The postsynaptic density (PSD) is a cytoskeletal specialization at neuronal synapses that was originally identified as an electron-dense region at the membrane of a postsynaptic neuron, as viewed by electron microscopy. PSDs are usually comprised of L-glutamate neurotransmitter receptors, their molecular scaffolding molecules, cell adhesion molecules and a diverse set of other signaling proteins. PSDs vary in size and composition among brain regions. Many of the PSD proteins contain PDZ domains. Illustration of the major elements in a prototypical synapse. ... The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons rather than light to scatter off material, magnifying at levels up to 500,000 times. ... Glutamic acid (Glu) or glutamate (the anionic form) is one of the 20 standard amino acids used by all organisms in their proteins. ... Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cells plasma membrane, but also in the membranes of some subcellular compartments and organelles. ... Cell Adhesion Molecules (CAMs) are proteins located on the cell surface involved with the binding with other cells or with the extracellular matrix (ECM) in the process called cell adhesion. ... PDZ can be the abbreviation for two video games: Perfect Dark Zero for the Xbox 360 Panzer Dragoon Zwei for the Sega Saturn This page concerning a three-letter acronym or abbreviation is a disambiguation page—a list of articles associated with the same title. ...

Function

The PSD has been proposed to concentrate and organize neurotransmitter receptors to respond rapidly to neurotransmitter in the synaptic cleft. Some of the features of the PSD are similar to the neuromuscular junction and other cellular junctions, as the PSD has been modeled as a specialized cellular junction that allows for rapid, asymmetical signaling. A neuromuscular junction is the junction of the axon terminal of a motoneuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscles surface. ... Adherens junctions share the characteristic of anchoring cells through their cytoplasmic actin filaments . ...

Structure

The structure and composition of the PSD have been the focus of numerous molecular studies of synaptic plasticity, a cellular model of learning and memory. The term synaptic plasticity refers to the variability of the strength of a signal transmitted through a synapse. ...

Composition

Many proteins in the PSD are involved in the regulation of synaptic function. Key among these, are postsynaptic density-95 (PSD95), neuroligin, a cellular adhesion molecule, NMDA receptors, AMPA receptors, calcium/calmodulin-dependent protein kinase II and actin. As protein detection technologies have increased in sensitivity, such as with improvements in mass spectroscopy techniques, more numerous proteins have been attributed to the PSD. Current estimates are greater than several hundred proteins are found at PSDs among brain regions and during different states of development and synaptic activity. The NMDA receptor (NMDAR) is an ionotropic receptor for glutamate (NMDA (N-methyl d-aspartate) is a name of its selective specific agonist). ... The AMPA receptor (AMPAR) is a non-NMDA-type ionotropic transmembrane receptor for glutamate that mediates fast synaptic transmission in the central nervous system. ... Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ...

References

General Review

• Ziff EB. "Enlightening the postsynaptic density." Neuron. 1997; 19(6):1163-74. NCBI Pubmed
• Kennedy MB. "Signal-processing machines at the postsynaptic density." Science. 2000; 290(5492):750-4. NCBI Pubmed

Structure and Compostion

• Cohen RS, Blomberg F, Berzins K, Siekevitz P. "The structure of postsynaptic densities isolated from dog cerebral cortex. I. Overall morphology and protein composition." J Cell Biol. 1977; 74(1):181-203. NCBI Pubmed
• Blomberg F, Cohen RS, Siekevitz P. "The structure of postsynaptic densities isolated from dog cerebral cortex. II. Characterization and arrangement of some of the major proteins within the structure." J Cell Biol. 1977; 74(1):204-25. NCBI Pubmed
• Walikonis RS, Jensen ON, Mann M, Provance DW Jr, Mercer JA, Kennedy MB. "Identification of proteins in the postsynaptic density fraction by mass spectrometry." J Neurosci. 2000; 20(11):4069-80. NCBI Pubmed
• Peng J, Kim MJ, Cheng D, Duong DM, Gygi SP, Sheng M. "Semiquantitative proteomic analysis of rat forebrain postsynaptic density fractions by mass spectrometry." J Biol Chem. 2004; 279(20):21003-11. NCBI Pubmed
• Jordan BA, Fernholz BD, Boussac M, Xu C, Grigorean G, Ziff EB, Neubert TA. "Identification and verification of novel rodent postsynaptic density proteins." Mol Cell Proteomics. 2004; 3(9):857-71. NCBI Pubmed