ABCC7 p.Leu1399*
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[hide] C-terminal truncations destabilize the cystic fibr... J Biol Chem. 1999 Jul 30;274(31):21873-7. Haardt M, Benharouga M, Lechardeur D, Kartner N, Lukacs GL
C-terminal truncations destabilize the cystic fibrosis transmembrane conductance regulator without impairing its biogenesis. A novel class of mutation.
J Biol Chem. 1999 Jul 30;274(31):21873-7., 1999-07-30 [PMID:10419506]
Abstract [show]
Defective cAMP-stimulated chloride conductance of the plasma membrane of epithelial cell is the hallmark of cystic fibrosis (CF) and results from mutations in the cystic fibrosis transmembrane conductance regulator, CFTR. In the majority of CF patients, mutations in the CFTR lead to its misfolding and premature degradation at the endoplasmic reticulum (ER). Other mutations impair the cAMP-dependent activation or the ion conductance of CFTR chloride channel. In the present work we identify a novel mechanism leading to reduced expression of CFTR at the cell surface, caused by C-terminal truncations. The phenotype of C-terminally truncated CFTR, representing naturally occurring premature termination and frameshift mutations, were examined in transient and stable heterologous expression systems. Whereas the biosynthesis, processing, and macroscopic chloride channel function of truncated CFTRs are essentially normal, the degradation rate of the mature, complex-glycosylated form is 5- to 6-fold faster than the wild type CFTR. These experiments suggest that the C terminus has a central role in maintaining the metabolic stability of the complex-glycosylated CFTR following its exit from the ER and provide a plausible explanation for the severe phenotype of CF patients harboring C-terminal truncations.
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19 Premature stop codons were as follows: Q1412X (A. Wallace and M. Tassabehji; ⌬70); S1455X and L1399X (⌬26 and ⌬82, respectively).
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ABCC7 p.Leu1399* 10419506:19:101
status: NEW[hide] Localization of sequences within the C-terminal do... J Biol Chem. 2001 Jan 12;276(2):1291-8. Gentzsch M, Riordan JR
Localization of sequences within the C-terminal domain of the cystic fibrosis transmembrane conductance regulator which impact maturation and stability.
J Biol Chem. 2001 Jan 12;276(2):1291-8., 2001-01-12 [PMID:11022033]
Abstract [show]
Some disease-associated truncations within the 100-residue domain C-terminal of the second nucleotide-binding domain destabilize the mature protein (Haardt, M., Benharouga, M., Lechardeur, D., Kartner, N., and Lukacs, G. L. (1999) J. Biol. Chem. 274, 21873-21877). We now have identified three short oligopeptide regions in the C-terminal domain which impact cystic fibrosis transmembrane conductance regulator (CFTR) maturation and stability in different ways. A highly conserved hydrophobic patch (region I) formed by residues 1413-1416 (FLVI) was found to be crucial for the stability of the mature protein. Nascent chain stability was severely decreased by shortening the protein by 81 amino acids (1400X). This accelerated degradation was sensitive to proteasome inhibitors but not influenced by brefeldin A, indicating that it occurred at the endoplasmic reticulum. The five residues at positions 1400 to 1404 (region II) normally maintain nascent CFTR stability in a positional rather than a sequence-specific manner. A third modulating region (III) constituted by residues 1390 to 1394 destabilizes the protein. Hence the nascent form regains stability on further truncation back to residues 1390 or 1380, permitting some degree of maturation and a low level of cyclic AMP-stimulated chloride channel activity at the cell surface. Thus while not absolutely essential, the C-terminal domain strongly modulates the biogenesis and maturation of CFTR.
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229 However, the frameshift 4326de1TC resulting in truncation at residue 1398 and the premature stop L1399X also remove region II and hence also compromise the stability and ability to mature of the nascent chain.
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ABCC7 p.Leu1399* 11022033:229:97
status: NEW