Membrane Rafts in the Respiratory System

The literature data confirm that membrane rafts are required for the proper organization of signalling pathway within lung parenchyma. The physiological role of membrane rafts appears to be closely linked to their ability to modulate contraction, cell proliferation, matrix protein and mediator production by airway mesenchymal and airway/alveolar epithelial cells. In particular, the data obtained in endothelial cells suggest that in membrane rafts signalling complexes are assembled allowing a rapid, efficient and regulated response to extracellular stimuli. In fact, the presence of caveolae and Cav-1 is required in endothelial cells for short and long term mechano-transduction in blood vessels. The endothelium lacking caveolae is unable to couple changes in blood flow with proportional vascular remodeling, suggesting that caveolae might represent an initial flow mechano-sensor directly regulated by luminal blood flow. It is evident that membrane rafts, particularly caveolae, play critical roles in several cell types present in the lung and the aberrant regulation of caveolin expression may trigger pulmonary defects, including pulmonary hypertension, inflammation and fibrosis. A better understanding of dynamics of caveolae in transmembrane traffic in the lung might be of specific interest in drug targeting delivery.