For Brain Talk next week, we will have an external speaker, Dr. Christopher Obara from the Lippincott-Schwartz lab at Janelia/ HHMI. He will present his latest work titled: "Direct observation of dynamic subdomains at organelle contact sites by high speed single molecule imaging.” The talk will take place next Wednesday, July 1st via Zoom (CHECK EMAIL FOR DETAILS), from 12 to 1 pm. Please join us to welcome Chris and enjoy exciting science!

Abstract:
Membrane-bound organelles provide distinct compartments where incompatible biological processes can be separated from one another. However, biochemical reactions in these disparate environments must be coordinated to facilitate homeostasis, particularly in response to environmental changes. Sites of direct contact between the organelles play an important role in this process, serving as signaling hubs and locations of direct transfer for macromolecules. Mechanisms for regulating contact site structure and function remain enigmatic. Numerous specific molecular tethers have been implicated in the process, but the small size and dynamic nature of contact sites have prevented understanding of their spatiotemporal regulation. Here, we use high-speed single molecule imaging to directly observe tethering and release dynamics of putative tethers in individual contact sites between the ER and mitochondria. We demonstrate the existence of structurally-regulated subdomains within single contact sites by comparative imaging with 3D electron microscopy of vitreously-frozen samples. We show that distinct tethering molecules have unique patterns of motion, respond differently to nutrient availability, and can actively exclude one another from regions of high density. Thus, changes in the recruitment efficiency of individual tethers can support a change in contact site function without necessitating the breaking of one contact site and formation of another.

Organized by Pablo Damasceno, Ilia Vainchtein, and Han-Hsuan Liu