1
|
Towards next generation therapies for cystic fibrosis: Folding, function and pharmacology of CFTR. J Cyst Fibros 2020; 19 Suppl 1:S25-S32. [PMID: 31902693 PMCID: PMC7052731 DOI: 10.1016/j.jcf.2019.12.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 12/16/2019] [Accepted: 12/18/2019] [Indexed: 12/19/2022]
Abstract
The treatment of cystic fibrosis (CF) has been transformed by orally-bioavailable small molecule modulators of the cystic fibrosis transmembrane conductance regulator (CFTR), which restore function to CF mutants. However, CFTR modulators are not available to all people with CF and better modulators are required to prevent disease progression. Here, we review selectively recent advances in CFTR folding, function and pharmacology. We highlight ensemble and single-molecule studies of CFTR folding, which provide new insight into CFTR assembly, its perturbation by CF mutations and rescue by CFTR modulators. We discuss species-dependent differences in the action of the F508del-CFTR mutation on CFTR expression, stability and function, which might influence pharmacological studies of CFTR modulators in CF animal models. Finally, we illuminate the identification of combinations of two CFTR potentiators (termed co-potentiators), which restore therapeutically-relevant levels of CFTR activity to rare CF mutations. Thus, mechanistic studies of CFTR folding, function and pharmacology inform the development of highly effective CFTR modulators.
Collapse
|
2
|
Charge Pair Interactions in Transmembrane Helices and Turn Propensity of the Connecting Sequence Promote Helical Hairpin Insertion. J Mol Biol 2013; 425:830-40. [DOI: 10.1016/j.jmb.2012.12.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 10/25/2012] [Accepted: 12/02/2012] [Indexed: 11/21/2022]
|
3
|
Nadeau VG, Rath A, Deber CM. Sequence Hydropathy Dominates Membrane Protein Response to Detergent Solubilization. Biochemistry 2012; 51:6228-37. [DOI: 10.1021/bi201853n] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Vincent G. Nadeau
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S
1A8
| | - Arianna Rath
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Charles M. Deber
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S
1A8
| |
Collapse
|
4
|
Mulvihill CM, Deber CM. Structural basis for misfolding at a disease phenotypic position in CFTR: comparison of TM3/4 helix-loop-helix constructs with TM4 peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:49-54. [PMID: 21996038 DOI: 10.1016/j.bbamem.2011.09.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 09/15/2011] [Accepted: 09/26/2011] [Indexed: 11/15/2022]
Abstract
Understanding the residue-dependent effects of disease-phenotypic mutations in multi-spanning membrane proteins is an essential step toward the development of corrective therapies. As a systematic approach to further elucidate mutant-dependent mis-folding consequences, we prepared two libraries: one consisting of 20 helix-loop-helix ("hairpin") constructs derived from helices 3 and 4 of the human cystic fibrosis transmembrane conductance regulator (CFTR) (residues 194-241) in which the CF-phenotypic position Val-232 was substituted individually to each of the 20 commonly-occurring amino acids; and a second library consisting of 20 single-stranded TM4 peptides (CFTR residues 221-241) similarly substituted at position 232. Both libraries were analyzed to measure mutant-dependent variations in mobility on SDS-PAGE; size and shape on size exclusion chromatography; retention times on reverse phase HPLC; and helical content by circular dichroism spectroscopy. Analysis of a scatter plot between TM3/4 hairpin and TM4 peptide retention times showed a strong correlation (r=0.94, p<0.05), with retention times largely a function of residue hydrophobicity. In contrast, while the hairpin library migrated over a significant range on SDS-PAGE, migration rates for TM4 hydrophobic residues at position 232 converged at a single value, suggesting that residue-dependent re-orientations of hairpin van der Waals interfaces may expose varying faces of the TM3 and/or TM4 helices to the SDS detergent. The overall results suggest that mutant-mediated variations are a principal determinant of tertiary interhelical folding interactions in membranes.
Collapse
Affiliation(s)
- Cory M Mulvihill
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
| | | |
Collapse
|
5
|
Tulumello DV, Deber CM. Positions of polar amino acids alter interactions between transmembrane segments and detergents. Biochemistry 2011; 50:3928-35. [PMID: 21473646 DOI: 10.1021/bi200238g] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
α-Helical transmembrane (TM) segments in membrane proteins are comprised primarily of hydrophobic amino acids that accommodate insertion from water into the nonpolar membrane bilayer. In many such segments, however, polar residues are also present for structural or functional reasons. These latter residues impair the local favorable acyl interactions required for solvation by hydrophobic media such as phospholipids in native bilayers or detergents used for in vitro characterization. Using a series of Lys-tagged designed TM-like peptides (typified by KK-YAAAIAAIAWAIAAIAAAIAA-KKK) in which single-Asn residue substitutions (from Ile or Ala) were made successively from the center of the hydrophobic region toward the C-terminus, we demonstrate that polar residues strongly alter the nature of the interaction between TM segments and the solvating detergent. Through the application of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism spectroscopy, and tryptophan fluorescence, we observed drastic differences in the structures of the detergent-peptide complexes that contain relatively minor sequence differences. For example, the blue shift of the Trp fluorescence (indicating local detergent solvation at this location) differs by as much as ~10 nm depending upon the position of a single Asn substitution in an otherwise identical segment. The overall results suggest that polar point mutations occurring in a biological membrane will elicit comparable effects, placing a significant refolding burden on the local protein structure and potentially leading to disease states through altered protein--lipid interactions in membrane proteins.
Collapse
Affiliation(s)
- David V Tulumello
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | | |
Collapse
|
6
|
Kanelis V, Chong PA, Forman-Kay JD. NMR spectroscopy to study the dynamics and interactions of CFTR. Methods Mol Biol 2011; 741:377-403. [PMID: 21594798 DOI: 10.1007/978-1-61779-117-8_25] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a multi-domain membrane chloride channel whose activity is regulated by ATP at two nucleotide-binding domains (NBD1 and NBD2) and by phosphorylation of the regulatory (R) region. The NBDs and the R region have functionally relevant motions that are critical for channel gating. Nuclear magnetic resonance (NMR) spectroscopy is a highly useful technique for obtaining information on the structure and interactions of CFTR and is extremely powerful for probing dynamics. NMR approaches for studying CFTR are reviewed, using our previous NBD1 and the R region results to provide examples. These NMR data are yielding insights into the dynamic properties and interactions that facilitate normal CFTR regulation as well as pathological effects of mutations, including the most common disease mutant, deletion of F508 in NBD1.
Collapse
Affiliation(s)
- Voula Kanelis
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, Canada.
| | | | | |
Collapse
|
7
|
Qureshi T, Goto NK. Contemporary methods in structure determination of membrane proteins by solution NMR. Top Curr Chem (Cham) 2011; 326:123-85. [PMID: 22160391 DOI: 10.1007/128_2011_306] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Integral membrane proteins are vital to life, being responsible for information and material exchange between a cell and its environment. Although high-resolution structural information is needed to understand how these functions are achieved, membrane proteins remain an under-represented subset of the protein structure databank. Solution NMR is increasingly demonstrating its ability to help address this knowledge shortfall, with the development of a diverse array of techniques to counter the challenges presented by membrane proteins. Here we document the advances that are helping to define solution NMR as an effective tool for membrane protein structure determination. Developments introduced over the last decade in the production of isotope-labeled samples, reconstitution of these samples into the growing selection of NMR-compatible membrane-mimetic systems, and the approaches used for the acquisition and application of structural restraints from these complexes are reviewed.
Collapse
Affiliation(s)
- Tabussom Qureshi
- Department of Chemistry, University of Ottawa, Ottawa, ON, Canada
| | | |
Collapse
|
8
|
Grant CV, Yang Y, Glibowicka M, Wu CH, Park SH, Deber CM, Opella SJ. A Modified Alderman-Grant Coil makes possible an efficient cross-coil probe for high field solid-state NMR of lossy biological samples. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 201:87-92. [PMID: 19733108 PMCID: PMC2800166 DOI: 10.1016/j.jmr.2009.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2009] [Revised: 08/10/2009] [Accepted: 08/10/2009] [Indexed: 05/11/2023]
Abstract
The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the (1)H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B(1) field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the (1)H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194-241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed.
Collapse
Affiliation(s)
- Christopher V. Grant
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Yuan Yang
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Mira Glibowicka
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada
| | - Chin H. Wu
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Sang Ho Park
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Charles M. Deber
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada
| | - Stanley J. Opella
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
- Corresponding Author. , 858.822.4820
| |
Collapse
|
9
|
Neumoin A, Cohen LS, Arshava B, Tantry S, Becker JM, Zerbe O, Naider F. Structure of a double transmembrane fragment of a G-protein-coupled receptor in micelles. Biophys J 2009; 96:3187-96. [PMID: 19383463 DOI: 10.1016/j.bpj.2009.01.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 01/08/2009] [Accepted: 01/13/2009] [Indexed: 11/29/2022] Open
Abstract
The structure and dynamic properties of an 80-residue fragment of Ste2p, the G-protein-coupled receptor for alpha-factor of Saccharomyces cerevisiae, was studied in LPPG micelles with the use of solution NMR spectroscopy. The fragment Ste2p(G31-T110) (TM1-TM2) consisted of 19 residues from the N-terminal domain, the first TM helix (TM1), the first cytoplasmic loop, the second TM helix (TM2), and seven residues from the first extracellular loop. Multidimensional NMR experiments on [(15)N], [(15)N, (13)C], [(15)N, (13)C, (2)H]-labeled TM1-TM2 and on protein fragments selectively labeled at specific amino acid residues or protonated at selected methyl groups resulted in >95% assignment of backbone and side-chain nuclei. The NMR investigation revealed the secondary structure of specific residues of TM1-TM2. TALOS constraints and NOE connectivities were used to calculate a structure for TM1-TM2 that was highlighted by the presence of three alpha-helices encompassing residues 39-47, 49-72, and 80-103, with higher flexibility around the internal Arg(58) site of TM1. RMSD values of individually superimposed helical segments 39-47, 49-72, and 80-103 were 0.25 +/- 0.10 A, 0.40 +/- 0.13 A, and 0.57 +/- 0.19 A, respectively. Several long-range interhelical connectivities supported the folding of TM1-TM2 into a tertiary structure typified by a crossed helix that splays apart toward the extracellular regions and contains considerable flexibility in the G(56)VRSG(60) region. (15)N-relaxation and hydrogen-deuterium exchange data support a stable fold for the TM parts of TM1-TM2, whereas the solvent-exposed segments are more flexible. The NMR structure is consistent with the results of biochemical experiments that identified the ligand-binding site within this region of the receptor.
Collapse
Affiliation(s)
- Alexey Neumoin
- Institute of Organic Chemistry, University of Zurich, Zurich, Switzerland
| | | | | | | | | | | | | |
Collapse
|