Dynamics Intrinsic to Cystic Fibrosis Transmembrane Conductance Regulator Function and Stability

Abstract

The cystic fibrosis transmembrane conductance regulator (CFTR) requires dynamic fluctuations between states in its gating cycle for proper channel function, including changes in the interactions between the nucleotide-binding domains (NBDs) and between the intracellular domain (ICD) coupling helices and NBDs. Such motions are also linked with fluctuating phosphorylation-dependent binding of CFTR's disordered regulatory (R) region to the NBDs and partners. Folding of CFTR is highly inefficient, with the marginally stable NBD1 sampling excited states or folding intermediates that are aggregation-prone. The severe CFcausing F508del mutation exacerbates the folding inefficiency of CFTR and leads to impaired channel regulation and function, partly as a result of perturbed NBD1 -ICD interactions and enhanced sampling of these NBD1 excited states. Increased knowledge of the dynamics within CFTR will expand our understanding of the regulated channel gating of the protein as well as of the F508del defects in folding and function.

Conformational Changes Relevant to Channel Activity and Folding within the first Nucleotide Binding Domain of the Cystic Fibrosis Transmembrane Conductance Regulator

“…NMR has enabled us to probe these effects at a residue-specific level and demonstrate that the H620Q substitution associated with higher channel open probability and a dual corrector/potentiator compound give rise to similar conformational changes within NBD1. These results, as well as their synergy with other dynamic and energetic data on NBD1 (29,31,32,64), provide evidence for conformational properties of NBD1 that likely are involved in regulation of channel gating and in folding that may be tested in the future by studies on full-length CFTR.…”

“…With an understanding of allostery based on modulation of the energy landscape (67), NBD1 can be seen as a sensitive energetically malleable domain, with conformational sampling poised to be affected by a variety of perturbations such as compound binding (29). Thus, although the helix-coil transition for H8 and H9 may be qualitatively correlated with potentiation under some conditions, it is not necessarily quantitatively correlated with potentiation under all conditions, because the set of conformations accessible under different conditions (i.e.…”

“…Such structural level data would not only give information about how a compound functions but also facilitate the design of improved therapeutic compounds. Details on the conformational effects of binding of compounds can also provide insights into the dynamic properties and the energetic landscape of the CFTR protein, known to be critical for channel function and folding (29,30) A limitation, however, for these types of studies lies in the relatively poor solubility of most known CFTR modulator compounds in aqueous solution.…”

CFTR: A new horizon in the pathomechanism and treatment of pancreatitis

“…CFTR gating is regulated by the R domain which contains multiple PKA and PKC phosphorylation sites and which physically interacts with NBD1 [12][13][14][15] (Figure 4). Uniquely, CFTR uses the energy of ATP binding and hydrolysis to drive ligand-induced conformational changes in the protein that lead to the regulated opening and closing (gating) of the channel 'pore'.…”

The Cystic Fibrosis of Exocrine Pancreas

“…This phenomenon may not be only a consequence of lack of hydration or increased number of mucus secreting cells. It is proposed that HCO 3 2 is a chaotropic anion important in mucus expansion and, therefore, lack of CFTR function will impair mucus hydration (Quinton 2008;De Lisle 2009;Garcia et al 2009;Chong et al 2013). This may be of relevance to distal pancreatic ducts that contain numerous mucus secreting cells.…”