Program in Molecular Physiology
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The Program in Molecular Physiology (PMP) brings together a group of resident and visiting scientists who share common interests in the molecular bases of cellular physiology. Through diverse subjects the member laboratories focus on cellular plasticity and the properties of molecular transport mechanisms. A variety of experimental approaches are used ranging from molecular and biochemical methodologies, through biophysics, to advanced optical and electrochemical imaging techniques.
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Browsing Program in Molecular Physiology by Subject "Postsynaptic density"
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ArticleDistribution of postsynaptic density (PSD)-95 and Ca2+/calmodulin-dependent protein kinase II at the PSD(Society for Neuroscience, 2003-12-03) Petersen, Jennifer D. ; Chen, Xiaobing ; Vinade, Lucia ; Dosemeci, Ayse ; Lisman, John E. ; Reese, Thomas S.Postsynaptic densities (PSDs) contain proteins that regulate synaptic transmission. We determined the positions of calcium/calmodulin-dependent protein kinase II (CaMKII) and PSD-95 within the three-dimensional structure of isolated PSDs using immunogold labeling, rotary shadowing, and electron microscopic tomography. The results show that all PSDs contain a central mesh immediately underlying the postsynaptic membrane. Label for PSD-95 is found on both the cytoplasmic and cleft sides of this mesh, averaging 12 nm from the cleft side. All PSDs label for PSD-95. The properties of CaMKII labeling are quite different. Label is virtually absent on the cleft sides of PSDs, but can be heavy on the cytoplasmic side at a mean distance of 25 nm from the cleft. In tomograms, CaMKII holoenzymes can be visualized directly, appearing as labeled, tower-like structures reflecting the 20 nm diameter of the holoenzyme. These towers protrude from the cytoplasmic side of the central mesh. There appears to be a local organization of CaMKII, as judged by fact that the nearest-neighbor distances are nearly invariant over a wide range of labeling density for CaMKII. The average density of CaMKII holoenzymes is highly variable, ranging from zero to values approaching a tightly packed state. This variability is significantly higher than that for PSD-95 and is consistent with an information storage role for CaMKII.
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ArticlePersistent accumulation of calcium/calmodulin-dependent protein kinase II in dendritic spines after induction of NMDA receptor-dependent chemical long-term potentiation(Society for Neuroscience, 2004-10-20) Otmakhov, Nikolai ; Tao-Cheng, Jung-Hwa ; Carpenter, Stephen ; Asrican, Brent ; Dosemeci, Ayse ; Reese, Thomas S. ; Lisman, John E.Calcium/calmodulin-dependent protein kinase II (CaMKII) is a leading candidate for a synaptic memory molecule because it is persistently activated after long-term potentiation (LTP) induction and because mutations that block this persistent activity prevent LTP and learning. Previous work showed that synaptic stimulation causes a rapidly reversible translocation of CaMKII to the synaptic region. We have now measured green fluorescent protein (GFP)-CaMKIIα translocation into synaptic spines during NMDA receptor-dependent chemical LTP (cLTP) and find that under these conditions, translocation is persistent. Using red fluorescent protein as a cell morphology marker, we found that there are two components of the persistent accumulation. cLTP produces a persistent increase in spine volume, and some of the increase in GFP-CaMKIIα is secondary to this volume change. In addition, cLTP results in a dramatic increase in the bound fraction of GFP-CaMKIIα in spines. To further study the bound pool, immunogold electron microscopy was used to measure CaMKIIα in the postsynaptic density (PSD), an important regulator of synaptic function. cLTP produced a persistent increase in the PSD-associated pool of CaMKIIα. These results are consistent with the hypothesis that CaMKIIα accumulation at synapses is a memory trace of past synaptic activity.