Figure 3.

Self-assembly of neurofilaments. Monomers of NF-L, α-internexin (INA), or peripherin (PRPH) follow sequential steps to assemble into neurofilaments. First, monomers form head-to-tail coiled-coil dimers. Next, these dimers are aligned with opposite orientation to form a stable tetrameric complex without polarity. These tetramers then link end-to-end to form the unit-length filament (ULF), which expands 60 nm in length and 16 nm in width. Combinations of ULFs give rise to the filament. Finally, these filaments are helically twisted to build neurofilaments with a 10 nm diameter and more than 100 µm in length [29]. Mature neurofilaments are modified by the continuous turnover of NFs, the lateral NF subunit exchange, and the incorporation of new, shorter filaments by the interaction with any other of the neuron-specific Intermediate filaments (IFs), such as NF-M or NF-H.