STUDIES ON HUMAN PORIN .9. IMMUNOLOCALIZATION OF PORIN AND CFTR CHANNELS IN HUMAN SURFACE RESPIRATORY EPITHELIUM

The expression of the voltage-dependent anion channel (VDAC) ''Porin 3 1 HL'' and its cellular and subcellular immunocytochemical localizatio n in the human respiratory epithelium were studied with monoclonal and polyclonal antibodies using immunofluorescence and immunogold labelli ng with light (LM) and transmission electron microscopy (TEM), respect ively. Porin was identified in the apical domain of the ciliated cells and in the basal cells of the respiratory epithelium. Immunogold labe lling was present in the apical plasma membrane and subapical vesicles of the ciliated cells. In pre-embedded freshly dissociated surface ep ithelial cells, porin could also be identified with TEM at the outer p art of the plasma membrane of basal cells. By LM double immunolabellin g, both porin and cystic fibrosis transmembrane conductance regulator (CFTR) were identified in the apical domain of ciliated cells but not in basal cells where CFTR was never identified. On Western blots of so lubilized total membrane protein preparations from the same frozen sur face epithelial respiratory cells, the antibodies recognized a group o f 3 proteins of 31, 60 and 130-140 kDa with a strong reactivity for a 31 kDa protein, corresponding to the porin and a protein of 170 kDa wh ich is consistent with mature CFTR. These results suggest that porin m ight be part of a multi-component chloride channel complex which could interact with CFTR.