PALM-C100-CKAP4 transports SFTPAs from extracellular region to lamellar body

Stable Identifier
R-HSA-5686286
Type
Reaction [omitted]
Species
Homo sapiens
Compartment
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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 or 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). SFTPA and CKAP4 seem to enter the cell as a unit since both are found in early endosomes. At what point SFTPA and CKAP4 separate or whether CKAP4 chaperones SFTPA to the lamellar body is currently unknown. The receptors for the other surfactant proteins (SFTPB, C, D) that are also recycled are not yet identified.

Literature References
PubMed ID Title Journal Year
20054143 P63 (CKAP4) as an SP-A receptor: implications for surfactant turnover

Bates, SR

Cell. Physiol. Biochem. 2010
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