The postsynaptic density (PSD) is a massive dynamic cytoskeletal macromolecular machine consisting of a diverse group of specialized proteins that are anchored to the postsynaptic membrane and network together to form a large signaling assembly. The PSD is necessary for many processes such as long-term potentiation (LTP) and plays a significant role in learning and memory. In this work, 3D imaging through electron microscopic (EM) tomography was used to study the molecular level organization of the PSD. Dissociated rat hippocampal neurons that were highpressure frozen were maintained through freeze substitution. These spines were examined and imaged through dual axis EM tomography series. Detailed rendering and analysis of these reconstructions revealed that the PSD is composed of a core structural network consisting of vertical filaments perpendicular to the postsynaptic membrane. The filaments associate with major types of transmembane structures and several classes of horizontal filaments and other larger structures. The horizontal networks form distinct, characteristic patterns in certain regions, suggesting a possible role in stabilizing core membrane structures at the PSD. Thus, deciphering the structure of this core protein network of the PSD may provide critical insight to unravel the basic function of the PSD.
Last updated March 20, 2013