HGF/SF‐INDUCED SPREADING OF MDCK CELLS CORRELATES WITH DISAPPEARANCE OF BARMOTIN/7H6, A TIGHT JUNCTION‐ASSOCIATED PROTEIN, FROM THE CELL MEMBRANE

Changes in expression of the two tight junction‐associated proteins, barmotin/7H6 and ZO‐1, as well as the adherence junction‐associated protein, E‐cadherin, were followed during hepatocyte growth factor/scatter factor (HGF/SC)‐induced migration process of MDCK cells. Modulation of the HGF/SF‐induced migration process by staurosporine, an inhibitor of protein kinase C (PKC), was also examined. Cell migration induced by HGF/SF consisted of two distinct phases, initial cell spreading between 2 and 9h after the start of treatment, and the scattering phase which started ∼12h after treatment. Both ZO‐1 and E‐cadherin were expressed at the cell—cell border of adherent cells in the scattering phase, whereas barmotin/7H6, a barrier function‐related tight junction protein, was not seen during the early spreading phase. Confluent cultures of MDCK cells, which did not spread after HGF/SF treatment, were positive for barmotin/7H6 expression at cell—cell borders. Blocking PKC activation during HGF/SF treatment with staurosporine inhibited cell spreading, and the cells retained barmotin/7H6 expression until at 6h after HGF/SF treatment. The results indicate that disappearance of the tight junction protein, barmotin/7H6, is closely associated with cell spreading, with both barmotin/7H6 expression and cell spreading seemingly being regulated by PKC‐mediated signaling.