K. Fiedler et al., ANNEXIN XIIIB - A NOVEL EPITHELIAL SPECIFIC ANNEXIN IS IMPLICATED IN VESICULAR TRAFFIC TO THE APICAL PLASMA-MEMBRANE, The Journal of cell biology, 128(6), 1995, pp. 1043-1053
The sorting of apical and basolateral proteins into vesicular carriers
takes place in the trans-Golgi network (TGN) in MDCK cells. We have p
reviously analyzed the protein composition of immunoisolated apical an
d basolateral transport vesicles and have now identified a component t
hat is highly enriched in apical vesicles. Isolation of the encoding c
DNA revealed that this protein, annexin XIIIb, is a new isoform of the
epithelial specific annexin XIII sub-family which includes the previo
usly described intestine-specific annexin (annexin XIIIa; Wice, B. M.,
and J. I, Gordon. 1992. J. Cell Biol. 116:405-422). Annexin XIIIb dif
fers from annexin XIIIa in that it contains a unique insert of 41 amin
o acids in the NH2 terminus and is exclusively expressed in dog intest
ine and kidney, Immunofluorescence microscopy demonstrated that annexi
n XIIIb was localized to the apical plasma membrane and underlying pun
ctate structures. Since annexins have been suggested to play a role in
membrane-membrane interactions in exocytosis and endocytosis, we inve
stigated whether annexin XIIIb, is involved in delivery to the apical
cell surface. To this aim we used permeabilized MDCK cells and a cytos
ol-dependent in vitro transport assay. Antibodies specific for annexin
XIIIb significantly inhibited the transport of influenza virus hemagg
lutinin from the TGN to the apical plasma membrane while the transport
of vesicular stomatitis virus glycoprotein to the basolateral cell su
rface was unaffected. We propose that annexin XIIIb, plays a role in v
esicular transport to the apical plasma membrane in MDCK cells.