CHANGES IN EXPRESSION AND SUBCELLULAR-LOCALIZATION OF ANNEXIN-IV IN RABBIT KIDNEY PROXIMAL TUBULE CELLS DURING PRIMARY CULTURE

In the present study, we investigated the polarized expression of anne xin IV at various stages in the growth of rabbit kidney proximal tubul e cells (PTC) in primary cultures. The results of immunoblotting analy sis and indirect immunofluorescence studies using a specific anti-anne xin IV monoclonal antibody, indicated that annexin IV is expressed in proximal tubule cultured cells, although it was not detected in the pr oximal tubules present in frozen sections of kidney cortex and freshly isolated proximal tubule cells. In either non-confluent or confluent cells which remained attached to the collagen-coated support, annexin IV was mainly concentrated around the nucleus, whereas in PTC forming the monolayer of domes, it was restricted to the basolateral membrane domain. This basolateral localization was identical to that observed i n other polarized epithelial cell types such as enterocytes. When the domes burst, the cells returned to the collagen-coated support and the annexin IV was again localized around the nuclei. The fact that the c hange of localization was very rapid suggested the existence of a cons iderable difference between the differentiation states of dome forming and adherent confluent cells. Moreover, a transient association of an nexin IV with the basal body of apically located cilia also seemed to be correlated with a particular polarization state and/or differentiat ion states of adherent cultured cells, corresponding to the beginning of the polarized expression of aminopeptidase N, a hydrolase located i n the apical brush border membrane, and to the falling of cells onto t he support, subsequent to the bursting of the domes. In conclusion, th ese results provide evidence that annexin IV may constitute a new mark er of the basolateral membrane domain of polarized epithelial renal ce lls in primary cultures. (C) 1995 Wiiey-Liss, Inc.