Fig. 8. Schematic representation of vesicular transport of syntaxins between intracellular compartments. The 35 kDa isoform of syntaxin 5 used in this study is retained at the CGN by virtue of either the cytoplasmic domain (CD) or the transmembrane domain (TMD). Substitution of the cytoplasmic domain (CD-substitution), but not the transmembrane domain, of syntaxins 6, 7 and 8 with that of syntaxin 1A prevents their internalization. The di-leucine-based motifs in the cytoplasmic domains of syntaxins 7 and 8 have important, but distinct, roles in intracellular localization. Mutation of the di-leucine-based motif of syntaxin 7 (amino acids 162-168) inhibited internalization of syntaxin 7. By contrast, mutation of the di-leucine-based motif of syntaxin 8 (amino acids 77-83) resulted in accumulation of syntaxin 8 at the perinuclear Golgi region. The transport pathways of syntaxins 5, 6, 7 and 8 are denoted by gray, green, blue and red, respectively.