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- Ng, Ai Na, et al.
(författare)
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Dendritic EGFP-STIM1 activation after type I metabotropic glutamate and muscarinic acetylcholine receptor stimulation in hippocampal neuron.
- 2011
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Ingår i: Journal of Neuroscience Research. - : Wiley. - 1097-4547 .- 0360-4012. ; 89:8, s. 1235-1244
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Tidskriftsartikel (refereegranskat)abstract
- Several signaling pathways in neurons engage the endoplasmic reticulum (ER) calcium store by triggering calcium release. After release, ER calcium levels must be restored. In many non-neuronal cell types, this is mediated by store-operated calcium entry (SOCE), a cellular homeostatic mechanism that activates specialized store-operated calcium channels (SOC). Although much evidence supports the existence of SOCE in neurons, its importance has been difficult to determine because of the abundance of calcium channels expressed and the lack of SOC-specific pharmacological agents. We have explored the function of the SOCE-inducing protein STIM1 in neurons. In EGFP-STIM1-expressing hippocampal neurons, the sarco- and endoplasmic reticulum calcium ATPase (SERCA) inhibitor thapsigargin caused rapid aggregation (i.e., activation) of STIM1 in soma and dendrites. Upon STIM1 activation by thapsigargin, a dramatic reduction in STIM1 mobility was detected by fluorescence recovery after photobleaching (FRAP). By triggering release of ER calcium with 3,5-dihydroxyphenylglycine (DHPG) or carbachol (Cch), agonists of type I metabotropic glutamate receptors (mGluR) and muscarinic acetylcholine receptors (mAChR), respectively, STIM1 was activated, and calcium entry (likely to represent SOCE) occurred in dendrites. It is therefore possible that neuronal SOCE is activated by physiological stimuli, some of which may alter the postsynaptic calcium signaling properties. © 2011 Wiley-Liss, Inc.
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| 2. |
- Ng, Ai Na, et al.
(författare)
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Endoplasmic reticulum dynamics in hippocampal dendritic spines induced by agonists of type I metabotropic glutamate but not by muscarinic acetylcholine receptors.
- 2011
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Ingår i: Synapse. - : Wiley. - 1098-2396 .- 0887-4476. ; 65:4, s. 351-355
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Tidskriftsartikel (refereegranskat)abstract
- Neurons in the hippocampus exhibit subpopulations of dendritic spines that contain endoplasmic reticulum (ER). ER in spines is important for synaptic activity and its associated Ca(2+) signaling. The dynamic distribution of ER to spines is regulated by diacylglycerol and partly mediated by protein kinase C, metalloproteinases and γ-secretase. In this study, we explored whether pharmacological activation of type I metabotropic glutamate receptors (mGluRs) and muscarinic acetylcholine receptors (mAChRs) known to activate phospholipase C would have any effect on spine ER content. We found that DHPG (100 μM) but not carbachol (10 μM) caused a reduction in the number of spines with ER. We further found that ER Ca(2+) depletion triggered by thapsigargin (200 nM) had no effect on ER localization in spines.
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| 3. |
- Ng, Ai Na
(författare)
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Endoplasmic reticulum function in dendrites and dendritic spines of hippocampal neurons
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the hippocampus, dendritic spines are compartmentalized postsynaptic micro-domains in the excitatory synapse. Subsets of bigger and mushroom-shaped hippocampal dendritic spines contain tubules and cisterns of endoplasmic reticulum (ER) that are connected to the soma and dendrites of the neuron. These ER containing spines differ in their ability to retain ER. We hypothesized a functional coupling of the ER to the plasma membrane (PM) via protein-protein interaction at specialized junctions, which we believe to anchor ER within spines. Although the molecular composition of such an ER-plasma membrane junction (ERPMJ) is yet to be elucidated, we showed that a subset of ERPMJs containing type I transmembrane proteins sensitive to phorbol ester induced metalloproteinase and subsequent gamma-secretase mediated remodelling, and that these proteins may be involved in regulating spine ER dynamics. The gamma-secretase is a multimeric complex with presenilin protein as the catalytic component. Findings have implicated mutations in the presenilin genes clinically associated to familial Alzheimer’s disease (FAD) with altered store-operated calcium entry (SOCE) response. SOCE is a cellular homeostatic mechanism that is activated to restore the depleted ER calcium store via specialized store-operated calcium channels (SOC) localized in the PM. With SOCE-inducing protein STIM1, we explored the effect of a FAD M146V mutation in presenilin-1 (PS1) on spine ER dynamics as well as on STIM1 function. In EGFP-STIM1-expressing hippocampal neurons established from wild-type and FAD PS1 mutant mice, we used 3,5-dihydroxyphenylglycine (DHPG) and carbachol, agonist of type I metabotropic glutamate receptors and muscarinic acetylcholine receptors to trigger calcium release from the ER via IP3R. Surprisingly, STIM1 activation appeared not to be affected by the PS1-M146V mutation although SOCE was impaired. Separately, we showed that DHPG or carbachol stimulation in PS1-M146V neurons led to a significant ER loss from spines that was exclusively mediated by mechanisms controlling ER entry into spines. We hypothesized that the PS1-M146V mutation altered yet to be elucidated mechanisms regulating ER entry into spines, and which may well contribute to synaptic dysfunction in FAD. Looking forward, there is value in future research to elucidate novel molecules and signaling pathways vis-a-vis gamma-secretase and presenilin activity to spine ER dynamics.
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