CASTOR1: Cytosolic Arginine Sensor for mTORC1 Signaling
A key regulator of amino acid sensing and cellular growth
Gene Information Card
| Symbol | CASTOR1 |
|---|---|
| Full Name | Cytosolic Arginine Sensor for mTORC1 Subunit 1 |
| Gene Type | Protein coding |
| Chromosomal Location | 2q31.1 |
| NCBI Gene ID | 79856 ncbi.nlm.nih.gov/gene/79856 |
| Ensembl ID | ENSG00000162946 |
| UniProt ID | Q6B0I2 |
| OMIM ID | 617074 |
| HGNC ID | 26150 |
| Aliases | GATSL3, GATS-like protein 3, FLJ13154 |
Description
CASTOR1 encodes a cytosolic protein that functions as an arginine sensor for the mTORC1 signaling pathway. In the absence of arginine, CASTOR1 binds to and inhibits GATOR2, a positive regulator of mTORC1. When arginine levels are sufficient, arginine binds directly to CASTOR1, causing dissociation from GATOR2 and subsequent activation of mTORC1, thereby coupling amino acid availability to cell growth and metabolism.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Cancer (various) | Dysregulation of mTORC1 signaling via altered CASTOR1 expression or mutation may promote uncontrolled cell growth. | COSMIC; literature |
| Epileptic encephalopathy, early infantile | Biallelic loss-of-function variants in CASTOR1 have been associated with neurodevelopmental disorders. | ClinVar; OMIM |
| Primary microcephaly | Reported in patients with homozygous CASTOR1 mutations affecting brain development. | ClinVar; OMIM |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Testis | 12.5 | Medium |
| Brain (cerebellum) | 8.2 | Low |
| Liver | 6.1 | Low |
| Kidney | 5.8 | Low |
| Heart | 4.3 | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| HEK293 | 10.1 | Embryonic kidney cells |
| HeLa | 7.5 | Cervical cancer cells |
| HepG2 | 6.9 | Hepatocellular carcinoma cells |
| A549 | 5.2 | Lung cancer cells |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1?) | Missense | <0.01% | Loss of start codon; likely loss of function |
| c.202C>T (p.Arg68Trp) | Missense | <0.01% | Impaired arginine binding; reduced mTORC1 activation |
| c.415G>A (p.Gly139Arg) | Missense | <0.01% | Unknown functional effect |
| c.586C>T (p.Arg196*) | Nonsense | <0.01% | Premature stop; loss of function |
Mutation functional classification
Loss of Function (LOF)
Mutations that disrupt arginine binding or protein stability lead to constitutive inhibition of mTORC1, impairing cell growth.
Gain of Function (GOF)
Not well characterized; potential activating mutations could cause hyperactive mTORC1 signaling.
Dominant Negative (DN)
Not reported for CASTOR1.
View complete mutation data：
Gene Ontology (GO)
Pathways
• hsa04150: mTOR signaling pathway
• hsa05200: Pathways in cancer
• R-HSA-9639288: Amino acid sensing by CASTOR1
Protein Summary
CASTOR1 is a 396-amino acid protein containing a conserved ACT domain that mediates arginine binding. It forms homodimers and interacts with GATOR2 complex components. The protein acts as a cytosolic arginine sensor, directly binding arginine to relieve inhibition of mTORC1. Its structure includes a N-terminal domain involved in dimerization and a C-terminal arginine-binding pocket. UniProt ID: Q6B0I2.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| CASTOR1 Knockout HEK293 Cell Line | EDJ-KQ1158 | Human | 652968 | Details Get a Quote |
| CASTOR1 Knockout A-549 Cell Line | EDJ-KQ20399 | Human | 652968 | Details Get a Quote |
| CASTOR1 Knockout HCT 116 Cell Line | EDJ-KQ20400 | Human | 652968 | Details Get a Quote |
| CASTOR1 Knockout HeLa Cell Line | EDJ-KQ20401 | Human | 652968 | Details Get a Quote |
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