Systematic analysis of membrane contact sites in Saccharomyces cerevisiae uncovers a diversity of new organelle communication modules

Actively maintained close appositions between organelle membranes, also known as contact sites, enable the efficient transfer of biomolecules between cellular compartments. Several such sites have been described as well as their tethering machineries. Despite these advances we are still far from a comprehensive understanding of the function and regulation of most contact sites. To systematically characterize contact site proteomes and support the discovery of new tethers and functional molecules, we established a high throughput screening approach in Saccharomyces cerevisiae based on co-localization imaging. We imaged split fluorescence reporters for multiple different contact sites on the background of thousands of yeast strains expressing a mCherry-tagged yeast protein. By scoring both co-localization events and effects on reporter size and abundance, we discovered hundreds of new potential contact site residents and effectors in yeast. Mechanistic exploration into several of these has uncovered new modules for lipid transfer, novel regulatory concepts and unappreciated celluar functions. In general our work opens a new window into the diversity of functions that take place in contacts and underscore their cellular importance.