UNDERSTANDING THE FORMATION AND REGULATION OF CONTACT SITES BETWEEN PEROXISOMES AND OTHER ORGANELLES

In order to optimize their multiple cellular functions, peroxisomes must collaborate and communicate with surrounding organelles. A common way of communication between organelles is through membrane contact sites where membranes of two organelles are tethered, facilitating close-range interactions such as exchange of small molecules and intracellular signaling. In addition contact sites are important for controlling processes such as metabolism, organelle trafficking, inheritance and division. The extent of peroxisomal communication, their contact sites and their functions as well as how peroxisomes rely on contact sites for their various cellular activities are not yet fully characterized.

We created a split fluorescence sensor for peroxisomal contact sites in yeast by which one part of a fluorophore is fused to the outer membrane of peroxisomes while the other is fused to the outer membrane of other organelles. Only when the organelles are in very close proximity, such as that which occurs at contact sites, a fluorescent signal emitted. Using this method we found that peroxisomes interact with mitochondria, lipid droplets, plasma membrane and the vacuole.

To uncover the molecular tether between peroxisomes and other organelles as well as potential regulators of the contact sites we used an automated high content screen to find the effect of different yeast mutants on the sensor. We now further characterize the genes identified in these screens as well as study the physiological role of the identified contact sites.