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Domain unfolding in neurofilament sidearms: effects of phosphorylation and ATP
Helim Aranda-Espinoza1, Philippe Carl, Jean François Leterrier
1Institute for Medicine and Engineering, 1080 Vagelos Research Laboratory, 3340 Smith Walk, University of Pennsylvania, Philadelphia, PA 19104, USA. helim@mail.med.upenn.edu
Abstract:
Lateral projections of neurofilaments (NF) called sidearms (SA) affect axon stability and caliber. SA phosphorylation is thought to modulate inter-NF distance and interactions between NF and other subcellular organelles. SA were probed by atomic force microscopy (AFM) and dynamic light scattering (DLS) as a function of phosphorylation and ATP content. DLS shows SA are larger when phosphorylated, and AFM shows four unfoldable domains in SA regardless of phosphorylation state or the presence of ATP. However, the native phosphorylated SA requires three-fold higher force to unfold by AFM than dephosphorylated SA, suggesting a less pliant as well as larger structure when phosphorylated.