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Analysis of the localization of STE6/CFTR chimeras in a Saccharomyces cerevisiae model for the cystic fibrosis defect CFTRΔF508
Author(s) -
Paddon Chris,
Loayza Diego,
Vangelista Luca,
Solari Roberto,
Michaelis Susan
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1996.444973.x
Subject(s) - biology , cystic fibrosis transmembrane conductance regulator , mutant , saccharomyces cerevisiae , δf508 , yeast , genetics , microbiology and biotechnology , cystic fibrosis , gene
The use of yeast as a model system to study mammalian proteins is attractive, because yeast genetic tools can be utilized if a suitable phenotype is created. STE6, the Saccharomyces cerevisiae a‐factor mating pheromone transporter, and CFTR, the mammalian cystic fibrosis transmembrane conductance regulator, are both members of the ATP binding cassette (ABC) superfamily. Teem et al . (1993) described a yeast model for studying a mutant form of the cystic fibrosis protein, CFTRΔF508. The model involved expression of a chimeric molecule in which a portion of yeast STE6 was replaced with the corresponding region from mammalian CFTR. The STE6/CFTR chimera complemented a ste6 mutant strain for mating, indicating that it could export a‐factor. However, mating efficiency was dramatically reduced upon introduction of ΔF508, providing a yeast phenotype for this mutation. In human cells, the ΔF508 mutation results in retention of CFTR in the endoplasmic reticulum (ER), and possibly in reduction of its chloride‐channel activity. Here we examine the basis for the differences in STE6 activity promoted by the wild‐type and mutant STE6/CFTR chimeras. By analysis of protein stability and subcellular localization, we find that the mutant chimera is not ER‐retained in yeast. We conclude that the molecular basis for the reduced mating of the STE6/CFTRΔF508 chimera must reflect a reduction in its capacity to transport a‐factor, rather than mistrafficking. Thus, STE6/CFTRΔF508 in yeast appears to be a good genetic model to probe certain aspects of protein function, but not to study protein localization.