IMMUNOCYTOCHEMICAL STUDY OF MICROVILLI IN A GASTRIC CARCINOMA-DERIVEDCELL-LINE

To study the structural components of microvilli of the KATO-III cell, we used anti-villin, -ezrin, and anti-MVM (microvillous membrane prep ared against mouse intestinal microvilli) antibodies. Villin and ezrin cross-link actin bundles of microvilli such as those in the small int estine and renal proximal cells. Electromicroscopically, the cytoskele tal core of microvilli of the KATO-III cell was constituted of actin-f ilament bundles. The anti-villin antibody but not anti-ezrin antibody reacted with the KATO-III cell as demonstrated by FITC-immunofluoresce nce and PAP-staining. Anti-villin, anti-MVM, but not anti-ezrin antibo dy, reacted with the KATO-III cell surface and with intracellular mate rials. Western blot analysis using anti-villin and anti-MVM antibodies revealed proteins of similar to 95 kDa (villin), and 15 kDa in the mi crosomal membrane fractions of KATO-III cells, respectively. Immunocyt ochemical and confocal laser microscopic studies showed that the cell- surface and the intracellular microcysts of KATO-III cells were prefer entially decorated by anti-villin and anti-MVM antibodies. These data suggested that some actin-binding proteins, such as villin, were local ized at the cell surface and on some of the intracellular cytoplasmic structures of the KATO-III cell.