Cell biology of the neuron

AMPA receptor tetramerization is mediated by Q/R editing. Greger, I. H. et al. Neuron 40, 763–774 (2003)

The channel properties and trafficking of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors depend largely on their subunit composition. RNA editing of the GluR2 subunit at the 'Q/R site' controls trafficking of AMPA receptors from the endoplasmic reticulum to the synapse, and this study shows that RNA editing at this site also regulates tetramerization of AMPA receptor subunits. Edited GluR2 subunits are retained in the endoplasmic reticulum (ER) and do not readily tetramerize, whereas most unedited subunits are exported from the ER to the synapse and assemble into receptor tetramers.

Neurodegenerative disorders

Dietary Cu stabilizes brain superoxide dismutase 1 activity and reduces amyloid Aβ production in APP23 transgenic mice. Bayer, T. A. et al. Proc. Natl Acad. Sci. USA 100, 14187–14192 (2003)

In vivo reduction of amyloid-β by a mutant copper transporter. Phinney, A. L. et al. Proc. Natl Acad. Sci. USA 100, 14193–14198 (2003)

In APP23 transgenic mice, a model of Alzheimer's disease, overexpression of the amyloid precursor protein (APP) is associated with reduced activity of superoxide disumutase 1 (SOD1) and deposition of amyloid plaques. Bayer et al. find that dietary copper restores SOD1 activity in these mice, and also lowers levels of amyloid-β in the brain. In the second of these papers, Phinney and colleagues use another mouse model of Alzheimer's disease in which amyloid-β accumulates. When these mice are homozygous for a mutant copper transporter that causes accumulation of copper in the cytoplasm, levels of amyloid-β and deposition of amyloid plaques are reduced. These studies contrast with previous in vitro results, which indicated that copper increased amyloid-β assembly and toxicity, and indicate that treatment with copper might be useful in the early stages of Alzheimer's disease.

Neuropsychology

Altered awareness of voluntary action after damage to the parietal cortex. Sirigu, A. et al. Nature Neurosci. 30 November 2003 (10.1038/nn1160)

In electroencephalographic studies, the human experience of wanting to move is reported after, rather than before, the 'readiness potential', which indicates preparation for a movement. Sirigu et al. find that patients with damage to the parietal cortex cannot report awareness of an intention to move. They propose that activity in the parietal cortex is important for the generation of an internal model of a planned movement, and that this model might be necessary for awareness of motor planning.