Fig. 6. Identification of a region encompassing the basolateral signal in the b-tail. (A) Schematic representation of the wild-type PMCA2xb isoform (wt-2xb) used as a basic isoform for the determination of the basolateral-targeting motif present in the b-tail. (B-G) Apical surface-scan of the hair bundle (plane 2 in H, actin in red) and an orthogonal view of the basolateral plasma membrane (plane 1 in H) of a transfected hair cell expressing a transgene encoding EGFP-tagged (in green) PMCA2xb isoform (wt-2xb) and derived mutated isoforms, are presented in separated green and red, and merged channels. Small panels on the right show high-resolution basolateral cross-sectional scans (plane 3 in H). For each mutated variant, the corresponding mutation is shown in red on the b-tail aa sequence. The aa sequence Leu-Ile-Asp-Asp-Thr-Asp-Leu (LIDDTDL) at position 1153-1159 encompasses the crucial residues for the basolateral targeting of PMCA2xb (F). (I) Summary of our observations. 2xb, wild-type PMCA2xb isoform; b, b-tail; AP, apical PM localization; BL, basolateral PM localization. Bars, 5 µm.