Synaptic Proteome Changes
in a DNA Repair Deficient <i>Ercc1</i> Mouse Model of Accelerated
Aging
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Abstract
Cognitive decline is one of the earliest hallmarks of
both normal
and pathological brain aging. Here we used <i>Ercc1</i> mutant
mice, which are impaired in multiple DNA repair systems and consequently
show accelerated aging and progressive memory deficits, to identify
changes in the levels of hippocampal synaptic proteins that potentially
underlie these age-dependent deficits. Aged <i>Ercc1</i> mutant mice show normal gross hippocampal dendritic morphology and
synapse numbers, and <i>Ercc1</i> mutant hippocampal neurons
displayed normal outgrowth and synapse formation <i>in vitro</i>. However, using isobaric tag for relative and absolute
quantification (iTRAQ) of hippocampal synaptic proteins at two different
ages, postnatal days 28 and 112, we observed a progressive decrease
in synaptic ionotropic glutamate receptor levels and increased levels
of G-proteins and of cell adhesion proteins. These together may cause
long-term changes in synapse function. In addition, we observed a
downregulation of mitochondrial proteins and concomitant upregulation
of Na,K-ATPase subunits, which might compensate for reduced mitochondrial
activity. Thus, our findings show that under conditions of apparent
intact neuronal connectivity, levels of specific synaptic proteins
are already affected during the early stages of DNA damage-induced
aging, which might contribute to age-dependent cognitive decline