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Studies on CFTR protein expression and localization in native tissues or in primary cultures of human epithelial cells are scarce due to the intrinsic instability of this protein, its low expression in most tissues and also to technical difficulties. However, such data are of the highest importance to understand the pathophysiology of CF. The purpose of this article is to outline several assays for the characterization of primary epithelial cultures and to review different CFTR immunostaining protocols.

Detection of cystic fibrosis transmembrane conductance regulator (CFTR) protein is usually a difficult task to accomplish due to the low levels of expression and high turnover that this membrane protein is submitted to in the cell. Common biochemical methods can be used for the detection of CFTR but several critical points must be taken into account. The scope of this article is to outline biochemical methods commonly used to assess CFTR expression, processing and membrane localization.

Numerous factors, other than mutations in the CFTR gene, affect the phenotypic variability of cystic fibrosis (CF). With a two-dimensional electrophoresis (2-DE) analysis of total protein expression profiles (proteomics) of CF versus non-CF cells it is possible to obtain an integrative picture of CF cellular alterations. Through this approach, proteins that interact differently with wild type- and mutant-CFTR can also be identified (interactomics). This can provide insight into CF pathophysiology as well as clues for novel therapeutic targets. Additionally, protein profiling can ultimately identify novel disease markers with the potential for a CF diagnosis not based on the analysis of CFTR gene.

For most expression studies focusing on the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein, sensitive and specific antibodies (Abs) are critically needed. Several Abs have been produced commercially or by research laboratories for CFTR detection in both cell lines with heterologous or endogenous expression and native cells/tissues. Here, we review the applicability of most Abs currently in use in CF research for the biochemical and/or immunocytochemical detection of CFTR.

Reliable methods for determining the localisation of mutant CFTR protein in native cells from CF individuals are necessary to allow the degree of mislocalisation of any genotype to be defined and to assess the effect of therapeutic agents on CFTR trafficking. Here, we present procedures for obtaining ciliated epithelial cells from CF patients by nasal brushing and a description of protocols for immunolocalisation of CFTR. The protocols are a consensus, following comparison of some aspects of methods currently used in the authors' laboratories.