EN
Neuromuscular junctions (NMJs) in mammalian skeletal muscle undergo a postnatal topological transformation from a simple oval plaque to a complex branch-shaped structure. We previously demonstrated that podosomes, actin-rich adhesive organelles, promote the remodeling process and showed a key role for one podosome component, LL5β. To better understand molecular mechanisms of postsynaptic maturation, we purified LL5β protein complex from myotubes and showed that three regulators of the actin cytoskeleton – Amotl2, Asef2 and Flii – interact with LL5β. These and other LL5β-interacting proteins are associated with conventional podosomes in macrophages and podosome-like invadopodia in fibroblasts, strengthening the close relationship between synaptic and non-synaptic podosomes. We then focused on Amotl2, showing that it is associated with synaptic podosomes in cultured myotubes and with NMJs in vivo. Depletion of Amotl2 in myotubes leads to increased size of synaptic podosomes and corresponding alterations in postsynaptic topology. Depletion of Amotl2 from fibroblasts disrupts invadopodia in these cells. These results demonstrate the role Amotl2 plays in synaptic remodeling and support the involvement of podosomes in this process.