Am. J. Respir. Cell Mol. Biol., Vol 11, No. 1, Jul 1994, 75-84.
Fodrin and actin in the normal, metaplastic, and dysplastic respiratory epithelium and in lung carcinoma
R Sormunen, P Paakko, R Palovuori, Y Soini and VP Lehto
Biocenter, University of Oulu, Finland.
Distribution of actin and fodrin, a nonerythroid analogue of spectrin, was
studied in cytocentrifuge preparations and in tissue sections of normal and
pathologic respiratory epithelium by using immunofluorescence and
immunoelectron microscopy. In ciliated epithelial cells and in goblet cells
of normal bronchial epithelium, fodrin and actin were located in the apical
parts and along the lateral walls of the cells. In basal cells, fodrin and
actin were also seen diffusely in the cytoplasm. Immunoelectron microscopy
showed fodrin in close association with the basal bodies and rootlets of
the cilia and microvilli in the ciliated cells. In alveolar epithelium,
fodrin and actin were located at the apical membrane in type I pneumocytes
and along the apical and lateral membranes in type II pneumocytes. In type
II pneumocytes, fodrin was also seen in close association with the
secretory vacuoles. In metaplastic and dysplastic bronchial epithelium, a
diffuse cytoplasmic and a circumferential, membrane-associated staining for
fodrin and actin was seen. In all types of carcinomas, fodrin was seen
along the lateral walls and diffusely in the cytoplasm. The staining was
more intense than in the normal cells. In immunoblotting of the normal
bronchial epithelium, and peripheral lung and lung carcinomas, a single 240
kD band was recognized with antibodies to fodrin. The results show distinct
differences in the distribution of fodrin in the various cell types of the
respiratory epithelium. In ciliated cells, the close relationship with
cytoskeleton suggests a role of fodrin in the establishment of the
elaborate structural architecture of the apical compartment. In type II
pneumocytes, on the other hand, fodrin probably plays a role in secretion
of the surfactant. In basal cells, the diffuse distribution of fodrin
probably reflects the high proliferative capacity of this cell compartment.
Interestingly, a similar distribution was also seen in premalignant and
malignant cells.
