FIGURE 5.

The amount of α₁-unbound YFP-β₂ retained in the ER of MDCK cells is greater than that of YFP-β₁. Horizontal confocal microscopy sections of confluent monolayers (A) or dispersed colonies (B and C) of MDCK cells expressing either YFP-β₁ or YFP-β₂. Both YFP-β₁ and YFP-β₂ (green) are co-localized with the endogenous α₁ subunit (red) in the lateral membranes, but not inside the cells as detected by immunostaining of fixed cells using the monoclonal antibody against the Na,K-ATPase α₁ subunit (A and B). The intracellular retention of α₁-unassembled YFP-β₂ is more prominent than that of YFP-β₁ and more evident in dispersed colonies than in confluent monolayers. This intracellular fraction of YFP-β₂ (green) shows co-localization with the ER (red) as detected by transient expression of the fluorescent ER marker, DsRed2-ER (C). N, nucleous; PM, plasma membrane.