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

Archan Ganguly (1) , Yong Tang (1) , Lina Wang (1) , Kelsey Ladt (1, 2) , Jonathan Loi (1) , Bénédicte Dargent (3) , Christophe Leterrier (3) , Subhojit Roy (1, 2)

1 UC San Diego - Department of Pathology [Univ California San Diego]
2 Neuro - UC San Diego - Department of Neurosciences [Univ California San Diego]
3 CRN2M - Centre de recherche en neurobiologie - neurophysiologie de Marseille

Although actin at neuronal growth cones is well-studied, much less is known about actin organization and dynamics along axon shafts and presynaptic boutons. Using probes that selectively label filamentous-actin (F-actin), we found focal "actin hotspots" along axons-spaced ∼3-4 µm apart-where actin undergoes continuous assembly/disassembly. These foci are a nidus for vigorous actin polymerization, generating long filaments spurting bidirectionally along axons-a phenomenon we call "actin trails." Super-resolution microscopy reveals intra-axonal deep actin filaments in addition to the subplasmalemmal "actin rings" described recently. F-actin hotspots colocalize with stationary axonal endosomes, and blocking vesicle transport diminishes the actin trails, suggesting mechanistic links between vesicles and F-actin kinetics. Actin trails are formin-but not Arp2/3-dependent and help enrich actin at presynaptic boutons. Finally, formin inhibition dramatically disrupts synaptic recycling. Collectively, available data suggest a two-tier F-actin organization in axons, with stable "actin rings" providing mechanical support to the plasma membrane and dynamic "actin trails" generating a flexible cytoskeletal network with putative physiological roles.

Domaines: Neurobiologie

Archan Ganguly, Yong Tang, Lina Wang, Kelsey Ladt, Jonathan Loi, et al.. A dynamic formin-dependent deep F-actin network in axons. Journal of Cell Biology, 2015, 210 (3), pp.401 - 417. ⟨10.1083/jcb.201506110⟩. ⟨hal-01701424⟩