ABCC7 p.Val510*
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[hide] Correctors promote maturation of cystic fibrosis t... J Biol Chem. 2007 Nov 16;282(46):33247-51. Epub 2007 Oct 2. Wang Y, Loo TW, Bartlett MC, Clarke DM
Correctors promote maturation of cystic fibrosis transmembrane conductance regulator (CFTR)-processing mutants by binding to the protein.
J Biol Chem. 2007 Nov 16;282(46):33247-51. Epub 2007 Oct 2., 2007-11-16 [PMID:17911111]
Abstract [show]
The most common cause of cystic fibrosis (CF) is defective folding of a cystic fibrosis transmembrane conductance regulator (CFTR) mutant lacking Phe(508) (DeltaF508). The DeltaF508 protein appears to be trapped in a prefolded state with incomplete packing of the transmembrane (TM) segments, a defect that can be repaired by expression in the presence of correctors such as corr-4a, VRT-325, and VRT-532. To determine whether the mechanism of correctors involves direct interactions with CFTR, our approach was to test whether correctors blocked disulfide cross-linking between cysteines introduced into the two halves of a Cys-less CFTR. Although replacement of the 18 endogenous cysteines of CFTR with Ser or Ala yields a Cys-less mutant that does not mature at 37 degrees C, we found that maturation could be restored if Val(510) was changed to Ala, Cys, Ser, Thr, Gly, Ala, or Asp. The V510D mutation also promoted maturation of DeltaF508 CFTR. The Cys-less/V510A mutant was used for subsequent cross-linking analysis as it yielded relatively high levels of mature protein that was functional in iodide efflux assays. We tested for cross-linking between cysteines introduced into TM6 and TM7 of Cys-less CFTR/V510A because cross-linking between TM6 and TM7 of P-glycoprotein, the sister protein of CFTR, was inhibited with the corrector VRT-325. Cys-less CFTR/V510A mutant containing cysteines at I340C(TM6) and S877C(TM7) could be cross-linked with a homobifunctional cross-linker. Correctors and the CFTR channel blocker benzbromarone, but not P-glycoprotein substrates, inhibited cross-linking of mutant I340C(TM6)/S877C(TM7). These results suggest that corrector molecules such as corr-4a interact directly with CFTR.
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No. Sentence Comment
25 The Cys-less CFTR cDNA was also modified to include the V510X mutations.
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ABCC7 p.Val510* 17911111:25:56
status: NEW27 The V510X mutations were then introduced into ⌬F508 CFTR as described above.
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ABCC7 p.Val510* 17911111:27:4
status: NEW83 The ⌬F508 CFTR/V510X mutants were expressed in HEK 293 cells at 37 °C, and whole cell extracts were subjected to immunoblot analysis. Fig. 2D shows that introduction of an Asp mutation at position 510 was most effective in promoting maturation of ⌬F508 CFTR.
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ABCC7 p.Val510* 17911111:83:22
status: NEW