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. Author manuscript; available in PMC: 2012 Jun 6.
Published in final edited form as: Nat Cell Biol. 2004 Apr;6(4):282–284. doi: 10.1038/ncb0404-282

Figure 2.

Figure 2

Effects of selective inhibition of vesicle delivery to the apical or basolateral membrane. Tannic acid, a cell-impermeable fixative, was applied to either the basolateral (a, c) or apical (b) surface of polarized MDCK cells to selectively inhibit vesicle fusion on that surface. The delivery of GPI–YFP (green), p75–YFP (light green) and VSV-G–CFP (purple) was examined. (a) After application of tannic acid to the basolateral membrane, both GPI–YFP and VSV-G–CFP co-localize and accumulate in vesicles close to the tight junction where the Sec6/8–exocyst complex is located (yellow star), and neither protein is found on the plasma membrane. (b) After application of tannic acid to the apical membrane, VSV-G–CFP is delivered to the basolateral membrane via post-TGN vesicle carriers. However, GPI–CFP-containing vesicles are present below the apical surface, because of internalization from the basolateral surface and inhibition of fusion with the apical membrane. (c) After application of tannic acid to the basolateral membrane, p75–YFP is delivered directly to the apical membrane from the TGN. (d) On the basis of the results of Polishchuk et al., apical proteins such as GPI–YFP may be delivered to the basolateral surface from where they are internalized and re-targeted to the apical membrane. Other apical proteins, such as p75, are delivered directly to the apical membrane.