Autophagy, a conserved cellular catabolic pathway from yeast to mammals, involves the formation of autophagosomes to deliver long-lived proteins and damaged organelles for degradation and reuse. The core molecular machinery of autophagy includes the ULK complex, ubiquitin-like protein conjugation systems (Atg12 and Atg8/LC3), the class III phosphatidylinositol 3-kinase (PtdIns3K)/Vps34 complex, and transmembrane proteins (Atg9/mAtg9 and VMP1). These components are essential for autophagosome formation and maturation. Signaling pathways regulating autophagy include the PtdIns3K-Akt-mTORC1 pathway, AMPK, p53, and the Bcl-2 protein family. The PtdIns3K-Akt-mTORC1 pathway integrates upstream signals to control autophagy, with mTORC1 acting as a master regulator. AMPK senses cellular bioenergetics and activates TSC1/2 to inhibit mTORC1, promoting autophagy. p53 has both positive and negative roles in autophagy induction, depending on its localization. The Bcl-2 protein family can either inhibit or induce autophagy, depending on their interaction with Beclin 1. Understanding the molecular machinery and signaling regulation of autophagy is crucial for its potential therapeutic applications in various diseases.Autophagy, a conserved cellular catabolic pathway from yeast to mammals, involves the formation of autophagosomes to deliver long-lived proteins and damaged organelles for degradation and reuse. The core molecular machinery of autophagy includes the ULK complex, ubiquitin-like protein conjugation systems (Atg12 and Atg8/LC3), the class III phosphatidylinositol 3-kinase (PtdIns3K)/Vps34 complex, and transmembrane proteins (Atg9/mAtg9 and VMP1). These components are essential for autophagosome formation and maturation. Signaling pathways regulating autophagy include the PtdIns3K-Akt-mTORC1 pathway, AMPK, p53, and the Bcl-2 protein family. The PtdIns3K-Akt-mTORC1 pathway integrates upstream signals to control autophagy, with mTORC1 acting as a master regulator. AMPK senses cellular bioenergetics and activates TSC1/2 to inhibit mTORC1, promoting autophagy. p53 has both positive and negative roles in autophagy induction, depending on its localization. The Bcl-2 protein family can either inhibit or induce autophagy, depending on their interaction with Beclin 1. Understanding the molecular machinery and signaling regulation of autophagy is crucial for its potential therapeutic applications in various diseases.