lysosomelike

Lysosomelike is an adjective used in cell biology to describe vesicular compartments that resemble lysosomes in morphology, composition, or function, but are not identical to canonical lysosomes. These compartments may be fully lysosomal or partly so, and they arise from the endolysosomal system through maturation of late endosomes or fusion events that deliver hydrolytic enzymes and acidic conditions to a membrane-bound vesicle.

Core features of lysosomelike compartments include an acidic lumen maintained by proton pumps such as V-ATPases and the presence of acid hydrolases, including proteases (such as cathepsins), nucleases, lipases, and glycosidases. The limiting membrane often bears lysosome-associated proteins (for example, LAMPs) and may participate in degradation of biomolecules, autophagic turnover, or regulated secretory pathways. While they share many traits with true lysosomes, their content and specific roles can vary.

A prominent subclass is lysosome-related organelles (LROs), which are lysosomelike but specialized for particular cell types. Examples include melanosomes in pigment cells, lytic granules in cytotoxic lymphocytes, dense bodies in platelets, and lamellar bodies in lung epithelial cells. The biogenesis and function of LROs frequently depend on distinct gene sets and trafficking pathways, and disorders of LRO formation (such as Hermansky-Pudlak syndrome and related conditions) highlight the importance of proper lysosomelike organelle development.

In plants and fungi, vacuoles often fulfill degradative roles and share acidic, enzyme-rich characteristics with lysosomes, but they are not lysosomes in the strict sense. The term lysosomelike thus covers a spectrum of compartments that mirror lysosomal properties while serving diverse organism- and tissue-specific functions.