al., Rag GTPases as masters of neuronal metabolism (2013)