So Min Lee
“The Role of Myosin VI and Rab5 at Drosophila Presynaptic Terminals”
So Min Lee, Biljana Ermanoska, Avital A. Rodal
Myosins are a superfamily of actin-based motor proteins, consisting of close to 40 different subtypes. Myosin VI (Myo6) is the only motor protein that moves towards the minus (pointed) end of filamentous actin. Previous research in cell culture has shown that the unique directionality allows Myo6 to facilitate uncoated vesicle transport from the peripheral region of the cell, through the actin meshwork, to the more centrally located early endosomes. Although depletion of Myo6 induced actin cytoskeleton remodeling and redistribution of Rab5-positive early endosome (Rab5-EE) in cell cultures, this has yet to be demonstrated in neurons where endosomal trafficking is particularly important for synaptic development at the neuromuscular junction (NMJ).
To understand the role of Myo6 in neurons, we studied the presynaptic actin cytoskeleton and Rab5-EE in wild type conditions and upon Myo6 depletion, using the NMJ of third-instar Drosophila larvae as a model synapse. For this purpose, we down-regulated Myo6 in the fly nervous system and used genetically encoded, fluorescently labeled actin markers and endogenously GFP-tagged Rab5. We analyzed the effects of Myo6 depletion on actin and rab5-EE in the larval NMJ by using Airyscan microscopy followed by quantification of the fluorescence in the image processing program, Fiji. Depletion of Myo6 resulted in decreased abundance and distribution of actin, suggesting that Myo6 is important for actin stabilization at the synapse. Loss of Myo6 did not affect the distributions of Rab5-EE but decreased the size of Rab5-EE, indicating that Myo6 is not required in stabilizing Rab5-EE in neurons but could be involved in maturing early endosomes into late endosomes.
In summary, our preliminary results suggest that actin filaments in association with Myo6 could be potential regulators of early endosome maturation. Future research will focus on validating Myo6 involvement in dynamic association with actin and early endosomes by live imaging. Since mutations in Myo6 have been implicated in neurodegenerative diseases, understanding the role of Myo6 and Rab5-EE during early endocytic trafficking could potentially allow us to translate our findings to solving human-related diseases.
Support: SMURF (Summer MRSEC Undergrad Research Fellowship)