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Mutations in polycystin-1, polycystin-2, or fibrocystin account for autosomal dominant or recessive polycystic kidney disease. Renal cystogenesis is linked to abnormal localization and function of these cystoproteins in renal primary cilia. They are also expressed in extrarenal tissues in which their functions are unclear. Here we found that human type-II alveolar epithelial A549, airway submucosal Calu-3 cells, and rat bronchioles contain primary or multiple cilia in which we detected these cystoproteins. At sub-confluency, polycystin-1 was expressed on plasma membrane, while polycystin-2 was localized to the ER of resting cells. Both polycystins were detected on the spindle and mid-body of mitotic cells, while fibrocystin was on centrosome throughout cell cycle. Polycystins and fibrocystin may participate in regulating mucociliary sensing and transport within pulmonary airways.

Abnormalities of epithelial function in cystic fibrosis (CF) have been linked to defects in cell membrane permeability to chloride or sodium ions. Recently, a class of chloride channels in airway epithelial cells have been reported to lack their usual sensitivity to phosphorylation via cAMP-dependent protein kinase, suggesting that CF could be due to a single genetic defect in these channels. We have examined single chloride and sodium channels in control and CF human nasal epithelia using the patch-clamp technique. The most common chloride channel was not the one previously associated with CF, but it was also abnormal in CF cells. In addition, the number of sodium channels was unusually high in CF. These findings suggest a wider disturbance of ion channel properties in CF than would be produced by a defect in a single type of channel.