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Keywords:

  • Alzheimer’s Disease;
  • amyloid beta;
  • BDNF;
  • exon splicing;
  • Srp20;
  • TrkB

Abstract

Previously, we reported elevated levels of the neuron-specific tropomyosin receptor kinase B (TrkB) transcript, TrkB- sarc homology containing (Shc) in the hippocampus of Alzheimer’s disease (AD) brains. In this study, we determined how TrkB-Shc transcripts are increased in AD. Utilizing a TrkB minigene transiently transfected into SHSY5Y cells, we found increased exon 19 inclusion in TrkB minigene transcripts (to generate TrkB-Shc) following cellular exposure to amyloid beta 1–42 (Αβ42). As this suggested altered TrkB pre-mRNA splicing in AD, we conducted an in silico screening for putative splice regulatory protein-binding sites in the intron/exon splice regulatory regions of exons 18 and 19 of the TrkB gene and then assessed their gene expression profiles using a microarray database of control/AD post-mortem human hippocampal brain tissue. We found significant changes in serine/arginine protein 20 (Srp20) gene expression in AD cases and confirmed this using a second cohort of control/AD. In vitro, we found increased Srp20 mRNA levels in SHSY5Y cells treated with Αβ42 fibrils. Moreover, Srp20 over-expression was found to increase exon 19 inclusion in TrkB minigene transcripts and ratio of endogenous TrkB-Shc:TrkB-TK+ mRNA expression. Conversely, Srp20 expression knockdown produced the opposite effects. Our findings suggest that dysregulation of factors regulating TrkB pre-mRNA splicing may contribute to gene expression changes that occur in AD.