CFTR mutations altering CFTR fragmentation.
Most CF (cystic fibrosis) results from deletion of a phenylalanine (F508) in the CFTR {CF transmembrane-conductance regulator; ABCC7 [ABC (ATP-binding cassette) sub-family C member 7]} which causes ER (endoplasmic reticulum) degradation of the mutant. Using stably CFTR-expressing BHK (baby-hamster kidney) cell lines we demonstrated that wild-type CTFR and the F508delCFTR mutant are cleaved into differently sized N- and C-terminal-bearing fragments, with each hemi-CFTR carrying its nearest NBD (nucleotide-binding domain), reflecting differential cleavage through the central CFTR R-domain. Similar NBD1-bearing fragments are present in the natively expressing HBE (human bronchial epithelial) cell line. We also observe multiple smaller fragments of different sizes in BHK cells, particularly after F508del mutation (ladder pattern). Trapping wild-type CFTR in the ER did not generate a F508del fragmentation fingerprint. Fragments change their size/pattern again post-mutation at sites involved in CFTR's in vitro interaction with the pleiotropic protein kinase CK2 (S511A in NBD1). The F508del and S511A mutations generate different fragmentation fingerprints that are each unlike the wild-type; yet, both mutants generate new N-terminal-bearing CFTR fragments that are not observed with other CK2-related mutations (S511D, S422A/D and T1471A/D). We conclude that the F508delCFTR mutant is not degraded completely and there exists a relationship between CFTR's fragmentation fingerprint and the CFTR sequence through putative CK2-interactive sites that lie near F508.
Division of Medical Sciences, University of Dundee, Ninewells Hospital, Dundee DD1 9SY, U.K.
Kendra
K
Tosoni
Michelle
M
Stobbart
Diane M
DM
Cassidy
Andrea
A
Venerando
Mario A
MA
Pagano
Simão
S
Luz
Margarida D
MD
Amaral
Karl
K
Kunzelmann
Lorenzo A
LA
Pinna
Carlos M
CM
Farinha
Anil
A
Mehta
D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation / Q000235:genetics*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism
D010446:Peptide Fragments; D019005:Cystic Fibrosis Transmembrane Conductance Regulator