Autophagy is a process of cellular self-degradation, through which a double-membrane structure called the autophagosome is formed. This autophagosome engulfs damaged or excess organelles and protein aggregates within the cell, then fuses with lysosomes. Lysosomal hydrolases then degrade the contents of the autophagosome. Autophagy plays a crucial role in maintaining cellular homeostasis, responding to stress, and regulating immune reactions. Below are detailed characteristics and regulatory mechanisms of autophagy:
Autophagosome Formation: Double-membrane vesicles called autophagosomes form within the cell, engulfing damaged or excess organelles and protein aggregates.
Fusion with Lysosomes: Autophagosomes fuse with lysosomes to form autolysosomes.
Degradation and Recycling: Hydrolases within lysosomes degrade the contents of autophagosomes. The resulting degradation products are recycled by the cell to provide energy and nutrients.
mTOR Signaling Pathway:
mTORC1: mTORC1 is a major negative regulator of autophagy. When nutrients and growth factors are abundant, mTORC1 is activated and inhibits autophagy. Under nutrient deprivation or stress conditions, mTORC1 is inhibited, thereby promoting autophagy.
AMPK: AMPK acts as a cellular energy sensor. When cellular energy levels are low, AMPK is activated, inhibits mTORC1, and promotes autophagy.
ULK1 Complex:
ULK1: ULK1 is an initiator of autophagy. When mTORC1 is inhibited, ULK1 is activated and triggers the formation of autophagosomes.
ATG13, FIP200, ATG101: These proteins form a complex with ULK1 and collectively regulate the formation of autophagosomes.
PI3K-III Complex:
PI3K-III: The PI3K-III complex plays a significant role in the formation of autophagosomes, generating PI3P, which recruits autophagy-related proteins to the membrane.
Beclin-1: Beclin-1 is a key component of the PI3K-III complex and regulates the activity of PI3K-III.
ATG Proteins:
ATG5-ATG12: ATG5 and ATG12 form a complex that participates in the elongation of autophagosomes.
LC3: LC3 is a marker protein of the autophagosome membrane. During autophagosome formation, LC3-I is lipidated to form LC3-II, which marks the autophagosome.
Voisey
Voisey is a technical support specialist at EnkiLife, proficient in immunology and cell biology. She is committed to providing customers with professional and efficient technical support. Additionally, she is involved in research on customers' fields of study and designs highly cost-effective solutions for them.
