caveola

Caveola (plural caveolae) are small, flask-shaped invaginations of the plasma membrane found in many vertebrate cell types. They typically measure about 50 to 100 nanometers in diameter and are enriched in cholesterol and sphingolipids, forming ordered membrane microdomains. The main structural components are caveolins (CAV1, CAV2, and CAV3 in skeletal muscle) and cavin proteins (including PTRF/CAVIN1). Caveolin-1 and caveolin-2 are commonly expressed together and are essential for the formation and stability of caveolae; cavin proteins are required for caveolae biogenesis and maintenance. When these proteins are absent or dysfunctional, caveolae are reduced or absent.

Functions of caveolae include mediating clathrin-independent endocytosis, organizing and concentrating signaling molecules, and facilitating transcytosis in endothelial cells. They also participate in mechanosensing and membrane tension buffering, contributing to cellular responses to mechanical stress. In endothelial cells, caveolae harbor signaling enzymes such as endothelial nitric oxide synthase (eNOS) and various receptors and kinases, influencing pathways related to vascular tone, lipid metabolism, and vascular biology. Caveolae can internalize certain ligands, including cholera toxin B subunit and albumin, and they serve as platforms for selective signal transduction.

Distribution and clinical significance vary by tissue; caveolae are abundant in adipocytes, endothelial cells, and muscle cells, with lower density in some epithelial tissues. Genetic mutations affecting caveolin-1 or caveolin-1–related proteins (such as PTRF/CAVIN1) can cause lipodystrophy, muscular dystrophy, and pulmonary arterial hypertension, highlighting the role of caveolae in lipid homeostasis and vascular biology. Dysfunctions in caveolae have been implicated in metabolic disorders and cancer progression, making them a subject of ongoing research for therapies and drug delivery.