Endosomerlysomer

Endosomerlysomer is a proposed cellular compartment described in theoretical models and limited imaging studies as a transient hybrid vesicle formed by the fusion of late endosomes with lysosomes. In this concept, endosomerlysomers retain features of both organelles: the endosomal sorting machinery and receptor recycling, together with the hydrolytic enzyme content and acidic lumen characteristic of lysosomes.

Biogenesis and morphology are outlined as occurring during endocytic maturation when late endosomes fuse with lysosomes, yielding a vesicle that may display both endosomal and lysosomal markers and acquire hydrolases, with a lumenal pH around 4.5 to 5.5. They are envisioned as small to medium-sized, potentially transient structures that appear during cargo processing and may represent a convergence point of endosomal and lysosomal pathways.

Functionally, endosomerlysomers are proposed to serve as sites where endocytic cargo undergoes degradation while components are recycled, potentially aiding antigen processing or modulation of signaling pathways. They are discussed in the context of cellular efficiency in cargo handling and homeostasis, particularly for cargos requiring combined sorting and hydrolysis.

Scientific status and debate are central to the concept: evidence is limited and controversial, with many laboratories considering observed structures to be oversized endosomes or lysosomes or imaging artifacts. Robust, reproducible data are sought, including advanced imaging and proteomic profiling to distinguish a true endosomerlysomer from known organelles.

If validated, endosomerlysomers could have implications for drug delivery and for understanding diseases involving endolysosomal pathway dysfunction, such as certain neurodegenerative conditions. See also endosome, lysosome, autophagy, endolysosome.