title: Alteration of CFTR transmembrane span integration by disease-causing mutations.
abstract: Many missense mutations in the cystic fibrosis transmembrane conductance regulator protein (CFTR) result in its misfolding, endoplasmic reticulum (ER) accumulation, and, thus, cystic fibrosis. A number of these mutations are located in the predicted CFTR transmembrane (TM) spans and have been projected to alter span integration. However, the boundaries of the spans have not been precisely defined experimentally. In this study, the ER luminal integration profiles of TM1 and TM2 were determined using the ER glycosylation machinery, and the effects of the CF-causing mutations G85E and G91R thereon were assessed. The mutations either destabilize the integrated conformation or alter the TM1 ER integration profile. G85E misfolding is based in TM1 destabilization by glutamic acid and loss of glycine and correlates with the temperature-insensitive ER accumulation of immature full-length CFTR harboring the mutation. By contrast, temperature-dependent misfolding owing to the G91R mutation depends on the introduction of the basic side chain rather than the loss of the glycine. This work demonstrates that CF-causing mutations predicted to have similar effects on CFTR structure actually result in disparate molecular perturbations that underlie ER accumulation and the pathology of CF.
authors: Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA.
authors: Anna E
authors: AE
authors: Patrick
authors: Andrey L
authors: AL
authors: Karamyshev
authors: Linda
authors: L
authors: Millen
authors: Philip J
authors: PJ
authors: Thomas
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D003550:Cystic Fibrosis / Q000235:genetics*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry; D005998:Glycine / Q000737:chemistry; D006031:Glycosylation; D006801:Humans; D009154:Mutation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D013696:Temperature
chemical_list: C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D018698:Glutamic Acid; D005998:Glycine