title: PDZ-binding motifs are unable to ensure correct polarized protein distribution in the absence of additional localization signals.
abstract: The C-terminal PDZ-binding motifs are required for polarized apical/basolateral localization of many membrane proteins. To determine the specificity of the PDZ-binding motifs in establishing cellular distribution, we utilized a 111-amino acid region from the C-terminus of cystic fibrosis transmembrane conductance regulator (CFTR) that is able to direct apical localization of fused reporter proteins. Substitution of the C-terminal PDZ-binding motif of CFTR with corresponding motifs necessary for basolateral localization of other membrane proteins did not lead to the redistribution of the fusion protein to the basolateral membrane. Instead, some fusion proteins remained localized to the apical membrane, whereas others showed no specific distribution. The specificity of the PDZ-based interactions was substantially increased when specific amino acids located upstream of the classical PDZ-binding motifs were included. However, even the presence of a longer C-terminal motif from a basolateral protein could not ensure basolateral distribution of the fusion protein. Our results indicate that the C-terminal PDZ-binding motifs are not the primary signals for polarized protein distribution, although they are required for targeting and/or stabilization of protein at the given location.
authors.affiliation: Institute of Genetic Medicine, Johns Hopkins University School of Medicine, 600 North Wolfe Street, Baltimore, MD 21287, USA. milewski@imid.med.pl
authors.forename: Michał I
authors.initials: MI
authors.lastname: Milewski
authors.forename: Andrea
authors.initials: A
authors.lastname: Lopez
authors.forename: Monika
authors.initials: M
authors.lastname: Jurkowska
authors.forename: Jessica
authors.initials: J
authors.lastname: Larusch
authors.forename: Garry R
authors.initials: GR
authors.lastname: Cutting
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000737:chemistry; D004285:Dogs; D004847:Epithelial Cells / Q000737:chemistry; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis* / Q000737:chemistry* / Q000378:metabolism; D021382:Protein Sorting Signals / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism
chemical_list: C505032:CFTR protein, human; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator