Overexpression of syntaxin 3, but not of syntaxins 2 or 4, caused an inhibition of TGN to apical transport and apical recycling, and leads to an accumulation of small vesicles underneath the apical plasma membrane. All other tested transport steps were unaffected by syntaxin 3 over-expression. In contrast, we find no evidence for an involvement of NSF in TGN to apical transport while basolateral transport is NSF-dependent. We have investigated the subcellular localization of SNAP-23 in polarized epithelial cells. In contrast to its behavior in neurons, the distribution of SNAP-25 in MDCK cells remained unaltered by treatment with dibutyryl cAMP or forskolin, which, however, caused an increased growth of the primary cilia.
Most metazoan cells are 'polarized'.
One crucial aspect of this polarization is that the plasma membrane is divided into two or more domains with different protein and lipid compositions - for example, the apical and basolateral domains of epithelial cells or the axonal and somatodendritic domains of neurons. This polarity is established and maintained by highly specific vesicular membrane transport in the biosynthetic, endocytic and transcytotic pathways. A new superfamily Proc. This homology domain of approximately 60 amino acids is predicted to form a coiled-coil structure. The significance of this homology domain could be demonstrated by a partial suppression of the coiled-coil properties of the domain profile.