Synaptopodin regulates release of calcium from stores in dendritic spines of cultured hippocampal neurons

Tropomyosin (Tpm) has been regarded as the master regulator of actin dynamics. Tpms regulate the binding of the various proteins involved in restructuring actin. The actin cytoskeleton is the predominant cytoskeletal structure in dendritic spines. Its regulation is critical for spine formation and long-term activity-dependent changes in synaptic strength. The Tpm isoform Tpm3.1 is enriched in dendritic spines, but its role in regulating the synapse structure and function is not known. To determine the role of Tpm3.1, we studied the synapse structure and function of cultured hippocampal neurons from transgenic mice overexpressing Tpm3.1. We recorded hippocampal field excitatory postsynaptic potentials (fEPSPs) from brain slices to examine if Tpm3.1 overexpression alters long-term synaptic plasticity. Tpm3.1-overexpressing cultured neurons did not show a significantly altered dendritic spine morphology or synaptic activity. Similarly, we did not observe altered synaptic transmission or plasticity in brain slices. Furthermore, expression of Tpm3.1 at the postsynaptic compartment does not increase the local F-actin levels. The results suggest that although Tpm3.1 localises to dendritic spines in cultured hippocampal neurons, it does not have any apparent impact on dendritic spine morphology or function. This is contrary to the functional role of Tpm3.1 previously observed at the tip of growing neurites, where it increases the F-actin levels and impacts growth cone dynamics.

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Spike-Associated Fast Contraction of Dendritic Spines in Cultured Hippocampal Neurons

Neuron ◽

10.1016/s0896-6273(01)00314-2 ◽

2001 ◽

Vol 30 (3) ◽

pp. 751-758 ◽

Cited By ~ 52

Author(s):

Eduard Korkotian ◽

Menahem Segal

Keyword(s):

Dendritic Spines ◽

Hippocampal Neurons ◽

Cultured Hippocampal Neurons

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Fast imaging of [Ca]i reveals presence of voltage-gated calcium channels in dendritic spines of cultured hippocampal neurons

Journal of Neurophysiology ◽

10.1152/jn.1995.74.1.484 ◽

1995 ◽

Vol 74 (1) ◽

pp. 484-488 ◽

Cited By ~ 24

Author(s):

M. Segal

Keyword(s):

Calcium Channels ◽

Dendritic Spines ◽

Hippocampal Neurons ◽

Numerical Aperture ◽

Ccd Camera ◽

Charge Coupled Device ◽

Voltage Gated ◽

Voltage Gated Calcium Channels ◽

Calcium Indicator ◽

Cultured Hippocampal Neurons

1. Cultured hippocampal neurons were recorded with a patch pipette containing 100 microM of the calcium indicator Fluo-3, and one of their dendrites, carrying dendritic spines, was visualized with a x100, 1.3-numerical aperture oil objective. Calcium spikes evoked by depolarizing the somata and changes in free dendrite and spine calcium concentrations ([Ca]d and [Ca]s, respectively) were monitored with a cooled charge-coupled device (CCD) camera, acquiring images at a rate of 17-20 ms per frame. In the majority of spine-dendrite pairs, [Ca]s rose faster and to a higher level than the adjacent [Ca]d. Likewise, topical application of glutamate evoked a faster and larger change in [Ca]s than in [Ca]d. The rise of intracellular calcium concentration in response to a depolarizing current pulse, but not in response to glutamate, was reduced in the presence of the calcium antagonist verapamil in both dendrites and spines. It is suggested that dendritic spines possess voltage-gated calcium channels.

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