Autofagolisosomas

Autofagolisosomas, also known as autophagolysosomes, are the degradative compartments formed when an autophagosome fuses with a lysosome. They execute the final steps of autophagy by exposing cargo within a single lumen to lysosomal enzymes under acidic conditions, leading to breakdown and recycling of materials such as proteins, lipids, and nucleic acids.

Autophagosome formation begins with a phagophore that expands and sequesters cytoplasmic material. Maturation and docking to lysosomes involve small GTPases and tethering factors, with SNARE proteins mediating membrane fusion. Rab7, the HOPS tethering complex, and SNAREs such as syntaxin 17 on the autophagosome and SNAP29 and VAMP8 on lysosomes coordinate the fusion. Fusion yields an autolysosome with active hydrolases, and the luminal pH drops to around 4.5–5.5, enabling enzymatic degradation.

Contents are degraded by lysosomal enzymes, including cathepsins, and the resulting breakdown products—amino acids, fatty acids, and sugars—are transported back into the cytosol for reuse. Autofagolisosomas participate in both bulk (nonselective) autophagy and selective forms such as mitophagy, pexophagy, and xenophagy.

Physiological roles include maintenance of cellular homeostasis, adaptation to nutrient deprivation, and quality control of organelles. Dysfunctional autophagolysosome activity is associated with aging and diseases such as neurodegeneration and lysosomal storage disorders; in some contexts, autophagy can be protective, while in others it may contribute to pathology.

Researchers assess autophagic flux and autophagolysosome formation by monitoring markers and the co-localization of autophagosomal and lysosomal components, providing insight into cellular degradation pathways and their regulation.