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AnnexinA6-mediated disintegration of SNAP23 and
syntaxin-4 in CHO cells
Meritxell Reverter-Martín 1 , Carles Rentero 1 , Thomas Grewal 2 , Carlos Enrich 1 .
Facultat de Medicina, Universitat de Barcelona, 08036-Barcelona, Spain 1 , Department of
Pharmaceutical Chemistry, Faculty of Pharmacy, University of Sidney, Australia 2
Abstract:
We recently demonstrated that high levels of annexin A6 (AnxA6) are coupled with an
imbalance of intracellular cholesterol, sequestration of caveolin-1 in Golgi and the inhibition of
cytosolic phospholipase A2. Since alterations of arachidonic acid and cholesterol are crucial for
SNARE complex formation and functioning, a subset of t-SNAREs associated with cholesterol
and caveolin-1 transport were investigated. The comparison of immunofluorescence patterns
and the subcellular distribution of syntaxin-4 and SNAP23 in CHOwt and in overexpressing
AnxA6 cells (CHOanx6) showed a significant disintegration of these SNAREs at the plasma
membrane of CHOanx6 cells. We also examined syntaxin-6 and showed that overexpression of
AnxA6 induces a translocation of syntaxin-6, from the TGN into punctate cytosolic structures
and recycling endosomes. Finally, in order to find out whether the overexpression of AnxA6
perturbed the capability to form SNARE complexes, we analyzed the SNARE complex formation
ability of CHOanx6 cells. Immunoprecipitation of SNAP23 and syntaxin-4 showed significant
increased co-immunoprecipitation of VAMP3 in CHOanx6 cells. In conclusion, AnxA6 induces a
specific disintegration of t-SNAREs, disturbing the onward vesicular trafficking of caveolin-1.