Phagolysosome

In biology, a phagolysosome, or endolysosome, is a cytoplasmic body formed by the fusion of a phagosome with a lysosome in a process that occurs during phagocytosis.

[8] Phagocytosis and phagolysosome formation can be broken down into several discrete stages, each involving specific cellular processes and molecular players: The fate of the digested material can vary.

[4] Interestingly, some proteins are involved in multiple stages of this process, indicating mechanistic overlap between these seemingly discrete steps.

Research using model organisms, particularly Caenorhabditis elegans, has been instrumental in identifying the molecular players involved in these stages and ordering them into distinct pathways.

[10] C. elegans offers several advantages for studying phagocytosis, including the ability to observe the process in live animals with endogenous cargos in situ.

Most studies do not image the process of phagocytosis to completion, instead using lysosome fusion or acidification of the phagolysosome lumen as endpoints.

[9] Additionally, this resolution stage is less well understood compared to earlier phases of phagocytosis, as it can take a significant amount of time.

The resulting molecules can serve as raw materials and energy sources for various cellular processes, potentially including the facilitation of subsequent rounds of phagocytosis.

[9] This efficient recycling of engulfed material highlights the phagolysosome's role not only in cellular defense but also in nutrient acquisition and energy management.

[19] Similarly, when in its amastigote stage, Leishmania obtains all its purine sources, various vitamins, and a number of its essential amino acids from the phagolysosome of its host.

The process of phagocytosis showing phagolysosome formation. Lysosome(shown in green) fuses with phagosome to form a phagolysosome.
Amino acid transport and phagolysosome resolution in three stages: (A) Inside the phagolysosome, hydrolases break down proteins into amino acids, represented by pink and blue dots. Amino acid transporters, such as LAAT-1 (shown in pink) and SLC-36.1 (shown in blue), export these different amino acids from the phagolysosome lumen into the cytosol. (B) The exported amino acids activate mTOR (depicted in green). This activation leads to ARL-8-mediated tubulation. ARL-8 (shown in red) likely interacts with motor proteins and microtubules (represented in orange) to facilitate this process.(C) The tubulation process results in the formation of phagolysosomal vesicles. This cycle repeats until the phagolysosome is fully resolved.