Reduction in CHT1-mediated choline uptake in primary neurons from presenilin-1 M146V mutant knock-in mice

Abstract

The memory loss in Alzheimer's disease (AD) has been linked to cholinergic hypoactivity. Mutations in presenilin-1 (PS-1) may regulate cholinergic signaling, although their precise roles in cholinergic neurotransmission in AD are unsettled. Neuronal uptake of choline via the high affinity choline transporter (CHT1) is essential for cholinergic neurotransmission. CHT1 is a Na + -dependent, hemicholinium-3 (HC-3) sensitive choline transporter. Although cholinergic neurons in the nucleus basalis of Meynert are a major source of cholinergic projections for the cerebral cortex, it is unclear whether cortical neurons exhibit intrinsic CHT1 activity that is altered in AD. We now report that primary cortical neurons express intrinsic and biologically active CHT1, and that, in these neurons, CHT1-mediated choline uptake activity is significantly reduced in PS-1 M146V mutant knock-in mice. Further kinetic studies using HC-3 binding and cell surface biotinylation assays showed that the PS-1 mutation inhibits CHT1 mediated choline uptake by reducing the ligand binding affinity of CHT1 without significantly altering levels of CHT1 expression in the plasma membrane. Since human neocortex has recently been shown to possess intrinsic cholinergic innervation, our results indicate that alterations in CHT1-mediated high affinity choline uptake in cortical neurons may contribute to Alzheimer's dementia.

Relationships between Mitochondrial Dysfunction and Neurotransmission Failure in Alzheimer’s Disease

“…Mitochondrial-induced oxidative stress via nitrosylative stress hinders the recycling of choline from the synapse leading to ACh deficiency. In late stage AD, levels of presynaptic high-affinity choline transporter 1 (CHT1) were observed to be decreased in synaptosomes in the hippocampus and neocortex of humans [ 168 , 169 ] and Tg animals [ 170 , 171 ]. Cuddy et al demonstrated the internalisation of CHT1 in SH-SY5Y neuroblastoma cells after treatment with nitric oxide (NO) donor (3-morpholinosydnonimine), leading to peroxynitrite (ONOO - ) formation [ 171 , 172 ].…”

Neuroprotective Actions of Dietary Choline

“…This APPswe/PS1dE9 (APP.PS1; MGI ID: 3524957) AD model mouse strain was engineered to express murine App with the human Aβ amino acid sequence harboring mutations that cause a familial form of AD (the Swedish mutation APPK595N/M596L; APPswe) together with a mutated form of PSEN1 (PS1 with exon 9 deleted; PS1dE9) [ 115 ]. Though no model of AD fully recapitulates the human disease [ 116 ], APP.PS1 mice are characterized by: (1) high production of amyloid Aβ peptides in brain and accumulation of amyloid plaques by 4–6 months of age [ 117 ]; (2) cognitive impairments [ 118 , 119 , 120 , 121 , 122 ]; (3) cholinergic defects [ 123 , 124 , 125 , 126 , 127 , 128 ]; and (4) evidence of abnormal methylation of several genes [ 129 ]. Perinatal choline supplementation significantly reduced the average number of Aβ42 plaques in both 9- and 12-month old APP.PS1 female and male mice.…”

“…While the number of Aβ42 plaques increased with age in the control APP.PS1 mice, the plaque number was more stable in choline-supplemented mice, suggesting that Aβ42 synthesis, clearance, and/or aggregation may be altered in these mice to prevent additional plaque formation. A decline in cholinergic function and diminished expression of the cholinergic marker, CHAT, is apparent in aged humans and animals [ 130 , 131 , 132 ], in patients with Alzheimer’s disease (AD) [ 133 , 134 , 135 , 136 ], and in animal models of AD [ 118 , 123 , 124 , 125 , 126 , 127 , 128 , 135 , 137 ]. Thus, it has been postulated that abnormal cholinergic neurotransmission, due to dysfunction and/or degeneration of the septo-hippocampal cholinergic system, contributes to the memory deficits seen in advanced age and in AD [ 131 , 135 , 136 ].…”

Impact of Oxidative - Nitrosative Stress on Cholinergic Presynaptic Function

“…Experiments that involve the use of a variety of model systems indicate that the high-affinity choline uptake activity of CHT can be modulated by A, but the results are also variable. Some reports show that A can actually increase high-affinity choline uptake activity (Bales et al, 2006;Kristofikova et al, 2006), whereas others suggest that Aimpairs choline uptake (Apelt et al, 2002;Kar et al, 1998;Klingner et al, 2003;Kristofikova et al, 2001Kristofikova et al, , 2008Opazo et al, 2006;Payette et al, 2007) or that Ahas no effect on high-affinity uptake of choline (Forgon et al, 1998;Hartmann et al, 2004;Melo et al, 2002). It is known that cholinergic neurochemical function is affected directly by A in a manner that is not related to neuron degeneration, but it is not known to what extent these effects are due to the oxidant stress engaged by increasing A.…”