Elsevier

Neuroscience

Volume 417, 1 October 2019, Pages 45-56
Neuroscience

Research Article
p35 Hemizygous Deletion in 5xFAD Mice Increases Aβ Plaque Load in Males but Not in Females

https://doi.org/10.1016/j.neuroscience.2019.08.017Get rights and content

Highlights

  • •

    p35 hemizygosity increases Aβ plaque load only in male 5xFAD mice.

  • •

    Aβ plaque increases in males are correlated with increases in GSK3β activity.

  • •

    p35 hemizygosity results in sexually dimorphic glial cell responses in 5xFAD mice.

  • •

    p35 and p25 reduction leads to sex-specific changes in 6-month old 5xFAD mice.

Abstract

Increased amyloid beta (Aβ) deposition is implicated in early stages of Alzheimer's disease (AD). Although aberrant Cdk5 activity mediated by Cdk5/p25 is suggested to promote Aβ plaque deposition, the effects of Cdk5 inhibition on Aβ plaque loads in AD mouse models have been equivocal, possibly due to the fact that Cdk5 can be activated by p35 or p39 and their cleaved products. Here we evaluated the effect of p35 knockdown on Aβ plaque formation by constitutively knocking out a single p35 allele in 5xFAD mice. Surprisingly, our results show that the simultaneous reduction in the levels of p35 and p25 increases cortical Aβ plaque loads in male 5xFAD mice, but not in females. This change is associated with male specific decrease in pSer9 GSK3β levels. Furthermore, p35 hemizygous deletion has sexually dimorphic effects on Iba1 and GFAP protein levels. Our findings demonstrate sex differences in the effects of p35 reduction on biochemical pathways relevant to the modulation of Aβ plaque deposition and confirm the importance of examining both sexes in preclinical AD research.

Section snippets

INTRODUCTION

Increased amyloid β (Aβ) peptide deposition has been implicated in early stages of Alzheimer's disease (AD) (Selkoe and Hardy, 2016). Recent PET scan studies and cerebrospinal fluid (CSF) analysis have shown increased Aβ levels prior to the appearance of other pathological hallmarks of AD, such as neurofibrillary tangles and neuronal loss (Bateman et al., 2012, Jack and Holtzman, 2013). Aβ production occurs through the sequential cleavage of the amyloid precursor protein (APP) by β-site APP

Animals

B6 congenic 5xFAD transgenic (Tg) mice were obtained from Jackson Laboratories (Bar Harbor, ME). The 5xFAD mice co-express Swedish, London and Florida mutations in human APP, as well as two presenilin-1 (PS1) mutations under the control of Thy-1 promotor. These mice exhibit plaque deposition at 2 months of age, along with increased microgliosis and astrocytosis (Oakley et al., 2006). These 5xFAD mice were crossed with p35+/− mice maintained on a B6 background (Hallows et al., 2003) to generate

Aβ plaque load is increased in the cortex of p35 hemizygous null male 5xFAD mice but not females

It has been reported previously that 5xFAD mice show increased p25 levels starting around 2 months of age (Oakley et al., 2006, Sadleir and Vassar, 2012). However our examination of 6-month old 5xFAD mice show that p25 and p35 levels are not statistically different between 5xFAD and non-transgenic male or female mice (Fig. 1A). This could be due to the difference in the genetic background of 5xFAD mice used in our study. The animals used in this study were in B6 genetic background whereas the

DISCUSSION

A potential role of p25 in AD has been highlighted by a number of studies reporting elevated levels of p25 in the postmortem brains of AD patients (Patrick et al., 1999, Tseng et al., 2002, Swatton et al., 2004, Sadleir and Vassar, 2012). Likewise, the microRNA family miR-15/107, which post-transcriptionally downregulates p35 expression, is reduced in the hippocampus and temporal cortex of the AD brain (Moncini et al., 2017). These findings suggest that p35 and p25 may play a role in AD.

Acknowledgements

We would like to thank Austin Waddell for his help in brain sectioning. This work was supported in part by start-up funds and a Faculty Research and Creative Endeavors grant from Central Michigan University. TB participated in study design, performed all the experiments, analyzed data, and drafted manuscript. YM analyzed data and edited the manuscript. KP conceived of the study, designed and coordinated research, analyzed data, and drafted and edited the manuscript. All authors read and

Declarations of interest

None.

References (74)

  • G Kusakawa et al.

    Calpain-dependent proteolytic cleavage of the p35 cyclin-dependent kinase 5 activator to p25

    J Biol Chem

    (2000)
  • KY Lee et al.

    Interaction of cyclin-dependent kinase 5 (Cdk5) and neuronal Cdk5 activator in bovine brain

    J Biol Chem

    (1996)
  • F Liu et al.

    Regulation of amyloid precursor protein (APP) phosphorylation and processing by p35/Cdk5 and p25/Cdk5

    FEBS Lett

    (2003)
  • JP Lopes et al.

    Cdk5: multitasking between physiological and pathological conditions

    Prog Neurobiol

    (2011)
  • Y Ma et al.

    Activated cyclin-dependent kinase 5 promotes microglial phagocytosis of fibrillar β-amyloid by up-regulating lipoprotein lipase expression

    Mol Cell Proteomics

    (2013)
  • D Mao et al.

    p35 is required for CDK5 activation in cellular senescence

    J Biol Chem

    (2010)
  • K. Orford et al.

    Serine Phosphorylation-regulated Ubiquitination and Degradation of β-Catenin

    J Biol Chem

    (1997)
  • F Plattner et al.

    The roles of cyclin-dependent kinase 5 and glycogen synthase kinase 3 in tau hyperphosphorylation

    J Biol Chem

    (2006)
  • J Ryder et al.

    Divergent roles of GSK3 and CDK5 in APP processing

    Biochem Biophys Res Commun

    (2003)
  • KR Sadleir et al.

    Cdk5 protein inhibition and Aβ42 increase BACE1 protein level in primary neurons by a post-transcriptional mechanism: implications of CDK5 as a therapeutic target for Alzheimer disease

    J Biol Chem

    (2012)
  • J Seo et al.

    Activity-dependent p25 generation regulates synaptic plasticity and Aβ-induced cognitive impairment

    Cell

    (2014)
  • LJ Sittig et al.

    Genetic background limits generalizability of genotype-phenotype relationships

    Neuron

    (2016)
  • D Tang et al.

    An isoform of the neuronal cyclin-dependent kinase 5 (Cdk5) activator

    J Biol Chem

    (1995)
  • S Taniguchi et al.

    Calpain-mediated degradation of p35 to p25 in postmortem human and rat brains

    FEBS Lett

    (2001)
  • HC Tseng et al.

    A survey of Cdk5 activator p35 and p25 levels in Alzheimer's disease brains

    FEBS Lett

    (2002)
  • M Angelo et al.

    Improved reversal learning and altered fear conditioning in transgenic mice with regionally restricted p25 expression

    Eur J Neurosci

    (2003)
  • RJ Bateman

    Clinical and biomarker changes in dominantly inherited Alzheimer's disease

    N Engl J Med

    (2012)
  • DA Cross et al.

    Inhibition of glycogen synthase kinase-3 by insulin mediated by protein kinase B

    Nature

    (1995)
  • B De Strooper et al.

    A presenilin-1-dependet γ-secretase-like protease mediates release of notch intracelluar domain

    Nature

    (1999)
  • L Devi et al.

    Sex- and brain region-specific acceleration of beta-amyloidogenesis following behavioral stress in a mouse model of Alzheimer's disease

    Mol Brain

    (2010)
  • O Engmann et al.

    Crosstalk between Cdk5 and GSK3 β : implications for Alzheimer ’ s disease

    Front Mol Neurosci

    (2009)
  • O Engmann et al.

    Schizophrenia is associated with dysregulation of a Cdk5 activator that regulates synaptic protein expression and cognition

    Brain

    (2011)
  • K Franklin et al.

    The mouse brain in stereotaxic coordinates

    (1997)
  • P Giusti-Rodriguez et al.

    Synaptic deficits are rescued in the p25/Cdk5 model of neurodegeneration by the reduction of -secretase (BACE1)

    J Neurosci

    (2011)
  • SA Grathwohl et al.

    Formation and maintenance of Alzheimer's disease β-amyloid plaques in the absence of microglia

    Nat Neurosci

    (2009)
  • JL Hallows et al.

    Decreased cyclin-dependent kinase 5 (cdk5) activity is accompanied by redistribution of cdk5 and cytoskeletal proteins and increased cytoskeletal protein phosphorylation in p35 null mice

    J Neurosci

    (2003)
  • He YI, Li H, Xie W, Yang C, Cheung A, Yu HOI, Wang YUN (2007) The presence of active Cdk5 associated with p35 in...
    • View full text
    © 2019 IBRO. Published by Elsevier Ltd. All rights reserved.