Involvement of the heterodimeric interface region of the nucleotide binding domain-2 (NBD2) in the CFTR quaternary structure and membrane stability

The cystic fibrosis transmembrane conductance regulator (CFTR) is the only member of the ATP-binding cassette (ABC) superfamily that functions as a chloride channel. The predicted structure of CFTR protein contains two membrane-spanning domains (MSDs), each followed by a nucleotide binding domain (NBD1 and NBD2). The opening of the Cl− channel is directly linked to ATP-driven tight dimerization of CFTR's NBD1 and NBD2 domains. The presence of a heterodimeric interfaces (HI) region in NBD1 and NBD2 generated a head to tail orientation necessary for channel activity. This process was also suggested to promote important conformational changes in the associated transmembrane domains of CFTR, which may impact the CFTR plasma membrane stability. To better understand the role of the individual HI region in this process, we generated recombinant CFTR protein with suppressed HI-NBD1 and HI-NBD2. Our results indicate that HI-NBD2 deletion leads to the loss of the dimerization profile of CFTR that affect its plasma membrane stability. We conclude that, in addition to its role in Cl− transport, HI-NBD2 domain confers membrane stability of CFTR by consolidating its quaternary structure through interactions with HI-NBD1 region. •Inter-domain interactions are required for CFTR trafficking and membrane stability.•For CFTR, the NBDs dimerization is important for the Cl- channel activation and for the MSD rearrangement.•Dynamic restructuration of the NBD hetero-dimer interface (HI) is probably important for CFTR quaternary structure.•HI-NBD2 region is not important for CFTR folding, trafficking and maturation.•HI-NBD2 deletion increased CFTR proteasome-dependent degradation from the plasma membrane.•CFTR proteasomal degradation was the consequence of the loss of HI-NBD2-dependent dimerization of CFTR.•HI-NBD2 confers membrane stability of CFTR by consolidating its quaternary structure through interactions with HI-NBD1.