Fig. 3. Double staining of InsP₃R-3 and polarity markers in polarized MDCK cells: confocal analysis. MDCK plated at 10⁴ cells/cm² were cultured for 10-12 days and double stained using a monoclonal antibody anti-InsP₃R-3 and antibodies directed against the tight junction associated protein ZO-1 (A), the tight junction protein occludin (B), the lateral marker ErbB-2 (C) and the apical protein gp-114 (D). The immunolocalization obtained for each protein is presented, in addition to the merged image. In A and C, two xy sections taken at the apex and at the base of the cell layer were shown with an xz section taken at the level indicated by the arrow on the corresponding xy sections. In B and D, one apical xy section was shown with an xz section taken at the level indicated by the arrow on the corresponding xy section. The top and the bottom of the cell layer shown in the xz sections are indicated by asterisks (*). In each case a restricted distribution of InsP₃R-3 was observed in the tight junction zone, which corresponds to the frontier between the lateral and the apical pole. This restricted distribution is particularly visible in the xy and xz sections stained for InsP₃R-3 and the lateral marker ErbB-2 shown in C. Bar, 10 µm.

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