A dynamic formin-dependent deep F-actin network in axons

Abstract

Low-light live imaging of F-actin–selective probes, quantitative tools, and super-resolution microscopy reveals a dynamic, formin-dependent deep F-actin cytoskeletal network in axons.

RhoA regulates actin network dynamics during apical surface emergence in multiciliated epithelial cells

“…However, our results contrast with recent data that show that inhibition of formins increases the half time of actin turnover in other cell types, including M2 melanoma cells, neurons, vascular cells and fibroblasts (Fritzsche et al, 2013;Ganguly et al, 2015; Phng et al, 2015;Sahasrabudhe et al, 2016). Clearly, however, the functions of formin proteins differ between cell types and actin populations, because loss of formins decreased the mobile actin fractions in fibroblasts and neurons (Ganguly et al, 2015;Sahasrabudhe et al, 2016) yet left the mobile fraction unchanged in vascular cells (Phng et al, 2015), similar to the case here for MCCs. Moreover, in systems in which an actin network forms de novo, such as in the cortex of retracting blebs, actin turnover is almost tenfold higher compared with that in the mature cortex, suggesting that the molecular mechanisms regulating actin turnover in new cortices are different compared to those in mature networks (Bovellan et al, 2014).…”

Interaction between distinct actin pools controls activity-dependent actin dynamics in the dendritic spine

“…Both formins and Arp2/3 are enriched in the spine 24 , where the activity of the latter constitutes a well-established regulatory mechanism controlling local actin dynamics and synaptic function 9,[12][13][14]24 . Formin-dependent but Arp2/3-independent actin network can also be found in the axons where it is sensitive to low concentrations of LatA 5 , hinting that the labile pool observed on our experiments may involve formin activity. Alternatively, an actin-bundling protein Myosin II has been recently shown to antagonize Arp2/3-dependent actin dynamics at the leading edge of migrating cells 4 .…”

“…Although these networks may compete for actin monomers and regulatory factors [1][2][3][4] , the interaction between them remains poorly understood. Here, we show that disruption of the labile F-actin pool in neurons by limited actin depolymerization 5,6 unexpectedly triggers rapid enhancement of the F-actin content at the dendritic spine. Long-term blockade of NMDA-type receptors decreases spine actin polymerization, which is specifically restored by the labile pool ablation.…”

Uncovering the neuron’s internal skeleton

“…Actin polymers were rapidly assembling and disassembling in a phenomenon the researchers referred to as "actin trails" (3).…”

“…axon shaft, where actin fibers sprout and shrink, might help maintain proper actin concentrations, Roy speculates (3). And new insights provide clues as to how actin moves in waves to transport itself and how it collects in patches to allow axon branching (4,5).…”