Viewing protein interactions in brain cells

December 27, 2011

At the core of this new imaging technology is FRET (fluorescence resonance energy transfer), which occurs when two fluorescently tagged molecules come within 8 nanometers or less. Detecting the FRET serves as a proxy for the two proteins X and Y associating within a living cell (credit: University of Miami)

University of Miami (UM) biology professor Akira Chiba is leading a multidisciplinary team to develop the first systematic survey of protein interactions within brain cells. The team is aiming to reconstruct genome-wide in situ protein-protein interaction networks (isPIN) within the neurons of a multicellular organism.

Like all other cells, each neuron produces millions of individual proteins that associate with one another and form a complex communication network. Until recently, observing these protein-protein interactions had not been possible due to technical difficulties. Individual proteins are typically less than 10 nm (nanometers) in diameter, considered inaccessible even with super-resolution microscopy.

The researchers are creating genetically engineered fruit flies that are capable of expressing over 500 fluorescently tagged assorted proteins, two at a time. The fluorescent tags make it possible to visualize the exact spot where a given pair of proteins associates with each other.

The team utilizes a custom- built 3D FLIM (fluorescent lifetime imaging microscopy) system to quantify this association event within the cells of a live animal. FLIM shows the location and time of such protein interaction, providing the data that allow creation of a point-by-point map of protein-protein interactions.

The pilot phase of this multidisciplinary project, funded by the National Institutes of Health, employs advanced genetics, molecular imaging technology, and high-performance computation, among other fields.

In the future, they will begin to visualize directly how the individual proteins interact with one another in their “native environment,” the cells in our body.