| 1. |
- Kucharz, Krzysztof, et al.
(författare)
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NMDA receptor stimulation induces reversible fission of the neuronal endoplasmic reticulum.
- 2009
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- With few exceptions the endoplasmic reticulum (ER) is considered a continuous system of endomembranes within which proteins and ions can move. We have studied dynamic structural changes of the ER in hippocampal neurons in primary culture and organotypic slices. Fluorescence recovery after photobleaching (FRAP) was used to quantify and model ER structural dynamics. Ultrastructure was assessed by electron microscopy. In live cell imaging experiments we found that, under basal conditions, the ER of neuronal soma and dendrites was continuous. The smooth and uninterrupted appearance of the ER changed dramatically after glutamate stimulation. The ER fragmented into isolated vesicles in a rapid fission reaction that occurred prior to overt signs of neuronal damage. ER fission was found to be independent of ER calcium levels. Apart from glutamate, the calcium ionophore ionomycin was able to induce ER fission. The N-methyl, D-aspartate (NMDA) receptor antagonist MK-801 inhibited ER fission induced by glutamate as well as by ionomycin. Fission was not blocked by either ifenprodil or kinase inhibitors. Interestingly, sub-lethal NMDA receptor stimulation caused rapid ER fission followed by fusion. Hence, ER fission is not strictly associated with cellular damage or death. Our results thus demonstrate that neuronal ER structure is dynamically regulated with important consequences for protein mobility and ER luminal calcium tunneling.
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| 2. |
- Ng, Ai Na, et al.
(författare)
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{gamma}-Secretase and metalloproteinase activity regulate the distribution of endoplasmic reticulum to hippocampal neuron dendritic spines.
- 2008
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Ingår i: FASEB Journal. - : Wiley. - 1530-6860 .- 0892-6638. ; 22:8, s. 2832-2842
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Tidskriftsartikel (refereegranskat)abstract
- The neuronal endoplasmic reticulum (ER) contributes to many physiological and pathological processes in the brain. A subset of dendritic spines on hippocampal neurons contains ER that may contribute to synapse-specific intracellular signaling. Distribution of ER to spines is dynamic, but knowledge of the regulatory mechanisms is lacking. In live cell imaging experiments we now show that cultured hippocampal neurons rapidly lost ER from spines after phorbol ester treatment. ER loss was reduced by inhibiting gamma-secretase (DAPT at 2 microM) and metalloproteinase (TAPI-0 and GM6001 at 4 microM) activity. Inhibition of protein kinase C also diminished loss of ER by preventing exit of ER from spines. Furthermore, gamma-secretase and metalloproteinase inhibition, in the absence of phorbol ester, triggered a dramatic increase in spine ER content. Metalloproteinases and gamma-secretase cleave several transmembrane proteins. Many of these substrates are known to localize to adherens junctions, a structural specialization with which spine ER interacts. One interesting possibility is thus that ER content within spines may be regulated by proteolytic activity affecting adherens junctions. Our data demonstrate a hitherto unknown role for these two proteolytic activities in regulating dynamic aspects of cellular ultrastructure, which is potentially important for cellular calcium homeostasis and several intracellular signaling pathways.-Ng, A. N., Toresson, H. gamma-Secretase and metalloproteinase activity regulate the distribution of endoplasmic reticulum to hippocampal neuron dendritic spines.
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| 3. |
- Toresson, Håkan, et al.
(författare)
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Dynamic distribution of endoplasmic reticulum in hippocampal neuron dendritic spines
- 2005
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Ingår i: European Journal of Neuroscience. - : Wiley. - 1460-9568 .- 0953-816X. ; 22:7, s. 1793-1798
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Tidskriftsartikel (refereegranskat)abstract
- The role of the endoplasmic reticulum (ER) localized in dendritic spines has become a subject of intense interest because of its potential functions in local protein synthesis and signal transduction. Although it is recognized from electron microscopic studies that not all spines contain ER, little is know of its dynamic regulation or turnover. Here, we report a surprising degree of turnover of ER within spines. Using confocal microscopy imaging we observed continuity of spine-ER with dendritic ER in hippocampal primary neurons. Over 24 h, less than 50% of spine ER was stable. Despite this high degree of turn over, we identified a significant subset of spines that maintained ER for at least 4 days. These results indicate that within a single neuron, the organelle composition of a spine is unexpectedly dynamic and may explain aspects of the spine-to-spine variation in calcium spike magnitude and localized protein synthesis and trafficking.
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