Localization of Sequences within the C-terminal Domain of the Cystic Fibrosis Transmembrane Conductance Regulator Which Impact Maturation and Stability

doi:10.1074/jbc.M003672200

Localization of Sequences within the C-terminal Domain of the Cystic Fibrosis Transmembrane Conductance Regulator Which Impact Maturation and Stability*

Martina Gentzsch and
John R. Riordan‡

From the Mayo Foundation, S. C. Johnson Medical Research Center, Mayo Clinic Scottsdale, Scottsdale, Arizona 85259

Abstract

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.

Footnotes

↵* This work was supported by National Institutes of Health, NIDDK Grant DK54076 and a Fellowship from the Deutsche Forschungsgemeinschaft (to M. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ To whom correspondence should be addressed: Mayo Clinic Scottsdale, S. C. Johnson Medical Research Center, 13400 E. Shea Blvd., Scottsdale, AZ 85259. Tel.: 480-301-6206; Fax: 480-301-7017; E-mail: riordan@mayo.edu.
Published, JBC Papers in Press, October 5, 2000, DOI 10.1074/jbc.M003672200
↵2 X.-B. Chang and J. R. Riordan, unpublished data.
↵3 T. J. Jensen, B. G. Bone, and J. R. Riordan, unpublished data.
Abbreviations:

CFTR

cystic fibrosis transmembrane conductance regulator

ER

endoplasmic reticulum

NBD

nucleotide-binding domain

TMD

transmembrane domain

ABC

adenine nucleotide binding cassette

PDZ

PSD-95, disc-large, ZO-1

BFA

brefeldin A

ALLN

N-acetyl-leucinyl-leucinyl-norleucinal

MG-132

N-carbobenzoxyl-leucinyl-leucinyl-leucinal

NLVS

4-hydroxy-5-iodo-3-nitrophenylacetyl-leucinyl-leucinyl-leucinyl-vinylsulfone

PBS

phosphate-buffered saline
- Received May 1, 2000.
- Revision received September 12, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.