Alveolar surfactant is cleared by distinct pathways. Surfactant proteins (SFTPs) are reutilised by type II cells that internalise alveolar phospholipids destined for re-incorporation into LB for secretion. Alternatively, intra-alveolar or extracellular surfactant is degraded. A substantial portion of surfactant is reutilised (25-95%) in type II cells, promoted by SFTPA (the most abundant surfactant protein) via interaction with a high-affinity receptor present on the cell surface. A candidate for the SFTPA receptor detected on type II epithelial cells is cytoskeleton-associated protein 4 (CKAP4 aka p63), a reversibly palmitoylated transmembrane protein (PALM-C100-CKAP4), initially identified in the ER and Golgi apparatus (Bates 2010).