Postsynaptic density

Ultra-structural analysis of synapses in the brainstem of wild-type (WT)mice at embryonic day 18.5. Synapses of WT neurons in the pre-Bötzinger-complex area exhibit presynaptic vesicles (asterisks), a synaptic cleft and a distinct postsynaptic density (arrowheads). Scale bar, 250 nm. From Heupel et al., 2008

The postsynaptic density (PSD) is a cytoskeleton 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 composed 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.

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, asymmetrical signaling.

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. PSDs are sized on the order of 250 to 500 nanometres in diameter and 25 to 50 nanometres in thickness, depending on the activity state of the 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.

External links

• Postsynaptic Density- Cell Centered Database
• The postsynaptic density
• Molecular Composition of the Postsynaptic Density

References

General review

• Ziff EB (December 1997). "Enlightening the postsynaptic density". Neuron 19 (6): 1163–74. doi:10.1016/S0896-6273(00)80409-2. PMID 9427241. 
• Kennedy MB (October 2000). "Signal-processing machines at the postsynaptic density". Science 290 (5492): 750–4. doi:10.1126/science.290.5492.750. PMID 11052931. 

Structure and composition

• Banker G, Churchill L, Cotman CW (November 1974). "Proteins of the postsynaptic density". J. Cell Biol. 63 (2 Pt 1): 456–65. doi:10.1083/jcb.63.2.456. PMID 4419608. 
• Cohen RS, Blomberg F, Berzins K, Siekevitz P (July 1977). "The structure of postsynaptic densities isolated from dog cerebral cortex. I. Overall morphology and protein composition". J. Cell Biol. 74 (1): 181–203. doi:10.1083/jcb.74.1.181. PMID 194906. 
• Blomberg F, Cohen RS, Siekevitz P (July 1977). "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. 74 (1): 204–25. doi:10.1083/jcb.74.1.204. PMID 406264. 
• Walikonis RS, Jensen ON, Mann M, Provance DW, Mercer JA, Kennedy MB (June 2000). "Identification of proteins in the postsynaptic density fraction by mass spectrometry". J. Neurosci. 20 (11): 4069–80. PMID 10818142. 
• Peng J, Kim MJ, Cheng D, Duong DM, Gygi SP, Sheng M (May 2004). "Semiquantitative proteomic analysis of rat forebrain postsynaptic density fractions by mass spectrometry". J. Biol. Chem. 279 (20): 21003–11. doi:10.1074/jbc.M400103200. PMID 15020595. 
• Jordan BA, Fernholz BD, Boussac M, et al. (September 2004). "Identification and verification of novel rodent postsynaptic density proteins". Mol. Cell Proteomics 3 (9): 857–71. doi:10.1074/mcp.M400045-MCP200. PMID 15169875. 
• Baron MK, Boeckers TM, Vaida B, et al. (January 2006). "An architectural framework that may lie at the core of the postsynaptic density". Science 311 (5760): 531–5. doi:10.1126/science.1118995. PMID 16439662. 
• Collins MO, Husi H, Yu L, et al. (April 2006). "Molecular characterization and comparison of the components and multiprotein complexes in the postsynaptic proteome". J. Neurochem. 97 (Suppl 1): 16–23. doi:10.1111/j.1471-4159.2005.03507.x. PMID 16635246.