GO:0016237 microautophagy: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016237 microautophagy is a biological_process in which cytosolic components are directly engulfed by late endosomes, lysosomes or yeast-type lytic vacuoles through invagination of the compartment membrane, without prior sequestration into an autophagosome.
• Microautophagy is mechanistically distinct from macroautophagy and chaperone-mediated autophagy, and it delivers cargo wrapped in a single membrane derived from the invaginated lysosomal membrane.
• Multiple cargo classes are handled by microautophagy, ranging from bulk cytosolic material to selective substrates such as proteasomes, peroxisomes and lipid droplets.
• In mammals, lysosomal microautophagy is an emerging dimension of autophagy that intersects with endosomal sorting and lysosomal degradation pathways.
• Microautophagy contributes to proteasome homeostasis, nutrient stress responses and protein storage or degradation in plants, linking it to proteostasis and crop biology.
• CRISPR-based knockout, point-mutation, knock-in and overexpression models are powerful tools to dissect the causal roles of microautophagy-related genes in disease and cell physiology.
Description
Microautophagy (GO:0016237) is a conserved lysosomal degradation process in which cytosolic components are ingested by late endosomes, lysosomes or yeast-type lytic vacuoles through direct invagination of the compartment membrane, without prior sequestration into an autophagosome. This definition distinguishes microautophagy from macroautophagy and chaperone-mediated autophagy, and it places the engulfing membrane itself as the central structural feature of the pathway. Because the engulfing membranes fuse, cargo is delivered to the lysosome wrapped in a single membrane derived from the invaginated lysosomal membrane. For researchers, microautophagy matters because it is increasingly recognized as a selective and regulated route for the clearance of specific cytosolic proteins, organelles and lipid stores, and because its dysfunction has been linked to proteostasis imbalance and disease-relevant cellular stress. The pathway handles cargoes of many sizes, and distinct molecular mechanisms have been proposed for different cargo types, making it a rich area for mechanistic and genetic dissection. In mammalian cells, lysosomal microautophagy represents an emerging dimension of autophagy that intersects with endosomal sorting and lysosomal biology. This article summarizes the authoritative GO definition, the major stages and molecular players of microautophagy, its regulation, its links to human disease, and the experimental and CRISPR-based methods used to study it. All statements are grounded in the verified literature cited by number.
microautophagy At A Glance
| GO ID | GO:0016237 |
|---|---|
| GO term | microautophagy |
| Ontology | biological_process |
| Synonym | lysosomal microautophagy |
| Major function | Direct lysosomal or vacuolar engulfment and degradation of cytosolic components via membrane invagination, without an autophagosome intermediate |
| Cargo types | Bulk cytosol and selective substrates such as proteasomes, peroxisomes and lipid droplets |
| Compartments involved | Late endosomes, lysosomes and yeast-type lytic vacuoles |
| Membrane topology | Cargo is wrapped in a single membrane derived from the invaginated lysosomal membrane |
| Related processes | Macroautophagy and chaperone-mediated autophagy are distinct autophagy routes |
What Is GO:0016237?
According to the Gene Ontology, GO:0016237 microautophagy is a type of autophagy where cytosolic components are ingested by late endosomes, lysosomes or yeast-type lytic vacuoles by direct invagination of the compartment membrane without prior sequestration into an autophagosome. The engulfing membranes fuse, resulting in the lysosomal delivery of the cargo wrapped in a single membrane derived from the invaginated lysosomal membrane. Its synonym is lysosomal microautophagy, and it is classified as a biological_process.
Why Is microautophagy Important in Cell Biology?
Microautophagy is important because it provides a direct route for lysosomal clearance of cytosolic material and selective cargoes, and it is mechanistically and functionally distinct from macroautophagy and chaperone-mediated autophagy. Its role in proteasome homeostasis and in handling cargoes of many sizes places it at the center of proteostasis and nutrient-stress responses. In mammals, lysosomal microautophagy is an emerging dimension of autophagy with implications for endosomal sorting and lysosomal degradation, and in plants it contributes to protein storage or degradation in cereal grains. Understanding microautophagy therefore requires precise genetic tools to separate its contributions from other autophagy pathways.
• Provides a direct lysosomal degradation route for cytosolic components without an autophagosome intermediate.
• Handles cargoes of many sizes, including bulk cytosol and selective substrates.
• Regulates proteasome homeostasis, linking it to proteostasis control.
• Represents an emerging dimension of mammalian autophagy at the lysosome.
• Contributes to protein storage or degradation in cereal grains, with relevance to plant biology.
• Is mechanistically distinct from macroautophagy and chaperone-mediated autophagy, requiring pathway-specific assays.
• Involves late endosomes, lysosomes and yeast-type lytic vacuoles as the engulfing compartments.
• Is a lesser-known form of self-eating that is increasingly recognized in cell stress and disease contexts.
• Offers selective cargo recognition mechanisms that can be targeted for experimental perturbation.
• Provides a framework for CRISPR-based causal testing of microautophagy-related genes.
What Happens During microautophagy?
Cargo recognition and targeting to the lysosomal or vacuolar membrane
In simple terms: The cell first decides which cytosolic material should be degraded and brings it to the lysosome or vacuole surface.
Microautophagy begins with the selection and targeting of cytosolic components to late endosomes, lysosomes or yeast-type lytic vacuoles. Unlike macroautophagy, cargo is not first enclosed in a separate autophagosome; instead, it is engaged directly at the limiting membrane of the degradative compartment. Distinct molecular mechanisms have been proposed to handle cargoes of many sizes, implying that cargo recognition is a regulated and potentially selective step. Selective microautophagy of proteasomes and other substrates has been described, supporting the idea that cargo selection is not purely random.
Membrane invagination and cargo engulfment
In simple terms: The lysosome or vacuole membrane bends inward and wraps around the cargo.
The defining event of microautophagy is direct invagination of the compartment membrane, which engulfs cytosolic components at the lysosomal or vacuolar surface. This invagination occurs without prior sequestration into an autophagosome, distinguishing GO:0016237 from macroautophagy. The engulfing membrane then fuses, resulting in the lysosomal delivery of the cargo wrapped in a single membrane derived from the invaginated lysosomal membrane. The complexity of the underlying mechanisms is an active area of investigation, with multiple cargo-specific routes proposed.
Vesicle formation and delivery into the lysosomal lumen
In simple terms: The inward-bent membrane pinches off, carrying the cargo into the lysosome interior.
After invagination and membrane fusion, the cargo is delivered into the lysosomal lumen enclosed in a single membrane vesicle derived from the invaginated lysosomal membrane. This topology is a key diagnostic feature of microautophagy and distinguishes it from macroautophagic delivery, where cargo arrives in a double-membrane autophagosome. In yeast, the equivalent compartment is the yeast-type lytic vacuole, and in mammals late endosomes and lysosomes serve this role.
Cargo degradation and recycling
In simple terms: Once inside, the cargo is broken down and its building blocks are reused.
Following delivery, the engulfed cytosolic components are degraded in the lysosome or lytic vacuole, and the resulting metabolites can be recycled. This degradative output links microautophagy to proteostasis and to nutrient-stress responses, including proteasome homeostasis. In plants, microautophagy has been implicated in protein storage or degradation in cereal grains, indicating that the fate of cargo can be either storage-related or degradative depending on context. The pathway is therefore integrated with broader lysosomal and vacuolar degradation functions.
Key Genes Involved in GO:0016237 microautophagy
The following genes and proteins have been implicated in microautophagy or in the closely related lysosomal and vacuolar degradation machinery described in the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| LAMP1 | Lysosomal membrane protein marking the degradative compartment involved in microautophagy | Used as a lysosomal marker to visualize microautophagic invagination and delivery |
| LAMP2 | Lysosomal membrane protein contributing to lysosomal membrane integrity | Relevant to lysosomal microautophagy and chaperone-mediated autophagy distinctions |
| VPS4 | Endosomal sorting and membrane remodeling factor | Implicated in membrane dynamics relevant to microautophagic invagination |
| ESCRT components | Membrane scission and cargo sorting at endosomes and lysosomes | Candidate machinery for microautophagic membrane remodeling |
| Hsc70 | Chaperone involved in protein handling and selective degradation routes | Used to distinguish microautophagy from chaperone-mediated autophagy |
| mTOR | Central nutrient-sensing kinase regulating autophagy pathways | Key regulator whose inhibition or activation modulates autophagy including microautophagy |
| ATG proteins | Core autophagy machinery proteins | Used to separate macroautophagy from microautophagy in genetic studies |
| Proteasome subunits | Cytosolic proteolytic complexes subject to selective microautophagic clearance | Central to microautophagy-dependent proteasome homeostasis |
| Peroxisomal proteins | Organelle cargoes that can be degraded by selective autophagy routes | Relevant to selective microautophagy of organelles |
| Lipid droplet proteins | Cargoes associated with lipid storage and turnover | Implicated in microautophagic handling of lipid stores |
| Vacuolar membrane proteins | Yeast-type lytic vacuole membrane components | Essential for microautophagy studies in yeast models |
| Endosomal sorting proteins | Late endosome identity and cargo sorting | Relevant to microautophagy at late endosomes |
| SNARE proteins | Membrane fusion machinery | Candidate mediators of the engulfing membrane fusion step |
| Rab GTPases | Membrane trafficking regulators | Implicated in endosomal and lysosomal dynamics relevant to microautophagy |
| Storage proteins | Plant proteins subject to storage or degradation via microautophagy | Central to microautophagy in cereal grains |
| Proteasome regulators | Modulators of proteasome abundance and activity | Linked to microautophagy-dependent proteasome homeostasis |
| Lysosomal hydrolases | Degradative enzymes in the lysosomal lumen | Execute cargo degradation after microautophagic delivery |
| Autophagy receptors | Cargo recognition factors for selective autophagy | Candidate selectivity determinants for microautophagic cargoes |
How Is microautophagy Regulated?
Microautophagy is regulated by nutrient-sensing and autophagy-related signaling, with mTOR acting as a central kinase that controls autophagy pathways including microautophagy. The pathway is also subject to cargo-specific regulation, as distinct molecular mechanisms handle cargoes of many sizes and selective substrates such as proteasomes. In mammals, lysosomal microautophagy intersects with endosomal sorting and lysosomal biology, adding layers of regulation at the level of membrane trafficking. In plants, microautophagy regulation is linked to protein storage or degradation in cereal grains, indicating developmental and tissue-specific control. The complexity of these regulatory inputs is a major focus of current research.
microautophagy and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| Proteasome subunits | Proteostasis imbalance linked to microautophagy-dependent proteasome homeostasis | Knockout and overexpression cell models with proteasome activity assays |
| LAMP1 | Lysosomal degradation capacity relevant to neurodegeneration | Tagged knock-in for lysosomal imaging and microautophagy tracking |
| mTOR | Cancer and metabolic stress through autophagy regulation | Point-mutation and knockout models to test pathway-specific effects |
| Storage proteins | Cereal grain protein storage or degradation | Plant knockout and overexpression models for grain protein content |
| ESCRT components | Endosomal sorting defects affecting lysosomal delivery | Knockout cell models with membrane trafficking readouts |
Microautophagy and proteostasis-related disease
Because microautophagy regulates proteasome homeostasis, its dysfunction can perturb protein degradation balance and contribute to proteostasis-related pathology. The pathway handles selective cargoes such as proteasomes and other cytosolic components, so impaired microautophagic clearance may exacerbate the accumulation of damaged proteins. In mammals, lysosomal microautophagy is an emerging dimension of autophagy with relevance to lysosomal degradation capacity and cellular stress responses.
Microautophagy in neurodegeneration and lysosomal biology
Lysosomal microautophagy is mechanistically distinct from macroautophagy and chaperone-mediated autophagy, and its impairment may affect lysosomal clearance routes relevant to neurodegeneration. The single-membrane delivery topology of microautophagy means that cargo reaches the lysosome through a route that can be genetically separated from other autophagy pathways. Researchers can use this distinction to test whether microautophagy-related genes causally contribute to neuronal proteostasis.
Microautophagy in cancer and cell stress
Autophagy pathways, including microautophagy, influence cellular stress responses and nutrient sensing, which are relevant to cancer cell survival and metabolism. The mTOR pathway is a central regulator of autophagy and is frequently dysregulated in cancer, making microautophagy-related genes candidate modifiers of stress adaptation. Selective microautophagic cargo handling, such as lipid droplet turnover, may also intersect with metabolic reprogramming in cancer cells.
Microautophagy in plant biology and crop traits
In cereal grains, microautophagy has been implicated in protein storage or degradation, linking the pathway to seed biology and crop quality. This plant-specific context demonstrates that microautophagy is not restricted to mammalian lysosomal systems but also operates in yeast-type lytic vacuoles and plant vacuoles. Understanding its regulation in plants may inform strategies for modifying storage protein content.
From microautophagy-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is a candidate gene required for microautophagic cargo delivery? | CRISPR knockout cell line with lysosomal cargo flux assays |
| Does a disease-associated variant alter microautophagy function? | Point-mutation knock-in cell line expressing the variant |
| Where does a microautophagy protein localize during invagination? | Tagged knock-in with fluorescent or epitope tag |
| Does increased expression of a microautophagy gene enhance clearance? | Overexpression cell model with degradation readouts |
| Which genes modify microautophagy under nutrient stress? | CRISPR library screening combined with bioinformatics |
| Is microautophagy conserved in plant storage tissue? | Plant knockout and overexpression models for grain protein analysis |
How to Study the microautophagy Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Electron microscopy | Membrane invagination and single-membrane cargo delivery | Defining microautophagy ultrastructure |
| Fluorescence imaging | Lysosomal membrane dynamics and cargo colocalization | Tracking microautophagic delivery in live cells |
| Proteomics | Lysosomal cargo composition | Identifying selective microautophagy substrates |
| Cargo-flux assays | Degradation rate of specific cytosolic proteins | Quantifying microautophagic activity |
| CRISPR knockout | Requirement of a gene for microautophagy | Causal gene function testing |
| CRISPR knock-in tagging | Protein localization and dynamics | Visualizing microautophagy machinery |
| CRISPR library screening | Genome-wide modifiers of microautophagy | Discovery of novel pathway regulators |
| Bioinformatics analysis | Pathway enrichment and candidate prioritization | Interpreting screening and omics data |
Imaging microautophagic invagination and delivery
Electron microscopy and fluorescence imaging of lysosomal or vacuolar membranes are used to visualize direct invagination and single-membrane cargo delivery, the defining features of GO:0016237. Tagged lysosomal membrane proteins such as LAMP1 enable tracking of the engulfing membrane and its fusion with the lysosomal lumen. These approaches help distinguish microautophagy from macroautophagic double-membrane structures.
Proteomic and cargo-flux analysis
Proteomic profiling of lysosomal contents can identify cargoes delivered by microautophagy, including proteasomes and other selective substrates. Cargo-flux assays that measure degradation of specific cytosolic proteins help quantify pathway activity and distinguish it from other autophagy routes. Such analyses are essential for linking microautophagy to proteostasis outcomes.
Genetic and CRISPR-based dissection
CRISPR knockout, point-mutation, knock-in and overexpression models allow causal testing of microautophagy-related genes. By comparing these models with macroautophagy-deficient backgrounds, researchers can separate microautophagic contributions from other autophagy pathways. Library screening and bioinformatics can nominate modifiers of microautophagy under defined stress conditions.
Model organism and plant studies
Yeast models with lytic vacuoles have been central to defining microautophagy mechanisms and membrane topology. Mammalian cell models are used to study lysosomal microautophagy and its intersection with endosomal sorting. Plant models, including cereal grains, are used to investigate microautophagy in protein storage or degradation.
How CRISPR Can Be Used to Study GO:0016237 microautophagy
Knockout
CRISPR knockout of candidate microautophagy genes allows researchers to test whether a gene is required for direct lysosomal invagination and cargo delivery. Knockout models can be combined with cargo-flux assays to quantify loss of microautophagic degradation. Comparing knockouts with macroautophagy-deficient cells helps separate pathway-specific effects.
Point Mutation
Point-mutation knock-in models can be used to test whether specific residues or disease-associated variants alter microautophagy function. Such models preserve endogenous expression and regulation, providing more physiological readouts than overexpression. They are particularly useful for dissecting membrane remodeling and cargo recognition steps.
Knock-in
Tagged knock-in of microautophagy-related proteins enables visualization of lysosomal membrane dynamics and cargo delivery in live cells. Knock-in reporters can also be used to monitor pathway activity under nutrient stress or mTOR modulation. These models support high-content imaging and quantitative analysis of microautophagic flux.
Overexpression
Overexpression models can test whether increased levels of a microautophagy gene enhance clearance of selective cargoes such as proteasomes or lipid droplets. They are useful for gain-of-function studies and for identifying rate-limiting components of the pathway. Overexpression should be interpreted alongside knockout data to establish causality.
How EDITGENE Supports microautophagy Research
Researchers studying microautophagy-related genes often need to determine whether a candidate gene is causally involved in direct lysosomal invagination, cargo delivery or downstream degradation, rather than merely correlating with pathway activity. EDITGENE provides CRISPR-based cell models and screening services designed to support this causal dissection across knockout, point-mutation, knock-in, overexpression and library-screening formats.
Contact EDITGENE today to design your custom CRISPR model for microautophagy research.
Frequently Asked Questions About microautophagy
What is microautophagy?
Microautophagy (GO:0016237) is a type of autophagy where cytosolic components are ingested by late endosomes, lysosomes or yeast-type lytic vacuoles by direct invagination of the compartment membrane without prior sequestration into an autophagosome.
What is the GO ID for microautophagy?
The Gene Ontology ID for microautophagy is GO:0016237, classified as a biological_process with the synonym lysosomal microautophagy.
How is microautophagy different from macroautophagy?
Microautophagy delivers cargo by direct invagination of the lysosomal or vacuolar membrane, whereas macroautophagy first sequesters cargo into a double-membrane autophagosome.
What genes are involved in microautophagy?
Genes and proteins implicated in microautophagy include lysosomal membrane proteins such as LAMP1 and LAMP2, endosomal sorting and ESCRT components, mTOR, ATG proteins, proteasome subunits and plant storage proteins.
What cargoes are degraded by microautophagy?
Microautophagy handles cargoes of many sizes, including bulk cytosol and selective substrates such as proteasomes, peroxisomes and lipid droplets.
Does microautophagy regulate proteasome homeostasis?
Yes, microautophagy has been shown to regulate proteasome homeostasis, linking the pathway to proteostasis control.
Is microautophagy present in mammals?
Yes, lysosomal microautophagy is an emerging dimension of mammalian autophagy that intersects with endosomal sorting and lysosomal degradation.
What is the role of microautophagy in plants?
In cereal grains, microautophagy has been implicated in protein storage or degradation, linking the pathway to seed biology and crop traits.
How is microautophagy regulated?
Microautophagy is regulated by nutrient-sensing pathways including mTOR and by cargo-specific mechanisms that handle different substrate sizes and types.
How can CRISPR be used to study microautophagy?
CRISPR knockout, point-mutation, knock-in, tagged knock-in and overexpression models allow causal testing of microautophagy-related genes, while CRISPR library screening can discover genome-wide modifiers of the pathway.
Conclusion
Microautophagy (GO:0016237) is a distinct autophagy route in which cytosolic components are directly engulfed by late endosomes, lysosomes or yeast-type lytic vacuoles through membrane invagination, without an autophagosome intermediate. Its single-membrane delivery topology, selective cargo handling and links to proteasome homeostasis and plant protein storage make it a biologically important and experimentally tractable pathway. In mammals, lysosomal microautophagy is an emerging dimension of autophagy with relevance to lysosomal biology and disease. Because microautophagy overlaps with other autophagy and endosomal pathways, causal dissection requires precise genetic models. CRISPR-based knockout, point-mutation, knock-in, overexpression and library-screening approaches provide the tools needed to determine which genes truly drive microautophagic cargo delivery and degradation.
References
- 1. Yamamoto H et al.. 2024. Molecular Mechanisms of Macroautophagy, Microautophagy, and Chaperone-Mediated Autophagy.. J Nippon Med Sch 91(1):2-9 PMID: 37271546
- 2. Wang L et al.. 2023. The emerging mechanisms and functions of microautophagy.. Nat Rev Mol Cell Biol 24(3):186-203 PMID: 36097284
- 3. Li J et al.. 2020. Microautophagy regulates proteasome homeostasis.. Curr Genet 66(4):683-687 PMID: 32077993
- 4. Sakai Y et al.. 2026. Microautophagy: definition, classification, and the complexity of the underlying mechanisms.. Autophagy 22(1):3-9 PMID: 40928057
- 5. Kuchitsu Y et al.. 2024. Lysosomal microautophagy: an emerging dimension in mammalian autophagy.. Trends Cell Biol 34(7):606-616 PMID: 38104013
- 6. Schuck S. 2020. Microautophagy - distinct molecular mechanisms handle cargoes of many sizes.. J Cell Sci 133(17) PMID: 32907930
- 7. Plott S et al.. 2025. Microautophagy in cereal grains: protein storage or degradation?. Trends Plant Sci 30(7):736-744 PMID: 39843340
- 8. Li WW et al.. 2012. Microautophagy: lesser-known self-eating.. Cell Mol Life Sci 69(7):1125-36 PMID: 22080117
