The Furin Cytoplasmic Domain is Localized to the trans-Golgi Network of Yeast

Kex2p and furin are well-characterized, structurally similar, membrane-bound proteases localized to the trans-Golgi network (TGN) of yeast and animal cells. While their N-terminal and lumenal catalytic domains are highly homologous, they do not share common sorting signals in their C-terminal cytoplasmic tails. To study furin’s localization in yeast, we created a chimera with the N-terminal regions of Kex2p and the C-terminal regions of human furin. Our mating, biochemical, and immunofluorescent studies of the KFp chimeras in yeast have demonstrated sorting consistent with furin’s trafficking patterns in human cells. Next, to see if furin sorting signals are recognized by yeast sorting machinery, key signals were mutated. For two chimeras (KF5p/6p) mating activity was abolished indicating that the Kex2p enzyme is no longer resident to the yeast TGN. This is surprising since this furin sorting signal in animal cells binds a sorting protein (PACS-1) not known to exist in yeast