Li Shen Loo1,2, Ning Tang3,4, Muthafar Al-Haddawi1, Gavin Stewart Dawe3,4,and Wanjin Hong1,5.
1 Institute of Molecular and Cell Biology, Singapore 138673.
2 Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 637553.
3 Department of Pharmacology, Neurobiology and Ageing Programme, National University of Singapore.4 Singapore Institute for Neurotechnology, Singapore.5 Department of Biochemistry, National University of Singapore, Singapore 117597.
Published in Nature Communications on 24 January 2014.
Sorting nexin 27 (SNX27), a PDZ-domain containing endosomal protein, was recently shown to modulate glutamate receptor recycling in Down’s syndrome. However the precise molecular role of SNX27 in GluA1 trafficking is unclear. Here we report that SNX27 is enriched in dendrites and spines, along with recycling endosomes. Significantly, the mobilization of SNX27 along with recycling endosomes into spines was observed. Mechanistically, SNX27 interacts with K-ras GTPase via the RA domain; and following chemical LTP stimuli, K-ras is recruited to SNX27-enriched endosomes through a Ca2+/CaM-dependent mechanism, which in turn drives the synaptic delivery of homomeric GluA1 receptors. Impairment of SNX27 prevents LTP and associated trafficking of AMPARs. These results demonstrate a role for SNX27 in neuronal plasticity, provide a molecular explanation for the K-ras signal during LTP, and identify SNX27 as the PDZ-containing molecular linker that couples the plasticity stimuli to the delivery of postsynaptic cargo.
Figure Legend: SNX27 mediates recycling endosome transport. (a) Loss of SNX27 from spines following glycine treatment. Time-lapse imaging following the loss and subsequent recovery of SNX27 signal (green) with time following glycine treatment, but not in the presence of NMDA receptor antagonist APV. Glycine stimulation was applied from 0-5min. Time is indicated in min and sec. Scale bar, 4 µm. (b) Quatitative analysis of loss of SNX27 GFP signal normalized against the spine mcherry signal (n= 87 and 90 spines from 5 neurons for Gly and Gly/APV treatment respectively, error bars=s.e.m.). (c ) Absence of SNX27 interferes with recycling endosome transport. Wild type and SNX27-depleted neurons were saturated with Alx-Tf for 30 min, washed and further incubated in neurobasal media, glycine or glycine/APV for 25min. Representative images showing the loss of Alx-Tf from wild type and SNX27-deficient neurons following 25 min treatment with neurobasal media, glycine or glycine/APV. Scale bar, 5 µm. (d) Quantitative analysis of intracellular fluorescence remaining following 25 min treatment with neurobasal media, glycine or glycine/APV; n=10 neurons respectively, error bars=s.e.m.
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