Caveolae and caveolins in the respiratory system.

Caveolae are flask-shaped invaginations of the plasma membrane that are present in most structural cells. They owe their characteristic Omega-shape to complexes of unique proteins, the caveolins, which indirectly tether cholesterol and sphingolipid-enriched membrane microdomains to the cytoskeleton. Caveolins possess a unique scaffolding domain that anchors receptors, ion channels, second messenger producing enzymes, and effector kinases, thereby sequestering them to caveolae, and modulating cellular signaling and vesicular transport. The lungs express numerous caveolae and high levels of caveolins; therefore they likely play an important role in lung physiology. Indeed, recent and ongoing studies indicate important roles for caveolae and caveolins in the airway epithelium, airway smooth muscle, airway fibroblasts, airway inflammatory cells and the pulmonary vasculature. We review the role of caveolae and caveolins in lung cells and discuss their involvement in cellular signaling associated with asthma, COPD, lung cancer, idiopathic pulmonary fibrosis and pulmonary vascular defects.