Cystic fibrosis transmembrane conductance regulator intracellular loop 4 (CFTR)

CFTR is an integral membrane glycoprotein belonging to the ATP-binding cassette (ABC) transporter family, uniquely functioning as a cAMP-activated chloride and bicarbonate ion channel, essential for maintaining epithelial fluid and salt homeostasis. It comprises two membrane-spanning domains, two nucleotide-binding domains, and a regulatory (R) domain. Within the structure, CFTR contains intracellular loops (ICL1–ICL4) that connect its transmembrane helices; these loops are crucial for proper protein folding, trafficking, and functional coupling between ATP hydrolysis and channel gating. ICL4 specifically mediates association between nucleotide binding domain 1 (NBD1) and the second transmembrane domain (TMD2), and mutations or deletions in ICL4 can disrupt protein maturation and channel function, leading to severe cystic fibrosis phenotypes[1][3][5][7]. Current therapies target CFTR as a whole, not its individual loops[7]. The term "Cystic fibrosis transmembrane conductance regulator intracellular loop 4" is not a standard target but rather a subregion of CFTR, implicated in functional and folding defects, especially in the common F508del mutation[7]. CFTR is a therapeutic target for cystic fibrosis, and all regulatory drugs interact with the full protein, not ICL4 alone[7][8]. Dysfunction in ICL4 affects protein processing/delivery and gating but it is not targeted independently by drugs; research focuses on correcting defects that involve ICL4 associations[7].

Other names

CFTRABCC7cystic fibrosis conductance regulatorcystic fibrosis protein

Potentiation of CFTR gating (e.g., ivacaftor increases channel open probability); Correction of CFTR folding, trafficking, and membrane stability (e.g., lumacaftor, tezacaftor, elexacaftor help rescue F508del-CFTR); Combined mechanisms (triple combination therapy for maximal effect)