microautophagy

Definition

Target type: biologicalprocess

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. [PMID:14679207, PMID:15798367, PMID:16973210, PMID:9566964]

Microautophagy is a type of autophagy, a cellular process that involves the degradation of cellular components within lysosomes. Unlike macroautophagy, which involves the formation of double-membrane vesicles called autophagosomes to engulf cargo, microautophagy directly engulfs cytoplasmic material through invaginations or protrusions of the lysosomal membrane.

This process begins with the inward budding of the lysosomal membrane, creating small vesicles within the lysosome. These vesicles, called microautophagic vesicles, can either form through the invagination of the lysosomal membrane or by the protrusion of the lysosomal membrane into the cytoplasm.

The engulfment of cargo can occur in a selective or non-selective manner. In selective microautophagy, specific cargo, such as protein aggregates, damaged organelles, or invading pathogens, are targeted for degradation. This selectivity is often mediated by the interaction of specific cargo receptors with proteins on the lysosomal membrane. In non-selective microautophagy, the process is less specific, and a wider range of cellular components can be engulfed.

Once the cargo is enclosed within the microautophagic vesicles, lysosomal enzymes degrade it. The breakdown products, such as amino acids, fatty acids, and sugars, can then be recycled back into the cell for use in other metabolic processes.

Microautophagy is crucial for maintaining cellular homeostasis by removing damaged or unnecessary components. It plays a role in various cellular processes, including:

- **Quality control:** Removal of damaged or misfolded proteins.
- **Organelle turnover:** Degradation of aged or dysfunctional organelles.
- **Nutrient recycling:** Breakdown of cellular components to provide essential nutrients.
- **Defense against pathogens:** Degradation of invading pathogens.
- **Development and differentiation:** Regulation of cellular development and differentiation.

Microautophagy is a highly regulated process that is influenced by various factors, including nutrient availability, stress conditions, and cellular signaling pathways. Dysregulation of microautophagy has been implicated in various diseases, including cancer, neurodegenerative disorders, and aging.
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Proteins (1)

Compounds (10)