Figure 5.

Distribution of sortilin and its co-localization with NCC. Two days after Cos-7 cells were transfected with indicated plasmids, immunostaining and confocal microscopy were performed. (A) In A, sortilin WT in green seems to be distributed in the perinuclear region and peripheral granular structure as well as plasma membrane. In B, TGN 38 is shown in red. C shows the merged picture, indicating the co-localization of sortilin WT with TGN 38 in the perinuclear region in yellow. In D, the truncated sortilin TRU in green is mainly retained in the perinuclear region and some in the plasma membrane, but its expression pattern seems to be different from sortilin WT's, because the peripheral granular structure is lost. In E, TGN 38 is shown in red. F shows the merged picture, indicating the co-localization of sortilin TRU with TGN 38 mainly in the perinuclear region in yellow. (B) In A and D, sortilin WT and sortilin TRU seem to be distributed in the similar patterns as described in A, respectively. In B, NCC in red is distributed in the perinuclear, cytoplasmic, and plasma membrane regions. C shows the merged picture, indicating the co-localization of NCC with sortilin WT in the perinuclear and cytoplasmic regions in yellow. In E, NCC in red is mainly distributed in the perinuclear region with some in the plasma membrane. F shows the merged picture, indicating that the co-localization of NCC with sortilin TRU in yellow is mainly in the perinuclear region, and its peripheral co-localization with NCC seems be less. These findings suggest that the truncated sortilin TRU may prevent NCC from WNK4-promoted degradation through the lysosomal pathway by retaining NCC in the perinuclear region (TGN) or diverting NCC to other vesicular compartments other than lysosomes. Bar = 10 μM.