To understand the molecular mechanisms underlying sorting of apical an
d basolateral membrane components in human intestinal epithelial cells
, we have cloned the human homolog of rat syntaxin 3 and looked for it
s subcellular localization. Endogenous human syntaxin 3 was found to b
e localized at the apical membrane of colon epithelial and Caco-2 cell
s. This apical localization was confirmed by confocal microscopy after
transfection of the cDNA coding for either full length or N-terminall
y truncated human syntaxin 3 in Caco-2 cells. Furthermore the signal(s
) and machinery targeting human syntaxin 3 to the apical membrane of e
pithelial cells are conserved between species since human syntaxin 3 w
as also localized at the apical membrane of canine MDCK cells and of e
pithelial cells in transgenic Drosophila melanogaster.