WS17.2 Hydrostatic pressure induced stretch activates CFTR in native pulmonary epithelium

Abstract

The small intestinal mucus is of one type and mainly consists of the goblet cell secreted gel-forming mucin MUC2. Another type of mucins is the membranetethered mucins MUC3, MUC12 and MUC17 that are anchored in the apical plasma membrane of enterocytes. These mucins build the enterocyte glycocalyx and are thought to protect the brush border membrane. Secretion of the gel-forming mucin MUC2 is triggered by the cholinergic agonist carbachol. The same stimuli cause the enterocytes to relocalize the CFTR channel to the apical membrane to secrete chloride and bicarbonate necessary for proper mucin unfolding and hydration. Simultaneously, the NHE exchanger is relocated from the apical membrane to limit apical secretion of protons that should have neutralized bicarbonate. Interestingly, at the same time the transmembrane mucin MUC17 is also relocalized from the apical membrane into intracellular vesicles [1]. Both CFTR and MUC17 have C-terminal PDZ-binding motifs and both also bind to the PDZ protein PDZK1. This is an adapter family protein that controls proper localization of plasma membrane proteins by linking them to the cytoskeleton. By using an intestinal human cell line as model system, the interaction of PDZK1 with CFTR and MUC17 is analyzed by immunofluorescent co-staining and coimmunoprecipitation of native and mutant constructs. Phospho-specific analyses of the proteins are carried out to characterize interaction regulation due to phosphorylation.