Cool photo alert! James Zheng’s lab at Emory is uncommonly good at making photos and movies showing how neurons remodel themselves. They recently published a paper in Journal of Cell Biology showing how dendritic spines, which are small protrusions on neurons, contain concentrated pools of G-actin.
Actin, the main component of cells’ internal skeletons, is a small sturdy protein that can form long strings or filaments. It comes in two forms: F-actin (filamentous) or G-actin (globular). It is not an exaggeration to call F- and G-actin neurons’ “nuts and bolts.”
Think of actin monomers like Lego bricks. They can lock together in regular structures, or they can slosh around in a jumble. If the cell wants to build something, it needs to grab some of that slosh (G-actin) and turn them into filaments. Remodeling involves breaking down the filaments.
At Lab Land’s request, postdoc and lead author Wenliang Lei picked out his favorite photos of neurons, which show F-actin in red and G-actin in green. Zheng’s lab has developed probes that specifically label the F- and G- forms. Where both forms are present, such as in the dendritic spines, an orange or yellow color appears.
Why care about actin and dendritic spines?
*The Journal of Cell Biology paper identified the protein profilin as stabilizing neurons’ pool of G-actin. Profilin is mutated in some cases of ALS (amyotrophic lateral sclerosis), although exactly how the mutations affect actin dynamics is now under investigation.
*Also, there’s been a surge of interest in the process of synaptic pruning, which appears to go off track in conditions such as autism and schizophrenia. To prune the synapses, you need to remodel the spines.
*In fragile X syndrome, dendritic spines are hyperabundant.
*Shannon Gourley’s lab has accumulated evidence that after adolescent cocaine exposure, dendritic spines sprout more or are trimmed back, depending on the region of the brain.
Siarhei Hladyshau and Denis Tsygankov in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech contributed to the paper.