caveosomes

Caveosomes are intracellular membrane-bound compartments that were described in studies of caveolae-mediated endocytosis in mammalian cells. They were proposed as a distinct endocytic compartment that forms from caveolae and is separate from the classical early endosome and lysosome pathways.

These structures are enriched in caveolin-1 and cholesterol and were reported to lack the early endosome marker EEA1. They were described as having a relatively neutral pH compared with degradative lysosomal compartments, suggesting a unique trafficking route for cargo taken up through caveolae.

Proposed roles for caveosomes included serving as sorting stations that can direct certain internalized cargo to the endoplasmic reticulum or Golgi apparatus, thereby avoiding rapid lysosomal degradation. Some studies also associated caveosome-like structures with the uptake and intracellular trafficking of specific pathogens and lipid-rich cargo.

The existence of a distinct, stable caveosome compartment has been a subject of controversy. Subsequent work questioned whether caveosomes constitute a separate organelle or simply transient, caveolin-containing endosomal structures formed during caveolar endocytosis. As a result, the term caveosome has fallen out of widespread use in many contemporary studies, with researchers describing caveolar trafficking without invoking a separate caveosome entity.

See also caveolae; endocytosis.