GO:1990316 Atg1/ULK1 kinase complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990316 (Atg1/ULK1 kinase complex) is a serine/threonine protein kinase complex that initiates autophagosome formation.
• The complex contains Atg1 (yeast) or ULK1/ULK2 (mammals) together with Atg13 and scaffold proteins such as Atg17 in yeast or RB1CC1 (FIP200) in mammals.
• It integrates nutrient and stress signals, notably through mTOR-dependent regulation, to switch autophagy on or off.
• The Atg1/ULK1 kinase phosphorylates downstream targets including Atg13, RB1CC1, and components of the Hsp90 chaperone machinery.
• Atg1/ULK1 activity is linked to selective autophagy, ubiquitin-like conjugation of Atg8, and deubiquitinase-dependent antagonism.
• Dysregulation of the complex is associated with cancer, neurodegeneration, and metabolic stress responses, making it a key experimental target.
Description
The Atg1/ULK1 kinase complex (GO:1990316) is the most upstream protein kinase complex in the autophagy initiation pathway, conserved from yeast to humans. It consists of the serine/threonine kinase Atg1 in yeast or its homologs ULK1 and ULK2 in mammals, together with the regulatory subunit Atg13 and additional scaffold proteins such as Atg17 in yeast or RB1CC1 (also known as FIP200) in mammals. Because autophagy is a major catabolic route for degrading damaged organelles and aggregated proteins, the Atg1/ULK1 complex sits at a decision point that determines whether cells survive or die under nutrient stress. Researchers study GO:1990316 to understand how nutrient sensing, kinase signaling, and autophagosome biogenesis are coupled, and to identify therapeutic entry points in cancer, neurodegeneration, and metabolic disease. The complex is also a model for how scaffold proteins organize kinase signaling in space and time.
Atg1/ULK1 kinase complex At A Glance
| GO ID | GO:1990316 |
|---|---|
| GO term | Atg1/ULK1 kinase complex |
| Ontology | cellular_component |
| Synonym | ULK1 complex; ATG1-ATG13 complex; autophagy-initiation complex; ULK1-ATG13-FIP200 complex |
| Major function | Serine/threonine protein kinase activity that initiates autophagosome formation |
| Core subunits | Atg1/ULK1/ULK2, Atg13, Atg17 (yeast) or RB1CC1/FIP200 (mammals) |
| Upstream regulation | Nutrient and stress signaling, including mTOR-dependent control |
| Downstream processes | Autophagosome nucleation, Atg8/LC3 conjugation, selective autophagy |
What Is GO:1990316?
GO:1990316 describes a protein complex that contains Atg1, or its mammalian homologs ULK1 and ULK2, together with Atg13 and other proteins that regulate its function, such as Atg17 in yeast or RB1CC1 (FIP200) in mammals. The complex possesses serine/threonine protein kinase activity and is required for autophagosome formation.
Why Is Atg1/ULK1 kinase complex Important in Cell Biology?
The Atg1/ULK1 kinase complex is important because it is the earliest known kinase-driven checkpoint in autophagy, converting nutrient and stress signals into autophagosome formation. Its activity determines whether cells recycle damaged components or undergo autophagic cell death, and it is therefore central to cancer biology, neurodegeneration, and metabolic stress responses. Understanding GO:1990316 also clarifies how scaffold proteins and ubiquitin-like modifiers coordinate kinase signaling in selective autophagy.
• Initiates autophagosome formation, the first committed step of autophagy.
• Integrates nutrient and energy signals through mTOR-dependent regulation.
• Phosphorylates downstream effectors such as Atg13 and RB1CC1.
• Links autophagy to the ubiquitin-like protein Atg8/LC3 conjugation system.
• Coordinates selective autophagy through scaffold proteins.
• Is antagonized by deubiquitinases such as Leon/USP5.
• Modulates the Hsp90 chaperone machinery during autophagy activation.
• Is implicated in cancer, neurodegeneration, and metabolic disorders.
• Provides a target for pharmacological autophagy modulation.
• Serves as a paradigm for kinase-scaffold assembly in cellular signaling.
What Happens During Atg1/ULK1 kinase complex?
Nutrient sensing and complex activation
In simple terms: The complex listens to nutrient signals and switches autophagy on when nutrients are low.
Under nutrient-rich conditions, mTOR signaling suppresses the Atg1/ULK1 complex; upon nutrient deprivation, the complex becomes active and initiates autophagy. This regulation ensures that autophagy is engaged only when catabolism is needed.
Kinase activation and substrate phosphorylation
In simple terms: The kinase subunit phosphorylates partner proteins to start the autophagy program.
Atg1/ULK1 phosphorylates Atg13 and RB1CC1, and also targets the Hsp90 chaperone machinery, thereby propagating the autophagy signal. These phosphorylation events are required for downstream autophagosome nucleation.
Scaffold assembly and autophagosome nucleation
In simple terms: Scaffold proteins hold the complex together and help build the autophagosome.
Atg17 in yeast or RB1CC1/FIP200 in mammals acts as a scaffold that organizes the complex and recruits downstream factors for autophagosome formation. Scaffold proteins also contribute to selective autophagy by linking cargo receptors to the initiation machinery.
Coupling to Atg8/LC3 conjugation
In simple terms: The complex connects to the ubiquitin-like conjugation system that decorates the autophagosome.
Binding of the Atg1/ULK1 kinase to the ubiquitin-like protein Atg8 regulates autophagy, linking initiation to the conjugation machinery that lipidates LC3 family proteins. This coupling ensures that autophagosomes are properly marked for cargo recruitment.
Antagonism by deubiquitinases
In simple terms: Deubiquitinases can put the brakes on the complex.
The deubiquitinase Leon/USP5 interacts with Atg1/ULK1 and antagonizes autophagy, providing a negative layer of control. This interaction highlights the importance of ubiquitin-dependent regulation in autophagy initiation.
Key Genes Involved in GO:1990316 Atg1/ULK1 kinase complex
The following genes and proteins are core components or regulators of the Atg1/ULK1 kinase complex (GO:1990316).
| Gene | Major Role | Research Relevance |
|---|---|---|
| ULK1 | Mammalian serine/threonine kinase subunit of the complex | Central to autophagy initiation; target for cancer and neurodegeneration studies |
| ULK2 | Mammalian homolog of ULK1 | Compensatory kinase in autophagy initiation |
| ATG13 | Regulatory subunit phosphorylated by ULK1 | Essential for complex assembly and activity |
| RB1CC1 (FIP200) | Mammalian scaffold protein | Required for autophagosome formation and selective autophagy |
| ATG17 | Yeast scaffold protein | Model for scaffold function in autophagy initiation |
| ATG1 | Yeast serine/threonine kinase | Foundational model for ULK1 function |
| ATG8 | Ubiquitin-like protein | Binds Atg1/ULK1 and regulates autophagy |
| LC3B | Mammalian Atg8 homolog | Autophagosome marker linked to ULK1 activity |
| USP5 (Leon) | Deubiquitinase | Antagonizes Atg1/ULK1 and autophagy |
| HSP90 | Chaperone | Phosphorylated and inhibited by Atg1/ULK1 during autophagy |
| MTOR | Upstream kinase | Suppresses ULK1 under nutrient-rich conditions |
| AMPK | Energy sensor kinase | Activates ULK1 under low energy |
| PGAM1 | Glycolytic enzyme | Functions as a metabolic-autophagy checkpoint |
| ATG101 | ULK1 complex subunit | Stabilizes the complex in mammals |
| ATG2 | Downstream effector | Recruited for autophagosome expansion |
| ATG9 | Transmembrane protein | Works with ULK1 complex in autophagosome nucleation |
| WIPI2 | PI3P effector | Links ULK1 complex to downstream nucleation |
| VPS34 | PI3K | Generates PI3P for autophagosome nucleation |
How Is Atg1/ULK1 kinase complex Regulated?
The Atg1/ULK1 kinase complex is regulated by upstream nutrient and energy sensors. mTOR suppresses the complex under nutrient-rich conditions, while AMPK activates it during energy stress. Phosphorylation of Atg13 and RB1CC1 by ULK1 further modulates complex activity. The deubiquitinase Leon/USP5 interacts with Atg1/ULK1 and antagonizes autophagy, adding a negative regulatory layer. Additionally, the glycolytic enzyme PGAM1 functions as a metabolic-autophagy checkpoint that coordinates growth and stress tolerance.
Atg1/ULK1 kinase complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ULK1 | Cancer, neurodegeneration | ULK1 knockout and point-mutation cell lines |
| RB1CC1 | Cancer, autophagy deficiency | RB1CC1 knockout models |
| ATG13 | Autophagy-related disorders | ATG13 phospho-mutant knock-in |
| USP5 | Autophagy antagonism | USP5 overexpression and knockout |
| PGAM1 | Metabolic stress | PGAM1 knockout and overexpression |
Cancer
Altered ULK1 complex activity affects tumor cell survival under metabolic stress, and the complex is considered a therapeutic target in multiple cancers. Autophagy initiation downstream of ULK1 can either promote or suppress tumorigenesis depending on context.
Neurodegeneration
Defective autophagy initiation by the Atg1/ULK1 complex contributes to accumulation of protein aggregates in neurodegenerative diseases. Enhancing ULK1 activity is explored as a strategy to clear toxic aggregates.
Metabolic disorders
The complex integrates nutrient signals, and its dysregulation is linked to metabolic stress and insulin resistance. PGAM1-dependent metabolic-autophagy crosstalk highlights its role in growth and stress tolerance.
From Atg1/ULK1 kinase complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is ULK1 kinase activity required for autophagy? | ULK1 kinase-dead point-mutation knock-in |
| How does Atg13 phosphorylation regulate complex assembly? | ATG13 phospho-mutant knock-in |
| What is the role of RB1CC1 in selective autophagy? | RB1CC1 knockout cell line |
| How does USP5 antagonize autophagy? | USP5 overexpression and knockout |
| Does PGAM1 coordinate metabolism and autophagy? | PGAM1 knockout and overexpression |
| Where does the complex localize during starvation? | Tagged knock-in of ULK1 or ATG13 |
How to Study the Atg1/ULK1 kinase complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Co-immunoprecipitation | Protein-protein interactions | Complex subunit assembly |
| Phosphoproteomics | Kinase substrate phosphorylation | ULK1 target mapping |
| LC3B flux assay | Autophagosome formation and degradation | Functional autophagy readout |
| CRISPR knockout screening | Gene requirement for autophagy | Identify novel regulators |
| Proximity labeling | Spatial interactome | Complex localization |
| In vitro kinase assay | Kinase activity | ULK1 catalytic function |
| RNA-seq | Transcriptional changes | Autophagy gene expression |
| Live-cell imaging | Dynamic complex assembly | Starvation response |
Proteomics and interactomics
Affinity purification coupled to mass spectrometry identifies subunits and interactors of the Atg1/ULK1 complex, including scaffold proteins and deubiquitinases.
Phosphoproteomics
Quantitative phosphoproteomics maps ULK1-dependent phosphorylation events on Atg13, RB1CC1, and Hsp90 machinery components.
Imaging and autophagy flux assays
Fluorescence microscopy of LC3B puncta and tandem fluorescent reporters measures autophagosome formation and flux downstream of the complex.
Genetic screens and CRISPR libraries
CRISPR knockout libraries and targeted knock-ins dissect the contribution of individual complex subunits to autophagy and cell survival.
How CRISPR Can Be Used to Study GO:1990316 Atg1/ULK1 kinase complex
Knockout
CRISPR knockout of ULK1, ATG13, or RB1CC1 abolishes autophagy initiation and reveals essential subunits of GO:1990316.
Point Mutation
Kinase-dead or phospho-site point mutations in ULK1 and ATG13 dissect catalytic and regulatory functions of the complex.
Knock-in
Tagged knock-in of ULK1 or ATG13 enables live-cell imaging and proteomic tracking of the complex.
Overexpression
Overexpression of ULK1 or USP5 modulates autophagy flux and tests gain-of-function effects on the complex.
How EDITGENE Supports Atg1/ULK1 kinase complex Research
Researchers studying Atg1/ULK1 kinase complex-related genes often need to determine whether a candidate gene is causally involved in autophagy initiation or merely correlated with it. EDITGENE provides the CRISPR tools and bioinformatics support required to build such causal evidence.
Contact EDITGENE today to design your custom CRISPR model for Atg1/ULK1 kinase complex research.
Frequently Asked Questions About Atg1/ULK1 kinase complex
What is the Atg1/ULK1 kinase complex?
It is a serine/threonine protein kinase complex that initiates autophagosome formation and corresponds to GO:1990316.
What genes are involved in the Atg1/ULK1 kinase complex?
Core genes include ULK1, ULK2, ATG13, RB1CC1 (FIP200), and ATG17 in yeast, along with regulators such as USP5 and PGAM1.
What is the function of GO:1990316?
GO:1990316 functions in autophagy initiation by phosphorylating downstream targets and assembling the autophagosome nucleation machinery.
How is the ULK1 complex regulated?
It is regulated by mTOR and AMPK in response to nutrients and energy, and by deubiquitinases such as USP5.
What diseases are linked to the ULK1 complex?
Cancer, neurodegeneration, and metabolic disorders have been linked to dysregulation of the complex.
What is the difference between Atg1 and ULK1?
Atg1 is the yeast kinase, while ULK1 and ULK2 are its mammalian homologs within the same complex.
How can I study the Atg1/ULK1 kinase complex?
Common methods include knockout and knock-in models, phosphoproteomics, imaging of LC3B, and CRISPR library screening.
Does the ULK1 complex interact with Atg8?
Yes, binding of the Atg1/ULK1 kinase to the ubiquitin-like protein Atg8 regulates autophagy.
What is the role of RB1CC1 in the complex?
RB1CC1 (FIP200) is a scaffold protein required for autophagosome formation and selective autophagy.
Can CRISPR be used to study GO:1990316?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect complex function.
Conclusion
The Atg1/ULK1 kinase complex (GO:1990316) is the central kinase module that initiates autophagy by integrating nutrient signals and phosphorylating downstream effectors. Its core subunits, regulatory scaffolds, and interacting proteins provide a rich experimental landscape for understanding autophagy in health and disease. CRISPR-based models and bioinformatics workflows now make it feasible to causally test the role of each component in cancer, neurodegeneration, and metabolic stress.
References
- 1. Papinski D et al.. 2016. Regulation of Autophagy By Signaling Through the Atg1/ULK1 Complex.. J Mol Biol 428(9 Pt A):1725-41 PMID: 27059781
- 2. Mizushima N. 2010. The role of the Atg1/ULK1 complex in autophagy regulation.. Curr Opin Cell Biol 22(2):132-9 PMID: 20056399
- 3. Kraft C et al.. 2012. Binding of the Atg1/ULK1 kinase to the ubiquitin-like protein Atg8 regulates autophagy.. EMBO J 31(18):3691-703 PMID: 22885598
- 4. Backe SJ et al.. 2023. Activation of autophagy depends on Atg1/Ulk1-mediated phosphorylation and inhibition of the Hsp90 chaperone machinery.. Cell Rep 42(7):112807 PMID: 37453059
- 5. Wong PM et al.. 2013. The ULK1 complex: sensing nutrient signals for autophagy activation.. Autophagy 9(2):124-37 PMID: 23295650
- 6. Eickhorst C et al.. 2020. Scaffold proteins in bulk and selective autophagy.. Prog Mol Biol Transl Sci 172:15-35 PMID: 32620241
- 7. Zhang Y et al.. 2026. The glycolytic enzyme PGAM1 functions as a metabolic-autophagy checkpoint to coordinate growth and stress tolerance.. Nat Cell Biol 28(9):1830-1845 PMID: 42527668
- 8. Pai YL et al.. 2023. The deubiquitinase Leon/USP5 interacts with Atg1/ULK1 and antagonizes autophagy.. Cell Death Dis 14(8):540 PMID: 37607937
