论文部分内容阅读
Postsynaptic membrane rafts, as well as postsynaptic density (PSD), is believed to form a major site important for postsynaptic signal transduction.However, roles of this domain have not been well studied.We have been studying postsynaptic membrane rafts, hypothesizing that two major signaling domains, postsynaptic membrane rafts and PSD, interact physiologically and work together in vivo.I would talk about the recent progress in the research on the postsynaptic membrane rafts and discuss about the possible roles ofraft-PSD complexes.We have previously reported the existence of numerous so called "PSD proteins" in the DRM prepared from SPM (SPM-DRM) (Suzuki et al., 2008, J Neurochem 104: 596-610).Comprehensive identification of proteins in the SPM-DRM by LC-MS/MS and comparison with those in the PSD confirmed an extensive overlapping of proteins in the SPM-DRM and PSD fractions, while some proteins showing biased distribution to the SPM-DRM suggest roles of postsynaptic membrane rafts (Suzuki et al., 2011, J Neurochem 119: 64-77).To know why so many PSD proteins are present in the SPM-DRM,we re-examined detergent effects very carefully during purifications of SPM-DRM and PSD with the aid of an electron microscope, and we identified membrane raft-PSD complex in the SPM-DRM preparation (Suzuki et al., 2011, J Neurochem 119: 64-77).The presence of the raft-PSD complex suggests the association of these subcellular structures in vivo.To further strengthen the evidence that the two domains associate in vivo, we tried reconstitution of purified SPM-DRM, which is PSD-free, and PSD in vitro.We found the specific binding of PSD structures to the PSD-free DRM.The binding was confirmed by mass spectrometry, Western blotting and electron microscopy.This binding was not due to non-specific interaction.These results provide evidence that postsynaptic raft and PSD are physically associated in vivo, which may be essential for fulfilling postsynaptic functions, including those in synaptic plasticity.