Sensory neurons help us sense external stimuli and transform these stimuli into messages that are communicated to the brain. The structure of a sensory neuron influences its receptive field and is thus important to how it functions. During Josephine Mitchell’s time as a Ph.D. student in the Integrated Program in Biochemistry (IPiB), she studied how a protein called Pickpocket gets to where it needs to be in the sensory neurons of Drosophila (fruit flies) larvae to mediate the sensation of external stimuli, such as pain.
Mitchell decided to explore how Drosophila neurons regulate intracellular trafficking to deliver proteins to the correct location (in the case of Pickpocket, the dendritic plasma membrane) shortly after she rotated through associate professor Jill Wildonger’s lab. Wildonger is now an associate professor at UC San Diego.
“During my rotation, I was immediately hooked when I could see motor protein transport occurring in a living neuron,” she says. “I peered through the eye pieces of the microscope into a live fruit fly sensory neuron and could see tiny bright dots moving back and forth in the axon, just like cars on the highway!”
Mitchell’s experiments showed that Pickpocket is part of the membrane that grows dendrites; that levels of Pickpocket in the dendrites scale to maintain constant density as dendrite length decreases; and, that another protein called Rab11 helps carry Pickpocket to the dendritic plasma membrane. Overall, Mitchell says, these discoveries indicate that the Pickpocket ion channel is an integral part of the sensory neuron’s plasma membrane. As the neuron grows and establishes its structure, it is simultaneously establishing its function: to perceive external stimuli.
During her defense, Mitchell will share more about these findings as well as a novel tool developed in collaboration with Cornell University associate professor Dr. Chun Han. The tool marks membrane-expressed proteins in vivo and was used to monitor Pickpocket membrane expression in Mitchell’s research, which is available as a pre-print on BioRxiv.
Mitchell thanks her mentors, including her high school science teacher Mr. Wicks, her undergraduate research advisor professor Rachel Powers, her graduate advisor Jill Wildonger, and teaching faculty member Mario Pennella and professor Rick Amasino for encouraging and inspiring her throughout her scientific journey thus far. Later this year, she will start work as an assistant professor at Kalamazoo College. You can read more about Mitchell, her leadership roles, and her artwork in our story from last year.
To learn more about Mitchell’s research, attend her Thesis Defense on Friday, June 17 at 10 am CT in Room 1211 of the DeLuca Biochemical Sciences Building.