Serine Phosphorylation of IRS1 Correlates with Aβ-Unrelated Memory Deficits and Elevation in Aβ Level Prior to the Onset of Memory Decline in AD

Nutrients. 2019 Aug 17;11(8):1942. doi: 10.3390/nu11081942.

Abstract

The biological effects of insulin signaling are regulated by the phosphorylation of insulin receptor substrate 1 (IRS1) at serine (Ser) residues. In the brain, phosphorylation of IRS1 at specific Ser sites increases in patients with Alzheimer's disease (AD) and its animal models. However, whether the activation of Ser sites on neural IRS1 is related to any type of memory decline remains unclear. Here, we show the modifications of IRS1 through its phosphorylation at etiology-specific Ser sites in various animal models of memory decline, such as diabetic, aged, and amyloid precursor protein (APP) knock-in NL-G-F (APPKINL-G-F) mice. Substantial phosphorylation of IRS1 at specific Ser sites occurs in type 2 diabetes- or age-related memory deficits independently of amyloid-β (Aβ). Furthermore, we present the first evidence that, in APPKINL-G-F mice showing Aβ42 elevation, the increased phosphorylation of IRS1 at multiple Ser sites occurs without memory impairment. Our findings suggest that the phosphorylation of IRS1 at specific Ser sites is a potential marker of Aβ-unrelated memory deficits caused by type 2 diabetes and aging; however, in Aβ-related memory decline, the modifications of IRS1 may be a marker of early detection of Aβ42 elevation prior to the onset of memory decline in AD.

Keywords: AMPK; Alzheimer’s disease; Aβ; IRS1; aging; diabetes; energy depletion; hippocampus; memory decline; serine phosphorylation.

MeSH terms

  • Aging
  • Alzheimer Disease / complications
  • Alzheimer Disease / metabolism*
  • Amyloid beta-Peptides / metabolism*
  • Amyloid beta-Protein Precursor / metabolism*
  • Animals
  • Brain / metabolism
  • Diabetes Mellitus, Type 2 / complications
  • Diabetes Mellitus, Type 2 / metabolism
  • Humans
  • Insulin / metabolism*
  • Insulin Receptor Substrate Proteins / metabolism*
  • Male
  • Memory Disorders / etiology
  • Memory Disorders / metabolism*
  • Memory*
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Phosphorylation
  • Serine / metabolism
  • Signal Transduction

Substances

  • Amyloid beta-Peptides
  • Amyloid beta-Protein Precursor
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Irs1 protein, mouse
  • Serine