Vear, a novel Golgi-associated protein with VHS and gamma-adaptin "ear" domains

The molecular basis of the selectivity and the details of the vesicle forma tion in endocytic and secretory pathways are still poorly known and most pr obably involve as yet unidentified components. Here we describe the cloning , expression, and tissue and cell distribution of a novel protein of 67 kDa (called Vear) that bears homology to several endocytosis-associated protei ns in that it has a VHS domain in its N terminus. It is also similar to gam ma-adaptin, the heavy subunit of AP-1, in having in its C terminus a typica l "ear" domain. In immunofluorescence microscopy, Vear was seen in the Golg i complex as judged by a typical distribution pattern, a distinct colocaliz ation with the Golgi marker gamma-adaptin, and a sensitivity to treatment o f cells with brefeldin A. In cell fractionation, Vear partitioned with the post-nuclear membrane fraction. In transfection experiments, hemagglutinin- tagged full-length Vear and truncated Vear lacking the VHS domain assembled on and caused compaction of the Golgi complex. Golgi association without c ompaction was seen with the ear domain of Vear, whereas the VHS domain alon e showed a diffuse membrane- and vesicle-associated distribution, The Gels association and the bipartite structure along with the differential targeti ng of its domains suggest that Vear is involved in heterotypic vesicle/subo rganelle interactions associated with the Golgi complex, Tissue-specific fu nction of Vear is suggested by its high level of expression in kidney, musc le, and heart.