Histochemistry and Cell Biology

Biography

Biography: Harish C Pant

Abstract

Aberrant hyperphosphorylation of proline directed serine/threonine (pSer/Thr-Pro and KS/TP) residues in neuronal cytoskeletal proteins is one of the major pathological hallmarks of neurodegenerative disorders such as Alzheimer disease (AD), amyotrophic lateral sclerosis (ALS) and Parkinson’s disease (PD). Human NF-M/H comprises a large number of multiple KSP repeats in the carboxy-terminal tail domain. The phosphorylation sites of NF-M/H from AD brains have not been analyzed. Here, we used quantitative phosphoproteomics, iTRAQ (isobaric tag for relative and absolute quantitation) and analyzed the phosphorylation sites of NF-M/H from AD brain. We identified 14 hyperphosphorylated sites of NF-M and 9 Lys-Ser-Pro (KSP) sites; two variant motifs, Glu-Ser-Pro (ESP) Ser⁷³⁶ and Leu-Ser-Pro (LSP) Ser⁸³⁷; and 3 non-S/TP motifs, Ser783, Ser788 and Thr750. All the Ser/Thr residues were phosphorylated at significantly greater abundance in AD brain compared to normal brain. 11 hyper phosphorylated sites have been identified on C-terminal tail domain of NF-H corresponding to KSP motifs with greater abundance of phosphorylation in AD brain compared to normal brain, including the non-SP site, Thr642. Our data provided the direct evidence that NF-M and NF-H are hyperphosphorylated in AD compared to normal brain and suggested the role of both proline-directed and non proline-directed protein kinases in AD. This study represents the first comprehensive analysis of iTRAQ quantification of phosphorylation sites of human NF-M and NF-H from AD brain and establishes that the aberrant and hyperphosphorylation of neuronal intermediate filament proteins is involved in AD. In addition, the topographic phosphorylation of squid giant axon as a model system was analyzed in detail. This study provided the molecular and cell biological mechanisms associated with this unique novel neurobiological process.