title: Axonal damage in the making: neurofilament phosphorylation, proton mobility and magnetisation transfer in multiple sclerosis normal appearing white matter.
abstract: OBJECTIVE
  Multiple sclerosis (MS) leaves a signature on the phosphorylation and thus proton binding capacity of axonal neurofilament (Nf) proteins. The proton binding capacity in a tissue is the major determinant for exchange between bound and free protons and thus the magnetisation transfer ratio (MTR). This study investigated whether the MTR of non-lesional white matter (NLWM) was related to the brain tissue concentration of neurofilament phosphoforms.
  
  
  METHODS
  Unfixed post-mortem brain slices of 12 MS patients were analysed using MTR, T1 at 1.5 T. Blocks containing NLWM were processed for embedding in paraffin and inspected microscopically. Adjacent tissue was microdissected, homogenised and specific protein levels were quantified by ELISA for the Nf heavy chain (NfH) phosphoforms, glial fibrillary acidic protein (GFAP), S100B and ferritin.
  
  
  RESULTS
  Averaged hyperphosphorylated NfH (SMI34) but not phosphorylated NfH (SMI35) levels were different between individual patients NLWM. The concentration of hyperphosphorylated NfH-SMI34 correlated with T1 (R=0.70, p=0.0114) and - inversely - with MTR (R=-0.73, p=0.0065). NfH-SMI35 was not correlated to any of the MR indices.
  
  
  CONCLUSIONS
  Post-translational modifications of axonal proteins such as phosphorylation of neurofilaments occur in NLWM and may precede demyelination. The resulting change of proton mobility influences MTR and T1. This permits the in vivo detection of these subtle tissue changes on a proteomic level in patients with MS.
authors.affiliation: UCL Institute of Neurology, Department of Neuroinflammation, Queen Square, London WC1N 3BG, UK. a.petzold@vumc.nl
authors.forename: A
authors.initials: A
authors.lastname: Petzold
authors.forename: D J
authors.initials: DJ
authors.lastname: Tozer
authors.forename: K
authors.initials: K
authors.lastname: Schmierer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001370:Axonal Transport / Q000502:physiology; D001369:Axons / Q000378:metabolism* / Q000473:pathology*; D015415:Biomarkers / Q000378:metabolism; D003711:Demyelinating Diseases / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005293:Ferritins / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000378:metabolism* / Q000473:pathology*; D009414:Nerve Growth Factors / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism; D014015:Tissue Banks
chemical_list: D015415:Biomarkers; D005904:Glial Fibrillary Acidic Protein; D009414:Nerve Growth Factors; D016900:Neurofilament Proteins; D010750:Phosphoproteins; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579160:S100B protein, human; D005293:Ferritins